WATERMELON RESPONSE TO COPPER AND A COMPLETE MICRONUTRIENT SOURCE1

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1 0 FLORIDA STATE HORTICULTURAL SOCIETY, 966 WATERMELON RESPONSE TO COPPER AND A COMPLETE MICRONUTRIENT SOURCE S. J. Locascio, J. G. A. Fiskell, P. H. Everett, and j. m. crall Abstract On a virgin Lakeland sand and Norfolk loamy sand near Westville, additions of pounds per acre of Cu to a -0-0 fertilizer increased fruit yields 8% over yields from plots fertilized with -0-0 alone. Cu additions to a fertilizer increased yields 6%. The addition of 0 to 60 pounds per acre of Frit 0 to the -0-0 fertilizer resulted in a yield equivalent to that produced where Cu alone was added. On Blanton and Lakeland soils at Leesburg and at Live Oak, the addition of Cu or Frit did not significantly affect the fruit yields. Cu levels in plant tissues were high at both locations and were not increased by Cu fertilization. On a virgin Leon fine sand at Gainesville and on an Immokalee fine sand at Immokalee, a lack of Cu in the fertilizer resulted in severe Cu deficiency symptoms. Cu additions to the -0-0 fertilizer increased yield,600% and 900% at the respective locations. Cu additions to the fertilizer used resulted in yield in creases of,900% and 00% at these locations. At Gainesville, a further yield increase was ob tained with the addition of Frit 0 to the -0-0 fertilizer. Tissue Cu was increased with Cu or Frit application on both soils. Native Cu levels in these soils were between and. These data would indicate that with these Cu levels on flatwoods soils having relatively high organic matter content, Cu fer tilization is necessary for economical water melon production. Introduction The need for Cu fertilization of organic soils for vegetable production () and on sandy soils lflorida Agricultural Experiment Stations Journal Ser ies No.. Associate Horticulturist, Vegetable Crops Department, Gainesville. Soils Biochemist, Soils Department, Gaines ville. Associate Soils Chemist, South Florida Laboratory, Immokalee. Plant Pathologist, Watermelon and Grape In vestigations Laboratory, Leesburg, IFAS, University of Florida. for citrus () has long been recognized. Re cently, the need for supplemental Cu was dem onstrated for watermelons grown on virgin Leon soil (). A response to Cu was also indi cated on Immokalee fine sands by a yield in crease and higher tissue Cu content with addi tions of Frit and Es-Min-El to the fertilizer (). Earlier work by the authors () indicated that the Cu requirement for watermelons is over. pounds per acre and could be supplied in the fertilizer or as foliar sprays. Copper requirements of watermelon has not been studied on upland soils. The purpose of experiments reported here was to evaluate watermelon response to Cu and a complete micronutrient source when grown on flatwoods and upland soils typically used for watermelon production. Experimental Procedure Six experiments were conducted on flatwoods and upland soils throughout Florida in the spring of 966. Locations, soil type, and soil Cu contents are shown in Table. Lime was ap plied as needed. Treatments used were as fol lows: () -0-0 fertilizer formulated from NHNO, (NH)HPO,KC and K^SO.,, () -0-0 plus pounds per acre Cu from CuSO.HO, () formulated from NHNO, ammoniated superphosphate, and KC, () plus pounds per acre Cu, () -0-0 plus 0 pounds per acre of Frit 0 and (6) -0-0 plus 60 pounds per acre of Frit 0. All treatments were applied at each location except that treatments and 6 were not used at Immokalee. rates in all treatments were equivalent to,00 pounds per acre of at Immokalee and Leesburg. These were applied in equal applications at Immoka lee. At Leesburg, one-third was applied in the bed at planting and the remaining two-thirds were banded 8 inches from the bed center 6 weeks later. rates were equivalent to,600 pounds per acre of at the other loca tions. These were applied in applications. 'Charleston Gray' watermelons were grown in plots 0-0 feet long with replications in all

2 LOCASCIO ET AL: WATERMELONS MICRONUTRIENTS experiments. Row widths were 0 feet apart at Immokalee and Leesburg and 9 feet apart at the other locations. Plant spacing varied from to feet between the different locations. Watermelons were seeded at Immokalee on February. Whole plants were taken for chem ical analysis () at.thinning on March 8, and mature leaves were taken on May 0. The crop was planted on March, at Gainesville and whole plants were taken at thinning on May. At Leesburg, seeding occurred on February 8, and mature leaf samples were taken on April 9. Seeds were planted at Live Oak on March, and whole plants were sampled at thinning on April. At Westville, the crop was seeded on February. Fruit were harvested in or more pickings as they matured. Results and Discussion Flatwood Soils: The response to Cu fertiliza tion was somewhat similar on the Leon and Immokalee soils at the widely separate locations. Additions of Cu to either the -0-0 or fertilizer significantly increased early watermel on plant growth at Immokalee (Table ). Vine lengths of plants receiving Cu were over 0 inches long as compared to vine lengths of - inches in plots without additional Cu. The Cu and P contents of whole plants taken at thin ning were also increased by this treatment. Where Cu was not added to the fertilizer, tissue Cu and B contents were much higher with the fertilizer than with the Foliar symptoms typical of Cu deficiency be came evident at both Immokalee and Gainesville as runners began to develop. Symptoms were severe in all plots not receiving additional Cu or micronutrients in the fertilizer. Similar symptoms of Cu deficiency on Leon fine sand have been previously described (, ). The Cu content of mature tissue increased and the B content decreased with Cu additions to both fertilizers at Immokalee. Fruit yields were increased from.7 to 7. tons with the addition of pounds per acre of Cu to the -0-0 fertilizer. Similar Cu additions to the fertilizer increased yields from. to. tons. The slightly higher yield without Cu added to the fertilizer as compared to the -0-0 fertilizer without Cu was probably as sociated with a higher Cu content in the fertilizer (). This was also indicated by the higher tissue cu content of plants fertilized with the. On the Leon soil at Gainesville (Table ), Cu and P in the plant tissue were increased with Cu additions to the -0-0 and fertilizers. Tissue P contents were lowest in plants receiv ing the fertilizer without Cu. Early plant growth was extremely poor in plots receiving the -0-0 fertilizer without Cu. Growth of plants receiving without Cu was nearly normal at that time. Later growth, however, was greatly reduced and severe symptoms of Cu deficiency developed. Fruit yield from these plots without additional Cu averaged 0. tons per acre. The addition of pounds per acre of Table. Location, soil type and preplant analysis of soils used in the experiments. Location Soil type PH Ca Mg K Cu O.M.- Immokalee Immokalee f.s Gainesville Leon f.s Leesburg Blanton f.s..6 0 Live Oak Lakeland s Westville Norfolk l.s Westville Lakeland s Organic matter content.

3 FLORIDA STATE HORTICULTURAL SOCIETY, 966 Table. Effect of Cu and micronutrients on early watermelon plant growth, tissue composition, and fruit yield on flatwoods soils at Immokalee and Gainesville No treatments Plants at Cu B W >m thinning P Sizea inches Mature Cu tissue B P Yield Immokalee' lb/a Cu + lb/a Cu.. 7.,0.,7 6.,.,,.6, ,.,.0, ,. 8, b Gainesville lb/a Cu + lb/a Cu -0-OK0 lb/a Frit 0-0-0^-60 lb/a Frit 0, gm,,,.9, avine measurements made four days after thinning. bf value: Immokalee.. Early Cu and P contents and vine length were higher** with treat ments and than with treatments and. B was lower** with treat ment than with,, or. Cu contents of mature tissues were increased** by treatments and but B contents were reduced**. Fruxt yields were increased** by treatments and. a Tissue Cu and P content and fruit yields were higher** with treat ments and than with treatments and. Cu content and plant dry weight increased with increased rates of Frit* these values, B content, and yield for treatments and 6 were higher** than with treatments,,, and. Cu to the -0-0 fertilizer increased yields to.9 tons and to 0.9 tons when Cu was added to the fertilizer. The addition of 0 pounds per acre of Frit 0 to the -0-0 further in creased yield to.8 tons per acre. At both Gainesville and Immokalee, the use of the with added Cu resulted in higher yields than the -0-0 with added Cu. This may indicate that some other micronutrient in addition to Cu was also limiting growth and being supplied in the. Further evidence of this is indicated by higher yields at Gainesville in plots receiving the -0-0 fertilizer with 0 pounds per acre of Frit 0 (a complete micronutrient source). Upland Soils: Early plant growth and de velopment was good at both the Leesburg and Live Oak locations. treatment signifi cantly influenced Cu and B content of mature tissue at Leesburg and young plant tissue at Live Oak (Table ). Although yields tended to be slightly higher with Cu or Frit additions to the fertilizer, treatment did not have a signifi cant effect on yield. Tissue Cu levels at both

4 LOCASCIO ET AL: WATERMELONS MICRONUTRIENTS Table. Effect of Cu and micronutrients on the tissue composition and yield of watermelons at Leesburg and Live Oak No. treatments Leesburga Mature tissue Cu B Fruit yield Young Cu Live Oaka plants B Fruit yield lb/a Cu i f+ lb/a Cu lb/a Frit lb/a Frit af values: Leesburg. Treatments and showed higher Cu content in mature tissue than and *. Cu* and B** content increased with increased rates of Frit (treatments and 6). B content was higher** with Frit treatments than others. Fruit yield was not significantly affected by treatment. Live Oak. Treatment had no effect on Cu content of young tissue. B content was higher** with Frit treatments. Fruit yield was not significantly affected by treatment. locations were relatively high even without the addition of Cu or Frit to the fertilizer. West Florida Upland Soils: Severe deficiency symptoms were not observed in either experi ment conducted at Westville. Plant growth rates in all plots appeared to be similar. The only visual symptom observed was in the experiment conducted on the Lakeland fine sand. Plants growing in these plots without added Cu or Frit in the fertilizer were slightly chlorotic. Even though yields tended to increase with Cu addi tions to the fertilizer on both soils (Table ), these differences were not significant when the two experiments were considered separately. When data from both experiments were pooled, significant differences were found. Fruit yield was increased significantly with the addition of Cu to the -0-0 and fertilizers. This in crease was. tons with the -0-0 fertilizer and.0 tons with the fertilizer. The ad dition of Frit to the -0-0 fertilizer did not increase yields beyond that obtained with the use of Cu alone. Results of these experiments indicate that Cu fertilization of watermelons grown on flatwoods soils was necessary to prevent Cu defici ency from limiting yield. Yield responses to Cu fertilization on the upland soils occurred on of the soils studied. These responsive soils had total Cu contents of.60 and.8. Al though yields increased from to 6 tons with the addition of pounds per acre of Cu to the fertilizer, Cu deficiency symptoms were not evi dent. On flatwoods soils which contained con siderably higher Cu levels, responses to Cu were in the 0 to 0 ton range; also, Cu deficiency symptoms were severe where Cu was not added. It is probably that watermelons were better able to utilize Cu in the better drained upland soils due to greater root penetration. Flatwoods soils tended to restrict root growth because of their poorly drained, acid nature (). Also, total soil Cu was probably not a satisfactory indicator of the need for Cu fertilization. The availability of Cu appeared to be related to the level of soil organic matter (7). On soils with high organic matter content (above %), the Cu response, and therefore the requirement, was greater than where this content was lower. In these studies, added Cu on upland soils did not visibly improve

5 FLORIDA STATE HORTICULTURAL SOCIETY, 966 Table. Effect of fertilizer treatments on watermelon yield at two Westville locations No. treatment Soil Typea Norfolk l.s. Lakeland s. Mean tons/a lb/a Cu lb/a Cu lb/a Frit lb/a Frit af values: Treatment responses were similar at both Westville locations, Mean yields from the two locations for treatments and were higher** than yields from treatments and. plant growth even though yields were sometimes increased. On these soils with low organic mat ter, responses to Cu fertilization are most like ly to occur where yields are high due to a greater Cu need and to depletion of the low native Cu levels. Since watermelons are generally grown on "new land," the possibility of micronutrients, particularly Cu, limiting growth should be con sidered. Tests to date (,, 6) indicated that on flatwoods soils such as Leon and Immokalee sands, maximum yields have been obtained where pounds per acre of Cu as copper sulfate were added to the fertilizer. Similar high yields have been obtained with the addition of Frit 0 and Es-Min-El to the fertilizer at the rate of 0-60 pounds per acre. In the fertilization of welldrained upland soils such as Lakeland and Blanton sands, the need for Cu appears to be less than on flatwoods soils having a similar Cu content. To insure against the possibility of Cu limiting production, similar materials can be added to the fertilizer. It was noteworthy that in none of these experiments has the addition of these materials significantly reduced yields, while in many experiments, yields have been substantially increased. Acknowledgements The authors wish to acknowledge the assis tance of Dr. H. H. Bryan, H. W. Lundy, J. E. Davis, L. M. Scott, and L. D. Taylor, in con ducting these experiments. LITERATURE CITED. Allison, R. V., O. C. Bryan and J. H. Hunter. 97. The stimulation of plant response on the raw peat soils of the Florida Everglades through the use of copper sul fate and other chemicals. Fla. Agric. Exp. Sta. Bui Everett, P. H., S. J. Locascio, and J. G. Fiskell. 96. Factors involved in liming soil for watermelon pro duction. Proc. Fla. State Hort. Soc. 78: Floyd, B. F. 97. Dieback, or exanthema of citrus trees. Fla. Agric. Exp. Sta. Bui. 0.. Locascio, S. J., P. H. Everett and J. G. Fiskell. 96. Copper as a factor in watermelon fertilization. Proc. Fla. State Hort. Soc. 77: Locascio, S. J. and J. G. Fiskell Copper re quirements of watermelons. Proc. Amer. Soc. Hort. Sci. 88: Locascio, S. J. and H. W. Lundy. 96. Lime and minor element studies with watermelons. Proc. Fla. State Hort. Soc. 7: Steenbjerg, F., and E. Boken. 90. Copper contents and copper deficiency in Danish soil types. Plants and Soils. : 9-.