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D. R. Earhart, M. L. Baker and F. J. Dainello

In a field experiment, fertilizer source (poultry litter vs. commercial), plastic mulch, row cover, and fertilizer rate (residual from 1990 study vs. additional) were applied in factorial combinations to determine the effect on vegetative growth and production of triploid watermelons. Litter (3.12 % total N) was re-applied at the rate of 13.2 Mt·ha-1 along with commercial fertilizer (6N-10.5P-20K) at 1.1 Mt·ha-1. Plastic mulch showed the greatest influence on vegetative growth and production variables by increasing vine length 26.1 cm, leaf area 61.8 cm2, yield 4207 kg·ha-1, melon number 741 ·ha-1, and average melon weight 0.8 kg, over unmulched plots. Plastic mulch with or without row cover increased melon number significantly when compared to plots without mulch or row covers. Poultry litter increased vine length, yield, and average melon weight 15.4 cm, 1971 kg·ha-1, and 0.5 kg, respectively, when compared to commercial fertilizer. Poultry litter in combination with row cover increased yield by 3864 kg ·ha-1 over commercial fertilizer with row cover, and approximately 2567 kg·ha-1 over poultry litter and commercial fertilizer without row cover. Additional fertilizer increased average melon weight 1.3 kg.

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M.L. Baker, D.R. Earhart and V.A. Haby

When poultry litter (PL) is applied to meet the nitrogen (N) needed for plant growth, phosphorus (P) can accumulate, leading to non-point source pollution of surface water. This study was conducted at Overton, Texas on a Bowie fine sandy loam (fine-loamy, siliceous, thermic, Plinthic Paleudults) to investigate the use of warm- and cool-season forage legumes in rotational cropping systems to remove excess P. Cropping systems were: spring legume—fall vegetable (SL-FV), spring vegetable—fall legume (SV-FL), and spring vegetable-fall vegetable (SV-FV). Warm- and cool-season legumes were Iron and Clay cowpea and crimson clover, respectively. Poultry litter rates were 0, 1X, 2X, 4X, and commercial blend (CB) as subplots. Fertility treatments were applied to vegetable plots only. The crop, IX PL and CB rate for each season were: spring 1995—watermelon, 2.2 t·ha-1, 48.8N—12.2P—28K kg·ha-1; fall 1995—turnip, 8.3 t·ha-1, 89.6N—24.4P—28K kg·ha-1; spring 1996—tomato, 6.7 t·ha-1, 100.9N—17.1P—78.5K kg·ha-1. Soil P increased at all depths sampled (0-15, 15-30, and 30-45 cm) as PL rate increased. Residual P from CB was equal to the control. Through spring 1996, soil P concentration in the surface 0-15 cm was increased by all systems. System SV-FL reduced P accumulation by 35.6 mg·kg-1 when compared to SL-FV and 44.7 mg·kg-1 when compared to SV-FV. Residual P continued to increase as PL rate increased. Rate of increase was reduced by a system of SV-FL.

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D.R. Earhart, M.L. Baker and V.A. Haby

Phosphorus (P) concentration in surface waters from non-point agricultural sources is an increasing resource management concern. This study was conducted at Overton, Texas, on a Bowie fine sandy loam (fine-loamy, siliceous, thermic, Plinthic Paleudults) to evaluate cool-season legumes for P uptake following poultry litter (PL) application rates on spring vegetables. Treatments were PL rate (0, 1X, 2X, 4X) and a commercial blend (CB) for comparison. Cool-season legumes, consisting of crimson clover, berseem clover, hairy vetch, and red clover, were the subplots. The vegetable crop in Spring 1995 was watermelon. The 1X PL rate was 2.2 t·ha-1 and the CB was 44.8N-0P-32.5K kg·ha-1. Dry matter yield was decreased by the 4X PL rate. Plant P concentration increased linearly as PL rate was increased. The greatest P uptake (4.1 kg·ha-1) was at the 2X rate. Hairy vetch had the greatest yield (1,875 kg·ha-1), plant P concentration (0.53%), and P uptake (9.6 kg·ha-1). PL rate increased soil P concentration at all depths. The least amount of P accumulation was from CB and was equal to the control. Hairy vetch appears to have the capability of removing a greater amount of P and reducing soil concentration when compared to the other legume species tested.

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D. R. Earhart, F. J. Dainello and M. L. Baker

Response of triploid watermelon [Citrullus lanatus (Thunb.) cv. Tiffany] to fertilizer source (FS) [poultry litter (PL) vs. commercial fertilizer (CF)1, black plastic mulch (BPM), and spunbonded floating row cover (SFC) was evaluated in 1990 on an East Texas Fuquay-Darco sandy loam soil. Plant growth and percent soluble solids were equated by FS. Vine fresh weight, number and total melon weight per plot, average melon weight, and percent soluble solids were increased 27%, 29%, 45%, 24%, and 17%, respectively, by BPM when compared to no mulch treatment. BPM + SFC treatment decreased vine fresh weight but increased total melon number which in turn increased plot weight. PL increased plant P, K, and Mg 16%, 12%, and 24%, respectively, when compared to CF. Plant Ca was increased 21% by CF. Plant N, P, Ca, and Mg were increased 18%, 16%, 22%, and 15% by the use of BPM. A reduction in plant N was found when SFC was used alone and with treatments lacking BPM or BPM + SFC. Mean soil temperature was increased on the average 2°C at 10 cm depth by BPM when compared to all other treatments. Mean 24 hr air temperature 2 cm above BP and bare ground under SFC was increased 5°C above ambient.

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D.R. Earhart, M.L. Baker and V.A. Haby

A factored experiment was established at the Texas A&M Univ. Research and Extension Center at Overton in Spring 1995. The objective was to investigate the use of warm- and cool-season legume cover crops in vegetable cropping systems for reducing phosphorus (P) accumulation from poultry litter (PL) and commercial blend (CB) fertilizer. PL rates were based on soil test nitrogen (N) requirement of the vegetable crop and percent N content of the litter. This was considered the 1X rate. Fertility treatments were applied to the vegetable crop only. PL was applied at O, 1X, 2X and 4X rates. CB was applied at recommended rates for N, P, and K. The vegetable crops were: Spring 1995—watermelon; Fall 1995—turnip; Spring 1996—tomato; Fall 1996—collard; Spring 1997—squash. The legumes were: spring—Iron and Clay cowpea; fall—crimson clover. Dry-matter yield of cowpeas and clover was not affected by fertility treatment in any of the years studied to date (Spring 1995, 1996, 1997). Plant concentration of P for both cover crops was increased all 3 years as rate increased. PL applied at the 1X rate maintained P levels in the surface 0—15 cm of soil at 60 mg·kg-1 over the five-season study period. CB maintained levels of P equal to the control. A cropping system of spring vegetable—fall legume greatly reduced P accumulation. A reduction in P was also noted from a system of fall vegetable—spring legume, but not as pronounced. The greatest accumulation was with a system of spring vegetable—fall vegetable.

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John R. Duval, Frank J. Dainello, Vincent A. Haby and D. Ron Earhart

The objectives of this study were to determine if the use of leonardite as a fertilizer supplement improved crop growth and if there was a residual effect from previous applications. Three planting sequences were established and leonardite applied at 0, 50, 100, 200, and 400 lb/acre (0, 56.1, 112.1, 224.3 and 445.6 kg·ha−1). Subplots were treated at the first, the first and second, or all at three planting sequences. `Purple Top White Globe' turnip (Brassica rapa L.) and `Florida Broadleaf' mustard greens (Brassica hirta L.) were used as the indicator crops in the first two and last sequences, respectively. No differences in plant growth were observed among number of applications or treatment rate. Differences in soil potassium and iron were observed.

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J.T. Baker, D.R. Earhart, M.L. Baker, F.J. Dainello and V.A. Haby

Triploid watermelon (Citrullus lanatus Thunb.) was grown on the same plots in 1990 and 1991 and fertilized with either poultry litter or commercial fertilizer. Additional treatments included bare soil or plots mulched with black polyethylene, and plots with or without spunbonded fabric row covers over both bare soil and mulch. Watermelon yields were unaffected by fertilizer source in 1990 but were significantly higher for poultry litter than for commercial fertilizer treatment in 1991. Polyethylene mulch significantly increased postharvest soil NO3 and leaf N concentrations in 1990 and increased yield and yield components in both years. There were no beneficial effects of row covers on yield in either year, presumably because no early-season freezes occurred.

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D.R. Earhart, V.A. Haby, M.L. Baker and A.T. Leonard

Primary environmental concerns regarding application of poultry litter (PL) for crop production are nitrate leaching into ground water and increased levels of P in the soil that can erode into surface water. This study was initiated to investigate use of warm- and cool-season annual forage crops to remove excess nutrients supplied by PL in rotational-cropping systems on a Bowie fine sandy loam (fine-loamy, siliceous, thermic, Plinthic Paleudults). PL was applied at one (1×) or two (2×) times the recommended rate in the spring, fall, or spring and fall. Rates were based on N requirement of the crop and percent N in the litter. Comparisons were made to fertilizer blends (FB) and control treatments with no PL or FB. After 3 years of treatments, NO3-N increased at the 122-cm depth by 30 and 50 mg·kg–1 from the 1× and 2× rate, respectively. The greatest accumulation was from FB (72 mg·kg–1). With PL applied in spring only, spring vegetables followed by a fall cover showed a significant reduction in NO3-N leaching and accumulation. Regardless of cropping system, rate, or time of application, P concentration increased by 40 mg·kg–1 in the surface 15 cm of soil when compared to FB. If applied in an environmentally sound manner, PL will be less of a threat to pollution of ground water than similar rates of FB. Applying PL rates sufficient to meet crop needs for N results in P accumulation that can lead to nonpoint source pollution of surface waters.

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J. V. Davis, D. R. Earhart, A. T. Leonard and V. A. Haby

The potential for east Texas to produce Brassica that could compete favorably with the import market exists. This study was conducted to establish optimum nitrogen and boron rates for 4 Brassica spp. grown on highly leachable east Texas soil, a Bowie series (fine-loamy, siliceous, thermic, Plinthic Paleudult). Broccoli (Brassica oleracea L. Italica, var. Green Comet), cauliflower (Brassica oleracea L. Botrytis var. White Contessa), Chinese cabbage (Brassica rapa L. Pekinensis var. Monument), and Chinese mustard (Brassica rapa L. Chinensis var. What-A-Joy) were field grown using 5 rates of N (0, 50, 100, 150, and 200 kg·ha-1) interacted with 3 rates of B (0, 1.25 and 2.5 kg·ha-1) in a complete randomized design with 3 reps. Harvested broccoli heads increased average head weight (HW), average head size (HS), and total yield (Y) for each increase of N. Cauliflower HW, HS, and Y increased up to 150 kg N ha-1. B supplementation did not statistically affect HW, HS, and Y of broccoli or cauliflower. Chinese cabbage Y increased up to 150 kg N ha-1 and produced less Y at 200 kg N ha-1 than at 50 kg N ha-1. Chinese mustard Y increased 50% for the 50 (kg·ha-1) N over no added N with additional N producing statistically equal Y. B at 1.25 (kg·ha-1) significantly increased cabbage Y, but had no effect on mustard Y.

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A. T. Leonard, D. R. Earhart, J. V. Davis and V. A. Haby

The increase of the Asian population in Texas has created a demand for specialty vegetables including Chinese cabbage. Chinese cabbage (Brassica rapa L. Pekinensis var. Monument) was grown in a greenhouse to study the main effects of P, K, Ca, Mg, S, Fe, Mn, Zn, B, and Mo on plant growth. A randomized complete block design with 4 replications was used. The elements were incorporated and tested at three rates in soil from the Ap horizon of the Darco series (loamy, siliceous, thermic Grossarenic Paleudult). Treatments consisted of a check, where no nutrients were incorporated, all nutrients incorporated at 1X rates, and all nutrients at 2X rates. Each nutrient was tested individually at the 0 and 2X rates, while the remaining nutrients were held constant at the 1X rate. Analysis of variance indicated plant growth was affected by applications of P, K, S, Zn, B, and Mo. Regression analysis indicated positive growth responses to P, K, S, and Zn, and negative growth responses due to B and Mo applications.