ABSTRACT EFFECTS OF SUBSOIL ASPHALT BARRIERS ON THE PRODUCTION OF PADDY RICE AND SUGARCANE ON SAND SOILS IN TAIWAN by Alvin J. Marion Smucker Asphalt barriers were installed in a deep fine sand soil in southern Taiwan at several depths below the soil surface. Paddy rice and sugarcane were the index crops used to evaluate the effects of the asphalt barrier on water consumption and crop production of tr0pical sand soils. A subsoil drainage system was installed in the asphalt lined paddies which provided a method for draining the asphalt paddies. Natural drainage occurred off the edge of the barriers in the sugarcane experiment. The asphalt sand rice paddies required less irrigation water than most conventional clay paddies. A new drainage schedule was adapted to accommodate the fertilization and aeration requirements of the paddies. Excellent rice yields were produced on all the barrier treatments of both the spring and summer crops. Asphalt barriers installed at a depth of A0 cm. proved most desirable for rice production on these soils. The sulfate nitrogen carrier had essentially no detrimental effects on rice pro- duction during this study. Alvin J. Marion Smucker Asphalt barriers installed 75 cm. below the soil surface reduced the irrigation requirements of sugarcane by 70% or by 225 mm. water and doubled the production of sugarcane during the growing season. The 75 cm. barrier appeared to give the best water-air relationship in the root zone of the sugarcane. Rice and sugarcane root penetration had essentially no effect upon the permeability of the asphalt barriers. EFFECTS OF SUBSOIL ASPHALT BARRIERS ON THE PRODUCTION OF PADDY RICE AND SUGARCANE ON SAND SOILS IN TAIWAN By Alvin J. Marion Smucker A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Soil Science l969 TO'BETTY This thesis is dedicated to my wife for her encouragement and willing sacrifices during this investigation. ACKNOWLEDGMENTS The author would like to thank Dr. A. E. Erickson for his guidance and encouragement during the course of this study and for his constructive criticisms during the preparation of this manuscript. The author also wishes to thank Dr. R. L. Cook, Dr. K. Lawton, Dr. C. M. Harrison and Dr. J. F. Davis for their helpful criticisms during the preparation of this manuscript. A special note of appreciation is extended to Mr. K. Y. Li and the staff of the Taiwan Sugar Experiment Station for their assistance with the data collection. The writer would also like to thank Mrs. Bess Quinlan for her assistance in the statistical analyses of the data. Financial assistance by the Institute of International Agriculture and Nutrition, Michigan State University and the Joint Commission on Rural Reconstruction, Taipei, Taiwan are gratefully acknowledged. Chapter TABLE OF CONTENTS ACKNOWLEDGMENTS LIST OF TABLES . . . . . . . . . . . LIST OF FIGURES... LIST OF APPENDICES . . . . INTRODUCTION . . . . . LITERATURE REVIEW. . . . . . . . . . MATERIALS AND METHODS. . . . . . . . General Description. . . . . . Soil type . . . . . . . . . Climatic conditions. . . . . Irrigation water . . . Asphalt barrier installation Rice Experiment. . . Asphalt paddy construction . Experimental design. . . . . Cropping practices . . Plant growth and production measurements. . . , Root distribution studies. Soil measurements. . . . . . Sugarcane Experiment . Asphalt barrier construction Experimental design. . . . Cropping practices . . . . Soil water measurement . . Plant growth and production measurement . . . . . Root distribution studies. . TABLE OF CONTENTS, Continued Chapter Page IV. EXPERIMENTAL RESULTS AND DISCUSSION . . 37 Rice Experiment. . . . . . 37 Efficiency of asphalt .soil water barrier . . . . . . . . 37 Soil drainage and aeration . . . #0 Rice growth and production . . . 43 Nitrogen carriers. . . . . . 57 Root growth and distribution . . 57 Sugarcane Experiment . . . . . . . . 6h Soil water retention , , . . Sugarcane growth . . . . . . . . 80 Sugarcane root growth. . . . 85 Sugarcane production . . . . 88 v. CONCLUSIONS. . . . . . . . . . . . . . . 92 APPENDIX . . . . . . . . . . . . . . . . 96 LITERATURE REVIEWED. . . . . . . . . . . 98 LIST OF TABLES Table Page I Physical properties of the Fusan Farm sand soil . . . . . . . . . . . . . . II 2 Chemical properties of the Fusan Farm sand soil . . . . . . . . . . . . . . l2 3 Climatic conditions at Taiwan Sugar Experiment Station. . . . . . . . . . l5 h Irrigation, pan evaporation, and precipitation of the I967 spring and summer rice crops . . . . . . . . 38 5 Irrigation water costs in central Taiwan. . . . . . . . . . . . . . . . 39 6 Irrigation water applied to the spring and summer rice crops. . . . . #0 7 Plant growth rates of spring rice cr0p. . . . . . . . . . . . . . . . . A6 8 Plant growth rates of summer rice crop. . . . . . . . . . . . . . . . . #6 9 Visual observations of experimental rice plants during spring crOp. . . . #7 l0 Tillering of spring rice crop. . . . . . 52 Il Tillering of summer rice crop, , , , , , 52 l2 Brown rice yields of spring and summer rice crops. . . . . . . . . . . . . . 53 l3 Plant characteristics at harvest of the spring and summer rice crops, , , 5h vi LIST OF TABLES, Continued Table Ih l5 l6 l7 l8 I9 20 2I 22 23 24 Plant characteristics at harvest of the rice variety Tainan #5 grown on asphalt lined sand paddies and clay paddies . . . . . . . . . . . Effects of nitrogen carrier upon paddy rice grown on sand soils lined with 0 cm. asphalt barrier. Root distribution of spring rice crop 6h days after transplanting in asphalt lined sand soil . Root weight per hill at harvest of spring planted paddy rice variety Tainan #5 grown on asphalt sand paddies. . . . . . . . . . . Root weight per hill at harvest of summer planted paddy rice variety Tainan #5 grown on asphalt sand paddies. . . . . . . . . . . . . . . Root penetration of 3 mm. asphalt barrier during spring rice crop. . . . Soil water content of sand soil five days after l3h mm. rainfall. . SoiI moisture regime of asphalt sugarcane experiment . . . . . . . . . Oxygen diffusion rates at a soil depth of IO cm. as measured by the platinum microelectrode. . . . . . Soil water tension measurements of asphalt sugarcane experiment . . . . . Effect of distance upon soil water at edge of barrier . . . . . . . vii Page 56 58 58 60 6] 63 65 68 7] 73 75 LIST OF TABLES, Continued Table Page 25 Supplemental irrigation added to sugarcane experiment . . . . . . . . 77 26 Leaf analysis of l27 day-old sugarcane . . . . . . . . . . . . . 79 27 Germination of sugarcane variety F-l56 grown on Taiwan fine sand. . . 8O 28 Root distribution of asphalt sugarcane - expressed as percent dry weight . . 87 29 Effects of asphalt barriers on sugar- cane production. . . . . . . . . . . 89 vii Figure IO ll l2 LIST OF FIGURES Soil water retention curve for the Ap horizon of the Fusan Farm fine sand - analysis by C.C. Yang of T.S.E.S. Road surfacing asphalt applicator used to apply asphalt barriers. Diagrammatic illustration of asphalt rice paddy . . . Service pit for surface and subsurface drains . . . . . . . . Field design of asphalt rice experiment . . . . . . . . Drainage and fertilization schedule for asphalt rice paddy . . . . Asphalt barrier for sugarcane cul- tivation in fine sand soil . Field design of asphalt sugarcane experiment . . . . . . . . . . . Concrete irrigation lateral of sugarcane experiment showin the placement of the Parshall f ume and the exit gates . . . . . . . Oxygen diffusion rate at I0 cm. in sand and clay soil rice paddy. . Growth rates of the I967 spring and summer asphalt rice crops. Rice growth 96 days after trans- planting of control (upper center) and surrounding asphalt treatments . . . . . . . . . Page l4 l8 20 22 23 25 3O 32 33 #2 AA 48 LIST OF FIGURES, Continued Figure l3 Tillering rates of the I967 spring and summer asphalt rice crops . . . . . . . l4 Soil moisture regime and rainfall of asphalt sugarcane experiment . l5 Effects of asphalt barrier depth on soil water content . . . . . l6 Soil water tension in 50 cm. barrier treatment of asphalt sugarcane experiment . . . . . . . . . . . l7 Sugarcane growth on asphalt barrier treatment (right) and on control treatment (left) . . . . . . . . l8 Plant growth rates of asphalt sugarcane experiment . . . . . . Page SI 66' 69 72 BI 83 Chapter I INTRODUCTION Most of the water used by plants must be stored in the soil. The water storage capacity of a sand soil is very small and reduces the productivity of these soils unless supplemental irrigation is applied. However, the additional water applied to maintain optimal soil moisture conditions for plant growth is expensive. Therefore a combination of supplemental irrigation practices and a soil treatment similar to the asphalt moisture barrier devel0ped by Erickson and Hansen of Michigan State University could be used to bring many of the deep well-drained sand soils of the world into production. Taiwan, a small island country in the South China Sea, has greatly improved its agriculture during the last two decades. Recent land reforms, rural improvement programs and agricultural research, sponsored by the Joint Commission on Rural Reconstruction, have laid the foundations for maximum production of Taiwan's arable land. This nation's major problem, however, is that additional arable land is scarce. Hsi and Liao (30) indicated that land is in such demand that more than two-thirds of the marginal land in Taiwan is cultivated. As a result of this land shortage, many sand soil reclamation projects are in progress in the river bed and coastal areas of Taiwan. This study resulted from the combined efforts of the Soil Science Department, Michigan State University (M.S.U.), the Institute of International Agriculture, M.S.U., the Joint Commission on Rural Reconstruction (J.C.R.R.) of Taiwan, and the Taiwan Sugar Corporation (T.S.C.). Both the author and his major professor traveled to Taiwan for this study. The author remained in Taiwan for six months while the major professor returned to M.S.U. shortly after the installation of the experiment and the first crops were planted. Staff members of the Soils and Agronomy Departments of the Taiwan Sugar Experiment Station (T.S.E.S.) harvested the second rice crop and the spring planted sugarcane crop. Two experiments were conducted in this study. The first was conducted to evaluate the use of asphalt barriers for creating rice paddies on sand soils. The second was conducted to evaluate the effects of asphalt barriers upon soil water conservation and sugarcane production on tr0pical, deep, well-drained sand soils. The experiments were conducted on the Fusan farm of the T.S.C. Chekan Sugar Mill located five kilometers south of Tainan, Taiwan. Laboratory facilities and technicians were provided by T.S.E.S. The primary objective of the rice experiment was to establish rice paddies on sand soils with subsurface asphalt barriers. Other objectives of this study included: I. The determination of the minimum barrier depth which would assure maximum yield and protect the barrier from tillage. 2. The development of a method for periodically draining the asphalt paddy. 3. An evaluation of the effects of urea and ammonium sulfate nitrogen carriers on rice grown in asphalt-lined sand soil paddies. A. An evaluation of the effects of rice roots on the asphalt barrier. 5. The determination of the water efficiency of the barrier. The primary objective of the sugarcane experiment was to determine the quantity of water that could be conserved for sugarcane production by the installation of asphalt barriers below the root zone. Other objectives of this study included: I. The determination of the effects of the asphalt barrier depth upon water storage, irrigation efficiency, and sugarcane production. An evaluation of the effects of reduced soil oxygen on sugarcane production. The determination of the sugarcane root-asphalt barrier relationships. Chapter II LITERATURE REVIEW Many research workers have shown that the amount of water retained by sand soils is a function of soil texture, depth, and uniformity (7, 37, 8). Baver (8) showed that non- capillary pores in the root zone of sand soils are readily drained by the soil moisture tension created in the continuous capillaries of deep homogenous sand soils. Since a small quantity of available water is retained by these coarse soils, frequent additions of supplemental irrigation water are required in order to maintain Optimum soil moisture conditions for plant growth. The higher costs resulting from frequent irrigations, to replenish water that is lost due to deep percola- tion, and additional fertilizers added to replenish those nutrients lost by leaching, greatly reduce the economic productivity of these soils. Arable land is scarce in the small island country of Taiwan. Approximately 75% of the total land area of 35,760 square kilometers is mountains and thousands of hectares of land are covered with sand soils (36). Approximately 24% of the total land area is cropped leaving a very small area for expansion. Rice is the chief food of the Orient where it sustains more than one-half the world's population (52). In Taiwan more than 60% of the arable land is cultivated for paddy rice, producing approximately two million metric tons of brown rice annually. More rice would be grown, however, if suitable paddy soils were available. Sugarcane, the second most important crop in Taiwan, is grown in the alluvial soils. Many of these alluvial soils are coarsely textured and have a low water storage capacity. Yeh, gt. g1. (59) reported that the soil moisture contents of many unirrigated cane fields approach the permanent wilting percentage during the summer and autumn growing seasons. Preliminary studies by T.S.E.S. have indicated that the yield of sugarcane grown on sand soils may be tripled when an optimum available moisture content is maintained throughout the growing season (unpublished data). Therefore, steps must be taken to reduce the loss of natural and irrigation water from the root zone of these soils before maximum sugarcane yields can be economically obtained. Recently, the irrigation facilities provided by the government have increased sugarcane yields in many of these sand soil areas. However, much of this valuable water is wasted as the irrigation frequency and water quantity are controlled by irrigation water availability rather than by cr0p demands. Crops are excessively irrigated when water is available reducing the efficiency of both water and nutrients. Consequently, when plant demands for soil mois- ture are high the remaining water supply is rapidly depleted. Soil stratification increases the moisture holding capacity of sand soils. This phenomenon is especially true when the soil band is impermeable to water. Grant (26) reported beach sand soils that were underlined with boulders could be flooded and converted into rice paddies. Tremendous quantities of water and nutrients were required, however, to produce respectable rice yields on these sand soil paddies as the boulders did not form a water-tight moisture barrier. Hishomoto (29) showed an increased in rice yields of rain-fed sand soil paddies when vinyl sheets were installed below the root zone. Less water and fewer nutrients were lost by the vinyl treatment. Vinyl sheets are excellent moisture barriers although it is extremely difficult to produce an infinite moisture barrier of practical use for sand soil paddies as the joints between the vinyl sheets rupture during installation, reducing the efficiency of the moisture barrier (unpublished data). Erickson and Hansen at Michigan State University showed-that the moisture holding capacity in the root zone of sand soils was doubled by installing a 3 mm. layer of asphalt 60 cm. below the soil surface (un- ’published data). Asphalt moisture barriers limited the natural drainage of sand soils by disrupting the deep capillaries, thereby reducing the water tension in the root zone: Since the asphalt barrier is impermeable to water, low tension water can be stored above the barrier. They also showed that fewer irrigations were required to maintain available soil moisture conditions in the root zone above the asphalt barrier. The above considerations suggest that if the subsoil asphalt barriers were continued to the soil surface, thereby stopping both the horizontal and vertical movement of the soil water, economically productive rice paddies could be constructed on sand soil. The leaching of mobile nutrients through coarse soils is related to water movement. Bates (5) has shown that nitrate movement varies directly with the pore size distribution and the quantity of water moving through the porous soil. Other studies (54) have shown that large quantities of potassium are also removed from intensely irrigated sand soils. There- fore it seems feasible that the asphalt moisture barrier may also conserve soil nutrients. Soil texture is also important in the retention and availability of nutrients. This is especially true for paddy culture where most nutrients are absorbed in the reduced form. The low exchange capacity of coarse textured soils reduce nutrient retention by these soils. The combined effects of high permeability and low exchange capacity allow for excess nutrient leaching. Excessively irrigated sand soil paddies are not desirable for rice production because the soil in the root- zone is not adequately reduced. Inadequately reduced soil does not allow iron to go into solution, anaerobic bacteria are not active, and the nitrification-denitrification cycle is not developed (40), consequently rice production. decreases. "Akiochi" (4), suffocation disease (l6), and other rice physiology diseases often occur on I'degraded" paddies, especially on soils low in iron. Mitsui and others (4l,, I7), suggest a heavy basal application of ammonium sulfate increases the incidence of this disease. For this reason an ammonium sulfate treatment was included with the 40 cm. barrier treatment. Chapter III MATERIALS AND METHODS General Description Soil type The soil type of the Tiger Mountain section of the Fusan Farm was a fine sand which is representative of many droughty sugarcane soils in Taiwan. The physical properties of this very loose fine sand are recorded in table I. These physical properties were analyzed by the commonly used methods outlined in the Agronomy Monographs No. 9 (l). The high permeability, the particle size distribution, and the low organic content indicate the beach-like properties of this sand soil. The uniform distribution of the separates throughout the soil profile also indicate the homogenicity of this soil. Soil core samples indicated this homogenicity continued to depths greater than three meters below the soil surface. Since this soil was relatively free of fine soil lenses it was described as an excessively drained soil. The soil was also analyzed for its nutrient content before the begin- ning of the experiment, table 2. The high pH, available phosphorous, and exchangeable calcium content in the Ap horizon probably resulted from the lime filter cake that IO II .m.m.msh .mcm> .0 Jo >9 m_m>_mc<* _.o m.m “.m: k.~ :._ N.: m.: ~.mm o.- m.o o xoo_-o~_vmum _.o :.m m.m: N.~ :._ N.m m.m m.m~ o.m_ ~.o o Ao~_-mmv_om m.o :.m o.m¢ N.~ :._ o.m _.m o.mm ~.m_ ~.o o Amm-~mvu~m m.o _.m m.N: N.~ :._ m.o _.m m.mm m.- m.o o ANm-o~vu_m ~._ m.m N._m ~.N m._ ~.m v.0 . m.km m.:_ _.m o Ao~-ova< JfllmwnflMdflAfi. >m_o ocmm pcmm pcmm ocmm pcmm /mm mm nmwmm am as... ..._.> mod ..._ _.o .z 35 .0 m6 .o.> o; wws one .9 AI II.nxu:m -fio..3A. .90 -9. -RN NHo au /8 1.9 m0.0 . UIZ I. Jl. HG. o/od 1A9 5P . 0|. 9 ”cm... m l Ww bugmgépcicofiafcum; 33.. .83ch ucoocom mu A; *ZOm ocmm Eco... Emma... 93 mo mozcoaoa 233.3; ._ 03m... I2 Table 2. Chemical properties of Fusan Farm sand soil++ o o o c .— _. _. O In .0 .o .o N . «)3 «1E m «IE 0 I U: mx:E cuaE czas Can .c —-o ——c1o. mono. mn-o. maoo. .c «ILSR °-IDCL £:m¢1 J:L)Q. £:c¢1 III-«H “H ‘00 U“ U— Om --c1 1: o«- >4: x<> xco x10 (>0 o. h—: <:o. qu. uIU uIE urn AP * (0-20) 80L.> 0.16 192.0 5409 22.] 2.9 Blt (20-52) 709 0013 3605 5'03 308 2.2 Bgt (5 -85) 6.6 0.l4 25.0 72.5 l.5 l.7 BC (85-120) 5.8 0.12 14.0 17.0 1.5 1.5 BC 5.5 0.l2 9.0 22.6 l.4 l.0 (123-160) * I5-25%, by volume, filter cake incorporated‘into surface horizon ++ Analysis by T.S.E.S. l3 was incorporated into the surface soil. These nutrients were also analyzed by the commonly used methods outlined in the Agronomy Monographs No. 9 (2). The moisture retention curve in figure I was determined by the tension table and pressure plate methods commonly used in determining the effects of tension on soil water. This curve shows the greatest water loss occuring at tensions between 35 and 55 cm. of water. The data from this figure then, suggested the depths at which the asphalt barriers should be installed. The soil water content is approximately l9.6%, by volume, at field capacity while the soil moisture contents at IOO, 75, and 50 cm. of water tension are 20.4, 25.9, and 34.5% by volume, respectively. Therefore as the asphalt barrier is brought closer to the surface a larger percent of the soil pore space will be filled with water. The moisture retention curves for the horizons from l2-l20 cm., were similar to the Ap horizon reported in figure I; See table I in appendix. Climatic conditions Taiwan's location astride the Tropic of Cancer gives it a subtropical climate with abundant rainfall during the monsoon season. Table 3 shows the I967-I968 climate Tension - cm. water 300 275 250 225 200 I75 l50 l25 I00 75 50 25 I4 . l5 atmosphere i percentage 5 I0 15 20 25 30 35 no 45 so Soil water content - % by volume Figure I. Soil water retention curve for the Ap horizon of the Fusan Farm fine sand - analysis by C.C. Yang of T.S.E.S. l5 A_m .omo-_ .cmwv _.m_ _:.w~ .m :.~ --- k.:a~_ ~.:mm_ .m>m Enos «m m.m_ m.- :m ~.~ o.wom.~__ k.~_o~ N.m-_ .muou to mmmLo>< xm_-_v m.o_ N.m_ mm k.m k.:~m.m m.om _.mm mm. stmatamu m... :.m~ _w m.~ ~.~om.~ m.-_ m.: stmacms N.o_ m.- om N.— m.mmn.m m.m__ m.o Laneoumo m.n_ “.5N mm :._ m.m¢m.m ~.:~_ A... Lmnegoz m.m_ m.m~ Nm m.~ N.omo.m ~.:m_ ~._~ canouoo :.N~ m.om mm A._ m.mm_.m :._~_ ~.m tansouaom N.:~ m._m mm 0.. k.~mm.x _.mw_ w.mm~ um=m=< o.:~ m.mm mm 5.. o.mmo.~_ m.mo~ m.om_ >_:s _.:~ :.om mm m._ m.~_o.__ m._m_ m.mmm mass m.- o._m mm A._ m.o::.__ m.m_~ m.:o~ >mz m.m_ m.m~ om m.~ m.mm~.m _.~m_ m.~__ __La< _.m_ m.m~ mm ~.~ N.om_.o_ m.:m_ :.m sotmz Mm~--v m... ~.- Nm m.m m.moo.m m.mm_ m.o_ No. Emstnmu uo.anu uo.anu “$>H_U_E:; m\E _I>mo I.Eo .EE .EE E:E_c_E E:E_me o>wum_oc nc_3 ._mo .m co_umLoqm>m __mmc_mm coco: com: com: com: com: comummomm Awwm_ .m. >Lmacnou I mom. .NN >cmzcnomv co_uMum ucoE_LoQXu cmmsm cm3_mh um mco_u_ocoo u_umE__u .m m_nmh l6 was very similar to the average climate during the past 52 years. Two medium velocity typhoons occurred during the sugarcane crOp, one of which occurred during the summer rice crop. The subtropical climate allows for three rice crops or two rice crops and a vegetable crop or a l2 month sugarcane crop. Irriqation water Deep wells provided good quality irrigation water for both the rice and sugarcane experiments. For the rice experiment: the well water was warmed to ambient tempera- ture during transport to and storage in a small open re- servoir. A gasoline powered pump and a plastic hose were used to transfer the irrigation water from the reservoir to the individual paddies. Small flow meters, 2.5 cm. I.D., were used to measure the irrigation water. For the sugar- cane experiments: The well water was applied directly to the individual plots by a concrete lined open irrigation ditch. Parshall flumes were used to record the irrigation rate, as high as 25 liters per second, and volume of water that was added to each plot. Asphalt barrier installation The subsurface asphalt barriers were installed by the I7 cut and fill method using manual labor. The experimental sites were surveyed, cleared of plant debris, and leveled before excavation. During excavation the topsoil and sub- soil were separately excavated and stored. The sides of each treatment were cut at a l:l sl0pe while the I'floor'| was cut at the prescribed depth and parallel to the soil surface. Prior to asphalt application the newly exposed soil was treated with insecticide, leveled, and sprinkled with'water. Asphalt grade #50 was sprayed on the soil at the rate of IS M.T./Ha., forming a thin, 3 mm., homogenous asphalt barrier. The asphalt, which was transported in 50 gal. barrels, was heated and then sprayed on the prepared soil. The three-man road surfacing asphalt sprayer illustrated in figure 2 was used to construct the asphalt barriers. Following solidification the barrier was inspected, re- paired, and covered with soil. .Asphalt barrier installation expenses were much greater in Taiwan than in the United States. The addi- tional expense arose from the tremendous quantity of manual labor employed to install the Taiwan barriers for a total cost of nearly U.S. $2,500 per hectare. Nearly 50% of the total installation costs arose from labor fees for excavating and refilling the soil while the cost of I8 Figure 2. Road surfacing asphalt applicator used to apply the'barriers. l9 labor used to apply the asphalt was approximately 30% of the total expense. The remaining 20% of the total installa- tion expense was spent for asphalt materials. Therefore the mechanical asphalt applicator, which will apply a subsurface asphalt barrier for approximately U.S. $500/Ha. including the asphalt materials, has a decided economical advantage. Rice Experiment Asphalt paddy construction The subsurface asphalt barrier was continuous to the soil surface which essentially isolated the contents within the paddy from the surrounding soil. At the soil surface a brick wall, 20 cm. high, separated the flood water of adjacent paddies. However, further studies in- dicated that asphalt-lined soil dikes similar to that shown in figure 3 could be constructed to resist breakage during normal paddy manipulations. The isolated asphalt paddy also necessitated the installation of a drainage system. Perforated plastic pipe, 7.6 x 300 cm., were wrapped with palm sheaths and positioned in the center of the plot on the asphalt floor. This subdrainage system was covered with fine gravel and joined to an outlet in the wall. A short plastic pipe was also Figure 3. 20 ASPHALT MEMBRANE RICE PADDY SOIL DIKE 0’ mm Incl Ir/Ien [loader/a - -------- Soil -----------—---- ---- surface'Q3 E o O Gravel . . 0'" ("P9 4 AspIIoIIQ asphalt rice paddy. “I - DRAINAGE ' DITCH Diagrammatic illustration of I 2I installed at the original soil surface in the same wall. Both outlets drained into an adjacent service drainage pit, figure 4. The drains were plugged during flooding and opened for draining and aerating the paddy soil. Experimental design The square asphalt rice paddies, four meters on a side, were arranged in the randomized block design shown in figure 5. There were four asphalt treatments and the control (A-E) fertilized with urea and one 40 cm. barrier treatment (F) fertilized with ammonium sulfate. The five treatments were replicated four times. Concrete lined irrigation and surface drainage ditches were placed between the paddies according to the diagram in figure 5. Sand soil paddies were also constructed around the perimeter of the experiment as border plots. A three-meter bamboo windbreak was also placed along the north and west sides of the rice experiment. The center 5.70 m.2 of each paddy was evaluated for plant growth and production. The remaining rows, 4 per side, were designated as guard rows. Croppjng practices Two rice crops were grown during this investiga- tion. The spring crOp was transplanted on 22 ., . D; ‘3. ). " . ‘ . .: .. V «1 "i "m 1 s. -_s.:...-, 111111 II 11; ‘u' ' , . ' Figure 4. Service pit for surface and subsurface drains. 23 ucoE_Loaxo ou_c u_m;amm mo cm_mmo o_o_m .m oc:m_m muo_a LopLOm _I.1IIIIII u_. .u H111 I 1.1..II u n u "u H111 u.“ MII... H «MIIIII n.11 n IIIIJ.I"IIIHIIIJ... -. . — . . no u . c .. .. x x .n L "' 'J --fi' I| EEEETLEHH Lou_o ommc.mLoI IIIII gljlljl4_ Lou_o co_umvaLp1 -1-' - :1 3 II 5': ”IF! II I I II I L1. N'NI 1IIII... I cu».o ommc.mtb1 ".".Il"|"|-l|'|"l JqI IIJ111141IIIJ+111J r .. I d H J ---4 . .. .. .u .. u .. .. ._ . II... LrIII LFIIILPI IILrIIIL I I I L I I l I I I I I I I I I I I I I I I I: 1' I I I I I I I. sucoz muopa.cooL0m J; . . .- _IPIIII .llllLPlI ILPIIILPIIILFIIIL-IIIIL—IIIIL- E_j CEI1. somuxqzzv Lo_ccmn .Eo o: Lo_ccmn .Eu om Lo_ccmn .50 o: Lo_ccmn .50 cm co_ccmn .Eu om Lo_ccmn o: I _ocucoo - mxsn __om m mxsu xu_tm (mUDLIJLL 24 February 22, I967 and the summer crop was transplanted on July l0, I967. For the spring crop, the rice grown on the asphalt treatments was harvested on June l8 while the control treatments were harvested on July 3, I967. The entire summer crop was harvested on October l6, I967. Rice variety Tainan #5 (Oryza sativa L.) was used for both crops. This short strawed variety was released in I964 for high production by Taiwan plant breeders. Nursery plants, 8-l0 cm. tall, were transplanted in hills of six plants each. The hills were spaced at l5 cm. intervals within the row and 25 cm. between the rows. Most of the cultural practices in this study were similar to those followed by Taiwan paddy rice farmers. Therefore the weeding, fertilizing, Spraying, etc., were done by manual labor. However, additional fertilizer was required to maintain adequate fertility and a new fertilization schedule was developed, figure 6. Fertilizer was applied to the paddies before the flooding and transplanting of both the spring and summer rice crops. Nitrogen was applied to all treatments of the spring crop at the rate of Il3 Kg./Ha. While nitrogen 25 xocma oo_c “.mzamm LOm o_:oocom co_umN___ume pcm ommc_mco .o oc:m_u mc_co___u mc_co___u mc_ucm_a ON— ~m_ .muop Imcmch o N J m . m . o. . N. ON ON ON cm wm u N. 8 2 3 a 82 {magnum [aAal JaneM 'LUD 26 was applied to the asphalt paddies of the summer crop at the rate of l32 Kg./Ha. Two additional side dressings of nitrogen were added to the control treatments 36 and 46 days after transplanting. Consequently, an additional 50 Kg./Ha. of nitrogen was applied to the control treatments of the summer crop. Phosphorus and potassium ‘were applied to all the treatments of both crops in the forms of calcium superphosphate and potassium chloride. Phosphorus was added before transplanting while potassium was added according to the schedule in figure 6. The water level on the asphalt paddies was maintained according to the schedule in figure 6. The asphalt paddies were drained and aerated five times for 48 hours and one time for 96 hours during the growing season, figure 6. Soils in the control paddies were flooded for l2 and I8 hours per day for the spring and summer crops, respectively. Chemical pest control was similar to the methods followed by Taiwan rice farmers. Parathion, fumiron, “WC and blasteiden S were used to control the leaf- hopper, weevil, stem borer, and the rice blast disease, respectively. 27 Plant growth and production measurements The plant height and tiller quantity were determined at weekly intervals for the duration of both rice crops. Plant height was determined by measuring the aerial portion of the plant from the soil surface to the end of the longest plant part. Tillers were those branch Stems, arising from the initial setting with more than' one leaf. The average value of 20 hills per treatment was recorded for that treatment. Brown rice and straw yields were harvested from the center, 5.70 square meters of each paddy. Dry grain yields were recorded at a l2% moisture content. The straw yield was the weight of the threshed plants which were dried in a 70 C forced air oven for three days. Plant height, panicle quantity and length, tillers, and grain quantity per panicle were determined by measuring the plants from 20 randomly selected hills per replica- tion. Harvest data of the spring crop was taken from replications 2, 3, and 4 because replication l was destroyed by an overdose of fungicide. Four replications were used for all measurements of the summer crop. Root distribution studies Rice root distribution was determined by analyzing triplicated postharvest soil samples. A square metal 28 frame, I5 x 25 cm. and open at both ends, was forced through the soil to the asphalt barrier or to a depth of 50 cm. in the control treatment. The surrounding soil was excavated and the soil volume containing the rice crown and roots was extracted. Then the soil was wetted, removed from the frame, and dissected at 5 cm. intervals parallel to the soil surface. The roots in each segment were washed, dried at 70 C for three days, and weighed. The asphalt barrier below each excavated plant was exam- 2 ined and the number of roots which penetrated a l00 cm. area of the barrier was recorded. Soil measurements Various soil measurements were taken during the rice experiment. The density changes in the soil were period- ically measured (l). Soil pH was measured by the glass electrode using a l:l soil-water ratio. During the drainage period oxygen diffusion rates were also deter- mined by the platinum microelectrode according to the procedures outlined by Erickson, Van Doren, and Lemon (20. 35). 29 Sugarcane Experiment Asphalt barrier construction Both sides and one end of the subsurface asphalt barrier were continuous to the soil surface of the rectan- gular sugarcane plots. The remaining end was not sealed with asphalt allowing subsoil drainage, figure 7. This plot design created an infinite barrier in three directions and permitted good subsoil drainage. Experimental design This experiment was conducted in the same sugarcane field which was adjacent to the rice experiment. Sugarcane was grown on rectangular plots that were 8.75 x 25.0 m. The treatmentsrconsisted of three asphalt barriers placed at 50, 75, and l00 cm. below the soil surface henceforth refered to as the 50, 75, and l00 cm. treatments and two control treatments. One control was cut and filled to a depth of l00 cm., which will be referred to as the disturbed control, while the other control was undisturbed. Each treatment was replicated six times. The thirty plots were arranged in the randomized block design illustrated in figure 8. Border sugarcane plots, l0 m. wide, were placed around the perimeter of the experiment. Two concrete lined irrigation laterals were installed in the middle two corridors of this experiment, figure 8. 30 __om Ucmm mc_m c_ co_um>_u_:o mcmumeam LOm Lo_ccmn u_m:am< .n ocsm_u ommc_mco 3o_> oo_m P _ u x .57234 :msmma. _ .50 mn _ oommcam __0m 3o_> new _ Lowccmn mfi u_m;am< _ _ .80 mm _ mommcam __0m .r 3l m_mcoum Eutoz “cos_coaxo mcmocmmzm u_m;amm mo cm_mmn p_o_m .m 0L:m_m .1 n m o m o m o < m m u m m o m m o < m .E mm m. flu wm_ u < u < o m o u moo—a LmULOm In .0cucou nmntaum_o -m Lm_ccmn .Eo oo_1q Lo_ccmn .50 mm .0 Lm_ccmn .80 cm um _0cucou I< 32 Irrigation water was metered by a 7.6 cm. Parshall flume which was positioned at the junction of the irrigation main and each concrete lateral, figure 9. A system of exit gates, installed in each lateral, permitted independent irrigation of each plot. Surface drainage ditches were also constructed of soil in each corridor of the sugarcane experiment, figure 8. Cropping practices A twelve-month sugarcane crop was grown for the asphalt sugarcane experiment. The sugarcane variety F-l56 (Saccarum officinarum L.) was planted on March 5, I967 and harvested February 26, I968. This moderately drought resistant variety was released by T.S.E.S. plant breeders in I965 and yields approximately 92.00 M.T. of sugarcane per hectare (T.S.E.S. Agronomy Department, unpublished data). Seedpieces, each having two nodes, were treated with calcium water and fungicide and planted in rows spaced at l.25 m. and 0.30 m. within the row. Seedpieces were planted at a rate of 27,000 per hectare. Gradulated inorganic fertilizer was the only source of nutrients added to the sugarcane experiment. Ammonium sulfate was applied to all treatments at the rate of 350 Kg. N per hectare. SuperphOSphate and potassium chloride were applied to all treatments at the rates of 33 Figure 9. Concrete irrigation lateral of sugarcane experiment showin the placement of the Parshall f7ume and the exit gates. 34 j 200 Kg. K20 per hectare. The basal fer- uded l25, IOO, and ISO Kg. of N, P205, and respectively. The remaining nitrogen 7, l0, l3, and 20 weeks after planting at . 65, 65, and 30 Kg. per hectare, respect- .gle potassium side dressing was applied planting. uation and pest control practices used in ‘6 similar to those followed by the other I ‘ the Taiwan Sugar Company. :asurement I water content in the root zone was determined ron scattering method (39). A Nuclear Chicago Ire probe and portable scaler, model 2800 were termine the water content of each plot three week. Aluminum access tubes, 5 cm. I.D. x 50 cm., s talled in the soil to a depth of 30 cm. Two access 2:7h"-'vere placed in each plot. The tubes were positioned )OSIte ends in row 3 and row 5 and were 8 m. from end. The P-l9 readings were taken at a depth of cm. giving the average soil water content in the upper J cm. of the soil (33). Soil samples were taken to gravimetrically determine the soil water content through- out the profile. Porous cup water tensiometers were also 26 was applied to the asphalt paddies of the summer crop at the rate of l32 Kg./Ha. Two additional side dressings of nitrogen were added to the control treatments 36 and 46 days after transplanting. Consequently, an additional 50 Kg./Ha. of nitrogen was applied to the control treatments of the summer crOp. Phosphorus and potassium 1were applied to all the treatments of both crops in the forms of calcium superphosphate and potassium chloride. Phosphorus was added before transplanting while potassium was added according to the schedule in figure 6. The water level on the asphalt paddies was maintained according to the schedule in figure 6. The asphalt paddies were drained and aerated five times for 48 hours and one time for 96 hours during the growing season, figure 6. Soils in the control paddies were flooded for l2 and I8 hours per day for the spring and summer crops, respectively. Chemical pest control was similar to the methods followed by Taiwan rice farmers. Parathion, fumiron, “BHC and blasteiden S were used to control the leaf- hopper, weevil, stem borer, and the rice blast disease, respectively. 27 Plant growth and production measurements The plant height and tiller quantity were determined at weekly intervals for the duration of both rice crops. Plant height was determined by measuring the aerial portion of the plant from the soil surface to the end of the longest plant part. Tillers were those branch Stems, arising from the initial setting with more than' one leaf. The average value of 20 hills per treatment was recorded for that treatment. Brown rice and straw yields were harvested from the center, 5.70 square meters of each paddy. Dry grain yields were recorded at a l2% moisture content. The straw yield was the weight of the threshed plants which were dried in a 70 C forced air oven for three days. Plant height, panicle quantity and length, tillers, and grain quantity per panicle were determined by measuring the plants from 20 randomly selected hills per replica- tion. Harvest data of the spring crop was taken from replications 2, 3, and 4 because replication l was destroyed by an overdose of fungicide. Four replications were used for all measurements of the summer crop. Root distribution studies Rice root distribution was determined by analyzing triplicated postharvest soil samples. A square metal 28 frame, l5 x 25 cm. and open at both ends, was forced through the soil to the asphalt barrier or to a depth of 50 cm. in the control treatment. The surrounding soil was excavated and the soil volume containing the rice crown and roots was extracted. Then the soil was wetted, removed from the frame, and dissected at 5 cm. intervals parallel to the soil surface. The roots in each segment were washed, dried at 70 C for three days, and weighed. The asphalt barrier below each excavated plant was exam- 2 ined and the number of roots which penetrated a l00 cm. area of the barrier was recorded. Soil measurements Various soil measurements were taken during the rice experiment. The density changes in the soil were period- ically measured (l). Soil pH was measured by the glass electrode using a l:l soil-water ratio. During the drainage period oxygen diffusion rates were also deter- mined by the platinum microelectrode according to the procedures outlined by Erickson, Van Doren, and Lemon (20, 35). 29 Sugarcane Experiment Asphalt barrier construction Both sides and one end of the subsurface asphalt barrier were continuous to the soil surface of the rectan- gular sugarcane plots. The remaining end was not sealed with asphalt allowing subsoil drainage, figure 7. -This plot design created an infinite barrier in three directions and permitted good subsoil drainage. Experimental design This experiment was conducted in the same sugarcane field which was adjacent to the rice experiment. Sugarcane was grown on rectangular plots that were 8.75 x 25.0 m. The treatmentsfconsisted of three asphalt barriers placed at 50, 75, and I00 cm. below the soil surface henceforth refered to as the SO, 75, and I00 cm. treatments and two control treatments. One control was cut and filled to a depth of IOO cm., which will be referred to as the disturbed control, while the other control was undisturbed. Each treatment was replicated six times. ,The thirty plots were arranged in the randomized block design illustrated in figure 8. Border sugarcane plots, l0 m. wide, were placed around the perimeter of the experiment. Two concrete lined irrigation laterals were installed in the middle two corridors of this experiment, figure 8. 30 __0m pcmm mc_m c_ co_um>_u_:o mcmocmmam LOm Lo_ccmn u_m;am< .m oczm_u mmmc_mco 3o_> op_m . \ . AWI ._ u \ co_ccmn.d, u_mzom< _ .50 mm _ oummcam __0m 3o_> new _ Lo_ccmn “fl u_m:am< _ — .Eu mm _ oommcsm __0m 2. 3l m_mcoum 1\ cutoz ucmE_Loaxm ocmocmmsm u_m;amm mo cm_mmp p_o_u r .m oc:m_m moo—a LmoLOm In _oLucoo amatsum_o -m Lm_ccmn .Eo oo_ua Lo_ccmn .Eo mm .0 co_ccmn .Eo om 1m .oLucou I< 32 Irrigation water was metered by a 7.6 cm. Parshall flume which was positioned at the junction of the irrigation main and each concrete lateral, figure 9. A system of exit gates, installed in each lateral, permitted independent irrigation of each plot. Surface drainage ditches were also constructed of soil in each corridor of the sugarcane experiment, figure 8. Cr0ppinggpractices A twelve-month sugarcane crop was grown for the asphalt sugarcane experiment. The sugarcane variety F-l56 (Saccarum officinarum L.) was planted on March 5, I967 and harvested February 26, I968. This moderately drought resistant variety was released by T.S.E.S. plant breeders in I965 and yields approximately 92.00 M.T. of sugarcane per hectare (T.S.E.S. Agronomy Department, unpublished data). Seedpieces, each having two nodes, were treated with calcium water and fungicide and planted in rows spaced at l.25 m. and 0.30 m. within the row. Seedpieces were planted at a rate of 27,000 per hectare. Gradulated inorganic fertilizer was the only source of nutrients added to the sugarcane experiment. Ammonium sulfate was applied to all treatments at the rate of 350 Kg. N per hectare. Superphosphate and potassium chloride were applied to all treatments at the rates of 33 Figure 9. Concrete irrigation lateral of sugarcane experiment showing the placement of the Parshall flume and the exit gates. 34 IOO Kg. P205 and 200 Kg. K20 per hectare. The basal fer- tilization included l25, l00, and ISO Kg. of N, P205, and K20 per hectare, respectively. The remaining nitrogen was applied at 7, l0, l3, and 20 weeks after planting at the rates of 65, 65, 65, and 30 Kg. per hectare, respect- ively. The single potassium side dressing was applied 20 weeks after planting. The cultivation and pest control practices used in this study were similar to those followed by the other plantations of the Taiwan Sugar Company. Soil water measurement The soil water content in the root zone was determined by the neutron scattering method (39). A Nuclear Chicago P-I9 moisture probe and portable scaler, model 2800 were used to determine the water content of each plot three times per week. Aluminum access tubes, 5 cm. I.D. x 50 cm., were installed in the soil to a depth of 30 cm. Two access tubes were placed in each plot. The tubes were positioned at opposite ends in row 3 and row 5 and were 8 m. from each end. The P-l9 readings were taken at a depth of 20 cm. giving the average soil water content in the upper 40 cm. of the soil (33). Soil samples were taken to gravimetrically determine the soil water content through- out the profile. Porous cup water tensiometers were also 35 installed to determine the tension exerted upon the soil water above the barrier. Daily readings were recorded at 8:30 a.m. The quantity of water required for each irrigation was determined by calculating the volume of water required to increase the soil water content to field capacity. First, the desired percent increase was determined by subtracting the current soil water content from the field capacity soil water content, figure I. Second, the desired volume of soil to be irrigated was calculated. Then the soil volume to be irrigated was multiplied times the desired change in the soil water content. This product was expressed in liters of water measured by the irrigation system. Plant growth and production measurements Plant height and tillering were measured at 30 day intervals throughout the growing season. Ten randomly selected plants in rows 3, 4, and 5 of each plot were measured from the seedpiece to the dewlap of the first leaf below the apical whorl of the main stalk. The num- ber of shoots which grew from the main stalk were re- corded as the tiller number. The production data was collected from replications III-VI while replications I and II were harvested sometime 36 later. Yields were determined by weighing the millable stalks in rows 3, 4, and 5 of each plot. After measuring the final plant height, the sugarcane was cut at the seedpiece, tOpped, stripped of leaves, then weighed. The same plants that were measured during the growing season were evaluated for the final plant height, stalk dia- meter, and sugar content. Root distribution studies Triplicated sugarcane root samples were extracted at I36 days after planting and at harvest. Four randomly selected sugarcane stools were sampled per treatment. A thin metal frame, 25 x 25 x 25 cm. and open at both ends was placed over the cane stool and forced into the soil. An area 625 cm.2 around the cane stool was extracted to the asphalt barrier or to a depth of l00 cm. in the treatments without barriers. Roots of each volume were washed, dried at 70 C. for three days and weighed. The asphalt barrier below each excavated plant was examined 2 and the number of roots which penetrated an area 625 cm. was recorded. Chapter IV EXPERIMENTAL RESULTS AND DISCUSSION Rice Experiment During this study, only a segment of the total effects of the asphalt barrier could be measured during the first two rice crops. Consequently the most convincing macro- parameters were selected for measurement. These measure- ments recorded and discussed below, show some of the effects of the asphalt barrier soil treatment on paddy rice growth and production on fine sand soils. Efficiengy of asphalt soil water barrier During this study the asphalt lined sand soils were flooded and paddy-like soil conditions were maintained for a prolonged period of time. The quantity of irrigation water applied to the asphalt paddies was I470 and 2397 mm. for the spring and summer crops, respectively, table 4. It was cal- culated that 570 mm. of water were discarded during the seven drainage periods, giving a net quantity of 900 mm. of irri- gation water applied to the asphalt paddies of the spring crop. In comparison, approximately I000 mm. of 37 38 water are applied to the clay soil paddies in Taiwan. Therefore the above data suggests the asphalt barriers in this study reduced soil water loss in sand soil paddies to a level below that of clay soil paddies. In contrast, the unlined control paddies required 7 and 20 times more irrigation water to maintain flooded conditions for l2 and I8 hours per day during the spring and summer crops, res- pectively. The above results indicate that subsoil .asphlat barriers continuous to the soil surface will discontinue the deep percolation of gravitational soil water and since these barriers are impermeable to water, large quantities of gravitational soil water can be stored by these asphalt lined sand soils. Therefore the asphalt barrier enabled the establishment of rice paddies on these highly permeable sand soils. Table 4. Irrigation, pan evaporation, and precipitation dur- " hg the I967 spring and summer rice crops. Spring crop Summer crop m. "In. Irri ation ontrol treatment l0,387 42,388 Asphalt treatments I,470 2,397 Pan evaporation 777 576 Precipitation 699 347 39 More than 40,000 m.m. of irrigation water were required to maintain flooded conditions for l8 hours per day on the control treatment of the summer crop, table 4. Table 5 shows that if this quantity of water was supplied by deep wells it would cost more than NT $62,000* per hectare for a paddy rice crop that was grown on sand soils without asphalt barriers. Since the installation cost of the asphalt barrier is approximately NT $l00,000 per hectare, when manual labor is employed, the reduced irrigation costs brought about by the presence of the asphalt barrier would compensate for the initial investment during the first two crops. Table 5. Irrigation water costs in central Taiwan Water source NT$ mm.'l ha.’I Natural 0.79 Shallow well l.9l Deep well I.56 Irrigation assn. 5.53 *The currenc exchange rate of NT$ to U.S.$ was approximately 40: in I967. 40 Table 6 shows the quantity of irrigation water applied to the .sand _ paddies was nearly the same for all the as- phalt treatments. Table 6 also shows that additional quan- tities of irrigation water were required by the asphalt paddies of the summer crop. This increased water require- ment resulted from the weather changes during this study, table 3, and by soil drainage. Table 6. Irrigation water applied to the spring and summer rice crops. Asphalt barrier depth-cm. Crop 20 30 40 60* 40-(NH4)ZSOH Average mm. mm. mm. mm. mm. mm. Spring I477 I436 ISSI I458 I429 I470 Summer 2335 2263 2464 2406 25l9 2397 Soil drainage and aeration The surface water of the asphalt paddies drained 8-l0 hours after the paddy drains were opened. Within 48 hours a dry soil mulch had formed on the surface of the 60 cm. treatments. The surface soil dried more rapidly on the 60 cm. treatment than on the shallower barrier treatments because a greater tension was exerted on the water in the surface soil of the deepest barrier treatment, figure I. 4l Little is known concerning the extent to which a paddy soil should be drained during the growing season. Conse- quently, measurements of the soil oxygen diffusion rate (ODR) were used as an index to determine the drainage time required for aeration of the rice root zone. Figure l0 shows the soil ODR of the asphalt paddies was 42 x I0'8 gm. cm.’2 min"I approximately 50 hours after the paddy drains were opened. Erickson (l9) showed this ODR to be the critical level for normal growth of upland crops. In contrast, the ODR of clay soil rice paddies changed very little during the midseason "drainage” period, figure l0 . Since most of the clay paddies in Taiwan are ”drained" for only five days during the rice crop, the above data suggest that the root zone of rice grown in clay soil is aerated very little during the "drainage" period. These studies suggest that sand paddies with asphalt barriers have a decided advantage over the fine textured paddies as they may be rapidly drained during the growing season for soil aeration, fertilization, and the removal of toxic soil materials. More information must be obtained, however, before the effects of periodic soil drainage and aeration can be established for paddy rice. Perhaps this phenomenon could be studied best on these asphalt sand paddies. 42 >Uoma oo_c __0m >m_o pcm pcmm c_ .Eo o. um mumc co_m:mm_p com>xo .o. ocsm_u oo— mczo; I mE_u ommc_mcp __0m mm 8.me R m: 3 mm am 3 8 m. o. m - j~ . q 1 J . IT . a q 4 d O t m all. >Uoma‘ N— :8 .65 m— -3 Ion .mm Lo_ccmn LN: Lo_ccma .m: Lm_ccmo .50 cm 0 L Lm_ccmn .Eo Om . :m >Uoma __0m ocmm poc__ u_msam< 00 w z_'wo '5 8'le - GJEJ uogsnjjgp uaBAxo .u! I 43 Preliminary pH studies indicated that soil flooding affected the hydrogen ion concentration of the Ap horizon very little as the pH changed from 8.4 to 8.2 during the first four months of flooding. Replicated undisturbed soil core samples indicated that the density of these sand soils increased during flooding as the bulk density changed from l.3l to l.52 g./cc. sometime during the spring crop. There was essentially no change, however, during the summer crop as the bulk den- sity was l.57 g./cc. after the second rice crop had been harvested from these sand soils. It was also observed that the jg_§j£g_water permeability rate on the control treatment was greatly reduced to 2.2 cm./hr. during the first few days of soil flooding. Therefore since the permeability rate was reduced soon after the soil had been puddled it appears that the above bulk density change may have occurred soon after the initial flooding of the spring crop. Rice growth andpproduction Good plant growth occurred on the asphalt lined sand paddies that were constructed for this investigation. The growth curves in figure ll indicate that a normal plant growth pattern occurred on the 40 cm. asphalt treat- ment throughout the growing seasons of both the spring 44 maoLo mu_c u_m;amm LmEEzm ocm mc_cam nmm_ ms“ mo moumc su30cu .__ mcsm_u m>wp I mc_ucm_amcmcu cmumm mE_h ow. o__ oo. om om 0m om 0m o: om ON 0— . q d u I u d O aoLo mc_camI _oLucou oII\\\\\\\ acco 11\\\\\\\\4 mc_camI Lm_ccmn.Eo 0:4 . QoLo LoEEJm I _oLucoo .I\\\\\\\\\\\ I aoLo Loeszm I Lm_ccmn .EU 03.. 0— ON on 0: 0m om on om om oo— o.— ‘wo - nqfigau queld 45 and summer crops. The rice plants from the summer crop grew taller than those from the spring crop. This phe- nomenon generally occurs in Taiwan as a result of the higher temperature and longer photoperiod during the summer growing season. Growth measurements of the other asphalt treatments indicated that barrier depth had essentially no affect upon plant growth in either crop, tables 7 and 8. In contrast, plant growth was reduced on the control treatments of both rice crops, figure ll. During the spring crop the drastic reduction of plant growth on the control treatment appeared to have resulted from the short I2 hour flooding period as plants became chlorotic soon after transplanting. As these deficiency symptoms progressively intensified plant growth on the control treatment was obviously reduced, figure l2. At a later stage of the growing season plants developed symptoms similar to those of the "Akiochi" disease (40), a physio- kufical disease that frequently occurs in rice grown on de- graded paddy soils in Japan. Consequently, maturation of plants on the control treatment of the spring crop was delayed, table 9. However, by increasing the flooding time and the nitrogen side dressings, plants on the control treatment of the summer crop grew at a rate similar, although somewhat depressed, to the rate of plant growth on the 40(NthzSou 60 reatment 40 *ASphalt Barrier depth - cm. 30 46 20 Control Plant growth rates of spring rice crop Ime a ter transplanting days Table 7. 303557504] 8OI77304 33 I2334 56679 2300798063 .......... 6972]]520m II2345567I II6732743] .......... 68734 38224 II234 556 79 22]7525287 509141428293 I223h55669 0]842]5908 68 95526387 ]]23455668 OOBIZSZZZO 890358263] 11‘12235 24 BI 59 66 73 45 52 ll6 40(NHh)2804 60 40 Treatment Asphalt barrier Hepth - cm. 30 20 Control Plant growth rates of summer rice crop days Time after transplanting Table 8. 392625.]069 980770 91403 ZZHII—ISIO/OBOJO 3!... 214.1... 08 992 .......... 787538 708m 223455688] 395785030] 77996II42rOo 223456789] h4/nulA8 .213AY4 nuRXonYo .RY4QY4 32345 688mm 714281-202I46 oooooooooo Ion/.0881... 7]..) 33145567890 7l26l46063 69509233l8 223141456 789 IS 22 29 36 43 50 57 64 7| 98 Table 9. 47 plants during spring crop. Visual observations of experimental rice Time after Plants Plants transplanting on on days barrier control Began tillering, 3 cm. new root l5 l0 cm. new root growth, chlorotic growth, green plants plants 48 K deficiency symptoms Chlorotic plants 50 Maximum tillering Began tillering 6I Rust-colored roots White-colored roots 76 Inflorescence Degraded plants 92 Grain in milk Inflorescence stage ll6 Harvest Grain in milk l3l stage Harvest I I -£. ~ ff Figure l2. 48 “If“ t’ ‘I .5 .1 “5‘57”“ Rice growth 96 days after transplant- ing of control (upper center) and surrounding asphalt treatments. 1+9 asphalt paddies of this crop. Therefore it appears that the reduced plant growth on the control treatments resulted from the incomplete flooding and severe leaching of these treatments. Seven weeks after transplanting rust-colored rectan- gular spots appeared on the older leaves of rice plants across the entire experiment. A comparative tissue analysis indicated that lower concentrations of N, P, and K existed in the spotted leaves. The results showed concentrations of N, P205, and K20 to be 3.75, 0.6l, and l.34% by weight, respectively,in the spotted leaves. While green leaves from the same relative position of other plants, which did not have spots, had 3.97, 0.55, and l.83% of N, P205, and K20 respectively. From the above data it was concluded that the potassium concentration was too low in the leaf tissue of the spotted plants. Therefore additional KCI was added to the experiment thereby eliminating the defi- ciency symptoms. Higher concentrations of plant nitrogen are also necessary during the effective tillering stage and 2 to 3 weeks before inflorescence (2I). Therefore, since most of the available soil nutrients are stored in solution the above information indicates the importance of periodic side dressings of both nitrogen and potassium during the growing season. Additional studies are needed, 50 however, before fertilizer recommendations can be made for these sand paddies. This study also shows more tillers were produced on the asphalt treatments. Figure l3 shows many more tillers were produced on the asphalt treatments of both crops as compared to the controls of these crops. This difference reaffirms the reductive effects of unflooded soil condi— I tions upon paddy rice tillering. The number of tillers on the 40 cm. treatment of the spring crop appears to be greater than for the summer crop. This trend suggests that the tillering of this rice variety is inversely re- lated to both temperature and solar energy. Tables I0 and II show that rice tillering was also unaffected by the depth of the asphalt barrier. Respectable yields of brown rice were harvested from the asphalt paddies of both the spring and summer rice crops, table I2. The cr0p failure on the control treatment in the spring cr0p resulted from the unflooded and leached soil conditions. However, despite the applications of additional water and nutrients, brown rice production was also lower on the control treatment of the summer crop. Yields also increased with barrier depth during the Spring crop as yields on the 20 and 30 cm. treatments were significantly less than the yield on the 60 cm. 5l aoLu no.0 aoLo coessm aoLo mc_Lam mocco mowc u_mcamm LmEEJm new mc_cam mom. osu mo moumc mc_co___h .m. o.:m_u mc_ucm_amcmcu Loumm m>mp I mE_h ON. 0.. oo. om cm on om 0m 0: 0m ow o— q . 4 1 1 q . 1 . q u 3 O o .Hllo I N .4: 53 - m .0. LN. I:— mc_cam I _o.fi.cooo .m. cos-cam I .o..pcoox I .6...ch .80 0.... I L®_LLMD .EU OJQ 1114 Jed $491111 60 Treatment 40 Asphalt barrier depth - cm. 30 52 20 Tillering of spring rice crop Control l0. days Time after transplanting Table BIO/833067] llllllll] llllllll] ‘11]11111 lllllllll IIIIIIIIII 40(NHh)250u 60 40 Treatment Asphalt barrier depth - cm. 30 207 Tillering of summer rice crop Control days Time after transplanting Table II. 92 7] 7639] 7 I'll] 56833]099 ‘1‘] I‘ll] 111]] 58 932 09990 ll] “urn/5765732 53 Table l2. Brown rice yields of spring and summer rice crops Spring Summer Treatments cr0p crop M.T./Ha. M.T./Ha. Control - no barrier 0.4 3.4 20 cm. barrier 4.5 .8 30 cm. barrier 4.9 4.6 40 cm. barrier 5.2 4.8 60 cm. barrier 5.6 4.8 L.S.D. at 0.0l level 0.7 N.S. treatment, while the yield on the 20 cm. treatment was significantly less than the yield on the 40 cm. treatment, table l2. This trend did not occur during the summer crop. Therefore it appears that the phenomena affecting the yields in this experiment were similar to those reported by the International Rice Research Institute (32) who showed that unless additional nutrients were added to paddy rice during the growing season rice yields could be reduced by barriers placed at depths leSs than 40 cm. be- low the soil surface. The plant characteristics which were measured at harvest were greatly improved by the presence of the as- phalt barriers. Table l3 shows the straw production, tiller number, and grain density were significantly higher on the asphalt treatments of the spring crop. Straw 54 .m>o. mo.o um .cmo.c.cm.m I .m>m. .o.o um acmu.c.cm.m*« III III .m.z kk:._ km.o .m.z Lassam. --- --- Io.~ IIm.. «I:.o RIG.“ mc.tam am. o.. ..Nm m.mw m.o. m.: ..:o. .messm m.o a.mm o.m~ m... ..m o.:m mc.tam mmmtm>m to.ttmm o.. m..m o.o~ --- m.: ~.~o. Emessm m.o a.mm m.mN o... m.m m.oo. mc.tam .m.ttma .50 co 0.. m..m m.o~ m.o. m.: ..mo. Luggam m.o ~.mm ..o~ m... m.m ..:m mc_.am .m_ttmn .50 o: o.. A..m m.m~ m.m m.: :.:o. Lassam m.o m.mm m.mw o.~. o.m ..mm mc_.am .m.ttma .20 am o.. :.mm m.o~ o.o. ..m m.mo. Lassam m.o m.mm ..m~ A... :.m m..m mc.tam Em.ttmn .20 ON m.o m.m. o.¢~ N.. ..m m.mm twee:m «.0 a.m. m.m. m.o m.. ...m mc_tam .Lo.ttma 0:. _oLucou ...s can ..mz\...z. o_umL At_m.m&v A.Em mcm___u o_m_> A.Eov aoco ucoEummch Zoeum o_um. .uz a.m. o>_ ZmLum u;m_mc km.m.a me....z coo. -uuswota .Eo .cm.a .mQOLo mu_c Cossam pcm mc_cam oz. mo umm>cmc um mo_um_copomcmcu “cm.a .m_ o_nmh 55 production and tillering were also increased in the summer cr0p by the asphalt barriers. The grain size was much more uniform on the asphalt treatments of both cr0ps. As a result the superior plant and grain characteristics accounted for the greater rice yields on the asphalt treatments. Asphalt barrier depth appeared to have more influence upon plant growth during the spring than during the summer crop. The height of plants and the production of straw tended to increase with the depth of the barrier in the spring crop, since plants on the 60 cm. treatment of the spring crop were significantly taller than those on the 20 cm. treatment and more straw was produced on the 40 to 60 cm. treatments than on the 20 cm. treatment. The plant characteristics measured at harvest were essentially uniform on the asphalt treatments of the summer crop. This data suggests that the minimum depth for the asphalt barrier is 40 cm. below the soil surface as shallower 20 and 30 cm. barriers will reduce rice pro- duction unless additional nutrients are applied, and rice production was essentially unchanged by increasing the barrier depth from 40 to 60 cm. The additional 56 cost required for the installation of the 60 cm. barrier does not warrant the placement of a barrier at this depth. The production and plant characteristics of rice grown in this experiment corresponded very closely to those of rice grown on the conventional clay paddies in Taiwan, table l4. Table I4. Plant characteristics at harvest of the rice variety Tainan #5 grown on asphalt lined sand paddies and clay paddies Spring planting. Summer plantipg Characteristic Sandi Clay Sand Clay paddy; __paddy** paddy+ paddy** Growing season (days*) ll6 ll9 98 95 Brown rice (M.T./ha.) 5.2 5.9 4.8 4.6 l000 grain wt. (9.)- 26.I 26.I 26.3 27.0 Plant height (cm) 94.l lOl.7 I06.l lO9.4 Milling ratio (% grain) 83.2 82.l 8l.8 82.6 *Time from transplanting to harvest +Data taken from 40 cm. barrier treatment **Data obtained through personal correspondence with Chiayi Agricultural Experiment Station, Chaiyi, Taiwan 57 Nitrogen carriers This study showed that the ammonium sulfate had no injurious effects on either the rice production or the plant characteristics of the first two rice crops grown on these sand paddies, table l5. This table also shows less roots were produced on the ammonium sulfate treatment. The above data also suggests that hydrogen sulfide problems, which frequently reduce the growth and yield of rice grown on paddysoils fertilized with sulfate fertilizers (l6 and I7), were nonexistent in the asphalt sand paddies. This phenomena most probably resulted from the periodic draining of these sand paddies which leached and/or oxidized any reduced compounds that accumulated in the rhizosphere. Root growth and distribution Rice root growth was enhanced on the barrier treatments Soon after transplanting. At ten days some preliminary observations indicated that root growth was 2-3 times greater on the asphalt paddies. Nine weeks after transplanting, replicated core samples taken in the row midway between the plants indicated that the roots in the barrier treatments had completely explored the soil above the respective barriers while only traces '58 0.. --- --- --- 0 IV.00100 0.0 --- --- --- 0 00-0: “.0 ..m --- --- 0 00-00 ..N. 0.. m.. . --- 0 00-0N ~.m. 0.0. 0... 0.00 0. 0~-0. 0.mm 0.00 m.mm :.m~ 0.00 0.10 I... 1%. 10.0.1 .00. 1.1.0 _ gamers... .80 I spawn Lo_ccmn a.msam< .Amm.aEmm 000;» $0 m:.m> mmmco>m mcu mucommcaoc 0L30.m comm. _.Om 0CMm vmc._ u.m;amm c. mc_ucm.amcmcu cmumm msmv :0 0000 00.. 0c_cam mo co_u:n_cum_0 0000 .0. 0.0mh m.~ ~.m 0.0. _.~0 m.0N 0.00 0.m mumm.:m E:_coEE< m.m 0.m N... m.~0 ~.0~ ..00_ 0.0 mmcz .mI\OHOZ .0 U_o_> ...; a.mcm N .mI.u3 .Eo .mI\.h.z _..c Ema Bmcum Ema 0.0m. a.mcm “50.0: n.m.> Lm_ccmo .03 0000 >L0 mco.__h 0c.___z 000. new—m oo.m cmmocu.z .Amaoco .05530 new 0c_cam N00. 0:0 00 ommcm>m on“ m. m:.m> comm. Lm_ccmn “.mcamm .20 0: 50.3 voc._ m..Om 0cmm co czocm 00.0 >Uuma con: Lo_ccmo ammocu.c 00 0000000 .0. m.nmp 59 of roots were found at a similar depth in the control treatment, table l6. By harvest, root growth on the control treatments of the spring crop had been reduced to 30% of that on the asphalt treatments, table l7. Root growth on the control treatments of the summer crop were also reduced in spite of the application of additional water and nutrients, table l8. These reductions were similar to and may have accounted for the reduced plant growth and yields on the control treatments of both crops. Post harvest root studies confirmed that most of the paddy rice roots are located near the soil surface. More than 80% of the roots were located in the .upper l0 cm. in all treatments except for the 60 cm. treatment where the greatest accumulation was in the surface 5 cm. of soil. The root weights and consequently the root dis- tribution of both crops are different as the crown was included in the 0-5 cm. sample for the spring crOp while only the roots were included in this sample for the summer crop. Rice roots explored the entire soil profile above the barrier in all the treatments of both crOps. During the spring crOp roots accumulated on the barrier of the 20 cm. treatment forming a mat-like mass parallel 6O 0.00. 0mm... 0.00. 000.0 0.8. 000.... ..W I 5.. H 111.1 -1- -1- 0.. 000.0 -11 11- 11- 1-1 0.. .00.0 1-- --- 1.. 1-- 0.. 0.0.0 --- 11- ..0 000.0 0.0 0...0 0.. 0.0.0 ... .0.0.0 ..0 00..0 0.0 00..0 0.0 000.0 ..0 00..0 0.. 0.0.0 0.0 00..0 0.0 .0..0 0.0 .00.0 0.0 00..0 ..0 ..0.0 0.0 00..0 0.0 000.0 0.. 0.0.0 ..0 00..0 0.0. 000.0 .... .00.0 0.. .00.0 0.0. 0.0.0 0..0 00..0 0.0. .00.0 ..0. ..Em. .8 ..Em. ..0. ..Em. 0000.0020100 00 00 .50 I 50000 cu...mn u.m;Qm< 0100— mafim 0.8. mad Q00. +2....— 0.~ 000.0 111 111 111 III 01~ 00..0 111 111 N1. 0_0.0 ..0 00..0 0... 000.0 0.0 000.0 ~1n mm~.0 0.0 00..0 0.0 000.0 0.0 000.0 0.0 000.0 0.0 0...0 0.0. 0.0-N ~10. 000.0 0..0 00... ..0. ..Em. ..0. ..Em. ..0. ..Em. 00 00 .OLucoo .000. 00100 00100 00100 00-00 00100 00100 00100 00100 0010. 0.-0. 0.10 010 .50 :#000- ..00 >um.Lm> mo.. .mm_unma 0cmm a.mzamm :0 :30.0 0% cmc.mh >Unma umucm_a 0:.000 mo um®>cmz um ...s .00 uzm.m3 uoom 1m. m_nmh 6| 0.00. 000... 0.8. 000.0 nu01.1uuu1 .mqu 000.0 -1 -- 0.0 .00.0 111 111 0.0 .00.0 1-- -- 0.. .00.0 0.. 0.0.0 ... 000.0 0.0 .00.0 0.. 000.0 0.. 000.0 0.. 000.0 ..0 .00.0 ..0 .00.0 0.0 000.0 0.0 000.0 ..0 000.0 0.00 000.0 0... 00..0 0.00 000.. 0.0. 000.. 0.00 00... .0. ..Em. .0. 0.500 0000.0:z.-00 00 0.00. 000.. 0.0 ..0.0 0.. 000.0 0.0 000.0 0.0 000.0 0.: 000.0 0.: 000.0 0.0 .0..0 0.00 000.. .001 ..Em. 0: 0.8. 00.. 0.00. .00.. 0.00. 0.00.. 0.0 0.0.0 111 111 III 111 0.. .00.0 111 III 0.0 000.0 0.: 000.0 0.0 040.0 0.0 000.0 ..0 000.0 0.0 000.0 0.0 000.0 0.00 000.0 ..00 000.0 0.0. :m..0 0.00 000.0 0.00 000.. 0.00 .00.0 .0. ..E0. .0. n.Em. .0. ..Em. 00 00 .OLucoo .50 1 50000 00..0mn u.m;Qm< .000. 00100 00100 0010: 0:100 0:100 00100 00100 00100 0010. 0.10. 0.10 010 .Eu 00000 ..00 >um_0m> mu.. >Unma nmucm.a 008530 00 umm>0mz pm ...5 .00 0:0.m3 uoox .00.00ma 0cmm u.m:amm :0 :30.0 00 cmc.m0 .0. m.nm0 62 and adjacent to the upper surface of the barrier. In contrast, the barriers at depths of 30 cm. and greater appeared to provide ample space for root development as roots did not accumulate at these barriers. Roots did not accumulate at the barrier of any treatment during the summer crop. Approximately IA, 8, and h% of the roots in the 60 cm. treatments explored soil depths greater than 20, 30, and #0 cm., respectively. Tables l7 and 18 also show that approximately l2 and 3% of the roots in the #0 cm. treatments explored soil depths greater than 20 and 30 cm., respectively. These findings suggest that the optimum depth for these barriers is 30 to #0 cm. below the soil surface. However, since the rice yield on the 30 cm. treatment was lower and since animal power is often used for paddy cultivation, it appears that the minimum depth for the asphalt barrier in sand soils is #0 cm. below the soil surface. The 3 "MLasphalt barriers used in this experiment did not physically impede rice root growth very much as most of the roots which contacted the barrier traversed and grew below it, table l9. In theory, after the mois- ture barrier has been installed the sand soil below the barrier should continue to drain becoming quite dry thereby retarding root growth. Consequently,roots which 63 penetrate the barrier will be aborted by the dry soil below the barrier. However, during this experiment the lateral movement of water from the heavily irrigated control and surrounding border paddies supplied enough water for rice root growth below the barrier. Post harvest studies of the asphalt barrier showed root penetration of the barrier to be inversely related to the depth of the barrier. Roots penetrated the shallow 20 and 30 cm. barriers 8.5 times more frequently than the 60 cm. barrier. Root penetration was decreased by 65% when the barrier depth increased from 30 to ho cm. It was observed that both fibrous and filamentous roots penetrated the shallow 20 and 30 cm. barriers while only the thinner more filamentous roots penetrated the deeper #0 and 60 cm. barriers. Table 19. Root penetration of 3 mm. asphalt barrier during spring rice crop. Number of roots Asphalt barrier depth-cm. contacting lOO cm. area of asphalt 20 30 no 60 barrier Above barrier mat 72 22 IO Below barrier 59 60 20 7 611 In conclusion, this experiment showed that sand soils which are lined with asphalt barriers provide an excellent medium for root growth. These sand paddies are low in organic matter, hence fewer toxic compounds are generated (52), there is less impedence of root growth (2h) and the root zone may be rapidly drained and aerated providing a medium for maximum rice plant growth during a minimum period of time.' It was also shown that the most favorable asphalt barrier depth was #0 cm. below the soil surface. Sugarcane Experiment Soil water retention Asphalt barriers doubled the moisture holding capa- city of these fine sand soils. Triplicated gravimetric samples showed that the soils of the asphalt treatments retained an average soil water content of nearly 28% while approximately l3% was retained by the natural soil, table 20. The asphalt barrier reduced soil water loss by discontinuing the soil capillaries below the root zone thereby reducing the tension exerted on the soil water in the root zone. Since the barrier is impermeable to water low tension water was stored above the barrier thereby increasing the quantity of water held by the sand soil. 65 Table 20. Soil water content of sand soil five days after l3# mm. rainfall - expressed as volume percent. Treatments Soil sample depth - cm. Disturbed' 50 cm. 75 cm. IOU cm. control barrier_ barrier barrier 0-20 ll.6 25.9 2h.7 2l.2 20-h0 lh.7 3l.9 32.2 3l.5 The low tension water is transported by the soil capil- laries to the root zone at a rate dependent upon the potential gradient in the soil. During the course of this study the additional water storage capacity above the barrier was maintained by rain- fall and irrigation. The moisture magazine above the barrier was filled at monthly intervals from April 20 to November l9 except for three fillings by rainfall in June and no filling in October. Obviously the asphalt barrier is most effective when the moisture magazine is filled as more low tension water is stored in the root zone but as the soil water was deleted. the soil water tension increased reducing the effectiveness of the barrier. Figure lh shows the soil water content in the root zone of the barrier treatment was nearly twice that of the control when the moisture magazine was 66 ucoE.cmaxo mcmocmmsm a.mzamm co ..mmc.m. 0cm .Eo 0010 c. 08.0m. 00:00.05 ..00 .0. 0.30.0 cmnEm>oz .0000o0 .mnEmuamm . umsmz< 0.30 10.0 0.. .00 0.0 0.. ..0 00 0.. _00 0.0 0 . :0 00 0 _ —- .—— q — 1!! u—¢q_q - 44— d _ - __ 1 O .0... 100% J. B 0001 - .00w . . .0...000.‘ « 0 0 0 0 « 0 0 + 0 0 0 "co.umm..._ H0 IIIIIIlIIIIIIIIIIii-iIII111IIII1III 11. \\ . 11/ 2, 7 .0 .0 0. a \x/ .a ‘0 .3 s 1 ’/ s s .000) 3.. ... (s < x. \s . o/o (\ \3 .x... .z. r-.. 0.00 .ogucou 1111111 0 m. .00n 00..0mn .EU 00 w J00 O m JUGJUOD aJnasgow [gos 67 periodically filled. However, in October when the water content above the barrier was too low the barrier had essentially no effect on the soil moisture content in the root zone. This figure also shows that in September,when very little water was added to the experiment,the barrier delayed irrigation for nearly two weeks. Table 21 shows the soil moisture regimes of the remaining asphalt and disturbed control treatments were similar to those reported in figure lh. Figure l5 shows that the water content at a given soil depth was inversely related to the depth of the barrier. As expected the soil moisture also increased with soil depth. The lower soil water content of the deep samples of the 75 and lOO cm. treatments, recorded in figure l5, appear to be the result of a sampling error as it was difficult to sample the saturated sand soil in the neighborhood above the barrier. The high water content in the soil of the 50 cm. treatment during the monsoon season suggested that soil aeration may fall below the critical level, described by Erickson (l9). Platinum microelectrode measurements showed low soil oxygen diffusion rates on the 50 cm. treatment for 2h hours after a heavy rainfall, table 22. Since more water was stored in the deeper horizons it is 68 Soil moisture regime of asphalt sugarcane experiment - expressed as percent moisture by volume. Table 2|. Treatment lOO cm. 75 cm. Disturbed 50 cm. control Control Date barrier barrier barrier 2810952873610555186921378 58725 39861155h1h-30763301832h9h019089 112222 lllll 21122221212‘111 08 5100706661“ 70 5566259537926h3 5980h66856u278771471587911.1820988 112322 lllll 211222222121] all-II 00.900..0/00939538038050.3014821478.Iu78 699 3638641411870551431405928 99988 Ila/.222 lllll 2113222222211! 32 7711.. 583276876286J91423h.ZOAASZZ I'll] lllllllllll] I'll] lllllllllll 1'85 0h.79.|h.8 ilk/08135814112 039 o o o o YYYYYYYYOoo cocoooooottttoooo llllllll gggggggggggggpppptttvv UUUUUUUUUUUUUUUUUUUHuueeeeCCCOO JJJJJJJJAAAAAAAAAAAAASSSSOOONN Soil water content - % by volume 69 38 36_ 3h_ 0 / \ 30. o 0"".-—-. 28- 26. 2h. 0‘0 22" / o 50 cm. barrier ‘ 20L ~ X”75 cm. barrier , lOO cm. barrier x,__.x l6~ O\ 12. 01.. 0-l0 20-30 hO-SO ' 60-70 80-90 l0-20 30-40 50-60 70-80 90-l00 A I Soil sample depth - cm. Figure l5. Effects of asphalt barrier depth on soil water content 70 conceivable that a portion of or the entire root zone of the 50 cm. treatment was oxygen deficient throughout the monsoon season. These low oxygen diffusion rates were not observed on the 75 and IOO cm. treatments. However, it is very likely lower rates did occur at soil depths near the barriers (23). Since these depths were below the root zone of the young sugarcane there were essen- tially no aeration problems in the root zone of the 75 and 100 cm. treatments during the monsoon season. The decline in the ODR on the control and later on the as- phalt treatments resulted from the decreasing soil water content to a point below that for which the pla- tinum microelectrode instrument was designed (20). The thin asphalt barriers used in this investigation proved to be excellent water barriers.as.the Soils above the asphalt barrier retained gravitational water for nearly three days while those without barriers were drained immediately, figure 16. This figure also shows that low tension water was stored above the as- phalt barrier for nearly a month which suggests that very little water was lost through the barrier. The gradual increase in water tension from December l2 to January 5 probably resulted from evapotranspirative water loss. 7l Table 22. Oxygen diffusion rates at a soil depth of 10 cm. as measured by the platinum micro- electrode - digfusion rates are expressed in g.xlO.-8 cm. min, HOUI'S ai ter ireatment cessation of 50 cm. 75 cm. ‘100 cm. Disturbed rainfall Control barrier barrier barrier control 6 60.9 3l.h 61.5 57.3 62.] I8 --- 52.5 --- 69.3 --- 2h 56.7 5h.3 63.9 63.3 55.5 36 54.9 63.9 69.3 63.3 5l.9 #8 5h.9 71.8 70.6 68.] 52.5 60 53.7 78.h 7h.2 73.6 #9.h 72 #7.6 8l.h 72.h 65.7 #2.8 8h “7.0 79.6 71.2 66.9 #5.8 96 hl.0 76.6 69.3 60.3 39.2 As expected the soil water tension gradient between the barrier and near the surface soil was much smaller on the 50 cm. table 23. treatment than on the 75 cm. treatment, This phenomenon shows the importance of soil water hydraulics for determining the proper depth of the asphalt barrier. too shallow. In this study the 50 cm. barrier was For both the tension measurements reported in table 23 and observations during the growing season indicated that the soil capillaries conducted low tension 72 ucmE_Loaxo mcmocmmam a.msamm mo ucoEumoLu Lo_ccmn .Eo om c_ co_mcou Loam: __0m .m_ ocam_u mums mu. m.. _-_ mN-~_ Jana. o~-~. w_-N_ N_-N_ m- 11, + 1 . . . . poumm_cu_ poo—m 4 <0 \4\\ C «W co_ccmn u<_|||\\|||aillllllll0\\\\\\\\o . C\.“ ilO\ <\1\\ ‘I t \ O cm_ccmn mo omuo soc; . Looms mco Ucm ammo Eo mN Lm_ccmnil\\3 uno:u_3 . N— om- 0:- ON- ON 0: om om 1 JGJEM [log UOI SUS 'LUD N.mNuu .i in ..u !. .- .3 an .- N.m_ {on m.mN N.—m nu :- ..u :.m_ :mu.c_mm ..... 0 mm mm :m :m :m m: m_ N. o o m_ N m _m mN o_ o Lo_ccmn or N: m. :m mN m_ u m J o o o_ N m .N N_ m 0 0m 0 N m m m J o o o o o N o o m. o— m o m— ..EU. .|. Spam—u cmuoEo_mcmh ..................... o\m M\w _\m _M\N mN\N mN\N mN\N oN\N m_\N :_\N m_\N __\N o_\N N\N m\m n\n mN\m :N\m "oumo acoEummLu .50 mm ucmEumocu Eu 0m . . . . . . . . a . c . . . u . . . - a . _ . . u o a ..... Loam: mo mcmn_ucoo c_ nommmcaxm mcm mo:_m> - ucm_nmcm co_mcou Loam: __0m osu con: swamp Lo_ccmn u_m;qmm mo uoommu .MN m_nmp 7h water from the barrier to the soil surface causing excessive water loss by evaporation greatly reducing the efficiency of this barrier. In contrast, the treatments at 75 and l00 cm. lost very little soil water by evaporation. The large gradient between the soil water tension at the barrier and near the soil surface, table 23, suggests that essentially no low tension water was transported to the surface of the 75 cm. treatment. Observations of the 75 and 100 cm. treatments also indicated that there was essentially no evaporation from the soil surface as a dry soil mulch formed soon after each application of water. Water retained by the barrier appeared to be affected very little by the soil water gradient along the edge of the barrier. Figure 16 shows that water, stored one meter on the edge of the barrier is partially drained. Table 2h shows soil drainage occurs from l.0 to l.5 meters onto the barrier. However, very little water is drained from the soil above the barrier. Water in the soil surrounding the barrier was rapidly drained discontinuing the horizontal capilaries thereby reducing the loss of water from above the barrier. 75 Table 2%. Effect of distance upon soil water at edge of barrier - soil water content expressed in volume percent. Distance from edge of barrier - m. Sample depth - cm. 0.5 1.0 1.5 2.0 0-10 6.5 6.8 7.3 8.3 10-20 9.5 9.6 10.7 11.8 20-30 11.9 12.2 15.3 15.# 30-40 13.6 15.1 18.9 17.5 40-50 15.7 17.h 20.6 22.3 50-60 19.6 19.9 26.5 25.8 60-70 21.6 26.9 28.8 28.6 26.0 29.4 30.1 30.6 70-80 76 Tremendous quantities of water were conserved by the asphalt moisture barriers during the sugarcane growing season. Table 25 shows that the asphalt treatments required 80% fewer irrigations reducing the quantity of irrigation water from 327 mm. for the control of 109 mm. for the asphalt treatments. From September through February, Taiwan's dry season, irrigation water was applied to the control and asphalt treatments at 30 and 7 day intervals, respectively. It appears that the interirrigation period could have been extended for the asphalt treatments if the entire moisture magazine had been filled at each irrigation, figure 1h. This reasoning led to the heavy irrigation of the entire experi- ment, on November 19, which provided enough water until harvest. Therefore the asphalt barriers reduced both water and the labor costs of sugarcane production. Table 25 shows that the depth of the barrier had essentially no effect upon the water requirements of sugarcane. The 11.8% less irrigation water that was added to the 50 cm. treatment resulted from the small quantity of water that was added to this treatment at the final irrigation. Further discussion concerning the effects of the final irrigation upon sugar production will be discussed in a later section. 77 Table 25. Supplemental irrigation added to sugarcane- experiment Treatment Asphalt barrier depth cm. Date Control __50_____75 100—7 Disturbed control W 7%“? WT W (m) March 9 .8 .8 .8 .8 .8 June 26 28.2 --- --- --- 29.6 July 5 22.5 --- --- 13.5 18.0 July 2h 22.5 --- --- --- 21.6 July 28 21.0 --- --- --- 22.2 September 11 18.6 --- --- --- --- September 18 21.0 --- --- --- 20.h September 25 21.0 19.8 18.9 --- 21.0 October 2 20.7 --- --- --- 19.8 October 9 19.8 --- --- --- 19.8 October 23 19.5 19.5 19.5 19.5 19.5 October 30 19.8 --- --- --- 19.5 November 13 21.0 19.8 20.3 20.h 20.h November 19 71.0 34.0 50.3 55.0 68.0 Total 327.’+ 93.9 109.8 109.2 300.6 78 The 8.2% less water that was applied to the disturbed control suggests that soil tillage has essentially no affect upon the water holding capacity of sand soil. It is well known that the frequency of sugarcane irrigation is dependent upon the soil type and the season. During this study the time between irrigations was reduced as a result of the experimental design. However, the results from this experiment indicate that when sugarcane is spring-planted on these as- phalt sand soils, a general wetting of the surface soil immediately after planting and two or three heavy applications of water during the dry season would I maintain Optimum soil moisture conditions throughout the growing season. For the fall-planted sugarcane the moisture magazine should be filled after planting and maintained until the maturation stage of the growing period. The more mobile nitrogen and potassium appeared to be conserved by the asphalt barriers (9 and 10), as greater quantities of these elements were found in the tissue of plants growing on the barrier treat- ments, table 26. The logical explanation for this phenomenon is that the moisture barrier decreased the loss of water and the loss of the more mobile nutrients 79 Table 26. Leaf analysis of 127 day-old sugarcane Nutrient Treatment N-% P-% K-% Control 2.1h 0.67 1.35 50 cm. barrier 2.h5 0.71 1.6h 75 cm. barrier 2.32 0.70 1.58 100 cm. barrier 2.36 0.79 1.67 Disturbed control 2.07 0.71 1.33 L.S.D. at 0.05 level 0.20 N.S. 0.26 80 from the root zone. Consequently more nutrients were absorbed; The higher nitrogen content in plants on the 50 cm. treatment appears to have resulted from the upward movement of soil water resulting in greater concen- trations of nitrogen in the upper portion of the root zone (55). The plant nutrient content was lower on the 75 cm. treatment as a result of the greater growth of plants on this treatment. Sugarcane qrowth Sugarcane growth on the asphalt treatments was superior to the controls throughout the growing season. One month after planting, plant counts indicated that germination was uniform throughout the experiment, table 27. By 19 weeks, plants on the asphalt treaments were visibly taller than the control, figure 17. This difference in- creased throughout the remainder of the growing season, Table 27. Germination of sugarcane variety F-156 grown on Taiwan fine sand-expressed as percent Ireatment‘ ' ‘ ' " Plant age 50 cm. 75 cm. 100 cm. Disturbed Control barrier barrier barrier control 30 days 91.4 92.1 93.0 92.6 91.1 Index 1.00 1.01 1.02 1.02 1.00 81 11%;: ”(##2ka 3111’}: 3,1,4 3; 1 11:12“ Figure 17. Sugarcane rowth on asphalt barrier treatment right) and on control (left). 82 figure 18. Although plants were taller on the treatment at 75 cm. the sugarcane growth rates on the treatments at 75 cm. and 100 cm. were similar during the last eight months of the growing season. The reduced growth on the treatment at 100 cm. appears to have resulted from the lower soil moisture content in the root zone of this treatment during the first few months of the growing season. Plant growth on the 50 cm. treatment was similar to the other asphalt treatments during the first half of the growing season. But growth on this treatment was severely retarded during the last half of the season. Since the plants in this treat- ment were visibly taller during the early stages of the growing season and the $10pe of the curve for this treatment decreased with time, the 50 cm. barrier may have been too shallow for maximum sugarcane growth. There are at least two reasons why the 50 cm. barrier reduced sugarcane growth. First, as discussed earlier, this shallow barrier maintained very high moisture con- ditions in the root zone during the monsoon season thereby reducing soil air which inevitably reduced plant growth. Second, the 50 cm. barrier restricted root growth directly, by physical forces, and/or indirectly by providing 83 ucoe_coaxm ocmocmmam a.msamm mo moumc guzocm “cm—m .m. oc:m_u m>mn 1 mc_ucm_a cmumm oE_h ofl 3m 9m 8m QWN EN EN ONN 08 be 8_ 0:1. 8.. 0.0— VJO . ;\ .1 cm 1 om 1 oo— ON— . OJ— 4 8. 0m. ooN \Rfi— .oLucou .11111110 _otucoo ponczum_ou Lo_ccmn .80 cm x111\\\\X1\\\\hV\\\\ o a o..\\\\ cm_ccmn .Eo oo_Lo 0.: 111 ..m o 111 111 111 111 m.: o oo_1mN m.w 111 N.N :.N_ m.o_ o 111 111 m.m :.: mN1om m.m. 111 o.m_ :.N_ :.w_ ..N N.w_ o.m 0.0. m.@ Om1mN N.mo 111 N.oN N.mN _._N m.Nm m._w o._m N._N :.mm mN1o “$207.; 303.3. a ummtmfimn mm. 3030: ..muImMm a .g 1.9% a ‘ a 9%. .80 1 swoop Lo_ccma u_m;am< o_aEmm u:m_oz >06 ucmocma mm powwocaxo 1 mcmocmmam u_m;amm mo co_ u:n_t0m_n “com .mN 0.3mp 88 support root growth. ,Therefore roots which penetrated the barrier were aborted forming a static physical plug. Consequently, roots which penetrated the barrier had essentially no effect upon the water retention properties of the asphalt barrier. Root growth appeared to be greatly enhanced on the treatment which was disturbed to a depth of 100 cm. Also, the quantity of roots was much smaller on the control treatment. This phenomenon may account for the somewhat taller plants on the 100 cm. disturbed treatment. Sugarcane production Sugarcane yields were much higher on all the as- phalt barrier treatments, table 29. The 75 cm. barrier produced the greatest quantity of sugarcane, 100 M.T./Ha., which essentially doubled the yield of the treatments without barriers. The remaining production characteristics recorded in table 29 were also much better on the asphalt treatments. Both the production of millable stalks and the final plant height were significantly greater on all the asphalt treatments. Plant height as well as stalk dia- meter were also significantly greater on the 75 and 100 cm. barrier treatments. Again plant size as well as sugar production were the highest on the 75 cm. 89 _0>0_ mo.o um 0cm0_c_cm_m* _m>m_ _o.o um ucmo_m_cm_mm* *m_. «o_. «*Jm._ xxmm.m 111 *¥_m.o ¥¥_o.m_ wo.m.4 oN.N m_.N mm.: _:.mm NN.w Nm.N_ mm.m: _oLucoo noncaum_o 0:.N mm.N :o.m mm.om o:.__ mm... No.Nm .zxccmn.Eo oo— m:.N mm.N mm.N mm.om wo.N_ mm.__ mm.¢o_ .Lm_ccmn.Eo mm mN.N om.N :o.m mm.mm o:.o. m:.N_ mN.mm co_ccmn.so om 0N.N o_.N N:.: .m._m N_.N NN.m_ NN.¢m. _oLucoo .Eo No_x .Eo mo_x.m.._\ mo_x.m1\ N .m_._\.._..z tmumEm_u 0;m_0; m9_mum mx_mum .m:\.».z 32> x_mum x_mum pmoo .o_nm cmmnm mmoLoam memo ucoEummch JP—_51 1me3m co_uu:pota ocmocmmam co mco_ccmn u_m;amm mo muQUkwu..rmN.UNAMP 90 treatment. The number of dead stalks was proportional to the plant population. Therefore, more dead stalks were recorded for the asphalt treatments. The available sugar content was lowest in the harvested plants from the 75 and 100 cm. barriers. This appears to have resulted from the effects of high soil moisture upon plants during the maturation period. Lin (37) reported sugarcane maturation was delayed and the sugar content reduced when a high soil moisture content was maintained during cane maturation. He also showed a 10% increase in the available sugar content of cane grown in soils containing less than 20% available soil moisture during maturation. The higher percent available sugar content in the plants grown on sand soils without barriers resulted from the lower soil moisture content during maturation. The sugar content is significantly higher on the 50 cm. barrier as the moisture reserved in this treatement was more rapidly depleted by evapo- transpiration. During the maturation period of the sugar- cane in this experiment the soil moisture content was certainly higher in the 75 and 100 cm. barrier treatments as 65% more water was added to these treatments at the final irrigation. 91 Disturbing the soil to a depth of 100 cm. did not significantly affect the sugarcane production in this experiment. Since the enhanced root growth, reported in an earlier section, affected neither plant growth nor production, the increased growth and production of sugarcane on the asphalt barriers was not enhanced by the manipulations of the soil during the installation of the barrier. Chapter V CONCLUSIONS A thin asphalt barrier can be used to construct rice paddies on fine sand soils. This procedure appears to be a practical method for reclaiming excessively drained soils for paddy rice production. These barriers retained free water in the root zone which resulted in the conservation of both water and nutrients while concurrently enabling the production of 5.2 and 0.8 M.T. of rice per hectare during the 1967 spring and summer crops. The adverse soil conditions of the control treatments caused a cr0p failure during the spring crop while 3.h M.T. of rice were produced per hectare during the summer crop. This experiment showed that barriers at less than 40 cm., below the soil surface, reduce plant growth and production and are also penetrated more frequently by the rice roots. Since rice grown on the 60 cm. barrier did not produce more than the treatment at #0 cm. it was concluded that the #0 cm. barrier provided adequate space for paddy rice root growth. 92 93 Subsoil drains installed on the surface of the asphalt barrier allowed rapid drainage of the paddy soil. Because of the speed and ease of drainage these paddies can be easily manipulated for soil aeration and fertilization. However, additional fertility studies are needed to deve10p a system whichwill give maximum production. Rice roots appear to affect the water retaining properties of the barrier very little unless large numbers of roots penetrate and continue to grow.through the asphalt barrier. The type of nitrogen carrier had no effect upon rice growth or production in these sand paddies although this hydroponic-like paddy culture does require more frequent applications of both nitrogen and potassium. Asphalt barriers can be successfully inStalled below the root zone of sugarcane grown on Taiwan fine sand soils. These barriers reduced the soil water tension in the root zone by halting the deep percolation of water. These alterations of the soil hydraulic pro- perties doubled the water holding capacity of this soil thereby increasing sugarCane plant growth and production while concurrently reducing the irrigation requirements of 94 a spring planted crop by 66%. This study showed at least 100 M.T. of sugarcane could be produced per hectare and approximately 215 mm. of irrigation water could be saved by using the asphalt barriers. Soil texture is the primary factor to consider when selecting an optimum depth for the asphalt barrier. This study demonstrated the barrier should be installed 75 cm. below the surface of fine sand soils used for sugarcane production. The 50 cm. barrier increased the water holding capacity of the soil providing an abundant supply of water to the young plants. But the very high soil water content throughout the root zone of the 50 cm. treatment re- duced soil aeration which retarded plant growth when the roots penetrated into the deeper soil horizons. The 100 cm. barrier increased the soil water content in the root zone very little as the texture of this soil was too coarse to retain water at this tension. Therefore the additional cost required for the 100 cm. barrier is unprofitable. The deep tilling of the sand soil had essentially no effect on sugarcane production. During this study preliminary soil aeration studies indicated that short term soil oxygen defi- ciencies reduced sugarcane growth and production. 95 The root zone at the 50 cm. barrier remained very wet after each heavy rainfall causing soil aeration problems. Consequently, plant growth was severely retarded during the monsoon season. Sugarcane roots which penetrated the barrier stopped growing when they encountered the dry soil below the barrier. Consequently the water retention properties of the asphalt barrier are affected very little by the root action at the surface of the barrier. The two experiments reported herein show that sub- surface asphalt barriers will allow the production of satisfactory yields of both rice and sugarcane on subtropical fine sand soils. The asphalt barriers will also greatly reduce the quantities of irrigation water that are normally required for satisfactory yields of both of the above cr0ps if they are grown on sand soils. The asphalt barrier procedures outlined in this ihvesti- gation could be used to ameliorate thousands of hectares of subtropicsl sand soils while concurrently saving tremendous quantities of valuable irrigation water and at the same time increasing the yields of these deep well-drained coarse soils. APPENDIX Soil moisture retention of Chekan fine sand. Table l. BCI 3% (0-20 cm.) (20-52 cm.) (52-85 cm.) (85-120 cm.) Horizon Bt] AP Moisture tension- Cmo 0 Vol.-% Vol. - % Vol. - % Vol, - % DF ’9 H20 51432143993731...53857890235h1122 000099989886337621098766650 “4403333333332 11111 77390372579326h663790017226 5553h2222087162865022009976 hhhhhhhhhh33322 11111111 5158290017148309829189H2788 .hh3331109887659h09765221O87 hhhhhhh4333333222 11111111 505640777800202209710136353 665hh3221108h93097543219876 hthhhhhhhh33222 1111111 214680123145678902141680214.6802 .00000 1111111111 222223333314.“ 06503068016811“000000000000 ooooooooooooooooooooooooo 11211—160250519039081810521009 111223356705593081810h1 112360559308 97 LITERATURE REVIEWED . Agronomy Monograph No. 9, Methods of soil analysis, part one: Physical and mineralogical pro- perties, including statistics of measurement and samplin , Am. Soc. of Agron. pp. 274-278, 299-314, 19 5. . Agronomy Monograph No. 9, Methods of soil analysis, part two: Chemical and microbiological pro- perties, Am. 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