H V Ml ! liwlll‘» a t t 1 WI 1 5% WI A STUDY ()5 '3'HE BENEFICML USE OF IRRIGATEON WATER ON SANDY LGAM SOILS Thesis for tho Degree 05 M. S. MICHIGAN STATE COLLEGE Paul Edward Schleusener 1949 .‘ "‘.T—x_._____—r__ 93 10586 3603 IIIII IIIIIIIIIIIIIIIIIII _ Thisiltomfgflmtthe thesis entitled A Study of the Bonoficial Use of Irrigation Vat-r on Sandy Inn 3011: Pmnted by Paul Edvard 8.2111,“. c ”r has been accepted “Wards f H men: 0‘ the requirement. for m- degree mm“ W- Major Pm‘mr D“°_I-:ch41,_19u9__ LIBRARIES 5.73—- RETURNING MATERIALS: PIace in book drop to remove this checkout from your record. FINES wi11 be charged If book is returned after the date stamped be10w. M _...—-_._-—«—-_. A STUDY OF THE BENEFICIAL USE OF IRRIGATION WATER 0N SANDY LOAM SOILS BY Paul Edward Schleueener ————-—" A THESIS Submitted to the School of Graduate Studies of Michigan State College of‘Agriculture and Applied Science in partial fulfillment of the requirements for the degree of Master of Science Department of.Agricultural Engineering 1949 Cc . (LY THF- 11 ACKNOWLEDGMENTS The author wishes to eXpress his appreciation to the following: Professor F. W. Peikert and other members of the Agri- cultural Engineering Department for their help in selecting and setting up the problem. Professor R“ L. Carolus of the Horticulture Department for his cooperation in conducting the eXperiment. Professor H. M. Brown of the Farm Crops Department and Professor Leo Katz of the Mathematics Department for their advice in selecting the experimental design and making the statistical analysis. Professor K. Lawton of the Soil Science Department for his help in solving soil, moisture, and nutrient problems. Mr. R. T. Tribble formerly of the Agricultural Engineering Department at Michigan State College for his help in conduct- ing the eXperiment. Rev. 0. E. Ames, owner of the land on which the experi- ment was conducted, for his cooperation. fr I. II. III. VI. 111 TABLE OF CONTENTS {ACKNOWLEDGMENTS TABLE OF CONTENTS TABLES AND ILLUSTRATIONS INTRODUCTION A. Definition of Drought Period B. Thirty Year Record.at Lansing C. Need for Irrigation Based on Drought Study D. Problems Associated with Irrigation EXPERIMENT A. Plot Layout B. Treatments RESULTS .A. Irrigation Practices and.Yields 1. Comparison of yields a. Snap beans b. Tomatoes c. Sweet corn 2. Result of statistical analysis B. Yields with Different Levels of Available Moisture 1. Weather conditions 2. Comparison of yields a. Snap beans b. Tomatoes 0. Sweet corn 11 111 m) cm at ca to P‘ +4 l4 4 id F1 Id F‘ is h’ +4 01 ca <3 0: cs la b: 17 18 18 18 20 27 VII. VIII. IX. iv C. Nutrient Supply 1. Procedure 2. Yield results 3. Availability of nutrients a. Field corn b. Sweet corn RECOMMENDATIONS FOR.FURTHER WORK A. Improvement of EXperimental Procedure B. Soil Compaction C. Nutrient Supply D. Statistical Analysis SUMMARY BIBLIOGRAPHY 51 32 55 35 35 35 56 56 59 39 4O 41 Table Figure Figure Figure Figure Figure Figure Figure Figure Table Table Table Figure Figure Figure Figure Figure Figure 1. 1. 2. 5. 4. 5. 6. 7. 8. 2. 5. 4. 9. 10. 11. 12. 15. 14. TABLES AND ILLUSTRATIONS Occurrence of Droughts over Thirty Year Period Pump Located by Water Supply Irrigation of EXperimental Plots Plot Layout on Snap Beans Plot Layout on Tomatoes Plot Layout on Sweet Corn Unirrigated Sweet Corn Irrigated Sweet Corn Effect of Irrigation on Sweet Corn Comparison of Yields Result of Statistical Analysis Rainfall on Irrigation Test Plots Available Moisture in Unirrigated Snap Beans Available Moisture in Snap Beans Irrigated 'by Blocks“ Available Moisture in Snap Beans Irrigated “by Blocks Plus Critical Time? Available Moisture in Unirrigated Tomatoes Available Moisture in Tomatoes Irrigated "by Blocks'l Available Moisture in Tomatoes Irrigated “by Blocks Plus Critical Time' CDNIQOIIRN 11 12 12 14 16 19 22 23 24 25 26 INTRODUCT ION The state of Michigan has an average rainfall of about 50 inches. During the growing season of May 15 to September 15 the average rainfall for the state is 12 inches. With proper distribution of this rain there should be sufficient moisture for obtaining maximum yields from the crops raised in Michigan. A study of the weather records reveals the fact that this ideal distribution scarcely ever occurs. Actually a number of drought periods can be expected during the growing season. Definition of Drought Period In this study a drought period is defined as a period of at least 14 days in which less than 0.25 inch of rain falls in any one day. Thirty Year Record at Lansing The average amount of rainfall for Lansing from May 15 to September 15 is 12.60 inches. It is distributed as follows: May, 1.71; June, 3.51; July, 3.10; August, 2.82; and September, 1.46 inches. A study of the daily precipitation records at Lansing for the years 1918 to 1947 inclusive revealed that there were a number of drought periods during the growing season. C - 2 - The droughts have been broken down into 2, 5, 4, 5, 6, 7, 8, and 11 week periods. The total number found in the 50 year period.and.the frequency of their occurrence are shown in Table 1. Table 1 Occurrence of Droughts over Thirty Year Period Length, weeks 2 3 4 5 6 7 8 11 Total number ' periods 53 18 5 l 1 2 1 1 Frequency of 7 3 l l l l l l occurrence in in in in in in in in (in years) 4- 5 6 30 SO 15 30 30 This table indicates that each year an average of VQ-weeks of drought can be eXpected during the period of May 15 to Sep- tember 15. Need for Irrigation Based on Drought Study The breakdown of drought periods that have occurred.at Lansing indicates that there is a deficiency of soil moisture some time during the growing season every year. With the pro- per distribution of rainfall even the 7% weeks of drought will not cause serious damage to the craps. However, it is highly improbable that an ideal distribution will ever occur. Under -5- normal circumstances, then, Michigan craps will suffer from lack of available soil moisture during the growing season. To obtain Optimum yields it is necessary to apply irrigation water whenever the available soil moisture has been materially reduced. Problems Associated with Irrigation The application of irrigation water to Michigan crops presents a number of associated problems. They are listed as follows: 1. Determine what crops will produce a signifi- cant increase in yield. 2. Per cent of available moisture at which craps must be irrigated to produce the Optimum yield. 5. Effect of irrigation on plant nutrients. The material that follows presents eXploratory data on the previously mentioned problems. EXPERIMENT Tests on the effect of different amounts and times of irri- gation on the following vegetable crepe were conducted in 1948: snap beans, tomatoes, and sweet corn. The craps were grown on a Hillsdale sandy loam located near East Lansing, Michigan. The soil was rather low in -4- fertility. A preplanting application of 800 pounds of 5-12-12 fertilizer was drilled over the entire area. The water for irrigating the craps was pumped from a stream near the field. Figure 1 shows the pump, power unit, main supply line and suction line located by the stream. Figure 1. Pump Located by Water Supply Quick coupling portable pipe carried the water to the plots. The application of water was made through fixed.type sprinklers fastened to a supply line supported on stands in the middle of each plot. Properly arranged sets of full, quarter and half circle sprinklers were used to obtain uniform distribution of water on the plots. Figure 2 see... some of the plots being irrigated. This type of equipment was used for its adaptability -5- for irrigating rectangular areas. The low angle of spray pre- vented excessive loss of water due to drift. u e , ,- ‘ l' ---. . irr‘, 1“ , a - .. .’ grip.- _,-c-§ .v b— “ - :. v.-._.4/ on” he 'II- I :I‘ ‘ ’ Figure 2. Irrigation of Experimental Plots Plot Layout The irrigation treatments were randomized in 15 by 35 foot plots and replicated three times. Ten foot alleys were left between each replication of plots. The plot layouts are shown in Figures 5, 4, and 5. madam amen do peohmq podm .m. enema.» x43 mmwmogmkm memw . . 2a a. VIRUS me me @wISJ. i 1 . m. . a i 0. Wheel .\ I i. {we are DC mole mz<4 POJQ Treatments The following irrigation practices were compared: 1. 2. 3. 4. Unirrigated. Irrigation when needed as determined by gypsum moisture blocks placed in the soil at 4 and 8 inch depths. The per cent of available soil moisture was determined by measuring the intensity of an electric current passed through the buried block. When the available moisture was less than 50 per cent, water was applied. The blocks were used in an attempt to determine the practicability of their use in speci- fying the time for irrigation, based on the amount of moisture in the soil that is available to the plant. One inch per week whenever the rainfall the previous week was less than one inch. This treatment was used to approximate the practice usually followed.by irrigators in Michigan. Same as number 2 with an additional inch of water at critical times in the growth of the plant. Critical times for snap beans were at full bloom and two weeks after full bloom. For tomatoes the critical times - 10 - were after the first and second clusters had formed and two weeks later. The critical times for sweet corn were at tasseling and at silking. .Additional applications of water at critical times in the growth of the plant were made to determine whether this practice re- sulted in a material increase in yield. 5. One and one-half inches of water per week whenever the rainfall the previous week was less than one and one-half inches. Treatments 6, 7, and 8 were unirrigated, light irriga- tion, and heavy irrigation, respectively. They were added for a study on root develOpment not associated with this problem. Moisture blocks were placed in two of the replications for treatments 1, 2, and 4. Block resistances were read with.a portable ammeter constructed for this purpose. It is easier to read than the Wheatstone bridge (used for deter- mining block resistances) but is not as accurate as the bridge. The portable ammeter reads directly in per cent of available moisture, thereby eliminating the necessity of converting resistance readings to per cent moisture. RESULTS Irrigation Practices and Yields In every case the irrigated crops showed more vigorous growth than the unirrigated. Figures 6 and 7 show the differ- ence between unirrigated.and irrigated sweet corn. The quality of the fruit produced by the irrigated crcps was markedly better than that produced.by the unirrigated craps. Figure 8 shows the effect of two irrigations on sweet corn. . . 2 ' -" V“‘ w I. .5 flr‘ .. . k '4'. . ~-—-'. ' v ’ ' lll . t'.‘ ’0 D“ ' . », .“*~ ' -- ' If" _. ,4 I”, ‘ Figure 6. Unirrigated Sweet Corn -12.. Figure 7. Irrigated Sweet Corn ’- - Figure 8. Effect of Irrigation on Sweet Corn - 13 - Campgrisgn of yields Yields from the small plots have been converted to yields per acre. Snap beans. The first picking of beans was made on August 1. The data in Table 2 indicate that an application of as little as 2 inches of water increased the yield 19 per cent. With 6 inches additional water the yield was increased an additional 24 per cent. The greatest increase in yield per inch of water was obtained with an application of only 5 inches. Tgmatges. Tomato plants were set in irrigated soil on May 51. As a result of sufficient moisture very little re- planting was necessary. Harvesting extended from.August 24 to October 1. A Climatic conditions were quite favorable and.resu1ted in high tomato yields in this general area. The data in Table 2 show that the treatments receiving 4 inches of irrigation water during the season produced larger increases in total weight than others receiving three to four times as much water. The number and weight of fruit on plots receiving either 11 or 16 inches of water were substantially lower than those on plots receiving 4 inches of water. In this experiment the heavy irrigaticns resulted in a lower fruit set. The size of fruit was increased up to 15 per cent by irrigation and was not influenced by the amount of water applied. Sgget cogg. The sweet corn was drilled in three foot rows on June 1. The plants were thinned to an average stand of 152 stalks per hundred feet of row. - 14 - Table 2 Comparison of Yields Treatment 1 2 5 4 5 SNAP BEANS Water applied, inches 2 8 5 15% Pounds per acre 4095 4884 5850 5540 5958 Per cent increase 19 45 50 45 Increase/inch of water, lbs. per acre 594 219 415 120 TOMATOES Water applied, inches 4 ll 4 16 Number of tomatoes (thousand per acre) 8804 12702 9802 10402 1010]. Per cent increase 44 ll 18 14 Average weight of fruit, lb. 0.54 0.59 0.59 0.58 0.58 Per cent increase 15 15 12 12 Bushels per acre 500 855 654 662 659 Per cent increase 67 27 52 28 Increase per inch of water, bushels/acre 85 12 40 9 SWEET CORN Water applied, inches 4 8 4 14% Tons per acre harvested 2.69 6.07 4.96 4.79 2.90 Per cent increase 126 84 78 7.8 Dozens of ears per acre harvested 1167 1771 1446 1444 1075 Per cent increase 52 24 24 -O.8 IAverage weight of ear, lb. 0.59 0.58 0.58 0.55 0.46 Per cent increase 49 49 41 18 .Dozens of ears per acre marketable 296 1482 1200 1208 746 Per cent increase 400 506 508 152 Increase per inch of water 296 115 229 51 Per cent marketable ears 25 84 85 84 70 - 15 - During the latter part of August the unirrigated corn showed the effects of drought by the rolled leaves and a dif- ference of about 12 inches in height. The corn was picked on August 50 and September 5. The corn was weighed.and counted. The data in Table 2 show the average weight per ear, the total weight, and dozens of harvested and marketable ears to the acre. Corn was benefited more by irrigation than either of the other craps. An increase of 400 per cent in the number of dozens of marketable ears resulted from the application of 4 inches of water. .About 25 per cent of the ears were market- able on the unirrigatedplots while irrigation increased the marketable ears to more than 80 per cent. Weight per ear was increased 49 per cent by an application of 4 inches of water. This increased size was due to a longer, better filled ear, resulting in better market quality. Rgsult of statistical analysis The results of the statistical analysis are shown in Table 5. The crepe grown, treatments used.and the level of significance are shown. Statistically, treatment 6 was better than 1 and 2 in the snap beans at the one per cent level. In the tomatoes treatment 2 was the on1y_one to show any statistical significance in the yields. .All irrigated plants produced larger tomatoes than the unirrigated. '14-; 'l _ 15 - Table 5 Result of Statistical Analysis Treatment SNAP BEANS Plot yield, lbs. Level of significance over tr. 1 Level of significance over tr. 2 98.7 117.7 141.0 128.6 145.6 5% 1% 1% 1% 1% 1% TOMATOES Plot yield, lbs. Level of significance 1158.4 1927.9 1466.1 1551.3 1478.5 over tr. 1 -- 1% -- -- -- Plot yield, number 5407 4906 5786 4022 5897 Level of significance over tr. 1 -- 5% -- -- - Av. wt./tomato, lb. 0.54 0.39 0.39 0.58 0.33 Level of significance over tr. 1 -- 1% 1% 1% 1% SWEET CORN Plot yield, lbs. Level of signif. Level of signif. over tr.l over tr.5 133.4 500.8 245.8 237.9 146.9 Level of signif. Level of signif. over tr.4 over tr.5 Plot yields, marketable ears Level of signif. Level of signif. Level of signif. Level of signif. over tr.l over tr.5 over tr.4 over tr.5 1% 1% -- “I2 '35 33'- 557 359 222 1% 1% 1% ”1% “is 7-3 The total weight of sweet corn and the number of marketable ears produced by plants receiving treatment 2 was significantly greater than those receiving any other irrigation treatment. Yields with Different Levels of Available Moisture It is evident that not all moisture present in the soil is available or suitable for rapid vegetative growth of a plant. Three divisions of soil moisture may be made on this basis: unavailable, available, and gravitational. Plants begin to show permanent wilting when the moisture content of the soil approaches the hygroscopic coefficient. Since any water below this point cannot be used for rapid vege- tative growth it may be called unavailable, though not entirely so. When free water is present in the soil, conditions detri- mental to growth are encouraged, the situation becoming more adverse as the saturation point is approached. The unfavorable effects of such.moisture on the plant arise largely from the poor aeration. Not only are the roots deprived of their oxygen, but favorable bacterial activities, such as nitrification, nitrogen fixation, and.ammonification, are much retarded. .More- over, adverse biochemical changes may be encouraged. This water is designated as gravitational. It is very evident that the most favorable moisture condi- tions for growth of plants, and.a1so for most micro-organisms, occurs in a soil when moisture is present is large enough amounts to be at a fairly low tension. This Optimum is not found at definite percentages of water, but exists between limits or as a zone, beginning near the hygroscOpic moisture content and extending somewhat into the zone of gravitational water. An abundant supply of rainfall during the early period of plant growth produces luxuriant foliage that cannot be supported during the drier days of late summer. Irrigation at low levels Of soil moisture availability will keep sufficient moisture in the root zone of the soil to prevent the drought damage of the later part Of the growing season. The following material shows the result of work done on a sandy loam soil. CrOp yield data of three different irrigation practices are compared. Charts of moisture availability during the growing period show the seasonal variations. Treatments 1, 2, and.4 are compared. Weather conditions Table 4 shows the rainfall from June 1 to September 15. The rainfall during this period was 8.62 inches as compared with an average of 10.88 inches for Lansing. There were two drought periods totaling almost seven weeks. The first period was from July 22 to August 10 and the second was from August 11 to September 9. This last period was particularly injurious to the sweet corn. The rainfall was well distributed during the remainder of the season. 0 is n i ds Snap beans. The moisture record for the unirrigated snap beans shows that damage was done during two periods of the - 19 - Table 4 Rainfall on Irrigation Test Plots 1948 Date Amount Date Amount June 4 .17 July 16 .17 .50 18 .15 8 .10 20 T 11 .21 21 .52 12 .15 22 .04 18 .19 25 .01 21 .47 27 T 22 1.55 29 .12 25 .04 .August 5 .04 27 .59 4 .15 28 .45 8 .02 29 .16 10 .71 July 1 .65 ll .08 10 T September 5 .05 ll .44 9 1.05 15 .01 15 .69 TOTAL 8.62 inches June July .August September Monthly totals 5.94 1.91 1.00 1.77 Monthly normals for Lansing 5.51 5.10 2.82 2.91 -20- picking season (Figures 9, 10, and 11). One period began about July 50 and ended with a drought breaking rain of 0.71 inch on August 10. The second began about August 18 and.was broken by a rain of 1.05 inches on September 9. The available moisture in the soil during the last period fell to less than 10 per cent. This certainly damaged the possible yield on those areas. The highest yield of beans was produced by adding water when the available moisture fell below 50 per cent and.again at the critical time in the growth of the plant. The critical time in the growth of the plant indicated that additional mois- ture was required about August 6. This came after the first picking had.been made. .Although.the available moisture in the soil was still above 60 per cent the additional water produced an increased yield of 50 per cent above the unirrigated. Statistically there was no significant difference between the two irrigated treatments. Tgmatoes. Examination of the soil moisture data for the unirrigated tomatoes will reveal that at the end of the yielding season a severe deficit in the available moisture occurred at both 4 and 8 inch depths (Figures 12, 15, and 14). The dry period from August 1 to August 9 also caused damage to the plants and reduced their total yield. The crOp receiving water by the Iby block' treatment yielded the highest number and weight of tomatoes (20 per cent better than the other irrigated crap). The next highest yielding crap received water ”by blocks plus critical time". sures ‘ '5 JIJJT pus I v A 'uc no 9 quUI mmccm deem Ooecmaaaaab ca oawpuaca a 2.9.0.. . 3:-.. candddmbd. .m scammesahu ohwnwyh ”Meaxntx .2. “EL . heart has. _ a- 1 _ C‘) '1‘ mm ed ‘84UQSIUfi otqwttwnv w A TUBO -22.. seuou; 'uoxlestszl pus {zséutua C‘J 1") It .83on as... he headed mmmcm doom ca Oawpmaoa.oancaam><_ .OH chewah H .seeo M .4:« a mean 535:: I Haxcuwam AIIihu unacn gnaw mIlII:II :raqw zoom eIlI.III. L1 e) ;>£1 é);' r-L191§”AY I)” r V‘ 1")? u. 1.. ('0‘. Q .A n r sauout ‘uotieszll pus [twguxsg O §\1 V) .32 2336 SE 333 an. downwaaau mason amen ca oaeauaca.oancaam>< .HH mhmwdh a when a .eaem a .mea b 1 r. In I CHIE. «I , r 4, III. a a a 1 Tl . 1 . a m m L _ . l i u. l m l m 1 fl \/ 1 _ 1 . 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H ease MHmmzwam green has“ e heme . ' nun-.- HHIIIL O N O ‘3‘ so quashed 'oxrgston a[qs[§unv - 27 - Comparison of the soil moisture data of the two irrigation treatments will reveal very little difference in the available moisture. They both received the same amount of irrigation water (four inches). However, the treatment with the applica- tion at the I'critical time“ received the first irrigation three days sooner than the other treatment. The moisture content of the soil in those plots must have been high enough that an addition of one inch of water reduced the yield rather than produced an increase. The I'by block" treatment was permitted to become quite low in available moisture before applying the irrigation water. .Apparently the conditions were more favor- able for maximum tomato yields at the lower range of available moisture supply. Swegt corn. The sweet corn was seriously damaged during the drought periods from July 22 to August 10 and August 11 to September 9 (Figure 15). Only the one rain of 0.71 inch on August 10 broke a continuous drought of seven weeks. This droughty condition shows clearly on the soil moisture record for the unirrigated plots. Both irrigated treatments received.the same amount of water during the season. The time of application did differ, however. The “critical time“ treatment did not receive water soon enough during the first drought period to prevent perma- nent damage due to wilting (Figures 16 and 17). On August 22 the available moisture in these plots again became too low. As a result, the crap receiving the I'critical time'I treatment yielded 92 per cent less marketable ears, 48 per cent less -23.. as V - w :19 I [?L;il' 'LOIQLWIJJI p E \ S {ll-'13.: 930 9025 downwaaadmb a.“ campmdoz candaambd H 5:4 IF 2‘ H \rfljna .mH chewed ”—1 L19 -4}. - .._ -. 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J‘ 41 4. 1 1 1 1 1 1 1 . + r w 1 y. . w . 1 1w 1 4 1 . 1 1 1 1 . .. « F r \ [17 1, hr L . l 1 Jr 1. .9 1 J. 1 1 _ 1. .. .. _. 1 1 a a . 13-1w... 1 1 1 1 _ 1 _, . 1+ 1w a, L * ). . fl .1. 1. .. m U f . M; 1 If; .11., «I II! J 1 >. fl..Y4 VIP f L w + .17 1r -1 z. . 1 1 1 1 . . 1 1 ....1... a. +i p 1 1, -, 1 "fi .1 ,. V “v1 1 1 1 ('1 .«f1rzll. 1 M F 1 1 ‘J N 7.}u1193’f ,nJ '3 . ( - 31 - total weight, and showed 8 per cent less weight per ear than the "by block“ treated crap. Both of the irrigated cr0ps yielded a profitable increase over the unirrigated (over 300 per cent more marketable ears). They also yielded ears that were at least 40 per cent heavier than the unirrigated. Statistically, the number of marketable ears produced by the crap irrigated by the “by block" method was greater than either of the other treatments. Corn irrigated "by blocks plus critical time' yielded more than the unirrigated - all at the one per cent level. A summary of the results of the statistical analysis is shown in Table 3. Nutrient Supply Water acts as the medium by which all nutrients are taken into the plant. It follows, then, that the nutrient materials must be in a soluble condition to become available to the plant roots. Being soluble the nutrients may be leached down to a depth.where they cannot be effectively utilized after irriga- tion water is applied. Exploratory data were obtained on the amount of soluble nutrients in unirrigated and irrigated areas. When applying irrigation water in the humid.region it is desirable to apply only enough water so that the soil moisture is brought up to field capacity to the depth of the principal feeding roots of the plant. Over-irrigation is not only an - 52 - unnecessary eXpense but may leach out the soluble nutrients. In this experiment these recommended practices were carried out. Therefore, excessive leaching should not have occurred. Egocedurg The field.used for this part of the experiment had been in alfalfa the two previous years. The corn was planted about June 1 and 200 pounds per acre of 2-12-6 fertilizer applied in the conventional manner. On June 50 an additional appli- cation of 370 pounds per acre of 2-12-6 was made. Three different treatments were set up on soil conditions as nearly alike as possible. The unirrigated plot was large enough and so located that the fine spray from the irrigations would not drift to the unwatered areas. Most of the field was irrigated and received an additional application of fertilizer through the water. A portion of the irrigated field was not treated with the fertilizer applied through the irrigation water. On July 28 the corn received the first irrigation. Three- fourths of an inch of water was applied and 100 pounds per acre of ammonium sulfate was drawn through the irrigation water. One-half pound of fertilizer per gallon of water was mixed in a 55 gallon drum and picked up by the suction line of the pump. This set up is illustrated in Figure 18. A second irrigation of one and one-half inches was made on August 3. Applications of water were made on the basis of gypsum meisture block readings. The time of irrigation happened to occur at the time of tasseling and silking of the corn plant. - 53 - Examination of the moisture record indicates that a third irrigation should have been made about August 17. Figure 18. Applying Fertilizer through Irrigation water Yield results All plots began with.a uniform stand. By the end of July the unirrigated corn showed signs of moisture deficiency. At the end of the season the irrigated corn retained its vigor- ous appearance. The unirrigated corn was badly damaged by lack of moisture. The plants were shorter and had smaller ears than the irrigated corn. Although the per cent of available moisture in the soil became quite low in the latter part of the season, irrigation increased the yields 65 per cent. Application of nitrates with.the irrigation water produced yields 98 per cent better than the unirrigated area and 19 per cent better than irriga- tion without nitrates. Comparative data for the three treat- ments are given in Table 5. Figure 19 shows the effect of two irrigations on field corn. Table 5 Yield Comparisons Unirrigated Irrigated Irrigated plus Nitrates water added at tasseling o g! a- water added at ‘ ' silking 0 1i” 1%“ Number ears per plot 250 409 422 Total weight per plot, lbs. (14% moisture) 68.2 113 134.5 AV. "0 per 631‘, lb. 0027 0028 0032 Bushels per acre 32.9 54.3 65 Per cent increase -- 65 98 - 55 - EFFECT OF TWO IRRIGATIONS ON FIELD CORN DURING |948 SEASON IRRIGATED UNIRRIGATED Figure 19. Effect of Two Irrigations on Field Corn Availability of nutgientg Field corn. Composite soil samples from the three treat- ment areas were taken to a depth of eight inches. The soil contained enough nitrates for good plant growth all through the season. The plot receiving supplementary fertilizer through the irrigation water contained more nitrates than the other irrigated.area., There was an inadequate supply of phosphates and potash in all field corn plots. Sweet corn. Analyses were made of composite samples taken in sweet corn. This field.had received a preplanting application - 55 - of 800 pounds of 3-12-12 fertilizer. A side dressing at the rate of 100 pounds per acre of ammonium nitrate was made about July 1. A month after the corn was planted.all plots contained an adequate supply of nitrates and potash. Later in the season the amount of these two nutrients in the irrigated plots fell below the optimum most desirable for good plant growth. There was an insufficient quantity of phosphates in all plots. Data on the amount of nutrients found in the various areas are shown in Table 6. Recommnons FOR FURTHER WORK The author has a number of recommendations for further work in supplementary irrigation. Improvement of Experimental Procedure The recommended practice for irrigation in this area is to apply only enough water to resupply the region in which the majority of plant roots thrive. This practice not only avoids the eXpense of over-irrigation but also prevents excessive leaching of plant nutrients. Insufficient data are available to indicate how deep different plant roots will penetrate in varying soil conditions in Michigan. On the plots on which this experiment was performed, irrigation water was applied.at the rate of one inch per hour. Nutrient Supply in Corn - 57 - Table 6 Total Partsigegogillion Water R s rve Extract 1’1“ Applied, ( e e ~ ) Inches NO3 P K July 3, 1948 Field corn, unirrigated 25 4 46 Field corn, irrigated 25 4 15 Field corn, irrigated (Nitrates) lO 4 12 Sweet corn, unirrigated 25 16 62 Sweet corn, irrigated "by bloek'l 25 21 95 Sweet corn, irrigated 1%- inches per week 1% 25 18 60 fl July 28, 1948 Field corn, unirrigated 25 2 30 Field corn, irrigated 3} 20 5 20 Field corn, irrigated . (Nitrates) it 55 5 15 Sweet corn, unirrigated ' 35 13 54 Sweet corn, irrigated “by block“ 12 15 68 Sweet corn, irrigated 1% inches per week 7 ll 36 August 18, 1948 Field corn, unirrigated 25 4 20 Field corn, irrigated 2% 15 4 12 Field corn, irrigated . (Nitrates) 2% 25 5 13 Sweet corn, unirrigated ‘ 30 18 48 Sweet corn, irrigated 'by block" 2 9 14 35 Sweet corn, irrigated 1% inches per week 11% lo 9 32 -5e-‘ In many cases puddling and runoff were observed. To prevent any further occurrence of this the rate of application should be reduced to at least three-fourths of an inch per hour. The attempt to apply water when the available moisture in the soil fell below 50 per cent was not always successful. Gypsum block readings were not taken at frequent enough inter- vals to prevent some drought damage. Blocks were available for only two of the three replications. On several occasions one of the replications showed a deficiency of moisture and the other contained enough.available moisture for good plant growth. .An application of water at this time benefited the dry plot but supplied more water than necessary on the other. Sufficient blocks should be obtained so that frequent readings may be taken and the proper level of moisture maintained on each replication. , The application of water‘at the critical time in the growth of the plant should be discontinued. This treatment did not show a significant increase in yield over the appli- cation of water 'by blocks“ for any crop. The additional application of water at this time was not needed and usually resulted in a decreased.yield. An additional irrigation practice should be tested. Some of the plants may produce maximum yields when the available moisture supply is above 50 per cent and others may thrive with less than 50 per cent available moisture. The "by block' treatment should be modified so that two ranges of available soil moisture may be maintained - one between 50 and 70 per cent and the other between 30 and 50 per cent. This should provide valuable information concerning the amount of available moisture that craps require for maximum yields. Soil Compaction There is some doubt as to the extent to which the appli- cation of irrigation water to the soil will compact the surface or succeeding layers. If irrigation does compact the soil thereby reducing aeration any benefits derived from irrigation will be offset by reduced.yields caused by poor soil structure. Additional work.should.be done to determine the amount of com- paction caused.by irrigation at different precipitation rates. Nutrient Supply The information obtained on the availability of nutrients on soils receiving different irrigation treatments was of an exploratory nature. If the amount of water applied is Just enough to increase the moisture supply in the root zone leachs ing should be avoided. However, the increased.moisture supply will produce greater foliage and fruit set thereby creating a demand for greater amounts of nutrients. Some of these nutrients may be applied.with the irrigation water. Further study of the availability of nutrients applied as a side dressing or with the water should be made. This study will give information concerning the amount and time of additional applications of fertilizers necessary for optimum growth. Statistical Analysis A statistical analysis of research data of this kind is highly desirable. However, it is quite difficult for research personnel to become intimately acquainted with all the possible eXperimental designs, the requirements for their use, and the mechanics of their analysis. The time consumed by members of a research organization-in making an analysis should be spent writing the report of the findings and planning further eXperi- mentation. An advisory group should be established to perform the following duties: 1. Consult with the research scientist and recommend an experimental design for the problem at hand. 2. Help plan the type of data to be gathered and.the methods of obtaining such data. 3. State the requirements necessary for tabu- lating the data to obtain complete informa- tion and for easier computation in the sub- sequent analysis. 4. Have equipment and statisticians to perform the required analysis and report the results of this analysis to the research organization. It is further desirable that research personnel be suffi- ciently familiar with statistical methods that consultation with the advisory group can be had at the prOper level. - 41 - SUMMARY A study of the precipitation record.at Lansing, Michigan, shows that every year an average of 7% weeks of drought can be expected during the period of May 15 to September 15. Supple- mentary irrigation is required to prevent drought damage to crops. In 1948 studies were made on a sandy loam soil to deter- mine the effect of irrigation water on (1) crop yields, (2) changes in the availability of soil moisture in the root zone and (3) nutrient supply. The following information was obtained: 1. 2. 3. 5. Yields of snap beans were increased 45 per cent in irrigated plots. Tomato yields were increased 60 per cent in irrigated plots. Irrigated sweet corn yielded four times as many marketable ears as the unirrigated. Application of water when the available moisture was less than 50 per cent resulted in greatest increases per inch of applied water. The available soil moisture was determined by measuring the intensity of an electric current passed through gypsum blocks buried in the soil. The plots that produced the highest yields - 42 - of tomatoes and sweet corn received water when the available soil moisture was less than 50 per cent. Irrigated corn plots contained a lower supply of plant nutrients than the unirrigated. Nitrates added with irrigation water at time of tasseling produced a 19 per cent greater yield than the irrigated area not receiving additional fertilizer. _ 45 - BIBLIOGRAPHY Baver, L. D. Soil Physics. John Wiley and Sons, Inc. New York. 1948. 398 pp. Bouyoucos, G. J. and Mick, A. H. A Fabric.Absorption Unit for Continuous Measurement of Soil Moisture in the Field. Soil Science. Vol. 66, No. 3. 1948. p. 217-231. Bouyoucos, G. J. and Mick, A. H. Improvements in the Plaster of Paris,Absorption Block Electrical Resistance Method for Measuring Soil Moisture under Field Conditions. Soil Science. Vol. 63, No. 6. 1947. p. 455-465. Christiansen, J. E. Irrigationgby aprinkling. University of California, College of Agriculture, Agricultural EXperi- ment Station. Berkeley, California. 1942. 124 pp. Cykler, J. F. Effect of Variations in.Available Soil Water on Yield and Quality of Potatoes. Agricultural Engineering. Vol. 27, No. 8. 1946. p. 363-365. Edlefsen, N. E. Effect of Soil Moisture Characteristics on Irrigation Requirements. Agricultural Engineering. Vol. 18, NO. 60 19570 p. 247‘2500 Goulden, C. H. Methods of Statistical Anal sis. John Wiley and Sons, Inc. New York. 1939. 2 7 pp. Love, Harry H. Experimental Methods in Agricultural Research. The Agricultural EXperiment Station of the University of Puerto Rico. Rio Piedras, Puerto Rico. 1943.229 pp. Peikert, F. W. Irrigation with Sprinklers and Portable Pipe. Agricultural Engineering. Vol. 29, No. 12. 1948. p. 541, 544. Peikert, F. W. Portable Pipe Irrigation Practices in Michigan. Michigan.Agricultura1 EXperiment Station_guarterly Bulletin. Vol. 29, No. 3. 1947. p. 194—204. Peikert, F. W. Light-Weight Portable Pipe for Irrigation. Agricultural Engineering. Vol. 28, No. 12. 1947. p. 567-568. Peikert, F. W. and Cook, R. L. Applying Fertilizer through Irrigation Water. Michigan Agricultural Experiment Stationflguarterly Bulletin. Vol. 30, No. 4. 1948. p. 437-444. -44- Schleusener, Paul E., Peikert, F. W., and Carolus, R. L. Results of Irrigation on Vegetable Crops. Michigan Agricultural Experiment Station Quarterly Bulletin. Vol. 31, No. 3. 1949. p. 343-350. Schoenleber, L. H. A Study of Garden Irrigation. Agricultural Eggineering. Vol. 24, No. 3. 1943. p. 75-78, 80. Snedecor, George W. Statistical Methods. The Iowa State College Press. Ames, Iowa. 1946. 485 pp. Staebner, F. E. Determining an Index of Supplemental Irrigation and its Application. Agricultural Engineering. Vol. 21, NO. 60 1940. p. 215-217. Staebner, F. E. Supplemental Irrigation. U. S. Department of Agriculture Farmers' Bulletin No. 1846. 1940. 73 pp. TiedJens, V. A. Applying Fertilizer in.Liquid Form. Agricul- tural Engineerigg. Vol. 22, No. 12. 1941. p. 440, 442. Veihmeyer, F. J. and Hendrickson, A. H. Water Holding Capacity of Soils and its Effect on Irrigation Practices. Agri- cultural Engineering. Vol. 19, No. 11. 1938. p. 487-490. Work, R. A. Soil Moisture Control by Irrigation. .Aggicultural Engineering. Vol. 20, No. 9. 1939. p. 359-362. ROOM USE. ON” a "fit '4: -J \ . ‘ . '- ' ‘ Jr , , .; c °.' 1 ’1 .. . ' 1 ~ . '.’o ’ . . ‘1 - ' ‘ l " I - ,4. ‘ l ‘ \ l ,. r . ‘ \ '.. / ‘0 \x IIlll“NIlllllllfllltllllluflllmll)H|||||H|||||||ll|Hll 31293105863