PHOSPHORUS AND COPPER EFFECTS

Transcription

1 EVERETT ET AL: PHOSPHORUS COPPER WATERMELONS 155 PHOSPHORUS AND COPPER EFFECTS ON GROWTH AND YIELD P. H. Everett, S. J. Locascio, AND J. G. A. FlSKELL1-2 Abstract OF WATERMELONS yields of some crops are reduced. The purpose of the work reported here was to evaluate fac torial combinations of P and Cu rates and to determine if these two elements interact in their effect on growth and yield of watermelons. The field experiments at Immokalee and Gainesville, conducted on virgin flatwood soils, factorial combinations of different rates of cop per and phosphorus were evaluated for their effect on growth and yield of watermelons. At Immokalee, there was a linear increase in yield with phosphorus (P) applications up to 15 pounds per acre. Phosphorous rates of 157 and 21 pounds per acre gave no further yield in crease and there was a trend toward slightly reduced yields at these high P rates. The yield also increased linearly as the copper rate in creased from to 4 pounds of metallic copper (Cu) per acre. In one experiment () yields were significantly affected by the interaction between P and Cu. The addition of one of these elements without the other resulted in no signifi cant yield increase. But with the addition of both the yield increase was highly significant. At Gainesville, only the main effects of P and Cu rates significantly influenced yield. However, a trend for an interaction of these elements occurred. For example, maximum yield with.5 pounds of Cu per acre was obtained when the P rate was 7 pounds per acre. But with 4 pounds of Cu per acre the highest yield was reached with 14 pounds of P per acre. Introduction The authors, in previous work (5, 6, 7), have reported a watermelon yield response to increas ed levels of both P and Cu. However, in these experiments P and Cu were studied separately and information was not obtained on the effect of combinations of the two elements on yield. There is evidence in the literature (1, 2, 3) that under certain conditions increased applications of P may decrease the plant absorption of cer tain minor elements to such an extent that lassociate Soils Chemist, South Florida Field Laboratory, Immokalee; Associate Horticulturist, Department of Vege table Crops; and Soils Biochemist, Department of Soils, Florida Agricultural Experiment Stations, Gainesville. 2Florida Agricultural Experiment Stations Journal Ser ies No Experimental Procedure Field experiments were conducted at Immo kalee in the springs of 1965 and using "Charleston Gray" watermelons as the test crop. In both experiments the field plots were located on recently cleared virgin Immokalee fine sand having an initial soil ph of 4.4. Lime, at a rate equivalent to two tons per acre each of dolo mite and high calcium limestone, was broadcast and disked into a depth of six inches. Factorial combinations of three rates of Cu and five rates of P were evaluated each year. The copper rates were, 2 and 4 pounds of metallic Cu per acre in combination with, 52, 15, 157 and 21 pounds per acre of P. Field plots were arranged in randomized block designs with there replications of each treat ment. The plots were seeded in late January of each year. Each plot contained five hills of watermelons with a plant spacing of 3' x 1/ All plots received a uniform application of 12 pounds of nitrogen (N) and 2 pounds of potassium (K) per acre. The N was derived from ammonium nitrate and ammonium sulfate (1:1.62 ratio) and the K from potassium sul fate. Various complete fertilizers were formu lated by mixing the N and K source materials with appropriate amounts of superphosphate to give the desired rates of P. Copper was added, as copper sulfate, to the various fertilizer form ulations to give the desired rates of Cu. These complete fertilizers containing N-P-K and Cu were applied in three equal applications, each being equivalent to 1 pounds per acre. Be cause of excessive rainfall during the ex periment the plots were side-dressed with an additional 2 pounds of N and 66 pounds of K per acre. In both experiments the soil in the plot area and the superphosphate used in the fertilizers were analyzed for their Cu content. In 1965 the soil and superphosphate contained approximate ly 1. and 2 ppm Cu, respectively. In

2 156 FLORIDA STATE HORTICULTURAL SOCIETY, these values were 1.5 ppm Cu in the soil and 9.5 ppm Cu in the superphosphate. Early vine-growth was evaluated by measur ing the length of the main runner approximately seven weeks after planting. Yield data were compiled for the weight and number of market able melons per acre and for the average weight per melon. At Gainesville, in a 2 x 4 factorial ex periment was conducted to compare two rates of Cu in combination with four rates of P for their effect on yield of "Charleston Gray" water melons. The Cu rates were.5 and 4. pounds of metallic Cu per acre and the P rates were, 35, 7 and 14 pounds of P per acre derived from ammoniated superphosphate and diammonium phosphate. The plot area was located on virgin Leon fine sand and the watermelon plants were grown on raised beds nine feet apart with plants spaced five feet apart in the row. The treatments were arranged in randomized blocks with four repli cations. The soil was limed at a rate equiva lent to three tons per acre on December 2, Complete fertilizers were formulated to give the desired Cu and P rates with the N and K held constant. The N was derived from ammonium nitrate and the K was derived equally from sulfate and muriate of potash. All plots received a total of 13 pounds of N and 18 pounds of K per acre from this complete fertilizer. Beds were made up and one-half of the fertilizer was banded in the bed on March 4,. Water melons were planted on the same day. The re maining one-half of the fertilizer was banded about 12" from the row center on April 28. Two side-dressings of 15 pounds per acre each of were applied on May 11 and on May 23,. Results The main effects of P and Cu rates in 1965 and at Immokalee are shown in Tables 1 and 2. In both experiments the yields increased linearly up to 15 pounds P per acre. However, in 1965 the yield increase between the zero and 52-pound rates was not significant, but in there was a highly significant yield increase from the addition of 52 pounds P per acre. Dur ing both years the yields at the 157 and 21- pound rates were less than at the 15-pound rate. This reduction in yield at the higher P rates was significant in but not in Table 1. Main effects of phosphorus rates on early vine growth and marketable yield P - rates of watermelons at Inunokalee. Tons of melons/a Vine length (in.) Z F value: P effects cubic in 1965** and **. Vine growth and watermelon yield increased quadratically with increased rates of applied Cu in both years (Table 2). The greatest response occurred between the zero and the 2 pounds of Cu per acre rates. The yield with 4 pounds of Cu per acre was significantly higher than with 2 pounds of Cu per acre in but not in The yield increase obtained in the two experi ments resulted from an increase in number and size of melons with the higher rates of both P and Cu. The early vine-growth where P was applied was significantly better than without P. However, growth was not increased by P rates higher than 52 pounds per acre, but neither was it reduced at higher P rates, as was the case with the yield. Differences in early growth between the 2 and 4-pound rates of Cu were not observed but growth at both Cu rates was much better than the growth when Cu was not added. In both the early vine-growth and mar ketable yields (Figures 2 and 3) were signifi cantly affected by both P and Cu rates. With out P, increased rates of Cu had little effect on growth, but with the addition of 52 pounds of P per acre there was a significant increase in growth at the 2 and 4 pounds rates of Cu. Rates of P higher than 52 pounds per acre re sulted in no increase in growth at that time with any of the Cu rates. The interaction effect of P and Cu on yield was even more pronounced. Table 2. Main effects of copper rates on early vine growth and marketable yield of Cu - rates 2 4 watermelons at Immokalee. Tons of meions/a Vine length (in.) F value: Cu effect is quadratic in 1965 and **.

3 EVERETT ET AL: PHOSPHORUS COPPER WATERMELONS 157 The addition of one of these elements without the other resulted in no significant yield in crease. When both P and Cu were applied to the plant there was a highly significant increase in yield. For example, when Cu was not added to the fertilizer, a yield of 7.4 tons was not in creased with the addition of P. But, where 2 pounds of Cu were added, fruit yield increased to 28 tons with the addition of 15 pounds of P. Where 4 pounds of Cu were supplied, the fruit yield increased to 3.9 tons with 15 pounds of fertilizer P. Although the similar effect of P and Cu on the 1965 yield (Figure 1) was not signficant the yield curves showed a trend which was similiar to that observed in. The main effect of P rates on yield in the experiments at Gainesville (Table 3) was a significant increase in yields (tons of melons per acre) with higher rates of P. This re sponse was not as great as in the Immokalee experiments. Yields were increased from 7. tons without added P to 9.8 tons with the addi tion of 7 pounds of P. Number of melons and the average weight of melons were increased but not significantly. The main effects of Cu rates on yield at Gainesville are given in Figure 4. When the added Cu was increased from.5 to 4. pounds per acre the yield, both tons and number of melons per acre, increased significantly. The average weight per melon was not affected. At Gainesville, the combined effects of P and Cu fertilization resulted in an interesting trend, although these yield differences were not statis tically significant (Figure 4). Maximum yield with.5 pounds of Cu per acre was obtained when the P rate was 7 pounds per acre. How ever, with 4 pounds of Cu per acre the highest yield was reached with 14 pounds of P per acre. Discussion The positive growth and yield response ob tained with increased rates of P in these experi ments resulted because there was a very low level of native P in the virgin flatwood soils on which these tests were conducted. The available soil P in the check plots was six and eight CO UJ X Q > 5- COPPER RATE 4 LB/A * - 2 LB/A NO Cu id Z UJ COPPER RATE 4 LB/A»- 2 LB/A *. * NO Cu Fig: 1. Watermelon yields as affected by P and Cu appli cations at Immokalee Fig. 2. Early vine growth as affected by P and Cu ap plication at Immokalee..

4 158 FLORIDA STATE HORTICULTURAL SOCIETY, Table 3. P - rates Main effects of phosphorus rates on watermelon yields at Gainesville. HeIons ton/a Melons number/a Av. Wt. lb./melon F values: P rade is linear** for tons of melons but not significant for number or average weight. pounds per acre P (ammonium acetate extractable at ph 4.8) at Immokalee and Gainesville, respectively. Plants which did not receive fer tilizer P were stunted early in the season (Table 1) and vine-growth lagged behind those that received phosphate. This lag period continued until the main vine had reached a length of several feet. The vine-growth which occurred subsequently was fairly vigorous, but never equal to the growth of plants supplied with P. This increased growth, late in the season, was probably the results of the roots extending into a larger volume of soil; this may indicate an early restriction of roots subjected to a limited P supply. This further emphasized the need for an adequate P supply for early plant develop ment, particularly, at lower temperatures which prevailed during the early part of these experi ments. The greatest variation in yield between 1965 and at Immokalee was where phos phate was not used. This seasonal response also could have been a location response because new land was used each year. From the similar soil test values for native soil P the location effect was not believed to be the major factor. Possibly the seasonal variation was a temperature effect. In 1965 when the melon yield without added P were almost double that in, the average maximum and minimum air temperatures were 6.2 and 2.4 F higher during the first six weeks of the test. The lower temperatures in could have retarded root-growth, thus making the limited supply of native soil P even more critical. Several workers (4, 8, 9), using test crops other than watermelons, have reported a close association between soil temperature and P uptake and their combined effect on plant growth. The higher yields with increased rates of Cu, both at Immokalee and Gainesville, further con firmed the earlier studies (6, 7) reported by the COPPER RATE.5 LB/A 4. LB/A Fig. 3. Watermelon yields at affected by P and Cu applications at Immokalee Fig. 4. Watermelon yield as affected by P and Cu fer tilization at Gainesville..

5 ORSENIGO: CELERY SEEDBED HERBICIDES 159 authors. The greater response to Cu in as compared to 1965 could not be explained on the basis of native soil Cu since this value was approximately the same both years. It is possi ble that the lower temperatures experienced in could have accentuated the Cu deficiency by reducing root-growth, thus limiting the soil volume from which the plant could absorb Cu. Copper-deficiency symptoms on plants not fertlized with Cu were much more pronounced in than in In 1965 the superphosphate contained 2 ppm Cu; therefore, when super phosphate was added Cu was also added. This may have been sufficient to mask Cu deficiency in the no-cu treatment, with a resultant higher yield. A similar situation existed in, but the Cu content of the superphosphate was only 9 ppm; therefore, the Cu added as a contami nant was less than in The effect of Cu fertilization on yield re sponse to P fertilization is shown in Figure 3. Both Cu and P were necessary to produce opti mum yields on virgin flatwood soils. The reduc tion in yield at the two higher P rates, even when 4 pounds of Cu per acre were added, sug gested the possibility of an antagonistic effect of P at the highest rates. The effect of high P absorption on Zn, Cu and Fe uptake has been reported (1, 2, 3) to occur under certain condi tions on several crops. It was evident that on virgin flatwood soils, similar to those on which the above experiments were conducted, the P requirement of water melons was approximately 15 pounds P (24 lbs. P2O5) per acre and the Cu above 2 pounds per acre. With Cu deficiency, response to phos phate fertilization was likely to be much less than where Cu was added or was adequate. Similarly, on new land, when well-limed, P was likely to be a limiting factor on growth and melon yield. From the present studies, both Cu and P were found to be major limiting factors for melon production on flatwood soils. There fore, the fertilization of melons on these soils should include Cu in the fertilizer unless ade quate Cu is known to be present in the soil or suitable Cu sprays are employed. LITERATURE CITED 1. Bingham, F. T Relation between phosphorus and micronutrients in plants. Soil Sci. Soc. Amer. Proc. 27: Bingham, F. T. and M. J. Garber Solubility and availability of micronutrients in relation to phosphorus fertilization. Soil Sci. Soc. Amer. Proc. 24: Burleson, C. A., A. D. Dacus, and C. J. Gerard The effect of phosphorus fertilization on the zinc nutrition of several irrigated crops. Soil Sci. Soc. Amer. Proc. 25: Dadykin, V. P Soil temperature as one of the factors determining the effectiveness of fertilizer. Pachvovedenie: (Cited from Proc. Amer. Soc. Hort. Sci. 75: 61-61). 5. Everett, P. H The effects of superphosphate on watermelon yields. Proc. Fla. State Hort. Soc. 74: Locascio, S. J., P. H. Everett, and J. G. Fiskell Copper as a factor in watermelon fertilization. Proc. Fla. State Hort. Soc. 77: Locascio, S. J. and J. G. Fiskell.. Copper require ments of watermelons. Proc. Amer. Soc. Hort. Sci. 88: Locascio, S. J. and G. F. Warren Interaction of soil temperature and phosphorus on growth of tomatoes. Proc. Amer. Soc. Hort. Sci. 75: Robinson, R. R., V. G. Sprague, and C. F. Gross The relation of temperature and phosphate place ment to growth of clover. Soil Sci. Soc. Amer. Proc. 23: POSTEMERGENCE HERBICIDES FOR CELERY SEEDBEDS1 J. R. Orsenigo2 Slow-growing celery seedlings cannot com pete effectively with annual weeds for nutrients, water, space and light. The control of weeds essential in celery seedbeds can be timeconsuming and expensive. Off-season and preplanting cultivation and flooding programs miti gate but not eliminate weed infestations. Preseeding soil fumigation treatments may not ef fectively control annual weeds on the organic lflorida Agricultural Experiment Stations Journal Ser ies No Associate Horticulturist, University of Florida, Ever glades Experiment Station, Belle Glade. soils of the Florida Everglades. Mechanical weed control methods are not applicable to broadcast or drill-seeded celery seedbeds. Man ual weed control may be costly and tedious; some broadleaf weed species are difficult to dis tinguish from celery seedlings during thinning, handweeding and transplant pulling operations. CDAA and CDEC3 are widely used for posttransplanting application (3), but these chemi cals are not well tolerated by germinating celery seed and young seedlings. Experience in pri- 3CDAA is 2-chloro-N, N-diallylacetamide. CDEC and other herbicides pertinent to this report are identified in Table 1.