FOLIAR APPLICATION OF VARIOUS SOURCES OF IRON, MANGANESE, AND ZINC TO CITRUS

Transcription

1 o 48 To ) X o A 46CH 73 > E 3 O 44(H 42 crease under the conditions of this study. For a developing Flatwoods navel orange grove on heavy soil, maintaining a soil moisture level of cbar throughout the year should provide a suitable growth environment. However, a higher soil moisture regime may be desirable in the fall in order to prevent fruit drop. It should be noted that tree size during the study period was equivalent to 5 to 7 year old trees. It is possible that differences in production among treatments could have occurred at higher production rates or if fully mature trees were used in the comparisons. Additionally, the re sponse of similar trees on the sandy Flatwoods soils which have recently been developed and planted, may be quite dissimilar. The limited water holding capacities of these soils coupled with shallow rooting depths makes proper water management on these sandy Flatwoods soils critical. CO 4 HHH HHL LLH HLL HLH LHH LHL LLL Fig. 4. Total fruit yield per acre by treatment for the 1988/89, 1989/9, and 199/91 seasons (treatment means are not significantly different at (p =.5). The treatments showed no consistent differences in yield or total soluble solids produced per tree during any of the seasons. However, those treatments receiving L-depletion during the SI stage tended to produce slightly more fruit (Fig. 4). Trees with the H-depletion level during the SI stage averaged 3.3 boxes tree"1 while those receiving L-depletion during the SI stage averaged 3.6 boxes tree"1 for the three-year total yield. The small increase in production resulting from the added irrigations required for the LLL treatments did not justify the time and energy expended to achieve the in Literature Cited Burman, R. D., P. R. Nixon, J. L. Wright, and W. O. Pruitt Water Requirements. In Design and Operation of Farm Irrigation Systems. M. E. Jensen (Ed.). ASAE Monograph No. 3. ASAE, St. Joseph, MI. Doorenbos, J., and A. H. Kassam Yield response to water. FAO Irrig. and Drain. Paper No. 33. Koo, R. C. J Effects of frequency of irrigations on yield of orange and grapefruit. Proc. Fl. St. Hort. Soc. 76:1-5. Koo, R. C. J., and J. W. Sites Results of research and response of citrus to supplemental irrigation. Soil and Crop Sci. Soc. Fl. 15: Reitz, H. J., and W. T. Long Water table fluctuations and depth of rooting of citrus trees in the Indian River area. Proc. Fla. State Hort. Soc. 68: Smajstrla, A. G., L. R. Parsons, K. Aribi, and G. Vellidis Response of young citrus trees to irrigation. Proc. Fl. St. Hort. Soc. 98: Wright, J. L New Evapotranspiration Crop Coefficients. J. Irrig. and Drain. Engr., ASCE. 18: Wright, J. L., and M. E.Jensen Peak Water Requirements of Crops in Southern Idaho. J. Irrig. and Drain. Engr., ASCE. 98: Proc. Fla. State Hort. Soc. 15: FOLIAR APPLICATION OF VARIOUS SOURCES OF IRON, MANGANESE, AND ZINC TO CITRUS A. K. Alva and D. P. H. Tucker Citrus Research and Education Center University of Florida, IFAS 7 Experiment Station Road Lake Alfred, FL 3385 Additional index words, alpha keto acid, ethylene diamine tetra acetic acid, lignin sulfonate, nitrates, NZN, oxides, sodium gluco heptanate, sulfates. Abstract. Effects of foliar application of various formulations containing Mn, Zn, and Fe [nitrates, lignin sulfonate, gluco heptanate, NZN, dry mix, alpha keto acid, and EDTA-chelated] were evaluated on 8-yr-old navel orange trees on Swingle citrumelo rootstock. These trees were showing moder ate to severe symptoms of deficiencies of the above micronutrients. During 1991, Mn and Zn were applied in 2 equal ap- The use of trade names in this paper does not imply endorsement by the University of Florida of the products named, nor criticism of similar ones not mentioned. Florida Agricultural Experiment Station Journal Series No. N plications (March and August), using a commercial airblast sprayer calibrated at 167 gal/acre, at.5 and 1. Ib/acre/yr, and Fe at.125 and.25 Ib/acre/yr. These metallic rates were doubled during Mineral analysis of 5-month-old spring flush leaves (sampled just prior to August spray), during both the years, showed very deficient levels of Mn and Zn and slightly deficient levels of Fe, regardless of rates or sources of the micronutrients. Only the 1991 data were reported on the concentrations of Fe, Mn, and Zn in the summer flush leaves. In most treatments, the micronutrient concentrations in the summer flush were slightly greater than those of spring flush. of the formulations significantly increased the concen trations of Fe in the leaves as compared to that in the control treatment. Whereas, nitrate and NZN formulations signifi cantly increased the concentrations of Mn and Zn in the sum mer flush. Considering the extremely sandy texture and low or ganic matter content of soils in major citrus producing areas of Florida, careful management of micronutrient availability is an important aspect of production manage ment. The discussion in this paper will focus on the correc- Proc. Fla. State Hort. Soc. 15: 1992.

2 Table 1. Selected chemical properties of the soil. Variables ph (water) ph(.1mcacl2) Mehlich 3 extractable P K Ca Mg Fe Mn Zn Cu Al Mean ± Std. dev. 8. ± ±.1 lb/ac 14 ± ± ± ± ±9.5 3 ± ± ± ± 4.2 tion of Fe, Mn, and Zn deficiencies. Koo (1987) and Koo and Reese (1971) conducted a 2-yr trial on single nutrient omissions using Pineapple oranges on rough lemon rootstock. The experiment was conducted using a Candler fine sand, which is a typical non-calcareous ridge soil. Omission of Mn or Zn resulted in a reduction in tree growth while omission of Fe had no effect. Fruit yield de creased by.4 box/tree when Mn was omitted; however, omission of Zn or Fe had no effect on yield. Large areas of calcareous soils are under citrus production along the East Coast, where deficiencies of micronutrients are wide spread. The current recommendations for micronutrient man agement for citrus (Koo et al., 1984; Knapp, 1992) are based on research conducted prior to the 198s (Ander son, 1984, 1986; Anderson and Leonard, 1982; Leonard, 1969; Leonard and Calvert, 1971; Stewart and Leonard, 1963). Accordingly, for correction of Mn and Zn deficien cies, foliar applications of 2-6 lb metallic Mn and lb metallic Zn per acre in the form of either nitrates, sulfates, or oxides were recommended. Foliar application of Fe is generally not effective for correction of Fe deficiency. Therefore, soil application of chelated Fe has been recom mended at oz Fe/tree (Koo et al., 1984; Leonard and Calvert, 1971). During recent years, considerable progress has been made in the development of micronutrient formulations for foliar applications. No information is available on the efficacy of some of the newer formulations for correcting micronutrient deficiencies in citrus. The objectives of this study were to determine: (1) the metallic rates of Mn, Zn and Fe in a foliar spray program required to correct mod erate to severe deficiencies of these micronutrients in ma ture citrus trees, and (2) the effects of type of chelate base used in micronutrient formulations on the efficacy of foliar uptake of the above micronutrients. Materials and Methods The experiment was started during spring of 1991 in Indian River County using 8-yr-old navel orange trees on Swingle citrumelo rootstock planted (25 x 15 ft) on double row beds. The soil was partly Manatee loamy fine sand and Rivera fine sand and some of its chemical properties are shown in Table 1. A soil sample was taken from each of 5 replicate plots per treatment at the -6 inch depth in the spring of Soil ph was measured in water and.1m CaCl2 at 1:1 ratio of soil solution. Concentrations of vari ous elements (Table 1) in Mehlich 3 extraction (Mehlich, 1984) were determined by using inductively coupled plasma emission spectroscopy (ICPES). During 1991, 6 sources of micronutrients were evaluated (Table 2). Except for the dry mix and EDTAchelated forms, the sources were in liquid concentrate form with respective chelate bases. All sources, except EDTA-chelated, were applied at 1. Mn, 1. Zn, and.25 Fe lb of metal per acre per year (high rate) and 5% of this rate (low rate) (Table 3). The EDTA-chelated source was applied at the low rate and manufacturer's recom mended rate (.26 Mn,.28 Zn, and.26 Fe lb per acre per year). The control treatment received routine grove care sprays without any sources of Fe, Mn, or Zn. All treat ments received uniform application of Cu as Champ (23% Cu hydroxide) at the rate of 2 gal/5 gal spray solution which was applied over the entire grove at the rate of 167 gal/acre. The fertilizer application, irrigation, and pesticide programs were according to the routine commercial grower practice but did not include any micronutrient ap plications. The annual rates of metals were sprayed in 2 equal applications during March and August of 1991 and Mature spring flush leaves were sampled for analyses in August prior to application of August spray. Summer flush leaves were again sampled in November. Therefore, at the time of sampling of mature spring flush leaves, the trees received only 5% of the annual metallic rates. An airblast sprayer calibrated at 167 gal/acre and set Table 2. Composition of various sources of micronutrients evaluated in this study. Sources of micronutrients Composition Nitrates Alpha keto acid* Lignin sulfonate Gluco heptanate NZN Dry mix EDTAchelated Forms of micronutrients Nitrates of «Nitrates of Fe and Mn; and NZN Nu-iron, Mn sulfate, Zinc oxide EDTAchelated Fe, Mn and Zn Chelate base Lignin sulfonate Gluco heptanate EDTA NO,-N (%) Urea-N (%) Concentrations (%) offe/mn/zn 1.5/6/6.75/3/3.75/3/3.75/3/3.75/3/3 3/13/ /13/14 *Not used during season. Proc. Fla. State Hort. Soc. 15:

3

4 Table 5. Concentrations of various nutrients in 5-month-old spring flush of 8-yr-old Navel orange trees on Swingle citrumelo rootstock. All values are means across 13 treatments with 5 replications (n = 65) during , and 16 treatments with 5 replications (n = 8) during Mean concentrations Nutrients N P K Ca Mg Na Cu zstandard deviation of the mean. yno data. Percent on dry wt. basis 2.72 ±.4z NDy.17 ±.3.15 ± ± ± ± ± ±.3.23 ±.3 ND.8 ±.2 ppm on dry wt. basis 14 ± ± 1.4 leaves of trees treated with Zn in the form of dry mix (high rate), or as nitrates or lignin sulfonate formulations (at low rate of Zn) were significantly greater than those of trees which received low rate of Zn as alpha keto acid or gluco heptanate formulations (Table 4). Concentrations ofmacronutrients and Cu in spring flush, and season: The concentrations of macronutrients and Cu in the spring flush leaves showed no significant differences be tween the treatments. Accordingly, mean concentrations are presented (Table 5). The mean concentrations fell within the optimum to high range for N, optimum for P, K, Ca, and Cu (during the first year only), and low for Mg (Koo et al., 1984). Considering the high soil ph (Table 1), the low concentration of Mg was expected. During the sec ond year, the concentration of Cu was much greater than that during the first year. micronutrient sprays did not show a significant increase over those of trees in the control treatment (Table 3). This was also true for Fe in the summer flush. In 5 out of 13 treatments, concentrations of Fe in summer flush leaves were within the optimal range. Although this seemed to indicate an improvement in Fe nutrition of these trees, spring flush leaves during the subsequent year showed Fe concentrations in the low range in all of 16 treatments (Table 4). The concentrations of Mn in the summer flush increased significantly in the trees which received Mn with NZN source as compared to those of trees in the other treatments including the control. The concentrations of Zn in the summer flush were significantly greater in the trees which received NZN source of Zn as compared to those of trees which were untreated or which were sprayed with Zn in all the other forms except nitrate or dry mix formulations. The concentrations of Zn in the summer flush of NZN treated trees were within the recommended optimal Zn concentrations. Concentrations of Fe, Mn, and Zn in spring flush, season: Very marginal responses to the various sources of micronutrients, in terms of concentrations in the leaves, suggested that the rates of micronutrients applied during the first year were inadequate for correcting severity of deficiencies existing in the experimental grove. Therefore, the metallic rates were doubled during the second year of the trial. However, the concentrations of all 3 micronut rients in the spring flush of 1992 did not increase to the optimal range (Table 4). Therefore, even the increased rates applied during the second year were not adequate to overcome the deficiencies in the spring flush. The concen trations of Fe in the leaves were not significantly influ enced by any of the foliar treatments as compared to those of leaves of trees which were untreated (Table 4). The concentrations of Mn in the leaves were significantly greater in the trees which received nitrate source of Mn as compared to those of the trees which were untreated or which received EDTA-chelated Mn at only.26 lb Mn per acre per year rate. With respect to the concentration of Zn, none of the treatments significantly increased the Zn levels in the leaves as compared to those in the leaves of un treated trees. However, the concentrations of Zn in the Proc. Fla. State Hort. Soc. 15: Conclusions The results of this study demonstrate that annual foliar applications of.5-1. lb each of Mn and Zn and lb Fe were not adequate to correct moderate to severe deficiencies of these micronutrients in mature citrus trees evaluated in this study. It should be emphasized that the purpose of this study was not to evaluate the maintenance applications of micronutrients, instead, to evaluate the ef fects of foliar applications of varying rates and sources of micronutrients to correct moderate to severe deficiencies of all 3 micronutrients in a mature citrus grove in a calcare ous soil. Chelate-based formulations of these micronutri ents showed very minor differences with respect to the efficiency of their uptake by the citrus leaves. Although there may have been cases in the past showing significant response to foliar application of micronutrients, those studies were all conducted by treating the trees with hand gun application, in which case the application rates of each metal per tree are very high. In contrast, the current study was done using commercial airblast sprayer taking into ac count variable losses during application of the micronu trients in commercial production conditions. The metallic rates will be further increased during the third year of the trial in order to determine the rates of these metals re quired to overcome the severity of deficiencies. The cor rection of deficiencies is evaluated on the basis of concen trations of the micronutrients in the leaves. Literature Cited Anderson, C. A Micronutrient uptake by citrus from soil applied zinc compounds. Soil Crop Sci. Soc. Fla. Proc. 43: Anderson, C. A Mineral uptake by citrus trees from soil applied manganese compounds. Soil Crop Sci. Soc. Fla. Proc. 45:46-5. Anderson, C. A. and C. D. Leonard Comparison of several zinc foliar treatments for the correction of zinc deficiency in citrus trees. Soil Crop Sci. Soc. Fla. Proc. 41: Knapp, J. L Florida citrus spray guide. Fla. Coop. Ext. Serv., Inst. Food Agr. Sci., Univ. Fla., Gainesville, FL. SP 43. p. 46. Koo, R. C. J Citrus micronutrients in perspective. Soil Crop Sci. Soc. Fla. Proc. 47:9-12. Koo, R. C. J., C. A. Anderson, I. Stewart, D. P. H. Tucker, D. V. Calvert, and H. K. Wutscher Recommended fertilizers and nutritional sprays for citrus. Agr. Expt. Sta., Inst. Food Agr. Sci., Univ. Fla., Gainesville, FL. Bui. No. 536D. p. 3. Koo, R. C. J. and R. L. Reese The effects of omitting single nutrient 73

5 elements from fertilizer on growth and performance of Pineapple Mehlich, A Mehlich 3 soil test extractant: A modification of orange. Proc. Fla. State Hort. Soc. 84: Leonard, C. D A comparison of soil and spray applications of four manganese sources for control of manganese deficiency in 'Valencia' Mehlich 2 extractant. Commun. Soil Sci. Plant Anal. 15: Stewart, I. and C. D. Leonard Effect of various salts on the avail ability of zinc and manganese to citrus. Soil Sci. 95: orange trees. Proc. Fla. State Hort. Soc. 82:12-2. Leonard, C. D. and D. V. Calvert Field tests with new iron chelates on citrus growing on calcareous soils. Proc. Fla. State Hort. Soc. 84: Proc. Fla. State Hort. Soc. 15: VARIATION IN EXTRACTABLE MINERAL ELEMENTS IN THE SOIL UNDER THREE CITRUS ROOTSTOCK TESTS Heinz K. Wutscher U.S. Department of Agriculture Agricultural Research Service U.S. Horticultural Research Laboratory 212 Camden Road, Orlando, FL 3283 Additional index words, soil variability, regional differences. Abstract. Soil ph and Mehlich 1 - ex tractable P, K, Ca, Mg, Na, Fe, Mn, Zn, and Cu under 5 trees of 'Valencia' orange on each rootstock in 2 rootstock tests in the flatwoods and 1 on the ridge involving 15 rootstocks were compared. Soil variability in tests 12 years old or older was greater in the flatwoods than on the ridge. Of trees on 4 rootstocks common in all 3 tests, the soil under trees Rangpur X Troyer had a higher ph and higher levels of P and K than soil under trees on sour orange. It is often assumed that soil in level, well-prepared blocks of trees is uniform if there are no visible signs of differences. There are few tree-by-tree studies to show that there can be differences, especially in the flatwoods (Cohen, 198; Don Myhre, personal communication). Brams and Fiskell (1967) studied variability of extractable nutrients in a 'Valencia' grove on the ridge and the impor tance of multiple sampling for estimating nutrient status and standardization of where the soil samples are taken in relation to the trees. Sampling under the dripline reduced variability compared to sampling in the middles, and root mineral content showed little similarity with soil nutrient levels. Trees modify the soil around their roots through nutrient uptake and exudation of compounds (Anony mous, 1951; Buckman and Brady, 196), effects that are influenced by rootstocks. Sampling and analyzing the soil around individual trees of approximately the same age in 3 rootstock tests was a way to determine the amount of soil variation under these trees. Materials and Methods Soil samples were taken at 3 locations with a 2.5-cm diameter auger to a depth of 3 cm at 4 sides under the The author is grateful to Mr. Orie Lee and Coca-Cola Foods for mak ing trees available for this study. Mention of a trademark, warranty, proprietary product, or vendor does not constitute a guarantee by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products or vendors that may also be suitable. dripline of each tree. The 4 cores were combined into 1 sample and brought to the laboratory in plastic bags. The planting design at Locations 2 and 3 was randomized, com plete blocks; therefore, sampling 5 replications of trees on different rootstocks provided a good pattern for multiple sampling of the areas. Location 1 was a demonstration planting with solid blocks of trees on different rootstocks distributed in an irregular pattern in a rectangular block. Five randomly selected trees in each plot were sampled. All groves were on level, unbedded land. Location 1 was irrigated by overhead gun, Location 2 by microsprinklers, and Location 3 by overhead sprinklers. Well water was used at all sites. Locations 1 and 2 were near St. Cloud, Florida, in the upper flatwoods area, 3 miles apart. Location 1 was land that had been in citrus at least 7 years, mostly Blanton soil (loamy, siliceous, thermic, Grossarenic Paleudults) that was reworked by shallow plowing in 1974 before the present trees were planted. The trees were 'Valencia' on 13 rootstocks, 11 of which were included in the analyses, planted at 4.5 x 7 m spacing. Samples were collected in September 1991, the rootstocks were the citrumelos, Citrus paradisi Macf. x Poncirus trifoliata (L.) Raf., Swingle, F8-3 and F8-8; Carrizo citrange, P. trifoliata x C. sinensis (L.) Osbeck; C , a Rangpur x Troyer, C. reticulata Blanco hybrid X (P. trifoliata X C. sinensis) hybrid; rough lemon, Milam (a rough lemon variant), and Volkamer lemon, C. limon Burm. f.; sweet lime, C. aurantifolia L. (Christm.) Swing.; sour orange, C. aurantium L.; and Cleopatra mandarin, C. reticulata Blanco. Location 2 was virgin land deep-plowed in 1979 and planted with 'Valencia' on 13 rootstocks, 8 of which were used in the test. The soil was mostly Pomona (sandy, silice ous, hyperthermic Ultic Haplaquods), with Myakka (sandy, siliceous, hyperthermic Aerie Haplaquods), Holopaw (loamy, siliceous, hyperthermic Grossarenic Ochraqualfs), Immokalee (sandy, siliceous, hyperthermic Arenic Hap laquods), and Ona (sandy, siliceous, hyperthermic Typic Haplaquods) in parts of the grove. Samples were taken in September 1991, 7 of the 8 rootstocks were the same as at Location 1 (Swingle citrumelo, Carrizo citrange, Rangpur x Troyer, Volkamer lemon, sweet lime, sour orange, and Cleopatra). The soil under trees on English small-flowered trifoliate orange, P. trifoliata, was also sampled, the trees were spaced 4.5 x 6.6 m. Location 3 was typical, deep sandy ridge land planted to citrus over 5 years near Sebring, Florida. The Valen cia' test on 19 rootstocks was planted 3.75 x 7.5 m on Candler sand soil (hyperthermic, uncoated Typic 74 Proc. Fla. State Hort. Soc. 15: 1992.