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R.M. Coolman and G.D. Hoyt

The physical characteristics of a particular soil affect its suitability for reduced tillage. Vegetable crops managed with reduced tillage generally will increase crop yields as drainage improves. Under reduced tillage, advantages over conventional tillage include better control of soil erosion, enhanced crop yields, soil water conservation, and more-efficient use of fossil fuel-based nonrenewable resources. Disadvantages with reduced tillage may include reduced soil temperature and increased soil moisture contents in udic soil moisture regimes, which can decrease crop yields.

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R.M. Coolman and G.D. Hoyt

Plant interactions are both competitive and cooperative. Farmers use intercropping to the mutual advantage of both main and secondary crops in a multiple-crop-production system. A vegetable crop has a competitive advantage over a younger secondary cover crop interseeded before vegetable maturity. Non-legume intercropped cover crops can use soil N, while a legume intercrop can increase N in agricultural systems by biological N fixation. Intercropping also may be more efficient than monocropping in exploiting limited resources. Relay-planting main crop and intercrop components so that resource demands (nutrients, water, sunlight, etc.) occur during different periods of the growing season can be an effective means of minimizing interspecific competition. Intercropping systems often exhibit less crop damage associated with insect and plant pathogen attacks, and they provide weed control.

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G.D. Hoyt and J.F. Walgenbach

Conservation tillage systems provide optimum conditions to reduce soil erosion and increase surface soil organic matter. This experiment was established with the long-term goal of developing conservation tillage systems that use either chemical inputs to produce vegetables and control pests, or legume cover crops, biological pesticides, and tillage to provide plant nutrition and control pests. The experiment consisted of cabbage (Brassica oleracea var. L. Capitata Group) grown by traditional-tillage (TT) or strip-tillage (ST) culture using either chemical or organic production methods for pest control. Cabbage heads were heavier with TT than with ST for the chemical production system. Although weed biomass was significantly higher with organic methods, there was a poor relationship between weed biomass at harvest and cabbage head weight. The lack of differences in lepidopterous pest damage suggests that the conservation tillage systems examined likely would not affect lepidopterous pest management systems using biological insecticides. Within tillage treatments, the organic production system resulted in less Alternaria infection than did the chemical production system. Since no fungicides were applied on any treatment, lower disease ratings in the organic production system may have been the result of reduced soil contact of the cabbage leaves from the increased soil coverage by the weed and intercropped legume canopy.

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A.M. Johnson and G.D. Hoyt

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G.D. Hoyt, D.W. Monks and T.J. Monaco

Conservation tillage is an effective sustainable production system for vegetables. No-till planters and transplanters and strip-till cultivation equipment are presently available for most vegetables. Lack of weed management tools (herbicides, cultivators, etc.) continues to be the cultural practice that limits adaptability of some vegetables to conservation tillage systems. Nitrogen management can be critical when grass winter cover crops are used as a surface residue. Advantages of using conservation tillage include soil and water conservation, improved soil chemical properties, reduction in irrigation requirements, reduced labor requirements, and greater nutrient recycling. However, disadvantages may include lower soil temperatures, which can affect maturity date; higher chemical input (desiccants and post-emergence herbicides); potential pest carryover in residues; and enhancement of some diseases.

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Juan Carlos Gilsanz, D. C. Sanders and G. D. Hoyt

Rye plus crimson clover cover crops were followed by spring potato and fall snap bean or sorghum or fallow. The soil samples at 15 cm increments to 90 cm were evaluated for nitrate levels after each crop and cover crop. After the cover crops, soil nitrate levels were reduced relative to the fallow area. After the potato, crop soil nitrate levels increased above initial spring levels due a uniform fertilization due to the amount of N applied and short cycle of the crop. Snap beans and sorghum had increased plant stands and reduced soil impedance after fall cover crops. HOW nitrate levels varied with soil depth and time will be discussed.

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G.D. Hoyt, J.E. Walgenbach and P.B. Shoemaker

This experiment was designed to compare best management practices for conventional and conservation tillage systems, chemical IPM vs. organic vegetable production, and rotation effect on tomatoes. Three vegetables were grown under these management practices with sweet corn (1st year) and fall cabbage or cucumber (2nd year), and fall cabbage on half of the field plots and tomatoes on the other half. The treatments were: 1) conventional-tillage with chemical-based IPM; 2) conventional-tillage with organic-based IPM; 3) conservation-tillage with chemical-based IPM; 4) conservation-tillage with organic-based IPM; and 5) conventional-tillage with no fertilizer or pest management (control). This poster describes sweet corn, cabbage, and cucumber yields from the various treatments over two 3-year rotations. Sweet corn yields were 34% higher in treatments with chemical fertilizer and pest control than with organic methods. Ear worm damage was high (58%) in the organic treatment compared to the chemical IPM program (14%). Fall cabbage was planted after sweet corn and cucumber harvest (all treatments were reapplied). Marketable cabbage yields were in the order: conventional-tilled-organic > strip-tilled-chemical > conventional-tilled-chemical > strip-till-organic > control for both years. Percent culls (< .9 kg heads) were in reverse order of marketable heads. Cabbage insect control was similar in chemical IPM and organic management. Cucumber yields were in the order: conventional-tilled-chemical > conventional-tilled-organic = strip-till-chemical > strip-tilled-organic > control for both years. Insect damage on cucumber fruit was 51% for organic systems and 1% for chemical methods of production. No differences were seen between tillage system within the same production system (chemical vs organic).

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D.C. Sanders, J.C. Gilsanz, W.J. Snerry and G.D. Hoyt

A 3-year study of cover crops (rye + crimson clover or sudex) and vegetable rotation systems was conducted using a Norfolk sandy loam soil. Cash crops were planted on all plots each spring, and in the fall, crops were snap beans/squash, sudex, or fallow. Late incorporation of cover crops depleted soil water content, resulting in a need for irrigation before spring plantings. Sudex residue had a high C: N ratio, delaying the total mineralization of N. Potato yields were not affected by rotation treatments. Cover crops improved snap bean emergence and yield. Snap beans had a differential uptake of Fe, Al, and B with cover crops. Tomato growth and yield were reduced with winter cover crops. Fall squash yield was not influenced by rotations.

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Danielle D. Treadwell, Nancy G. Creamer, Greg D. Hoyt and Jonathan R. Schultheis

A 3-year field experiment was initiated in 2001 to evaluate different organic sweetpotato production systems that varied in cover crop management and tillage. Three organic systems: 1) compost and no cover crop with tillage (Org-NCC); 2) compost and a cover crop mixture of hairy vetch and rye incorporated before transplanting (Org-CCI); and 3) compost and the same cover crop mixture with reduced tillage (Org-RT) were compared with a conventionally managed system (Conv) with tillage and chemical controls. Yield of No. 1 sweetpotato roots and total yield were similar among management systems each year, except for a reduction in yield in Org-RT in 2002. The percentage of No. 1 grade roots was at least 17% and 23% higher in Org-CCI and Org-NCC than Org-RT in 2001 and 2002, respectively, and similar to Conv in 2001 and 2004. Organic and conventional N sources contributed to soil inorganic N reserves differently the 2 years this component was measured. In 2002, soil inorganic N reserves at 30 DAT were in the order: Org-CCI (90 kg·ha−1) > Org-NCC (67 kg·ha−1) > Org-RT (45 kg·ha−1), and Conv (55 kg·ha−1). No differences in soil inorganic N reserves were observed among systems in 2004. Sweetpotato N, P, and K tissue concentrations were different among systems only in 2004. That year, at 60 days after transplanting, tissue N, P, and K were greatest in Org-CCI. In 2001 and 2004, N (4.09% to 4.56%) and K (3.79% to 4.34%) were higher than sufficiency ranges for N (3.2% to 4.0%) and K (2.5% to 3.5%) defined by North Carolina Department of Agriculture and Consumer Services recommendations for all treatments. No tissue macronutrient or micronutrient concentrations were limiting during this experiment. Reduced rainfall during the 2002 sweetpotato growing season may have contributed to the low microbially mediated plant-available N from the organic fertilizer sources. Despite differences in the nutrient content of organic and conventional fertility amendments, organically managed systems receiving compost with or without incorporated hairy vetch and rye produced yields equal to the conventionally managed system.

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K.M. Batal, D.R. Decoteau, D.M. Granberry, B.G. Mullinix, D.C. Sanders, G.D. Hoyt and R.J. Dufault

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.