EFFECTS OF RATE AND FREQUENCY OF FERTILIZER APPLICA

CALVERT: FERTILIZER EFFECTS VALENCIAS (citrus Section EFFECTS OF RATE AND FREQUENCY OF FERTILIZER APPLICA TIONS ON GROWTH, YIELD AND QUALITY FACTORS OF YOUNG 'VALENCIA' ORANGE TREES David V. Calvert Citrus Experiment Station I FAS Fort Pierce Abstract Three fertilization s and 3 application frequencies were combined factorially to give 9 treatment combinations used on both outside and inside rows of young 'Valencia' orange s on rough lemon rootstock planted on a -row bed on Felda soil. frequencies were 3, and 5 times a year and the 3 s of fertilization were approximately %, equal to, and % times the current recommendations for similar age s. Highest consistent growth and yield re sponses were obtained on inside rows with med ium fertilization and lowest application fre quency, while s planted where appreciable topsoil had been removed on outside rows re sponded most favorably to medium frequent applications and highest fertilizer. A sig nificantly greater number of s showed young decline symptoms in low fertility plots than higher fertility plots on the interior two rows of the -row bed. It is suggested that results of this experiment may be applicable to young citrus s planted in groves under both optimum and marginal soil conditions in the flatwoods and marshes. Introduction Very little information based on results from replicated field experiments is available on fer tilizer practices for young s planted on low land and calcareous soils in the flatwoods and Florida Agricultural Experiment Stations Journal Series No. 39. marshes. Rapid expansion of the citrus industry into more marginal soils in poorly drained areas has been accomplished without the benefit of ex perimental data regarding efficiency of fertilizer use and without the evaluation of problems which may be different from those of the established citrus growing areas. In a series of experiments on well-drained acid soils, Rasmussen and Smith () evaluated young citrus fertilizer prac tices and on the basis of their findings made sig nificant modifications to earlier recommendations in Bulletin 536 (7) and Bulletin 536A (8). These recommendations with some modifications appear fairly sufficient for young citrus s on the finer textured lowland and calcareous soils as in the Indian River area. However, fertilizer recom mendations for Florida citrus given in Bulletin 536B (9) were devised primarily for average sandy, well drained soils low in organic matter, such as the Lakeland and Blanton sands. The primary objective of the experiment re ported here was to test current recommendations regarding and of fertilization of young s under conditions of fine textured lowland soil, close plantings, and -row bed design. An additional objective was to investi gate and if possible eliminate soil fertility dif ferences related to poor growth on outside rows of a -row bed system. Experimental Procedure This study was initiated in January, 963 in The Coca Cola Company, Foods Division, Holman Cloud grove near Fort Pierce, Florida. The s, 'Valencia oranges on rough lemon rootstock, were planted in 96 on beds consisting of -rows spaced 7 feet apart with s 5 feet apart in the rows. The soil type in the experimental area is Felda fine sand. Measurements of ph made

FLORIDA STATE HORTICULTURAL SOCIETY, 969 on soil sampled from several locations in the experimental area showed that ph of the top inches of soil ranged from 6.5 to 8.3. The sur face soil horizon in the experimental area varies in color from gray to dark gray with subsurface layers grading into much lighter gray to white sand. The soil contains appreciable amounts of sandy clay loam at depths of 8 to inches. The sandy clay loam layer is usually underlain by highly pervious marine shell at depths of inches or more. Ditch spoil composed of a mixture of these soil layers was graded into the surface soil dur ing the -row bed construction. The crown of the -row citrus bed in the Cloud grove was graded approximately to.5 feet higher than the bed area immediately adjacent to the ditch berm on the sides of the bed. During the grading procedure to obtain the bed crown the dark gray surface soil (Ax horizon) was partially to com pletely removed from the outside row planting areas. Shifting the surface by grading markedly improved the soil quality for the interior rows, but exposed white, coarse, leached, sandy layers in the area on which the two outside rows were later planted. Three fertilization s (, and ) and 3 application frequencies (, and were combined factorially to give 9 possible treatment combinations. treatments con sisted of a medium fertilizer () which was approximately equal to the average recom mendation for similar age s in Bulletin 536B (9) and s Rx and which were V and % times the average recommendation, respectively. application frequencies were 3, and 5 times par year for the, and treat ments, respectively. Treatments were randomized in four replicate blocks. The experiment was duplicated on the outside and on the inside rows of a single -row bed containing approximately.3 s including ditches. Each plot consisted of 'Valencia' orange s with single buffer s Table. Dates of application of fertilizer and Treatment symbols R R. treatments. Low Medium High Low Medium High Low Medium High Frequency application 3 3 3 5 5 5 of Dates of application /5, /5, /5 /5, /5, /5 /5, /5, /5 /5,/5, 8/5, /5 /5,/5, 8/5, /5 /5,/5, 8/5, /5 /5, /5, 6/5, 8/5, /5 /5, /5, 6/5, 8/5, /5 /5, /5, 6/5, 8/5, /5 on each end of the plot. Approximate dates of application are presented in Table. The amounts of fertilizer applied for each of the 3 s dur ing the 6-year period are shown in Table. The fertilizer ratio was 8--8-6-.5-.5 for the first years and was changed to -6--9 with the first application in 965. Systematic field observations of condition were made or 3 times each year. Even more frequent observations were taken when it be came evident that a large number of s in this grove were showing young decline symptoms similar to citrus blight (5). Soil was sampled in May, 969 at 6-inch increments down to 7 inches from both declining and healthy s for ph and other determinations. Spring flush leaves from non-bearing twigs were sampled for mineral element analyses in early November, 96. Yield was obtained when the crop was har vested commercially, which generally was in late spring each year. Fruit quality measure ments were made each year, primarily in March. Trunk circumference measurements were taken in March, 963 and again in November, 968, while height and canopy diameter were measured only in June, 969. Tree canopy area was calculated from the height and diameter data. Data obtained in the study were analyzed statistically as a 3x3 factorial. Duncan's (3) multiple range test was applied to the data to detect individual differences among the 9 treat ment combinations. Pounds per year Seasons N PO5 KO MgO CuO MnO tre i tre< 963-65..8.7 9.5 38.3 57.6...36 9.58 9.5 8.73..8.7 9.5 38.3 57.6.8.36.5.36 8.73 3.9..75.6.5.9.5.8.75.6.5.9.5.8 965-69.63.5.88 5.. 5..3.63.9 5..63 5..5 75..88 5.. 5..7.9. 37.5 75..5

CALVERT: FERTILIZER EFFECTS VALENCIAS Irrigation, pest control, nutritional spraying and other grove management practices were carried out by The Coca Cola Company, Foods Division and were considered to be adequate. Results Tree Condition and Growth The fertilization and treatments on inside rows had no statistically significant or practical effects on increase in trunk circumference, foliage diameter and canopy area (Table 3). Sig nificant differences in height were detected among the, Rj and R., treatment combinations on inside rows. Increasing fertilizer on outside rows increased trunk circumference, height, foliage diameter, and canopy area, but these increases were not always significant. The treat ment combination which tended to give the maxi mum growth increases for the s on outside rows was the high fertilization applied with medium (), but the was not always statistically distinguishable from the lowest application for all these growth effects (Table 3). It is interesting to note that the R^F., combination gave by far the larg est square feet of canopy area. This area compared quite favorably with the largest canopy area attained for s on the inside rows (Table 3). Trees receiving the and fertilization s were distinctly greener and denser in foli age than s receiving the B, in both inside and outside rows, although this condition was more striking in the outside rows. In the early years of the experiment, s in outside rows receiving the Rj fertilization were thin and yellow in foliage, and the leaves generally showed N and Mg deficiency symptoms. Table shows a breakdown by treatment of the incidence of young decline symptoms in the fertility plots on inside and outside rows. These data reveal a trend for more young decline symptoms on s on the inside rows. Trees in Ra plots appeared to be affected most frequently. The average effect of disregard ing was a significantly greater num ber of s showing young decline symp toms in plots receiving the Rx fertilization than in plots receiving the and s (data not presented). Table 3, Effects of fertilizer and treatments on height, diameter, canopy area and trunk circumference of young 'Valencia' orange s. Inside rows 5 Outside rows.. 8abc n,8ab(. C 3.a...3 3. 5. 3 397 35 abc*.7a ** 5.3 5 39 67 6. 7. 6. 5.. 7. Height,.6ab :.8abc.3bc Diameter,.3.6. ft. ft. Canopy arcia, sq. 6 6 378 Trunk circumference increase 6.3 6...9bc 9 8C io!7bc.7bc.5c.9bc ft. 93e 37 97de 963-68 3.3abc.8C.8bc.bc.6bc.b.3abc.9bc.abc 33cd 9ie 36C, inches..8bc.7c 3.5abc. 3. QbC. 3. lab. la. 7C 359b a 9d 7b e,8ab 5. 6. 5a 9abc 3. Means for individual years and bed position followed by the same letter do not differ at P=.5. * Columns and rows of means without letters are.not statistically significant.

FLORIDA STATE HORTICULTURAL SOCIETY, 969 Table. Number of s showing young decline symptoms in fertilizer and plots on November, 968. Inside rows Fertilization Ri Outside rows Fertilization * ab 6^ ab Ob ab lb Number ab lb ab of s See footnotes of Table 3. Yield Table 5 shows that increasing fre quency of fertilizer applications had no practical effect on fruit yields on inside rows. In fact, fre quency treatments were significant only in the 96-65 season when more frequent fertilizer applications at the tended to decrease yields. Fertilization treatments on inside rows gave statistically different yields 3 years out of 5. There was a significant interaction be tween and treatments on inside rows only in the 966-67 season. The highest yielding treatment combination the first 3 years for inside rows was. In the last years of the experiment the treatment combina tion gave highest yields. Fertilization re sponses on inside rows followed a curvilinear trend as yield per leveled out or often de creased at the Rq. Table 5. Effects of fertilizer and treatments on yield of young 'Valencia orange s on rough lemon rootstock planted in inside and outside rows of a -row bed..b* 5k.3bc.58**.89.9.6bcd.5d 76k 76b.78b...96 Inside.77ab.55.55b.85.68.96 rows.6ab #9bcd.6ab.67a.ab.3ab.8.9.57.96a.7b.5b..9.83.bc 967-68 #ab.ab 968-69.9.6.6 BOXES/TREE 96-65 965-66 966-67.9a.6abc.33ab #67abcd.d #5bcd.9b.llb.'l5b.bc.9b.3b.cd.83d.bcd.6bc.bc.3abc i Outside #ab.b.8b.3b.9b.58ab.3bcd.65bc.77b rows.73abcd.8cd.9ab.ab.53abc.96c.36a.3a.b.39a.6ab.56ab.'9a.8b 76b.63a.66bc.8abc.8abc.5ab.69abc See footnotes of Table 3

CALVERT: FERTILIZER EFFECTS VALENCIAS Table 6. Effects of fertilizer and treatments on fruit weight and juice quality factors. Data represent 5 year averages. Inside rows Fertilization R 3 ] Outside rows Fertilization 5.98 5.6 5.9.56a.66a.6a #9abc.9ab.9a 3. 3..8 76.6e 78.e 85.e 55.8 55.6 5.96.b Il!ob.9bc '.87 *.89bcd -89bcd 3..9.9.6C.bc 3.bc Juice (%) 55.8 5.86 5. 55. 56. 5.9 Brix (%).76d.88C.88C.7b.8a.86a j Acid (%).85d -9ab,88bcd.9a.9abc #93ab Brix-to-acid ratio 3..7.3 3. 3..9 Fruit weight (g rams) #be 6 9.6abc 3.8ab 3.8a 6.bc 55.76 55.9 55..38*.8cd.9e.88bcd.86d.87cd 3. 3..7 9.8abc 9.6abc 3.8ab 55.6 55.78 56..5*.d.6d.8.89ab.87cd 3.5.9 3. 6.a 7.abc 8.6abc See footnote of Table 3. Fruit yields were significantly different due to in all seasons on outside rows. There were significant interactions between and treatments on outside rows in the last 3 seasons presented in Table 5. The consistently highest yielding treatment combination for out side rows was. The data show a trend in certain years for sizeable yield increases on out side rows with increasing fertilization s at both and application frequencies, but at the, there was no significant differances yields due to for any of the 5 years. In fact, on the average increasing number of fertilizer applications above per year tended to lower yields on both inside and outside rows. Fruit Quality The data shown in Table 6 are averages of quality analyses determined once each year over the 5 year period, 96 through 969. Years were used as replications for statis tical purposes and were significant statistically for percent acid and fruit weight determinations on inside rows and for degrees Brix and percent acid on outside rows. Significance of years means that quality differed considerably in different seasons. Most of the overall effect on juice qual ity can be ascribed to the fertilizer treat ments, however more frequent applications on the average increased soluble solids in fruit from outside rows. The treatment combination giving heaviest fruit on inside rows was, which apparently was due to an interaction of the fre quency and treatments. The average effect of increasing fertilizer on both inside and outside rows was to decrease soluble solids per fruit, decrease fruit acid slightly and produce a heavier fruit (Table 6). Brix-to-acid ratios and percent fruit juice by weight were not in fluenced significantly by any of the treatments. Leaf and Soil Analysis Rate and treatments did not significantly influence leaf N, Ca and Mg on inside rows as shown in Table 7. Increasing fertilizer significantly increased leaf P on inside rows at the and fre quencies. Leaves from outside rows generally had larger amounts of N, Ca and Mg with in creasing fertilizer s. Leaf K content in s on outside rows generally decreased as of fertilization increased. Interaction between

FLORIDA STATE HORTICULTURAL SOCIETY, 969 Table 8. Representative ph values determined on soil sampled from varying depths at the dripline of healthy and declining 'Valencia' orange from 6 8 3 36 8 5 Depth inches - to - - 8 - - 3-36 - - 8-5 - 6 Healthv s Tree A Tree 6.5. 3.6 3.6 3.. 7.5 7.8 8.6 8. 8.5.5.6 7.6 8. 8. 7.7 7.9 Soil B dh Declining Tree 7.5 7. 5.5 3. 3.5 3. 6.7 7. 8. A s Tree 8. 8. 8. 6.6 6.5 6.3 6.7 7.6 7.8 and was present in the leaf P data indicating the effects of and were not independent in influencing leaf P content. Values of ph obtained from soil sampled at varying depths from the dripline of both declin ing and apparently healthy s are presented in Table 8. No consistent differences in ph be tween the declining and healthy locations were obtained. Extremely low ph values were encountered frequently under both declining and healthy s. Soil from these low ph layers was usually of sandy loam texture. The soil has a light blue color with reddish mottled streaks which generally indicates chemically reduced con ditions, with some evidence for slight oxidation. Discussion requirements appear different for the center rows of young 'Valencia' s than for the outer rows on a -row citrus bed. Rate combination gave largest con sistent growth and yield responses on outside rows. The treatment combination accom plished the same function on inside rows. Overall, the fertilization treatments appeared to be of primary consideration, while treat ments were decidedly of secondary importance, especially on inside rows. Plots receiving fer tilizer applications in June ( treatment) usually had less growth and yield than plots receiving the same s, but less frequently and in drier periods. These results are in agreement with a number of workers (, 6,, ) who have shown that time of application is of little importance provided that fertilizer applications are made during the drier seasons of the year. The differential response to fertilizer, depending on location on the -row bed appears to be the result of differences in soil properties existing between the locations. Field observa tions of the experimental area reveal that soil B on which the center rows were planted is deeper, contains more fine textured material, including organic matter, than soil in outer row areas which is white, highly leached and often nearly devoid of organic matter. Extra fertilizer applied more often on outer rows apparently partly com pensates for the loss of topsoil. However, grow ers should keep in mind the additional expense of the higher s and more frequent applica tions which were necessary to obtain favorable responses for outside rows. The results of these experiments show that current recommendations in Bulletin 536B (9) were adequate and practical for young 'Valencia* s in center rows growing under better soil conditions. Maximum response at this bed loca tion was usually obtained at - combination which is similar to that recom mended for similar age s in Bulletin 536B. The results indicate that additional yield and growth responses were obtained under outside row conditions at fertilizer s and frequencies higher than currently recommended in Bulletin 536B. Inferences may be drawn from the results of these experiments to other young groves planted on soils with similar properties. Citrus s planted on white sandy soils in lowland areas comparable to the outside rows used in this experiment may respond to higher and more frequent applications than are recommended in Bulletin 536B. Whether the extra care necessary to produce these responses is economical will have to be decided in individual situations. The experiment is being continued to assess the relative at which s in the fertilizer plots show young decline symptoms. The influence of the highly acid layers (Table 8) in the soil profile as a possible contributor to the young decline is being investigated by soil and plant analyses. The highly acid soil layers quite possibly may be identical to the soil con dition described by Coleman and Thomas () as "cat clay." These workers found that certain coastal soils derived from marine parent mate rials and recently drained from swampland upon oxidation develop highly acid layers by conver sion of sulfides accumulated in the profile to sulfates. Summary Nine fertilizer and treatment combinations applied over a 6 year period gave

ANDERSON AND MARTIN: CALCIUM MINERAL UPTAKE wide ranges in growth, condition and fruit production of young 'Valencia' s on rough lemon rootstock. The treatment combination of medium fertilization and low application appeared satisfactory for s planted under soil conditions existing on interior rows of the -row citrus bed. Medium frequent appli cations and high fertilizer gave favorable results on exterior rows where appreciable top soil had been removed. Declining growth and yield responses to more than applications per year apparently was the result of applying fer tilizer during the rainy season when leaching losses are high. Young decline symptoms were significantly greater in low fertility plots on the interior rows of the -row bed. Results from this experiment can be extrapolated to young citrus s planted in groves on both optimum and marginal soil conditions in the flatwoods and marshes. Acknowledgments The author wishes to express his sincere appreciation for technical assistance to Mr. Fred Bistline and Mr. Ernest Lundberg of the Foods Division of The Coca Cola Company and to Dr. Frank Martin of the University of Florida Sta tistics Department. LITERATURE CITED. Calvert, David V. and Herman J. Reitz. 96. Effects of and of fertilizer applications on yield and quality of 'Valencia* oranges in the Indian River area. Proc. Fla. State Hort. Soc. 77:36-.. Coleman, N. T. and Grant W. Thomas. 967. The basic chemistry of soil acidity in Soil Acidity and Liming. R. W. Pearson (Ed.). Agronomy Monograph :-. 3. Duncan, D. B. 955. Multiple range and multiple F. tests. Biometrics :-.. Rasmussen, G. K. and P. F. Smith. 96. Evaluation of fertilizer practices for young orange s. Proc. Fla. State Hort. Soc. 7:9-95. 5. Rhoads, Arthur S. 936. Blight a non-parasitic disease of citrus s. Fla. Agr. Stat. Bull. 96. 6. Reitz, Herman J. 956. Timing fertilization of citrus in the Indian River area. Proc. Fla. State Hort. Soc. 69:58-6 7. Reitz, H. J., C. D. Leonard, J. W. Sites, W. F. Spencer, I. Stewart, and I. W. Wander. 95. Recommended fertilizers and nutritional sprays for citrus. Fla. Agr. Expt. Sta. Bull. 536. 8. Reitz, H. J., C. D. Leonard, I. Stewart, W. F Spencer R. C. Koo, E. J. Deszyck, P. F. Smith, and G. K. Rasmussen. 959. Recommended fertilizers and nutritional sprays for citrus. Fla. Agr. Expt. Sta. Bull. 536A. 9. Reitz, H. J., C. D. Leonard, I. Stewart, R. C. Koo, D. V. Calvert, C. A. Anderson, P. F. Smith, and G. K. Ras mussen. 96. Recommended fertilizers and nutritional sprays for citrus. Fla. Agr. Expt. Sta. Bull. 536B.. Reuther, Walter and Paul F. Smith. 95. Effect of method of timing nitrogen fertilization on yield and quality of oranges. Proc. Fla. State Hort. Soc. 67:-6. Sites, John W., I. W. Wander, and E. j. Deszyck. 953. The effect of fertilization timing and of applica tion on fruit quality and production of Hamlin oranges Proc. Fla. State Hort. Soc. 66:5-6. EFFECTS OF SOIL ph AND CALCIUM ON THE GROWTH AND MINERAL UPTAKE OF YOUNG CITRUS TREES Carl A. Anderson Florida Citrus Experiment Station Lake Alfred and Frank G. Martin University of Florida, I FAS Gainesville Abstract A soil ph added calcium factorial experi ment was started in 96 in a -year-old block of 'Valencia* oranges on rough lemon rootstock lo cated on newly cleared Lakeland fine sand. The Florida Agricultural Experiment Stations, Journal Series No. 3. treatments consisted of annual soil applications of sulfur, gypsum, soda ash (sodium carbonate), and calcitic limestone applied alone or in com binations to provide levels of soil ph (., 5., 6., and 7.), levels of added calcium (,,, and pounds calcium per per year), and all possible combinations for a total of 6 treatments. Striking differences in growth due to treatment were observed by October, 967. Maxi mum growth occurred at the highest ph level and maximum of added calcium. This treat ment consisted of liming the soil to ph 7. with calcitic limestone and supplementing the lime stone with gypsum to provide a total of pounds added calcium per per year. In gen eral,- the fastest - of growth.resulted- from the simultaneous increase in both soilpffahd added