WATERMELON PRODUCTION1

Transcription

1 EVERETT, LOCASCIO, FISKELL: LIMING WATERMELONS Orsenigo, J. R. and H. Y. Ozaki Herbicide evaluations at Plantation Field Laboratory, sea son. Plantation Field Laboratory Mimeo Report PFL Overman, A. J. and D. S. Burgis Soil nematocides and fungicides for the production of field seeded vegetables on sandy soils. Fla. Agr. Exp. Sta. Ann. Rep., pp Ozaki, H. Y Frost protection studies for vege table crops on the lower east coast a preliminary report. Proc. Fla. State Hort. Soc. 76: Rhoades, H. L Petroleum mulch. Fla. Agr. Expt. Sta. Ann. Rep., p Scudder, W. T. and J. F. Darby Equipment for the application of plastic and petroleum resin emulsions. Proc. Fla. Sta. Hort. Soc. 76: Stall, R. E. and N. C. Hayslip Mulching: trial Fla. Agr. Exp. Sta. Ann. Rep., p Sutton, P. and A. N. Brooks Fertilizer rates and plastic mulch for pepper. Fla. Agr. Expt. Sta. Ann. Rep., p o 41. Takatori, F. H., L. F. Lippert, and F. L. Whiting The effect of petroleum mulch and polyethylene films on soil temperature and plant growth. Proc. Amer. Soc. for Hort. Sci. 85: Thompson, B. D Plastic mulches for vege table crops. Fla. Agr. Expt. Sta. Ann. Rep., p Wilcox, G. E., G. C. Martin and R. Langston Root zone temperature and phosphorus treatment effects on tomato seedling growth in soil and nutrient solutions. Proc. Amer. Soc. for Hort. Sci. 8: FACTORS INVOLVED IN LIMING SOIL FOR WATERMELON PRODUCTION1 P. H. Everett, S. J. Locascio AND J. C. FlSKELL2 Abstract Experiments were conducted on acid flatwoods soils to determine the influence of such factors as time interval between liming and seeding, width and depth of lime placement, and rates of lime on the growth and yield of water melons Results show that when the time interval be tween liming and seeding is decreased from eight weeks to one day, there was no reduction in the growth or yield of watermelons. Both vine growth and yield were increased as the width and depth of lime placement increased. Higher yields and more vigorous vine growth were associated with higher lime rates. Introduction A review of the literature reveals that the benefits from the use of lime for watermelon production have not been consistent. Hartwell and Damon (4) reported a reduction in water melon yield with increased levels of lime. Locas cio and Lundy (6) reported that application of lime on soils where the ph was above significantly decreased watermelon yield in one experiment and had no significant effect on yield in four other experiments. Hartman and Gaylord (3) also found no effect on watermelon yield lflorida Agricultural Experiment Stations Journal Series No Associate Soils Chemist, South Florida Field Laboratory, Immokalee; Associate Horticulturist, Department of Vege table Crops; and Biochemist, Department of Soils, Florida Agricultural Experiment Stations, Gainesville. due to liming. In contrast, Eisenmenger and Kucinski (1) obtained an increase in early yield, and Waters and Nettles (8) reported an increase in both early total yield of watermelons with increased increments of lime. In recent work by the authors (5) a high degree of watermelon response was obtained to liming very acid flatwood soils. On these soils where the native soil ph was a linear yield increase was obtained with increased rates of lime to 6,4 pounds per acre of calcic limestone. Seedlings died without added lime. Everett (2) indicated the association of higher watermelon yields with increased levels of both soil and tissue calcium. A large part of the watermelons produced in Florida are grown on virgin f latwood soils which are very acid. The purpose of the studies report ed in this paper was to determine the influence of time, width, depth and rate of lime on the growth and yield of watermelons produced on these acid soils. Experimental Procedure Time Interval Study. Experiments were conducted at the South Florida Field Laboratory. in 1964 and 1965 to evaluate the effect of the time interval between liming and seeding on the growth and yield of Charleston Gray watermel ons using seep irrigation. In both years the field plots were located on virgin Immokalee fine sand with initial soil ph of 4.2 in 1964 and 4.4 in In 1964 the time intervals were 1, 1, 3 and 6 days. The field plots were arranged in a randomized block design with four replica tions of each time interval. The plots were 14 x 3 feet with one row containing 1 hills spaced

2 178 FLORIDA STATE HORTICULTURAL SOCIETY, 1965 three feet apart in the row. Lime equivalent to two tons per acre each of dolomite and calcic limestone was broadcast, ftat the appropriate time interval before seeding, over the entire plot area and then mixed with the top 6 inches of soil. At time of planting the beds were constructed using the limed soil. In 1965, the same time intervals between applying lime and planting seed were used, but the experimental design was altered to include three rates of lime;, 2 and 4 tons per acre. Factorial combinations of the three lime-rates and four time-intervals were arranged in randomized blocks with four replications of each combination. The field plots were feet with one row containing five hills spaced three feet apart in the row. The lime, equal parts dolomite and calcic limestone, was applied in the same manner as in In both years all plots were fertilized with three applications * of each equivalent to 1, pounds per acre. In 1964, 13-4 top-dresser at 1 pounds per acre was applied twice, and in 1965 a top dresser at the same rate was applied once. Early growth was evaluated by measuring the length of the main -runner and by observation of the general conditions of the plants. Soil samples were taken periodically during the experiments and were analyzed by the meth ods of the Florida Agricultural Extension Ser vice, Soil Testing Laboratory. In addition to the field studies, a laboratory experiment was conducted to study the progress of nitrification in newly limed soil, as compared to that in unlimed soil and soil that had been limed for several months. Two bulk soil sam ples of Immokalee fine sand were taken in May 1965 from the field plots. One sample was from the unlimed plots and the other from plots that were limed in October, Nitrate nitrogen was removed from the sample by washing with water. After washing lime equivalent to two tons per acre each of dolomite and calcic lime stone were mixed with one half of the bulk sam ple from the unlimed plots; no lime was added. to the other one half. No additional lime was added to the other bulk sample that had been previously limed. The rate of nitrification in these three soils, i.e., unlimed, newly limed and previously limed, was ascertained by determining nitrate nitrogen after, 9, 18 and 28 days. A similar experiment was conducted using Leon fine sand. Width of Lime Placement. In order to de termine if the entire bed need be limed to obtain optimum plant growth and yield, a width of liming experiment was conducted at Gainesville in 1964 with overhead irrigation. The field plots were located on a virgin Leon fine sand (ph 3.6) and were arranged in a randomized block design with six replications of each lime width. The plots were 9 x 3 feet with one row of plants containing six hills spaced five feet apart in the row. Yields were taken from only the four inside hills of each plot. Calcic limestone was applied at a rate equivalent to 3,2 pounds broadcast per acre on the beds in the following widths; no lime, 1, 2, 4 and 8 feet. In addition, the one-foot rate was applied in a two-inch band with the fertilizer, which gave a total of six treatments in the experiment. The lime was incorporated with the soil to a depth of 4 to 5 inches by roto-tilling. The beds were then re built by means of a bedder. A fertilizer was applied at 1,6 pounds per acre in split applications: one-half at planting and one-half at thinning. Two side-dressings of were applied during the season, the first at 8 pounds and the second at 2 pounds per acre. Plant stand counts were made early in the season and again after the final harvest. The effect of lime width on plant vigor was evaluated twice during the experiment by use of a numer ical rating system. Soil samples and leaf samples from near the runner tips were taken on May 15. Rate and Depth of Lime Placement. In 1965, at Gainesville, a 3 x 3 factorial experiment was conducted on a virgin Leon soil to study the effect of lime rate and depth of lime placement on the yield of Charleston Gray watermelons. The three rates of lime were 2, 4 and 6 tons of calcic limestone per acre and the three depths of place ment were -6, -12 and -18 inches. In addition to these nine treatments, a no-lime treatment was also included. The plots were 12x4 feet and the lime was applied on the basis of an acre six inch; for example, the six tons per acre applied -18 inches was actually 18 tons per acre of area. The field plots were arranged in randomized design with four replications of each treatment. All plots received a fertilizer at a rate of 1,6 pounds per acre applied in a split appli cation of 8 pounds per acre each. Copper sulfate was added to the fertilizer to supply two pounds of metallic copper per acre. Two sidedressings of were made, each at the rate of 1 pounds per acre. Copper sprays at one pound copper sulfate per acre were applied

3 EVERETT, LOCASCIO, FISKELL: LIMING WATERMELONS 179 twice during the season. Soil samples from the -6, 6-12 and inch depths were taken on April 1, and leaf samples of recently matured leaves were collected on June 1. Data were com piled on the weight and number of marketable melons and on the total number of melons. Results and Discussion Time Interval Study. Results from both the 1964 and 1965 experiments show that decreas ing the time interval between liming and seeding had no significant effect either on early vine growth (Table 1) or on yield (Table 2) of watermelons grown on a newly cleared acid flatwoods soil. When the rates of lime were varied in the 1965 experiment (Table 3) it was found that both early growth and yield increased linearly as the lime rate increased. The yield increase resulted from both an increase in number and size of melons from the higher lime rates. On March 22, plants in the unlimed plots were start ing to show symptoms of "wilt." By April 19, all plants in these plots had died, and some wilt was evident at the higher lime rates. A Fusarium was isolated from the wilted plants but inoculation studies have not as yet shown it to be pathogenic to watermelons. Efforts along this line are being continued. The finding that the amount of "wilt" decreased as the lime rate increased (Table 3) is in agreement with Stoddard (7) who reported that liming the soil to ph 6. reduced the incidence of Fusarium wilt of muskmelons as compared to that in soils of ph 4.8 or 4.1. In the laboratory study it was found that there was a lag period in the rate of nitrifica tion in a newly limed soil as compared to the same soil that had been limed for several months (Figure 1). With the Immokalee soils this lag Table 2. Effect of time interval between liming and planting on watermelon yield. Time interval (days) 1 i-i 32 6 Tons of melons/acre F values: Time interval not significant. Table 3. Effect of lime rates on early vine growth, yield, and on the severity of "Wilt11 of watermelons (1965). Lime rate (tons/a)* 2 4 L.S.D..5.1 Vine length (inches)** Yield (tons/a) Wilt *Equal parts dolomite and calcic lime stone. **Average per plant. r fi&u&i, nmmcavou rate is^ SOSLS AS INFLUENCED 8Y LIME. Table 1. Effect of various time intervals between liming and planting on early growth of watermelons. Time interval (days) Vine length (inches)* Average of 16 plants per treatment. F values: Time interval not significant. BAYS *»CUQAT { Figure 1. Rate of nitrification in newly limed soil as compared to that in previously limed and unlimed soils.

4 # 18 FLORIDA STATE HORTICULTURAL SOCIETY, 1965 period existed less than 28 days. With the Leon soil, the magnitude of the lag period was greater and still existed after 28 days, which was the last sampling date. The slightly decreased rate of nitrification in newly limed soil does not pre sent a serious problem because sufficient nitrate nitrogen for early growth can be supplied in the fertilizer. The increase in nitrification rate in the limed soils as compared to the unlimed soil indicates one important benefit that may be expected from liming either Immokalee or Leon fine sand. The initial and final soil ph of the two soils used in this test are shown in Table 4. After 28 days the ph of the newly limed soils was approximately the same as the ph of the corresponding soil that had been previously limed. There was a much greater increase of soil ph after 28 days in Immokalee fine sand than in the Leon fine sand, indicating a greater buffer capacity due to a higher organic matter content in the Leon soil. The results from these studies concerning the time interval between liming and seeding show that in a virgin sandy soil of low ph, calcium and buffer capacity, the full benefit of lime is derived even though it may be applied only a short time before planting, rather than two to six months as normally recommended. This does not necessarily mean that the lime has reached a state of equilibrium in the soil. However, it does indicate that if there, are sufficient particles of lime in the soil, regardless of how long they have been there, plant roots can develop and function normally. The significant of these findings is two-fold. First, it has practical application in that a grow er, for various reasons, may fall behind schedule in his preparation for planting. As a result of this delay there may be only a few days to apply lime before the desired planting date. In the past, if this situation occurred, the grower either postponed planting to allow enough time for the lime to "react" thus disrupting his entire time table for production and marketing, or in some cases did not apply any lime, which resulted in poor yields. Second, and of equal importance, in certain areas of Florida lime stimulates the growth of common bermudagrass, which can be a serious weed pest in watermelon fields. If lime is ap plied well in advance of planting the bermugagrass problem is increased due to the time allowed for regrowth. On the other hand, if lime is applied shortly before planting there is less time for the grass to form a heavy cover, thus reducing to some extent this weed problem. It should be emphasized that these results are not contradictory to the time honored recom mendation of applying lime well ahead of plant ing, but rather give a grower.the alternative of decreasing the time interval between liming and seeding if either of the two situations discussed above should arise. Width of Lime Placement, Seedling emer gence was not greatly affected by lime width. However on the no-lime and the two-inch-band plots growth was very slow after emergence and many seedlings died before reaching the three true leaf stage. As the season progressed there was a striking increase in vine growth and vigor as the width of the lime band increased (Figure 2). The effects of the width of the lime band on watermelon yield and on certain soil and plant properties are shown in Table 5. Yield increased linearly as the lime width increased from two to eight feet. No fruits were harvested from lime widths less than two feet or from the nolime plots. Soil ph was affected very little by lime width and was still quite low even after the addition of 3,2 pounds of lime per acre. In contrast, the exchangeable soil calcium and the calcium in the leaves increased linearly as the lime width increased. Rate and Depth of Lime Placement. The marketable yields of watermelons shown in Table 6, increased linearly as the depth of liming and rate of liming increased. The interaction between depth and rate was not significant. At the -6 depth yield was not affected by lime rate, while at the -12 and -18 inch depths, the yield tended to increase linearly with increased rates of lime. The figures in Table 7, showing the total number of fruit set, include both marketable and unmarketable melons. The total number of fruit set increased significantly in a linear fash ion as the depth of lime placement increased. Table 4. Initial and final soil ph (1:2 soil-water slurry) of soils used in nitrification study Soil Unlimed treatment Newly limed 4 tons/a Previously limed 4 tons/a TniDolcalee f.8. Initial Final Leon f t 8 Initial ft nal

5 EVERETT, LOCASCIO, FISKELL: LIMING WATERMELONS 181 Figure 2. Growth of watermelon vine as affected by width of lime band. Band widths, left to right: Top: No lime, 2 inches, and 1 foot. Bottom: 2, 4 and 8 feet. A linear increase in fruit set was obtained with increased lime rates but the response was not significant. The data from the width and depth of lime placement experimetns are consistent in that the results from both studies revealed a direct rela tionship between the growth and yield of water- melons and the volume of soil limed. For example, in both experiments there was little growth and even death of some plants where lime was not applied and in other treatments Table 6. Effect of rate and depth of lime placement on watermelon yield. Table 5. Effect of width of lime band on watermelon yield, soil ph, exchangeable soil calcium and leaf calcium Lime width Mo lime 2 inches 1 foot 2 feet 4 feet 8 feet Melons Tons per acre Number Soil ph Exchange Ca ppm Leaf Ca F values: Lime width had a highly significant linear effect on tons and number of melons per acre. Lime - Tons Depth of lime placement Rate per acre 6" -6" -12" -18" me a Tons of melons/acre Depth mean F values: Depth of lime - highly significant Lime rate - significant Depth x rate - not significant

6 182 FLORIDA STATE HORTICULTURAL SOCIETY, 1965 Table 7. Effect of rate and depth of lime placement on the total number of fruit set. Lime - Tons per acre 6" Depth of lime placement Rate -6" -12" -18" mean Fruit set (1/acre) Depth mean 1, F values: Depth of lime - highly significant Lime rate - not significant Depth x rate - not significant the vine length was correlated with the width or depth of lime applied. This indicates that the unlimed soil was toxic probably due to the presence of soluble aluminum in the very acid soil. Similarly in beds inadequately limed, i.e., with narrow bands or shallow depths, roots that grew into unlimed soil were also subject to in jury. This would explain why there was no yield increase with higher lime rates when the lime was applied to a depth of only six inches. It is apparent from these lime rate and placement studies that watermelon plants will not grow in very acid soil. Past wory by Locascio and Lundy (6) and by the authors (5) indicate that lime is the major limiting factor on flatwood soils where the ph is below 5. With the addition of lime, certain micronutrients, spe cifically copper, often become the limiting factor (5) and should be included in the fertilizer after liming these soils. Summary Experiments in 1964 and 1965, conducted on an acid, Immokalee fine sand revealed that there was no significant effect on growth or yield of Charleston Gray watermelons when the time be tween liming and seeding was reduced from 6 days to 1 day. In the 1965 experiment, when lime rates of, 2 and 4 tons per acre were used, there were significant increases in both vine growth and yield as the lime rate increased. In this same experiment a wilt, presumably Fusarium, invaded the plants and was much less severe at the highest lime rate. In the unlimed plots there was a 1 per cent loss of plants due to wilt. Lime placement studies in 1964 and 1965, conducted on a very acid, Leon fine sand showed that there were significant increases in growth and yield as the lime placement increased from a band two inches wide to a band eight fe& wide and the depth of placement increased from six to 18 inches. There was little vine growth and no marketable yield of melons from the un limed plots (p H3.5) in either experiment. Lime rate was varied in the 1965 experiment and the watermelon yield increased linearly as the lime rate increased from to 6 tons per acre. LITERATURE CITED 1. Eisenmenger, W. S., and K. J. Kucinski Mag nesium requirements of plants. Mass. Agr: Expt. Sta. Ann. Rept. p Everett, P. H The effect of superphosphates on watermelon yields. Proc. Fla. State Hort. Soc. 74: Hartman, J. D. and F. C. Gaylord Soil acidity for watermelons on sand. Proc. Amer. Soc. Hort. Sci. 38: Hartwell, B. L., and S. C. Damon The com parative effect on different kinds of plants of liming an acid soil. R. I. Agr. Expt. Sta. Bui 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 H. W. Lundy Lime and minor element studies with watermelons. Proc. Fla. State Hort. Soc. 75: Stoddard, D. L Nitrogen, potassium and cal cium in relation to Fusarium wilt of muskmelon. Phytopath. 37: Waters, W. E., and V. F. Nettles The in. fluence of hydrated lime and nitrogen on the yield, quality and chemical responses of the Charleston Gray watermelon. Proc. Amer. Soc. Hort. Sci. 77: A RAPID SOIL ph TESTER FOR THE HOME GARDENER Seton N. Edson1 Testing for soil reaction or ph is a routine test conducted by agriculturists. Mainly because it has so many direct and indirect implications luniversity of Florida, Gainesville. on soil fertility, it is considered the most impor tant of all soil tests. The term ph may be defined as the negative logarithm of the hydrogen ion concentration in the soil solution. Soil acidity is divided into active acidity and reserve acidity* It is important to