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). Growers often design their own mixes using compost and other organic amendments. Organic growers largely depend on compost to manage nutrient requirements of growing transplants. Incorporation of large proportions of compost in the growing medium is not

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fungicides, is useful information for turfgrass managers. Rev ™ (Dakota Peat, Grand Forks, ND) is a new organic amendment that is derived from naturally mined humic materials. The objective of this study was to investigate if the organic amendment sprayed

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, polyethylene mulch, irrigation, and soluble fertilizer application; open bed production includes herbicides, irrigation, and soluble fertilizer application. However, conventional vegetable growers rarely add organic amendments because the use of concentrated

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management, organic production systems rely heavily on inputs like composts and other organic amendments to build soil organic matter and meet crop nutrient demand ( Russo and Webber, 2007 ). These inputs have a direct impact on plant growth, soil fertility

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for matted-row systems ( Kelly et al., 2007 ). In effort to improve in-row weed control in organic matted-row strawberry, natural weed control products and practices have been evaluated. Corn gluten meal has shown promise as an organic amendment. It

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). Some management practices that are commonly used in agricultural systems (e.g., organic amendments, shallow tillage) have the potential to improve the quality of urban soils. The addition of organic amendments such as compost or manure to soils has

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Organic farming has increased to a $4.2 billion industry in the U.S. and continues to expand ≈20% annually. In Iowa alone, organic acreage for all crops has increased from 13,000 in 1995 to 120,000 in 1998. Organic farmers have requested an unbiased analysis of natural soil amendments/fertilizers and compost products on the market for certified organic vegetable and herb production. In our first-year trials at the ISU Muscatine Island Research Farm in 1998, a total of 1,120 `Hungarian wax' pepper plants were transplanted into rows at 31 × 61-cm spacing. Four replications of seven fertilization treatments were planted within the field. The goal of the fertilization program was to obtain equivalent nitrogen and calcium rates in the organic and conventional systems. Leaf height was not significantly different in plants fertilized with organic compost (poultry litter-based) at 50 and 100 kg/ha N compared with conventional fertilizers (at 100 kg/ha N). All organic and conventional treatments had greater biomass than the organic and conventional controls (no fertilizer), respectively (ANOVA, P = 0.05). First harvest fresh weights were greater in the organic treatments, with the greatest number of peppers and greatest fresh weight in the compost plus Bio-Cal® (a liming industry by-product) treatment. Total pepper fresh weight over the five harvest periods was not significantly different among treatments, demonstrating to organic farmers that comparable yields can be obtained in systems employing alternatives to synthetic nitrogen fertilizer.

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Use of biological amendments in vegetable transplant production may affect plant development. Rhizosphere bacteria can alter conditions in the root zone and affect plant growth even if root tissue is not colonized. Arbuscular mycorrhizae (AM) affect plant development through symbiotic relations. Abiotic factors may mediate effects of biotic amendments. Organically certified potting medium was inoculated with a mix of Sinorhizobium sp. bacteria or a mix of AM fungi. Controls consisted of no amendment. Bell pepper, Capsicum annuum L., cv. Jupiter, seed were sown in the medium and irrigated either twice a day for 3 minutes per application or three times a day for 2 minutes per application. Seedlings were treated with 8, 16, 24, or 32 mL·L–1 of an organically certified liquid fertilizer beginning 3 weeks after sowing. Use of bacteria improved plant height and dry weight. Interactions of bacteria and fertilizer rate or irrigation regime affected plant height or dry weight. When irrigated twice a day, plants were tallest when provided 16 mL·L–1 fertilizer, and heaviest when provided 24 mL·L–1 fertilizer. When irrigated three times a day, plants were taller at the lower rates of fertilizer and heaviest at the highest rate of fertilizer. Use of AM had little effect on plant height and dry weight. Most of the responses when AM was the amendment were the result of fertilizer rate and irrigation regime. When irrigated twice a day, AM-treated plants were tallest and heaviest when provided at least 24 mL·L–1 fertilizer. Regardless of biological amendment, plant heights were correlated with plant dry weights over fertilizer rates and irrigation regime. Use of Sinorhizobium sp. appeared to provide a benefit to the development of bell pepper transplants.

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Many producers who have used conventional production methods for vegetables, and who want to convert to organic production, will have to pass through a 3-year transition period before their land can be qualified for organic certification. This transition can produce unique challenges. Use of several amendments has received interest for inclusion in organic production. How these affect vegetable production during the transition period was examined. Land was taken from perennial pasture and converted to production of the vegetables: bell pepper (Capsicum annuum L.), cv. Jupiter; processing cucumber (Cucumis sativus L.), cv. Earli Pik; and sweet corn (Zea mays L.), cv. Incredible (se endosperm genotype) using organic materials and methods with comparison made to production using conventional methods. Conventional and transition to organic portions of the field were separated by 25 m with the buffer zone planted with the same sweet corn cultivar used in the experimental plots and minimally maintained by addition of organic fertilizer. To the organic portion of the field, three levels of humates (0, 112, and 224 kg·ha–1) and three levels of corn gluten meal (0, 448, and 896 kg·ha–1) were applied in nine combinations. Yields for all crops were determined for all years. In the first year, bell pepper yields for plants under conventional production were higher than for the plants in the transition plots. In the remaining 2 years, bell pepper yields were similar under the two production systems. In the first 2 years, cucumber yields for plants under conventional production were higher than for the plants under transition to organic production. In the last year, cucumber yields were similar under the two production systems. In all years, sweet corn yields for plants under conventional production were higher than for plants under transition to organic production. Humates and corn gluten meal did not benefit yields of crops. An economic analysis comparing yields, prices, and costs of production of the crops under conventional and the transition to organic indicated that conventional practices generally provided more net revenue than did transition to organic production. Net revenue for the three species under the transition to organic for the 3 years was $2749 for three hectares. Net revenue for the three crops under conventional production for 3 years was $61,821, a difference of $59,072. Costs, yield, and prices will have to be considered when decisions are made concerning the adoption of organic practices.

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Abstract

Green-manure systems of a tall fescue (Festuca arundinacea L.) sod and a rye (Secale cereale L.)-soybean (Glycine max. L.)-rye rotation were grown for 2 years to provide organic amendments to minesoil. One year after incorporating the green-manure crops, tomato (Lycopersicon esculentum Mill.), pepper (Capsicum annuum L.), and eggplant (Solanum melongena L.) were grown on the amended minesoil and on adjacent, unamended minesoil. Six levels (0.05 to 2.4 ppm) of solution P were established within each plot, based on phosphate sorption isotherms. P sorption decreased in the organic-amended minesoils, thereby reducing the inorganic P fertilizer needed to establish each P solution level. Levels of amorphous Al oxides decreased while exchangeable Al remained relatively constant in the amended minesoil. Moisture relationships and other physical properties were improved in each green-manure regime. Organic amendments had no effect on optimum solution P requirements as tomato and pepper produced highest yields at 0.20 and 0.40 ppm solution P while eggplant produced highest yields at 1.60 and 2.40 ppm solution P in all minesoils. Yields of vegetables were higher in the amended minesoils for most solution P levels, while tissue P and other nutrient concentrations remained unchanged. Yield increases at each P solution level were attributable to improvements in minesoil moisture properties, not to nutritional factors. No differences between the 2 green-manure systems were apparent in their effect on external (solution P) or internal (tissue P) P requirements of the vegetable crop.

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