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Fall-planted cover crops of hairy vetch (Vicia villosa Roth), Austrian winter pea (Pisum sativum subsp. arvense L. Poir), and crimson clover (Trifolium incarnatum L.) were each followed by spring-planted 'Sundance' summer squash [Cucurbita pepo var. melopepo (L.) Alef.] and 'Dasher' cucumber (Cucumis sativus L.). Squash and cucumber crops were followed by fall 'Florida Broadleaf mustard green [Brassica juncea (L.) Czerniak] and 'Vates' collard (Brassica oleracea L. Acephala group), respectively. The same vegetable sequences were also planted without benefit of cover crop. Three nitrogen (N) rates were applied to each vegetable crop. Squash following winter pea and crimson clover produced greater yields than did squash planted without preceding cover crop. Cucumber following crimson clover produced the greatest yields. No cover crop effect was noted with mustard or collard. Elimination of N fertilizer resulted in reduced yields for all crops, but yields of crops with one-half the recommended N applied were generally comparable to those receiving the full recommended rate.

Several prospective cover crops were sown into 1-m² monoculture plots on 9 Mar. 1987 and 10 Mar. 1988 at Bixby, Okla., and on 14 Mar. 1988 at Lane, Okla., after sites were plowed and fitted. Densities and dry weights of cover crops and weeds were determined in late April or early May of both years. Plots also were evaluated for degree of kill by glyphosate in 1988. Fourteen cover crops were screened at Bixby in 1987. Kentucky bluegrass (Poa pratensis L.) and three fescues (Festuca rubra L., Festuca rubra L. var. commutata Gaud.-Beaup., and Festuca elatior L.) were eliminated from further consideration due to inadequate cover density and inability to suppress weeds. Screenings of the 10 remaining covers were conducted at both locations in 1988. Annual ryegrass (Lolium multiflorum L.) and three small grains [rye (Secale cereale L.), barley (Hordeum vulgare L.), and wheat (Triticum aestivum L.)] were the most promising cover crops with respect to cover density, competitiveness against weeds, and degree of kill by glyphosate. Crimson clover (Trifolium incarnatum L.) and hairy vetch (Vicia villosa Roth) were the most promising legumes, but they generally were less satisfactory than the grassy covers in all tested aspects. A single application of glyphosate was ineffective in killing hairy vetch at both locations. Chemical name used: N-(phosphonomethyl)glycine (glyphosate).

The recent increase in the cost of synthetic fertilizer dramatically reduces the profit margin for pecan [Carya illinoinensis (Wangenh.) K. Koch] producers. The objective of this study was to investigate the effects of clover and poultry litter on the orchard soil, horticultural, and nut quality parameters of pecan in the southeastern United States. The following treatments were evaluated; 1) crimson clover (Trifolium incarnatum L.); 2) poultry litter; 3) crimson clover + poultry litter; 4) ammonium nitrate (NH₄NO₃); and 5) untreated control. Application of poultry litter with or without clover often led to higher soil phosphorous (P) and potassium (K). Poultry litter application with and without clover led to higher leaf P in the final year of study. The recurring low pecan leaf K in the presence of clover without additional K application suggests that K nutrition may be especially important in orchards where clover is used. Clover and/or clover + litter occasionally led to enhanced pecan leaf concentrations of iron (Fe), copper (Cu), and zinc (Zn). Over the course of the study, yields were more consistent from year to year in the clover, litter, and clover + litter treatments, as indicated by the low alternate bearing intensity (I) from 2008 to 2011. Leaf elemental tissue analysis, pecan yield, and quality indicate that poultry litter and clover provide adequate nitrogen (N) nutrition for pecan production.

Little information is available regarding the activity of soil quality biological indicators in southeastern U.S. pecan [Carya illinoinensis (Wangenh.) K. Koch] orchards. The objectives of this study were to examine the effect of poultry litter application and the use of crimson clover (Trifolium incarnatum L.) as a cool-season cover crop on soil chemistry and soil quality biological indicators, including mycorrhizal inoculum potential (MIP), microbial biomass carbon (MBC), and phosphatase activity in a southeastern U.S. Coastal Plain pecan orchard system. The use of clover as a cool-season cover crop between tree rows provided multiple benefits for pecan orchard soil quality, including increased MIP and MBC. Soil phosphatase activity was also enhanced by clover during two of the three years of study. Soil elemental properties, including total nitrogen (N), and soil organic matter (SOM) were also enhanced by clover and/or poultry litter, although there was an obvious time lag in the response of soil N to the treatments. Poultry litter application increased soil phosphorus (P) but did not consistently enhance soil biological activity parameters. At times, poultry litter appeared to neutralize or minimize the positive effects of clover on MIP.

Nitrogen (N) fertilizer application to plants at rates not adjusted for the N contribution from soil N availability may result in overapplication of fertilizer. Further understanding of proper timing of N applications based on soil N dynamics and plant demand can be valuable information for the efficient use of fertilizer N. The present study measures soil N dynamics in a pecan orchard under various N fertilizer regimes on a southeastern U.S. Coastal Plain soil. The following treatments were evaluated: 1) crimson clover (Trifolium incarnatum L.); 2) poultry litter; 3) crimson clover + poultry litter; 4) ammonium nitrate (NH₄NO₃); and 5) untreated control. Crimson clover provided from 20 to 75 kg·ha⁻¹ N over the course of the two growing seasons; however, most of the available N from crimson clover became available late in the growing season. As a result, supplemental N may be required in spring where crimson clover is used as an orchard cover crop. Poultry litter, with and without clover, provided available N consistently throughout the growing season with more N becoming available later in the season than earlier. This suggests that poultry litter applications for pecan should be timed before budbreak. Under optimum environmental conditions, N from NH₄NO₃ is most available within the first 30 days of application. Thus, it appears that synthetic fertilizer applications using NH₄NO₃ as the N source should be targeted at or 2 to 3 weeks after pecan budbreak.

Abstract

Field experiments were conducted on a Norfolk loamy sand (fine-loamy, siliceous, thermic Typic Paleudult) from 1983 through 1985 to determine the effects of tillage method, cover crop, and N fertilization on inorganic soil N and yield, yield components, and N content of snap bean (Phaseolus vulgaris L.). Hairy vetch (Vicia villosa Roth), hairy vetch plus wheat (Triticum aestivum L.), Austrian winter pea (Pisum sativum ssp. arvense L. Poir), Austrian winter pea plus wheat, wheat, crimson clover (Trifolium incarnatum L.) and no cover were the cover crop treatments. Inorganic N concentrations generally were greater in soil with cover crop treatments containing legumes than in soil with no cover and wheat treatments. The use of Austrian winter pea, hairy vetch, and crimson clover as cover crops without supplemental N resulted in snap bean yields comparable to those obtained when 90 kg·ha⁻¹ additional N was supplied. Supplemental N decreased the amount of dry matter partitioned into pods. Inorganic N profiles in the soil indicated that conventional tillage (CT) practices resulted in greater mineralization of N fixed by the legume cover crops than no-tillage (NT) practices. However, snap bean yields for NT were comparable to or greater than those obtained with CT, suggesting that N released from legume residues provided sufficient supplemental N for optimum growth and yield.

Conventional production of tomatoes (Lycopersicon esculentum Mill.) requires substantial investments, intensive management and high inputs of nitrogen. High N rates invariably leave residual soil NO₃-N with the potential of polluting ground water and posing health hazard to humans and animals. The objective of this study was to examine the value of cover crops as a substitute to synthetic N fertilizer in growing of tomatoes. The experimental treatments consisted of control (no N fertilizer or cover crop), Abruzzi rye (Secale cereale L), hairy vetch (Vicia villosa Roth), or crimson clover (Trifolium incarnatum L.) cover crop, and fertilization of N at 90 or 180 kg·ha^-1. The treatments were replicated four times over 2 years in a randomized complete block experiment for growing `Mountain Pride' tomato on a Greenville fine sandy loam soil. The parameters used to evaluate the performance of tomato consisted of leaf area index (LAI), gas exchange (GE), above ground plant dry weight, number of fruits, dry weight of fruits, and marketable fruit yield. Tomato LAI was similar under legumes and N fertilizers. Hairy vetch and applied N at 90 kg·ha^-1 influenced net photosynthesis (P_n) and transpiration (E) the most in both years at all stages of growth. Highest number of tomatoes were produced in hairy vetch and applied N at 90 kg·ha^-1 plots. There was no significant difference in the above ground plant dry weight, fruit yield and dry weight of fruits between legumes and N fertilizers. The results suggested that the legume cover crops compared favorably to N fertilizers in promoting tomato growth and development and may have potential of substituting N fertilizers in fresh-market tomato production.

Most vegetable farms in southern New England market directly to consumers and are characterized by high crop diversity and intensive cultivation. Growers rely on tillage to prepare fields for planting and control weeds, but are concerned about the negative effects of tillage on soil health. This study evaluated three tillage reduction strategies in a market garden system producing tomatoes, melons, cucumbers, cabbage, carrots, and lettuce. Treatments of strip tillage into a killed cereal rye (Secale cereale) cover crop mulch, perennial white clover (Trifolium repens), and ryegrass (Lolium perenne) living mulch between planting rows, and annual crimson clover (Trifolium incarnatum) living mulch interseeded between vegetable rows were established in 2010 and compared over 3 years to a control system using tillage to maintain bare ground between rows. Treatments were evaluated for effects on vegetable yield and soil biological, chemical, and physical properties. The strip tillage treatment was the most effective at promoting soil health, resulting in significant increases in soil aggregate stability, potentially mineralizable nitrogen, active soil carbon, and microbial activity relative to the control, and significant decrease in loss of soil organic matter. However, it was not effective for production of vegetables, with the strip-tillage plots having the lowest yields throughout the study. The perennial living mulch treatment produced yields of carrots, melons, and cucumbers similar to the control yields, but reduced yields of tomatoes, cabbage, and lettuce. Microbial respiration was significantly higher than in the control, and nitrate levels, and loss of soil organic matter were significantly lower. The annual living mulch treatment produced yields similar to the control for all crops, and soil health was similar to the control for all variables except soil nitrate, which was significantly higher than the control. Perennial living mulch shows the most promise for improving soil health while maintaining yields in some vegetable crops, but challenges remain in preventing competition between vegetables and living mulches.

Four tomato production systems were compared at Columbus and Fremont, Ohio: 1) a conventional system; 2) an integrated system [a fall-planted cover-crop mixture of hairy vetch (Vicia villosa Roth.), rye (Secale cereale L.), crimson clover (Trifolium incarnatum L.), and barley (Hordeum vulgare L.) killed before tomato planting and left as mulch, and reduced chemical inputs]; 3) an organic system (with cover-crop mixture and no synthetic chemical inputs); and (4) a no-input system (with cover-crop mixture and no additional management or inputs). Nitrogen in the cover-crop mixture above-ground biomass was 220 kg·ha^-1 in Columbus and 360 kg·ha^-1 in Fremont. Mulch systems (with cover-crop mixture on the bed surface) had higher soil moisture levels and reduced soil maximum temperatures relative to the conventional system. Overall, the cover-crop mulch suppressed weeds as well as herbicide plots, and no additional weed control was needed during the season. There were no differences in the frequency of scouted insect pests or diseases among the treatments. The number of tomato fruit and flower clusters for the conventional system was higher early in the season. In Fremont, the plants in the conventional system had accumulated more dry matter 5 weeks after transplanting. Yield of red fruit was similar for all systems at Columbus, but the conventional system yielded higher than the other three systems in Fremont. In Columbus, there were no differences in economic return above variable costs among systems. In Fremont, the conventional systems had the highest return above variable costs.

Planting polyculture mixtures of cover crops can optimize the benefits of their use. Thirteen polyculture mixtures of cover crops were evaluated in Columbus and Fremont, Ohio, to find a species mix that would establish quickly for erosion control, overwinter in Ohio, contribute sufficient N and have a C : N ratio between 20:1 and 30:1 to optimize N availability for subsequent crops, be killable by mechanical methods, and have high weed control potential. All of the mixtures in Columbus had achieved 30% ground cover 1 month after planting, but only four of the mixtures achieved this in Fremont due to poor conditions at planting. Above-ground biomass (AGB) accumulation in the mixtures ranged from 3631 to 13,642 kg·ha^-1 in Columbus, and 449 to 12,478 kg·ha^-1 in Fremont. Nitrogen in the AGB ranged from 74 to 269 kg·ha^-1 in Columbus, and 10 to 170 kg·ha^-1 in Fremont. Weed cover in the cover crop plots ranged from 1% to 91% eight weeks after cover crop kill in Columbus, and 12% to 90% seven weeks after cover crop kill in Fremont. Because one or more species in each screened mixture was determined not to be suitable, none of the mixtures was optimum. However, information gained about performance of individual species within the mixtures is also useful. `Nitro' alfalfa (Medicago sativa L.), ladino clover (Trifolium repense L.), subterranean clover (Trifolium subterraneum L.), Austrian winter peas [Pisum sativum ssp. Arvense (L.) Poir], and annual ryegrass (Lolium multiflorum Lam.) did not overwinter dependably in Ohio. Tall fescue (Festuca arundinacea L.), perennial ryegrass (Lolium perenne L.), and orchardgrass (Dactylis glomerata L.) did not compete well with taller, more vigorous species, and were not persistent in the mixtures. Medium and mammoth red clover (Trifolium pratense L.), annual and perennial ryegrass, and white and yellow blossom sweetclover [Melilotus alba Desr., and Melilotus officianalis (L). Desr.], were not killable by mechanical methods. Individual species that established quickly, were competitive in the mixtures, overwintered dependably, and were killed by mechanical methods were rye (Secale cereale L.), barley (Hordeum vulgare L.), crimson clover (Trifolium incarnatum L.), and hairy vetch (Vicia villosa Roth.)