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  • Author or Editor: R.J. Dufault x
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A 5-year study using winter cover crops (wheat or rye, crimson clover, and fallow) in a tomato and bean rotation indicated several soil responses to the cover crops. Advantages of crimson clover winter cover crop to the soil in a tomato-bean rotation included adding organic matter to the soil, which resulted in an increase in the amount of inorganic nitrogen in the upper levels of the soil profile and an increase in the soil's water-holding capacity. An additional benefit of winter cover crops to the soil was the potential of reduced nitrogen leaching.

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Cucumber and potato crops were tested in a rotation with winter cover crops at different locations in Georgia, North Carolina, and South Carolina from 1991 to 1994. Biomass DM of vegetable crops was greatest when grown after crimson clover. Clover plantings resulted in a greater biomass than wheat when preceded spring cucumber crop. Vegetable biomass produced on clover plots or with N rates of 60 to 120 kg·ha–l was equivalent. Nitrogen recovery by cover and vegetable crops was enhanced by clover plantings. Clover biomass (tops only) provided an average of 138 kg N/ha for the cucumber crop, compared to an average of 64 kg N/ha provided by wheat. Nitrogen recovery by vegetable crops was also enhanced with 60–120 kg N/ha rates. Yields were highest when high N rates were used and when crops were produced on clover plots. Vegetable yield, cover crop biomass, and N recovery were positively correlated with vegetable biomass and applied N.

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Tomatoes and beans were grown in rotation for 4 years with three cover crop treatments (bareground, wheat, and crimson clover) and three nitrogen rates (0, 60, and 120 kg N/ha). Over the course of the study, when no additional N was provided, lowest yields of tomatoes and beans were obtained with the wheat cover crop. With the highest N rate, however, there was little difference in yields of beans or tomatoes with any of the cover crop treatments. Considering the benefits associated with the use of cover crops, it is encouraging to see that with proper N amendment, yields obtained with cover crop systems can be comparable to conventional bareground systems.

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Pepper and sweet corn were tested in a rotation with crimson clover and velvet bean (Mucuna pruriens) cover crops at different locations in Georgia, North Carolina, and South Carolina from 1995 to 1996. Vegetable production with minimum-till following the cover crops was compared with two different conventional methods (following rye cover or fallow). All minimum-till/cover crop treatments caused reduction of total number of pepper fruit, compared to the conventional methods. Effects on premium grade (Fancy + U.S. #1) were similar to the effects on total fruit. The highest percentage of premium grade was produced by both conventional methods in 1996. Sweet corn responded similarly to these treatments in 1995. However, in 1996, clover plots had corn yields nearly as good as the conventional plots. As in bell pepper, plots with velvet bean cover produced lower yield in 1996. Treatment effects on number of marketable corn were the same as the effects on total ears produced.

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A vegetable production system using winter cover crops and N rates was evaluated for several years in Georgia, South Carolina, and North Carolina. Snap bean, cucumber, tomato, potato, and sweetpotato crops were tested at different locations. Cover crop plots produced higher yields and better quality in all locations as seasons progressed over 4 years. Soil N levels in fallow, wheat, and clover plots were similar at initiation, but N gradually increased in clover plots in successive years. Yield and quality of root crops improved with Crimson clover without N applications compared to fallow plots with 60 kg N/ha. Effects on yield and tuber size are discussed. Nitrate and NH4-N in the soil profile from 15- to 150-cm depth were monitored at all locations. Nitrogen availability, depletion, and leaching below the root zone were determined. At low N rate, clover plots had slightly higher NO3 in the soil profile; however, at high N rate, N supply by clover was not as critical, and N leaching was detected at much lower depths than at low N rates.

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Abstract

‘Champion’, ‘Georgia’, ‘Heavicrop’, and ‘Vates’ collards (Brassica oleracea L. var acephala) were planted in Fletcher and Lewiston, N.C.; Charleston, Clemson, and Florence, S.C.; and Attapulgus and Plains, Ga. to determine the most reliable method to predict harvest maturity based on temperature. Although cultivar differences existed within some of the planting dates, when pooled over all planting dates, cultivars yielded similarly within locations. Eight methods of calculating heat units from planting to harvest were applied to daily maximum and minimum air temperatures supplied from local weather bureaus for the spring and fall growing seasons from 1985 through 1987 in the three-state area. Coefficients of variation were used to determine which method was most reliable in predicting day of first harvest. The method with the lowest cv was to sum, over days for planting to harvest, the difference between the daily maximum and a base temperature of 13.4C; however, if the maximum was >23.9C, the base temperature was subtracted from an adjusted maximum equal to 23.9C minus the difference between the maximum and 23.9C. This method produced a cv of 9.1% compared to 11.4% for the standard method of summing the mean temperature minus the base of 4.4C over the entire growing season, or compared to 13.4% for counting days to harvest from planting.

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Interest in producing specialty melons (Cucumis melo) is increasing in Florida, but information on yield performance, fruit quality, and disease resistance of specialty melon cultivars grown in Florida conditions is limited. In this study conducted at Citra, FL, during the 2011 Spring season, 10 specialty melon cultivars were evaluated, in both certified organic and conventionally managed fields, including: Creme de la Creme and San Juan ananas melon (C. melo var. reticulatus), Brilliant and Camposol canary melon (C. melo var. inodorus), Ginkaku and Sun Jewel asian melon (C. melo var. makuwa), Arava and Diplomat galia melon (C. melo var. reticulatus), and Honey Pearl and Honey Yellow honeydew melon (C. melo var. inodorus). ‘Athena’ cantaloupe (C. melo var. reticulatus) was included as a control. ‘Sun Jewel’, ‘Diplomat’, ‘Honey Yellow’, and ‘Honey Pearl’ were early maturing cultivars that were harvested 10 days earlier than ‘Athena’. ‘Athena’ had the highest marketable yield in the conventional field (10.7 kg/plant), but the yield of ‘Camposol’, ‘Ginkaku’, ‘Honey Yellow’, and ‘Honey Pearl’ did not differ significantly from ‘Athena’. Under organic production, ‘Camposol’ showed a significantly higher marketable yield (8.3 kg/plant) than ‘Athena’ (6.8 kg/plant). ‘Ginkaku’ produced the largest fruit number per plant in both organic (10 fruit/plant) and conventional fields (12 fruit/plant) with smaller fruit size compared with other melon cultivars. Overall, the specialty melon cultivars, except for asian melon, did not differ significantly from ‘Athena’ in terms of marketable fruit number per plant. ‘Sun Jewel’, ‘Diplomat’, and ‘San Juan’ showed relatively high percentages of cull fruit. ‘Honey Yellow’, ‘Honey Pearl’, and ‘Sun Jewel’ exhibited higher soluble solids concentration (SSC) than ‘Athena’ in both organic and conventional fields, while ‘Brilliant’, ‘San Juan’, and ‘Ginkaku’ also had higher SSC than ‘Athena’ under organic production. ‘Honey Yellow’, ‘Sun Jewel’, ‘Brilliant’, and ‘Camposol’ were less affected by powdery mildew (caused by Podosphaera xanthii) and downy mildew (caused by Pseudoperonospora cubensis) in the conventional field. ‘Honey Yellow’ and ‘Camposol’ also had significantly lower aboveground disease severity ratings in the organic field compared with ‘Athena’, although the root-knot nematode (RKN) (Meloidogyne sp.) gall rating was higher in ‘Honey Yellow’ than ‘Athena’.

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