APPLE TREE ADAPTATION T0 MECHANICAL HARVESTING Thesis for the Degree 01%; D. ‘ _ * - MICHIGAN STAT-E UNIVERSITY f . - . . ' BERNARD BOND BIBLE .~ - .: , ‘ .. V , .- ‘ _ . my I . - H - - ' ’ .- -‘ ¢ ‘ ‘I . . - I. ,. . P > V .. . - ' ' '7 ' V J ~ ‘ ' ‘ 'IIJ' '«f .. .,.',_.,. " I, ._ ..,;.’.’:’-' "p ' .4 '..,", a'u’fiv' . ' .‘l.,c.,. 3;»; .4_ [O'vJ-fi’.‘?:l,n;;"ma [nr . .q . . .i ' {yrmpw '1': —-._ IIIIIIIIIIIIII IIIIIIIIIIIIII LIBRARY I I 3 1293 01106 7083 - - was Mzchzgan State University This is to certify that the thesis entitled APPLE TREE ADAPTATION TO MECHANICAL HARVESTING presented by Bernard Bond Bible has been accepted towards fulfillment of the requirements for Jinn—degree inflQfiieulture jig/fl; Major professor freer 5f #47 / 0-169 MI :_ +2315 ‘ I \..r «I. 0500 7" 2000 ABSTRACT APPLE TREE ADAPTATION TO MECHANICAL HARVESTING By Bernard B. Bible A "Lilliputian" apple production system consisting of high population densities of small trees was evaluated for two years. Trees planted in May of 1967 were used to determine the adaptability of this system to mechanized harvest. An economic study was conducted using 2,A30 com- binations of critical inputs. The vegetative growth of 'East Malling IX' transplants per unit area of land was maximal at the highest plant popu- lation of A3,560 trees per acre in both 1967 and 1968. Although the trees did not flower in 1968, the effect of competition on yield was inferred from the growth data. The highest fruit yield per acre would have occurred at some population higher than 43,560 trees per acre. The maximum plant pOpulation (10,890 trees per acre) of both 'Golden Delicious'/EM IX and 'Tydemans Red'/EM IX produced the highest yields of 720 and 119 bushels per acre respectively. Even these high populations did not produce the maximum yield per unit area of land during 1967 or 1968. 'Golden Delicious' yielded better than 'Tydemans Bernard B. Bible Red' at all tree populations tested. Both peach culti- vars, 'Suncling' and 'Redhaven,’ exhibited no effects of competition at tree populations up to 2,722 plants per acre based on growth and flowering observations. 'East Malling IX' trees grown on mulches had more terminal growth per plant at lower plant populations, but at the higher densities there was no response to mulching. The economic feasibility study indicated that a "Lilliputian" system may be most dependent on: a plant pOpulation of 10,000 trees per acre, a tree cost of $.25 each, and a minimum of four harvests over a seven year period. Factors of less economic significance were harvester cost, harvester capacity, and size of planting. The results reported here are not conclusive for all the factors concerning the practicality of a "Lilliputian" production system. It is hOped they will serve as guide- lines for the develOpment of a more efficient system for both apple production and mechanical harvesting. APPLE TREE ADAPTATION TO MECHANICAL HARVESTING By Bernard Bond Bible A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Horticulture I969 ACKNOWLEDGMENTS The author wishes to thank Dr. S. K. Ries for his assistance throughout the thesis studies, and Dr. R. F. Carlson, Dr. R. L. Carolus, Dr. A. L. Kenworthy, Dr. H. D. Both, and Dr. C. M. Harrison who have each con- tributed to the worth of his graduate studies. Appreciation is eXpressed to my wife and parents for their help during the course of this study. This research was supported by a grant from the MSU- NSF "Break Through Research Program." ii TABLE OF CONTENTS ACKNOWLEDGMENTS . . . . . . . . . . LIST OF TABLES . . . . . . . . . . . . LIST OF FIGURES . . . . . . . . . . . . INTRODUCTION . . . . . . . . . . . LITERATURE REVIEW . . . . . . . . . . . Trends Toward Mechanization of Tree Fruit Harvesting . . . . . . . . Physiology of Dwarf Apple Trees . . . . . . Plant Population Competition . . . . . . Response to Mulching . . . . . . .~ . Determining the Economic Feasibility of Proposed Mechanical Harvesting Systems . . . .. . . FIELD EXPERIMENTATION . . . . . . . . . . Materials and Methods . . . . . . . . . General Procedures . . . . . . . . Plant Population Studies Treatments to Increase Flower Initiation Mulch Treatments . . Mist Irrigation Treatment Results and Discussion . . . . . . . Plant Population Studies . . . . Modifying Flower Bud Initiation . . . Mulch Treatments . . . . . . . . . Mist Irrigation Study . . . . . . . . ECONOMIC FEASIBILITY ANALYSIS . . . . . . . Materials and Methods . . . . . . . . . Results and Discussion . . . . . . . . . SUMMARY 0 O O O O O O O I I 0 LITERATURE CITED . . . . . . . . . . . Page ii iv KO (hm-EN l2 l2 l2 l3 l6 17 18 18 18 31 32 35 37 37 Al ‘49 51 Table LIST OF TABLES Page The relationship of 'Golden Delicious'/ EM IX population with fruit size and quality in 1968 . . . . . . . . . . . 22 Terminal growth, branch number, and stem diameter/EM IX tree in relation to flower bud initiation treatments . . . . . . . . . 31 Terminal growth, branch number, and stem diameter/EM IX tree in relation to irrigation and spacing . . . . . . . . . . . . 35 Specific variables for economic feasibility program . . . . . . . . . . . . . 38 Non-Specific variables for economic feasibility program . . . . . . . . . 39 Equations utilizing Specific and non-specific variables for economic feasibility program . . A0 iv Figure l. 2. LIST OF FIGURES The relationships between EM IX population and growth parameters . . . . . . . . . . The relationships between 'Golden Delicious'/ EM IX population, growth, number of flowers, and yield of fruit . . . . . ., . . . . . The relationships between 'Tydemans Red'/EM IX. population and tree growth and yield . . ._ . The relationships between peach tree popula- tion, stem diameter, and flowering in 1968 . . The effect of in-row spacing and mulching on the growth/plant of EM IX trees during 1967 and 1968 . . . . . . . . . . . . . Break-even yields for "Lilliputian" production sand mechanical harvest with 7 A00, 12, 500; 37, 000 trees/acre and $135 or $200/acre per yr growing costs . . . . . . . . . . Break-even yields for "Lilliputian" production and mechanical harvest with 2, A, or 6 harvest- ing years out of seven and 7,400 or 12,500 trees/acre . . . . . . . . . Break-even yields for "Lilliputian" production and mechanical harvest with a $25, 000 or $35, 000 harvester . . . . . . . . . Page 19 23 26 29 33 A2 45 A7 INTRODUCTION Apple production for the fresh market in the United States consists of hand harvesting 27 to 800 large trees per acre. The apple industry has attempted to partially mechanize the harvest by the use of mobile picking plat- forms. Power operated tree shakers and vibrators have been used experimentally to harvest standard apple trees, how- ever serious bruising of fruit usually occurred. There also has been considerable effort to alter cultural prac- tices for mechanized harvest. The objectives of this study were to determine the feasibility of drastically altering both the cultural and mechanical approach to apple production. A "Lilliputian" system of apple culture was considered utilizing pOpula- tions as high as A3,000 trees per acre. Cultural practices tried were mulching, sprinkler irrigation, and treatments. to stimulate flowering. An economic analysis was made using the different production and mechanical harvesting inputs of tree density, tree cost, harvester cost, harvester capacity, size of planting, growing expense, and number of harvests. LITERATURE REVIEW Trends Toward Mechanization of Tree Fruit Harvesting Within the last twenty years horticultural production methods have progressed towards complete mechanization. This movement has been induced by higher returns for growers and forced by a growing scarcity of competent man- power. Harvesting has been the most difficult practice for horticulturists to mechanize. The extent of harvest mechanization will depend on the relative costs of hand and machine harvest, and the creative ability of men to develop new cultivars, cultural techniques, and machines. The fragile characteristics of the apple fruit have been the major obstacle to successful mechanical harvesting for the fresh market. Many attempts have been made to harvest apples mechanically or with picking aids. Most of these fall into two categories: the shake and catch method (80, 2, A2, A, 40) and the mobile picking platforms (8, 12, 59, 9, 3, Al, 5)- The shake and catch system utilizes a tractor-mounted hydraulically Operated, boom-type shaker to shake the fruit from the tree onto a canvas-covered collector under the tree which conveys the apples into bulk boxes (62). There 2 are variations of this technique (80). The shake and catch method has proven feasible for apples which are processed (42), but has not been satisfactory for the fresh market crop (A0). The percentage of bruised fruit from shaker harvested trees has been high, in some cases exceeding the acceptable limits for fresh market apples (NO). Shakers have worked very well for harvesting of cherries and their use has become an accepted practice (28). Other systems to completely mechanize apple harvesting have been tested (80). These machines shake the fruit from the tree into decelerating devices which slow the fall of the apple. Other innovations have been mechanical picking aids used by some growers (9, 3). They generally consist of some sort of mobile platform that moves between rows of trees with pickers harvesting from the platform, thus eliminating need for ladders and movement on foot. One obvious advantage of picking platforms is their easy con- vertibility to pruning platforms thus saving labor expense in that costly operation (Al). Berlage g£_§1. (12) sug- gested adapting orchards to picking platforms such that continuous tree walls 5 to 6 ft thick with drive rows 8 to 10 ft wide would be harvested by pickers riding on an auto- matic steering platform. Rollins (59) and others (Al) questioned the economic feasibility of using picking plat- forms. The history of mechanical harvesting has recorded a trend to complete mechanization of processes and not the deveIOpment of machines as accessories for human hands. Physiology of Dwarf Apple Trees The development of dwarf apple cultivars which come into bearing quickly may preclude the development of a straddle row mechanical harvesting technique for apples. The apple (Mains sylvestris) is a deciduous, woody perennial propagated asexually. Among apple tree populations there exists a certain percentage of dwarf variants, as is the case with most classes of plants (73). According to Pelton (55) the differences in size and other manifestations of dwarfism in plants are quantitative and not qualitative. Plant hormones probably play an important role in this phenomenon since they are reportedly essential to the con- trol and timing of growth rates in many plants (76). Auxins, gibberellins, and cytokinins have been intensively studied in relation to growth. Van Overbeek (76) reported that the reduced growth rate of some single gene dwarf plants was due to their higher rates of auxin destruction. Phinney (56) found reduced concentration of endogenous gibberellin to be a factor in dwarfism. Cytokinins have proven effective as both promoters and inhibitors of cell enlargement (29, 48). Jones (36) found cytokinin—like activity in apple stem xylem sap. He (36) later applied a synthetic cytokinin (benzyl adenine) to excised apple shoots which resulted in a marked stimulation of shoot growth. . Another possibility is the presence of growth inhibitors in dwarf apple trees. Luckwill (A7) detected two growth inhibitors in leaves of malus species that could inhibit shoot extension. Miller (50), using leaf extract from 'East Malling' II, VII, and IX, found that the extract inhibited growth in the same ratio as the known vigor of the rootstocks. Thus its conceivable that dwarf apple trees have higher rates of auxin destruction, lower endogenous levels of gibberellins, less production or transport of cytokinins, more growth inhibitors quantatively or qualita- tively, or any and all combinations of the above. Girdling and placing plants in a horizontal position are two methods used to bring apple trees into bearing quickly (72). Probably the most reliable way to do this has been to graft the desired scion on EM IX rootstock, consequently shortening the time to bearing (37, 71). The mechanism of action of this subtle interaction of stocks, scions, and environment has eluded researchers up to now. Dennis (2A) tried chemical regulators on apple seedlings, but failed to advance the time of bearing. An attempt to induce flowering of apple seedlings in the Juvenile stage by grafting onto bearing trees also failed (23). Radia— tion treatment in one case induced flowering of some one year seedling trees, but only one fruit set and it was seedless (70). Referring to the development of compact beans and tomato cultivars adapted to mechanical harvesting, Tukey (73) pointed out that similar developments were theoreti- cally possible with apples. The many generations needed and length of time involved are the critical problems that must be resolved. Plant Population Competition Plant growth and development is markedly affected by interplant competition. Donald (25) stated that "competi- tion occurs when each of two or more organisms seeks the measure it wants of any particular factor or thing that is below the combined demand of the organisms." He listed water, nutrients, light, oxygen, carbon dioxide, and some- times the agents of pollination as factors over which compe- tition between plants may occur. Holliday (33) classified the graphical presentations of crOp yield relative to number of plants/unit area into two types of curves. One, approximately parabolic in shape, typified situations where yield was some product of reproductive growth. With this type of curve a certain plant pOpulation gave a maximum yield, while higher or lower populations resulted in lower yields. The other curve was asymptotic and characterized the case where yield was a product of vegetative growth. Thus, a certain population would produce the maximum yield; however, the yield did not decrease at populations beyond this maximum. Wiggins (81) and Bleasdale (1A) discovered some exceptions to this generalization. Bleasdale (1A) showed that for onions at any given plant density the yield was lower from those plants grown at rectangularities (ratio of the between-row distance to within-row distance) greater than 5:1. He concluded that equidistant spacing, or nearly so, increased plant yield. Other workers (21, 30) have reported similar results with other crops. The experimental materials used to elucidate these principles of competition have been mainly herbaceous crOps. However, there have been plant density studies dealing with woody plants. 'Golden Delicious' and 'Jonathan' cultivars grafted on EM IX gave maximum yields at the highest pOpu- lation density (13A8 trees/acre) tested (A5, 5A). These high density plantings were economically feasible in Germany (77). MoEalova (51) found that apple tree popula- tions of 270 trees/acre outyielded plantings of 162 trees/ acre. He also observed less damage of frost susceptible varieties at the closer Spacing. Shoulders (63) worked with Loblolly and Slash pine seedlings at densities of 10, 20, 30 and A0 plants/ftz. He found root collar diameters decreased with increased population density, but heights of seedlings were unaffected. Standard sized 'Cox' apple trees yielded more fruit at medium and high plant densities as compared to the lowest densities (57). However, this work was done with mixed populations of standard, semi- dwarf, and dwarf trees; thus, the degree of competition was hard to assess. Serafimova (61) evaluated fig trees at spacing of 6xA, 6x6 and 6x8 M. He reported that the closest spacing reduced the growing period and tree size, but yield/tree and per unit area was greater at closer Spacing, and fruit ripened earlier. Response to Mulching The reported effects of mulching have been varied depending on the type of mulch and the conditions under which it is used. Tukey and Schaff (7A), working with decomposable mulches such as straw, observed lower soil temperature, increaSed soil moisture and increased water infiltration rates into the soil due to the mulch treat- ments. The most striking effects of mulch were on the physical prOpertieS of the soil. Black;polyethy1ene plastic mulch in most cases raised soil temperatures (31, 22, 69). Harris (31) reported that black plastic mulch increased soil moisture content; however Schales and Sheldrake (60) reported the opposite response. Clear and black plastic mulch treatments have resulted in earlier harvests for some crops (3A, A9). Several papers that dealt with mulching of apple trees explored its value as a substitute for nitrogen fertilizer (l, 35, 15, A3) and only incidentally mentioned the possibility of better soil moisture conditions under mulch. Lavee (AA) found that EM II apple rootstock responded with more vigorous growth to a mulching treat- ment of wood Shavings. Buller and Gibbs (17) noted more vigorous growth and less fatalities of pine trees grown on mulched soil. Other researchers (82, 10) observed that mulched apple trees had a very shallow lateral root deveIOpment. The spacial distribution of roots was altered, but the number of roots/plant was not affected (10). Citrus responded differentially to black plastic mulching, depending on the rootstock and location (18). Determining the Economic Feasibility of Proposed Mechanical Harvesting Systems Development of mechanical harvesting systems for cherries, prunes, and blueberries has stimulated work toward developing a mechanical harvester for apples. LaBelle (39) stated that there is potentially less economic advantage in harvesting the larger fruits (e.g., apples), where hand labor is more efficient. Rollins (59) pointed out that apple harvesting costs represented less than 25 per cent of the value of the crop, whereas cherry harvesting cost represented 75 per cent of the value of the crop. However, Fridley and Adrian (26) indicated that while a high per- centage of the grower's return was for hand harvest of cherries, only a low percentage for lettuce harvest, this has not diminished the interest in a mechanical lettuce harvester. LaBelle (39) speculated that even small economic lO advantages will eventually be exploited in this highly competitive field. A mechanical harvesting system must be economically sound in order to be useful. Fridley and Adrian (26) stated that the economic soundness of a mechanical harvesting system depended on three factors: amount of fruit lost in excess of hand harvesting losses, degree of mechanization achieved (equipment use per season), and the rate of harvest. Thus, before the actual development of a mechanical harvester and its components can be accomplished, the economic feasibility of the harvest system Should be analysed. Stout et_al. (66) undertook a study of the feasibility of a once over mechanical harvester for pick— ling cucumbers. They determined that once-over harvest was generally not feasible, and concluded that the success of a once—over harvest for cucumbers depended on the development of a good quality small vined cucumber. Stout (67), using a computer technique to analyze over 800 combinations of variables, determined the economic feasibility of asparagus mechanical harvesting systems. Fridley and Adrian (26) constructed nomograms to evaluate and compare the feasibility of mechanizing crop harvest for several fruits and vegetables. Stout (68) extended his computer routine to include a further study of asparagus harvesting systems and mechanical harvesting systems of cucumbers and tomatoes. II He concluded that mathematical models of harvesting economics can provide useful guide lines for predicting economic feasibility. FIELD EXPERIMENTATION Materials and Methods General Procedurei Experiments were conducted at East Lansing, Michigan on a Miami loam soil. The previous year the land had been planted to rye. The soil was disked and prepared for planting by May A, 1967. Soil analysis (conducted by the Michigan State Soil Testing Laboratory) for the plots indicated that pH ranged from 5.0 to 5.5 and the levels of P, K, Ca, and Mg were adequate for fruit trees. Three thousand rooted (mound layered) EM IX trees were hand planted May 5 to May 16, 1967 for various experi- ments. The transplants, approximately 18 inches long and 3/8 inch diameter, were planted 6 inches deep and pruned to 8 inches above ground level. Three hundred, 1/2 inch diameter 'Golden Delicious'/EM IX and 100 'Tydemans Red'/ EM IX of the same size were hand planted on May 5, 1967. A tractor mounted boom-type sprayer was used on May 22 to apply the herbicide Simazine at 2 lb/acre to all plantings of EM IX. The plantings of the larger 'Golden Delicious'/EM IX and 'Tydemans Red'/EM IX trees were Sprayed at the same rate of Simazine with 2 1/2 gallon knapsack Sprayer. Standard pesticides were Sprayed on all 12 13 apple trees throughout the experiment to control insects and diseases. Apple trees were treated with Arasan A2—S deer and rodent repellent on July 12 and December A, 1967 and July 8, 1968. Ammonium nitrate was applied twice (July 11, 1967 and May 2A, 1968) to all apple trees at a rate of 1/8 lb/tree. Overhead Sprinkler irrigation adjusted to apply approximately 1 inch/hr was used to provide moisture to all plots when rainfall was inadequate. Analysis of variance was used on all designs except the systematic spacing designs. Mean differences were compared by Duncan's multiple range test where applicable. Plant Population Studies A systematic Spacing design was used to study apple tree response to population density. These types of designs, in which plant density changes gradually over the block, are non-random. The advantages of this systematic approach were uniform block Size and only a small propor— tion of the plants were needed for guard rows. Nelder (53) indicated that when the major source of error variance was plant variation rather than soil variation systematic designs were valid. The design is best described by mutually perpendicular horizontal and vertical axes which divide a plot into A quadrants or replications. Starting from the point of axes intersection, points were designated 1A at one ft intervals over a range of 1 to 5 ft in both directions on both axes. If straight lines are drawn through all points on the axes a grid was formed, and at each point of intersection on the grid a tree was located. Guard rows were placed only on the outside edge of the planting. Four blocks of EM IX trees consisting of four replications each were measured October 1967 for terminal growth/plant and checked for number of branches/ plant. During October of 1968, trees in eight replications of this experiment were measured for terminal growth/ plant and stem diameter at 1 inch from ground level. The 'Golden Delicious'/EM IX and 'Tydemans Red'/EM IX trees were set out in the systematic design described above. The only difference was that the foot increments increased over a range from 2 to 5 ft. Three blocks (12 replications) were planted to 'Golden Delicious'/EM IX and one block (four replications) was planted to 'Tydemans Red'/EM IX trees. During October of 1967, these trees were measured and counted. The total number of flowers and flower clusters/tree were counted on May 11, 1968. In late October 1968, the fruit from each tree was harvested, counted, weighted and graded into the following categories on the basis of Size and defects: (1) 3 inch diameter or larger, (2) 2 1/2 to 3 inch, (3) 2 to 2 1/A inch, (A) 1 1/2 to 2 inch and (5) less than 1 1/2 inch. Any fruit with a Skin defect area of 1/2 inch or more in diameter was 15 placed in category (5). After the fruit were harvested the total terminal growth/tree and the stem diameter 2 inches above the graft union were measured. Four hundred peach trees (3/A—inch stem diameter) half of them 'Redhaven'/Seedling and the other half 'Suncling'/Seedling were planted in a systematic spacing design on May 16, 1967. The same design was used as before except the range of points on the axes was A to 7 ft and there were eight replications of each cultivar. On July 11, 1967 and June 21, 1968 NHuNO3 at approximately 1/8 lb/tree was applied to all peach trees. The contact herbicide paraquat was used at 2 lb/acre during the growing seasons of 1967 and 1968 to control weeds. The number of flowers/tree was counted on April 21, 1968 and the stem diameter at 8 inches from ground level measured on October 10, 1968. Data from systematic spacing designs were evaluated by the least squares analysis, with a CDC 3600 computer.1 The data for growth and yield/tree, and growth and yield/ ft2 of land were fitted to linear and curvilinear equations of the general forms: 1Control Data Corporation model 3600 computer. 16 Y = a + bX (Linear) Y = a + lel + ng2 (Quadratic) Y = a + lel + b2X2 + b3X3 (Cubic) Log Y = Log a + b Log X (Curvilinear) Log Y = Log a + (Log b) X (Curvilinear) Log Y = a + lel + b2X2 (Curvilinear) Log Y = a + b X + b X + b X (Curvilinear) l l 2 2 3 3 where Y equals growth or yield parameter: Xl equals plant population,/1000; and X2 = X12, and X3 = X13. The equation that gave the best fit was selected in all cases. If none of the general equations were Significant for a given dependent variable, that variable was considered not correlated with plant population. Treatments to Increase Flower Initiation Three methods of promoting flower initiation and increasing number of flowers/tree were Studied using the EM IX transplants set at 3 ft intervals in rows 5 ft wide and 21 ft long. Treatments consisted of transplanting (on May 5, 1967) at an angle of A50, foliar Sprays of 2, 3, 5-triiodobenzoic acid (TIBA) at 25 ppm in the early summer, and scoring of transplants. The plants were Sprayed with TIBA on the evenings of July 7 in 1967 and June 7 in 1968. All other non TIBA treated trees were Sprayed with tap water at the same time. The scoring was done, on July 7, 17 1967 and June 7, 1968, with a small knife by cutting a ring completely around the stem 1 inch above ground level. The cut was intended to temporarily interfere with phloem transport. The three treatments and a control were arranged in a randomized block design with 12 replications. Each treatment in each block had seven trees. The terminal growth was measured and number of branches counted during October, 1967. The following year the ter- minal growth and stem diameter were measured. Mulch Treatments The treatments tested were black polyethylene plastic mulch, straw mulch, straw spread on tOp of black poly- ethylene and clean cultivation (control). The spacings used were 1, 2, 3, and A ft in rows A and 5 ft between rows. The black plastic, 3 ft wide and 1 1/2 mils thick, was perforated and placed down around the base of the transplants three weeks after they were planted. The straw was placed around the transplants, forming a 3 ft wide, 2-3 inch deep cover over the soil or the black plastic, depending on the treatment. A modified split plot design was used in which between row Spacing treat- ments were main plots with mulch treatments as subplots, while the sub—subplots (in—row spacings) were arranged in strips across each replication of the subplots. Main plots were replicated four times. The same counts and 18 measurements were made as for the experiment on flower bud initiation. Mist Irrigation Treatment 'East Malling IX' trees were transplanted l, 3 and 5 ft apart in rows 3 ft wide. These spacings were compared under a mist irrigation of .10 to .15 inches/day and no mist irrigation. Mist irrigation was applied with rotary sprinklers fitted with l/l6—inch nozzles adjusted to apply .05 inches of water/hr between 11:30 AM and 2:00 PM when the air temperature was above 85 F with clear skies. Mist was applied 13 days in 1967 and 11 days in 1968 from June to August. Supplemental irrigation was used in both the control and mist plots when rainfall was inadequate. A split plot design was used with mist treatments not repli- cated, While the in-row spacings were replicated twice in each main plot. The same measurements and counts were made as for the experiment on flower bud initiation. Results and Discussion Plant Population Studies In 1967 the terminal growth and number of branches/ EM IX transplant were not correlated with population (from 1,7A2 to A3,560 trees/acre). The same trees in 1968 had reduced terminal growth and stem diameter/plant with population increases (Figure 1). Terminal growth/ft2 in 1967 and stem diameter/ft2 in 1968 increased Fig. 19 l.——The relationships between EM IX population and growth parameters. A. Terminal growth per plant and per square foot of land relative to plant population. (Plant population/1000 = X.) 1. 1967 Growth/ft2 Y = .182 + .612x, r = .83*** 2. 1968 Growth/plant i = 251.5x‘°1809, r = —.uu*** 3. 1968 Growth/ft2 i = 5.77X°8191, r = .91*** Stem diameter per plant and per square foot of land relative to plant population in 1968. (Plant population/1000 = X.) 1. Stem diameter/plant i = .998 — .0158x + .000212x2, R2 = .5o*** 2. Stem diameter/ft2 I = .O25A + .01605X, 1:: .979*** nmm mm’ (lo) mas mulmln’ (tn/loo) I”! 20 mumo Ix ." n I 0/. P \ " \Mlphm ,o’emsm' \ P”. /' P... a ‘\ ,/' \ ,/ \ ./ \ ./ \ ,/ an \ ./ \\“/'/ , ‘~~_. Ml!" ./ “~~-- nu nu '/ -~~~-- '/ M------- / 4 ‘1: r . v , ' V ' 0 mo ~~ ---------‘ Ir ' 1'0 ' .15 ' a‘b ' ‘3 RAM 'OPULAYIONIACII (X 1000) (ON/U!) INN/Um um (01) ”NH/Hm "mum 21 linearly with increasing population. During 1968 increase in population increased terminal growth/ft2, but at a decreasing rate. Competition occurred among EM IX trees in 1968 but not in 1967. The response of the trees in 1968 to compe- tition conformed to the general formula proposed by Kira (38) of wda = K where w is yield/plant, d is density, and K and a are constants. The terminal growth/unit area increased at a decreasing rate with population indicating competition. Donald (25) suggested that the minimum plant pOpula- tion that produced the ceiling yield of dry forage/acre was equivalent to the pOpulation that would produce the maximum grain yield. If terminal growth/ft2 in 1967 or 1968 was substituted for dry forage/acre, the minimum tree population that resulted in the maximum yield/acre of apples would have been greater than A3,560. Two year old 'Golden Delicious'/EM IX and 'Tydemans Red'/EM IX trees did not respond similarly to plant popu- lation stress. Terminal growth and branch number/tree in 1967 and terminal growth, Stem diameter, flower number, fruit number and fruit weight/tree in 1968 were not cor- related with number of 'Golden Delicious' trees/acre. During 1968 the terminal growth, stem diameter, flower number, fruit number and fruit weight/ft2 of 'Golden 22 Delicious' increased linearly with increasing pOpulation (Figure 2). The terminal growth/ft2 in 1967 increased at an increasing rate as the population increased. The fruit size and quality of 'Golden Delicious' were not con- sistently influenced by population, but at the highest pOpulation (10,890 trees/acre) the percentage of large fruits was reduced (Table 1). TABLE l.-—The relationship of 'Golden Delicious'/EM IX pOpulation with fruit size and quality in 1968.a Per cent of fruit in each Square Number category feet Trees of per per fruit Fruit Quality Ratings plant acre per tree 1 2 3 A 5 20.25 21Al 10.7 8 35 38’ 15 3 15.75 2766 9.0 9 32 37 18 A 12.25 2556 11.7 1A 32 A2 10 2 11.25 3872 11.8 7 35 36 16 2 9.00 A729 12.2 7 29 A1 20 8.75 A978 10.0 15 37 27 16 7.00 6223 11.5 10 37 39 13 6.25 6969 11.A 9 17 35 39 5.00 8712 7.9 10 27 A7 13 A.00 10890 9.1 1 26 A8 18 5 AVERAGE 10.5 9 31 39 18 3 aEach line of observations is mean of eight replica- tions. 23 Fig. 2.--The relationships between 'Golden Delicious'/ EM IX population and growth, number of flowers, and yield of fruit. A. Terminal growth and stem diameter per square foot of land relative to plant population. (Plant population/1000 = X.) l. 1967 Growth/ft2 Y = .915X1.1035, .76*** 2. 1968 Growth/ft2 i = 5.02x - 1.29, r = .86*** 3- 1968 Stem diameter/ft2 9 = .0179x - .001A9, r = .98*** B. Number of flowers, number of fruit, and fruit ‘ weight per square foot of land relative to plant pOpulation in 1968. (Plant population/1000 = X.) l. Flowers/ft2 § = 2.22X — .ou2, r = .6A*** 2. Fruit number/ft2 § = .12A + .222x, r = .60*** 3. Fruit weight/ft2 i = .052 + .060x, r = .62.%%* 27' COLD!” DIllCIOUSIM IX u- ,, I” 1” ‘Eu ‘/0 ’a 3 ‘/ 1” n . I E ,/ 1’ a \ 0/ ” ' a 0/ ” : ./ 1 1’ I In!!!” /, 1 , “on dbmlfl’ so P on... , , nu ‘ 0 ll ' 3,, /, ’1 3‘ - . I, g 5 ./. 1” m :u s ' ’7 A /./ 1’ 5. w 1' [’1 a 3 ‘I. ’1 mm 1—— 8 1 ” no: " " 1 ’1 In; J oc_ mom»; 0 A O A town 0' “MI! Fruit nomborlfl’ j 9 i (oat/II) ,uuuoms u 2 o' I um murmur/hen (x 1000) 5 :5 LL 25 The terminal growth/tree and per ft2 of land in 1967 and the stem diameter/ft2 in 1968 increased linearly as the pOpulation of 'Tydemans Red' trees increased (Figure 3). However, other expressions of vegetative growth in 1968 exhibited peculiar responses to various plant densities. These growth measurements were related to pOpulation by the cubic regression equation of the general form Y = a + b X + b X + b 11 22 3X3 equals plant popula- where y equals the growth measurement in inches; Xl tion/1000; and X2 = x12, and x3 = x13. The final equations, which explained more of the variation than any other of the general equations tested, were the following: For terminal growth/plant: - 2 3 2 — was Log Y - .389 + .39x - .067x + .00337X , R — .54 For terminal growth/ft2: A - 2 3 2 *** Log Y - .156 + .227X - .0312X + .OOlAAX , R = .69 For stem diameter/plant: § .322 + .317X - .05A5X2 + .oo27Ax3, R2 s ,30usu In 1968 there was no relationship between number of flowers and fruit or fruit weight/'Tydemans Red' tree and plant population. Fruit number and fruit weight/ft2 increased curvilinearly with population increases. 26 Fig. 3.--The relationships between 'Tydemans Red'/ EM IX population and tree growth and yield. A. Terminal growth per plant and per square foot of land, and stem diameter per foot square relative. to plant population. (Plant population/1000 = X.) l. 1967 Growth/plant Y = 26.39 + 3.06x, r = ,39*** 2. l967Growth/ft2 Y = l.AAX - 1.252, r = ,81*** 3. 1968 Stem diameter/ft2 I = .00A25 + .0186X, r = ,95*** B. Number of fruit and fruit weight per square foot of land relative to plant population in 1968. (Plant population/1000 = X.) 1. Fruit number/ft2 1.0133 9 = .llO6X r = .63*** 2. Fruit weight/ft2 i = 2.65X'879, r = .56*** 1.7 3.! 93:53:.» 23:8. .7 111/./ ,, .1 l, . m I /o I 1 1 m , . , 1. .m .0. ,1 1 am m ,, a u , 1. m 1, 1. u 1. n .m/ 1. WM, 1 ./ 1.1 x .1. s, 1. 1 /. / 1 ‘31 m w w w .8: S I: 8 at; is: 33.2: a. 3:5... 358. PLANT WNW/KI! (X 1000) 28 Two peach cultivars ('Suncling' and 'Redhaven') responded similarly at the various tree densities in 1968. The stem diameter and number of flowers/ft2 increased linearly with population (Figure A). Both cultivars flowered in 1968 but frost damage prevented fruit set. Donald (25) proposed that it was the community of suppressed plants which gave the greatest yield/acre. Thus at the plant populations necessary for maximum yield the intense competition resulted in quantitatively sub- normal plants. Since none of the populations tested cauSed reduced growth, flowering, or fruit/plant of 'Golden Delicious' trees; the maximum yield/acre was not attained. The increased growth/tree in 1967 with increasing competition of 'Tydemans Red' may be analogous to the increased height/plant of wheat caused by competition for light (78). There was an obvious interaction of plant population and cultivar considering the response of 'Golden Delicious' and 'Tydemans Red'. The more extensively branched and com- pact 'Golden Delicious' trees were better adapted to pro- duction at high plant populations than 'Tydemans Red'. No- such interaction was apparent for the two peach cultivars. Neither the maximum growth nor number of flowers/unit area was attained at the range of populations tested. 29 Fig. A.—-The relationships between peach tree popula- tion, stem diameter and flowering in 1968. A. Stem diameter per square foot of land relative to. plant population. (Plant population/1000 = X.) l. Suncling stem diameter/ft2 Y = 3.657x - .392, r = .91*** 2. Redhaven stem diameter/ft2 Y = .171 + 3.1AX, r = .95*** B. Number of flowers per square foot of land relative to plant population. (Plant population/1000 a X.) 1. Suncling flowers/ft2 Y = 1.A2AX — .0016, r = .A5*** 2. Redhaven flowers/ft2 Y = .052 + 1.13x, r = ,07*** 30 use use me HAN! WHOM IKII 31 Modifying Flower Bud Initiation Treatment with TIBA in 1967 increased the number of branches/tree, but planting at a A5o angle decreased the branches/tree of EM IX transplants (Table 2). TABLE 2.—-Terminal growth, branch number, and stem diameter per EM IX tree in relation to flower bud initiation treat- ments. Growth Branches dIEEEESr (inches) (no.) (inches) 1967 1968 1967 1968 1968 Control 22 ab2 126 5.5 b 20 .86 TIBA (25 ppm) 26 a 1AA 6.A a 20 .81 Planting (A5O angle) 20 b 120 A.5 c 17 .8A Scoring 23 a 137 6.3 ab 19 .8A 1At one inch above ground level. 2Values followed by uncommon letters are significantly different at the 5% level. Both TIBA and scoring treatments caused more terminal growth/tree than did planting at a A5o angle. Reappli- cation of these treatments in 1968 did not alter the number of branches, terminal growth, or stem diameter of EM IX trees. None of these treatments affected flower bud initiation, in fact, none of the EM IX trees flowered in 1968. 32 The failure of these treatments to promote flower initiation after only one year of growth was not unexpected (A6, 52). The reported modifications of tree form and flowering may not occur until after the second or third year of growth (16). The increased number of branches/plant caused by TIBA was consistent with other results which indicated disruption of apical dominance by TIBA (27). The increased terminal growth of TIBA treated trees was due to the extra branches/tree and not to more elongation/ branch. Carlson (19) reported that apple trees grown in an inverted position had fewer "bud breaks," however Tukey (73) indicated that apple trees planted at an angle of A50 had increased "bud breaks." The decreased number of branches/plant of the trees planted at a A5° angle supported the findings of Carlson. Although in planting the trees at a A50 angle, they may have inadvertently been set deeper thus more buds were beneath the soil line than for the upright trees. This also would have resulted in fewer branches/plant. The lack of response to TIBA in 1968 may have been due to the lateness of application. Mulch Treatments In both years (1967 and 1968) mulching and in-row spacing affected the terminal growth/plant of EM IX trees (Figure 5). The mulches did not affect growth at 33 Fig. 5.-—The effect of in-row spacing and mulching on the growth/plant of EM IX trees during 1967 and 1968. 3‘! s antral :5 ~zo pmo>hmnAmIZLHV on pause o>m£ Hafiz moose msmmz mo honesz m mm.umm.uwa.umo.uao. Aooso\ev moose no onoo HefioHeH oe ooo.amuoom.manooa.e Aoeoe\moosov eoaooasooo oeoaa as com I mma Asm\mASM\wV mmCHUHHdo one BSmEQHSUo wcflpmnmao mo pmoo one .wsaufiafipmmm mo pmoo new» mpnooopm nHomecoo ammo mcH©3H02H .moonp mofizonw mo pmoo ow ooo.mm:ooo.mm-ooo.ma nae topmoeese co omoo HoHoHeH mHo m. I o. I m. Aen\mmsomv moms pmo>emm m< 0mm . ems . om Amoeoev messeoao eo onsm a mosam> mo mwcmm coapofihomom HOQEmm .EmmwOLQ szHHnHmmow oHEocooo pom moanmfimm> ofimfiooom020200.m mqmde lIO TABLE 6.--Equations utilizing specific and non—Specific variables for economic feasibility program. Symbol Description Equation (Expressed in dollars) . . (1.03)(FC)(HP)(A) V 0 ' r < = C.L COot of fuel and lubricants (yr) CEL (AH)IEFC) , CIH - (SVH/IOO)(CIH) COH Cost of harvester overhead (per yr) CJH = Q1“ R CIH+(SVH/100)(CIH) + 100( 2 ) + (TS)(CIH) + (RHH)(CIH) 100 100 (A) CIT-(SVT/100)(CIT) ‘\ ' \' a 7 ( COT Cost of tractor overhead (per Jr) COT (AH)(AT)‘( SLT ) + R (CIT + (SVT/100)(CIT)) 100 2 (RMT)(CIT) (TS)(CIT) + 100 I 100 ) COL Cost of labor to operate tractor and . u harvester (per yr) CQL = (A)(P§g + CL“) CMH Cost of mechanized harvesting (per yr) CMH = CPL + COH + COT + COL GCI Growing cost plus interest on "a _ \ . x ,. , investment for tree cost (per yr) ”II ' (A((GL) + ((U)\H)(PI)(TC))/IOO PY Planting year total cost (per yr) PY = (A)(PP)(TC) + GCI HY Harvesting year total cost (per yr) HY a CMH + GCI RL Two harvests in 7 years (total cost RL . PY + AGCI + 2H7 for 7 years) RM Four harvests in 7 years (total cost for 7 years) RM = PY + 2GCI + AHY RH Six harvests in 7 years (total cost for 7 years) RH A1 Results and Discussion To aid interpretation of the economic analysis results the approximate value of the yield from 'Golden Delicious' trees was used. At 10,890 trees/acre the yield was .695 lb. of fruit/ft2 (Figure 2), this was transformed to gross return as follows: (.695 lb/ft2) x (A3,560 ft2/acre) e (A2 1b/bu) = 720 bu/acre (720 bu/acre) x ($2.00/bu) = $1,AAO/acre gross return/acre. The gross return value of $1,AAO/acre was used to test the economic soundness of the various combinations of variables. The break-even yields in dollars/acre per year for "Lilliputian" production and mechanical harvesting costs are presented in Figure 6. The assumptions were a planting of 150 acres, a $25,000 harvester, harvester capacity of .6 acres/hr, and four harvesting years out of seven. The tree population/acre, cost/tree, and growing costs/acre per year were assigned ranges of values. Using the $1,AAO/ acre value as a standard, the desirability of having not more than 10,000 trees/acre and trees costing $.25 each or less can be seen. The higher growing costs increased the break—even yield/acre about $120. A2 Fig. 6.-—Break-even yields for "Lilliputian" production and mechanical harvest with 7,A00; 12,500; 37,000 trees/acre and $135 or $200 growing costs. Assuming the following: Harvester cost of $25,000 Planting of 150 acres Four harvests out of seven years —_— ”—_.—‘ .._-.__. _____._ fl *. __— BREAK—EVEN YIELDS ($/acre per yr x100) 4‘3 I - - — $200/ocre Growing costs $135/ocre Growing costs / 45" 0 .0'1 .09 .1'7 .2'5 .53 INITIAL TREE cosr ($/TREE) AA Break-even yields are Shown for 2, A, or 6 harvesting years out of a seven year period, and 7,AOO or 12,500 trees/acre in Figure 7. A harvester cost of $25,000, 150 acre planting, $200/acre growing costs, and .A acre/hr harvester capacity were assumed. The economic benefit of having four harvesting years in seven years to at least break—even can be seen. The rate of harvest was not an important economic factor, but it determines the physical limitations of a harvester. For example, a harvester with a capacity of .2 acres/hr working 20 hr/day would take 37 1/2 days to harvest 150 acres. This indicates that certain points on the figures may be physically impossible or impractical. The effect of a range of harvester costs and size of plantings on break-even yields can be seen in Figure 8. A harvester capacity of .A acres/hr, tree population of 12,500/acre, $200/acre growing costs, and a tree cost of $.17 each were assumed. The initial cost of the harvester becomes increasingly important as the size of the planting decreases, although given the assumptions listed the har- vester cost would not preclude economic success. These graphs represented only a few of the possible combinations of variables used in this study. These par- ticular combinations were chosen because they dramatize the importance of tree pOpulation, cost/tree, and number of harvesting years on the economic soundness of "Lilli- putian" apple culture and mechanical harvest. AS Fig. 7.--Break-even yields for "Lilliputian" production and mechanical harvest with 2, A, or 6 harvesting years out of seven and 7,A00 or 12,500 trees/acre. Assuming the following: Harvester cost of $25,000 Planting of 150 acres Growing costs of $200/acre per yr ““"u BREAK-EVEN YIELDS ($locro per yr 1:100) 38 6“ 7,400 Trees/ac re .. - -12,500 Trees/acre .09 .17 .25 INITIAL TREE cosr (sluts) .33 A7 Fig. 8.--Break-even yields for "Lilliputian" production and mechanical harvest with $15,000; $25,000; or $35,000 harvester. Assuming the following: Tree cost of $.17/tree Trees/acre equal to 12,500 Growing costs of $200/acre Four harvests out of seven years BREAK-EVEN YIELDS ($Iocre per yr) 1310 I270 I230 "90 "50 50 $15,000 Harvester 615’ $ 35,000 Harvester suzs or PLANTING (acres) 25.000 Harvest: SUMMARY Tree density and cultural practices were tested using three apple cultivars, EM IX, 'Golden Delicious,‘ 'Tydemans Red', and two peach cultivars 'Suncling' and 'Redhaven'. The economic feasibility of "Lilliputian" apple production and mechanical harvest was considered using various com- binations of costs. During 1967 EM IX trees were not affected by high tree populations, but in 1968 modified vegetative growth indi- cated competition. The terminal growth/ft2 of land increased with tree population during 1967 and 1968. This suggested that the maximum fruit yield/acre would have occurred at some pOpulation higher than A3,560 trees/ acre. The growth, flowering, and fruiting/tree of 'Golden Delicious' were not altered over the range of tree populations from 1,7A2 to 10,890/acre. Thus the maximum fruit yield/acre was not attained in 1968. At the highest tree population the percentage of large size 'Golden Delicious' fruit was reduced. 'Tydemans Red' trees grew taller with increasing competition in 1967. 'Tydemans Red' growth measurements in 1968 were related to plant population by cubic equations. 'Golden Delicious' A9 50 out yielded 'Tydemans Red' at all pOpulations tested in 1968. The growth and flowering of the two peach cultivars were not altered by tree population from 600 to 2,722 trees/acre. Attempts to modify flower bud initiation of EM IX transplants were unsuccessful. Planting at a A5o angle reduced the branch number/tree in 1967, but TIBA increased it. None of the treatments altered growth in 1968. Three mulches were compared to clean cultivation at various in-row and between-row spacings in 1967 and 1968. The trees grew taller on mulch when spaced 3 and A ft apart in the row compared to the l- and 2—ft spacing. Certain combinations of cost variables indicated the economic soundness of "Lilliputian" production and mechani- cal harvesting. The results indicated a need for: a population of less than 10,000 trees/acre, a tree cost of less than $.25 each, and at least four harvesting years over a seven year period. Factors of less importance were harvester cost, harvester capacity, and size of planting. 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