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  • Author or Editor: Thomas Morris x
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There is little published data to support current recommended plant populations of 11,500 to 17,500 plants/acre (28,600 to 34,600 plants/ha) for fresh market sweet corn (Zea mays L.) in the northeastern United States. The plant population likely affects marketable yield and recovery of nitrate. Residual soil nitrate is of concern because of the potential for nitrate contamination of water supplies. Our objectives were to determine the effect of plant population on the yield of sweet corn grown for fresh market without irrigation and on the amount of nitrate in the surface 1 ft (30 cm) of soil at harvest. Seven main-season sweet corn varieties were planted in a total of eight experiments in 1995, 1996, and 1997. Seven experiments were in Connecticut and one was in New Hampshire. All but one of the varieties were standard (su) or sugary enhanced (se) varieties. The experimental design was a randomized complete block with four replications, and the treatments consisted of 12,000, 16,000, 20,000, 24,000, and 28,000 plants/acre (29,600, 39,500, 49,400, 59,300, and 69,200 plants/ha). The yield of marketable ears was classified based on the length of the ears. The results suggest that the current recommendations for plant population in the Northeast US may be too low. Populations of 20,000 and 24,000 plants/acre produced consistently greater yields of ears greater than 7.0 inches (178 mm) long. Soil nitrate-N concentrations at harvest were about 8 mg·kg-1 lower with 16,000 plants/acre or greater, compared with 12,000 plants/acre, which suggests that populations of 16,000/acre or greater should decrease the potential for nitrate contamination of water supplies in the fall, winter, and early spring.

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A composting facility in New Milford, Conn. (NMF), utilizes food-processing residuals, including spent tea leaves, coffee grounds, cocoa shell and cleanings, wastewater treatment sludge from a food ingredients manufacturing plant, and past-expiration processed vegetable products. Materials are composted in aerated, frequently turned windrows under cover. The range of inputs, combined with time constraints on the composting process, has resulted in a variable, immature compost product with a high rate of microbial activity. Users have expressed concern about potential phytotoxicity or nutrient immobilization from using NMF compost. Therefore, research was conducted to determine the influence of cured and uncured NMF compost amendments on potentially sensitive crops with high nutrient requirements. Arugula (Eruca vesicaria) and green bibb lettuce (Lactuca sativa) were grown on two Connecticut organic farm research sites in 1998 and 1999. Both sites have soils classified as coarse loamy over sandy or sandy-skeletal, mixed, mesic, typic, Dystraudepts. Farms differed in the length of time under organic farm management. One farm has been an organic farm since 1988 and consequently has high soil fertility, while the other was a first-year organic farm in 1998, and had relatively low soil fertility. Three amendment types were applied: cured compost, uncured compost, and organic fertilizer (5N-3P2O5-4K2O). Amendment application rates were estimated to provide a comparable range of plant-available nutrients for the amendments and a control without fertilizer. Compost application rates were 3.4, 6.8, 20.2, 35.8, and 71.7 Mg·ha-1 (dry-weight basis) in 1998 and 11.2, 22.4, 44.8, and 89.6 Mg·ha-1 (dry-weight basis) in 1999. Organic fertilizer application rates were 1.34, 2.68, 5.36, 10.72, and 21.44 Mg·ha-1 in 1998 and 1.34, 2.68, 5.38, and 10.72 Mg·ha-1 in 1999. Soil organic matter and nutrients increased with amendment application rate at both locations. Crop yields increased with amendment rate at the new, lower-fertility farm, but yields did not respond to amendments at the older, higher-fertility farm. Yield differences were minor between the uncured and cured compost treatments at both locations. This indicates that either cured or uncured NMF food-processing residual compost can be successfully used as an organic soil amendment for salad green production.

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The pre-sidedress soil nitrate test (PSNT) was evaluated in 27 fields in New Jersey, 6 in Connecticut, 5 in Delaware, and 2 on Long Island in New York for its ability to predict whether sidedress N is needed to grow fall cabbage (Brassica oleracea var. capitata) as a double crop. Soil NO3-N concentrations measured on 20 field sites on the day of transplanting and 14 days after transplanting indicated that NO3-N concentrations over this time period increased, and that residues from the previous crop were not causing immobilization of soil mineral N. The relationship between soil NO3-N concentration measured 14 days after transplanting and relative yield of marketable cabbage heads was examined using Cate-Nelson analysis to define the PSNT critical level. Soil NO3-N concentrations ≥24 mg·kg-1 were associated with relative yields >92%. The success rate for the PSNT critical concentration was 84% for predicting whether sidedress N was needed. Soil NO3-N concentrations below the PSNT critical level are useful for inversely adjusting sidedress N fertilizer recommendations. The PSNT can reliably determine whether fall cabbage needs sidedress N fertilizer and the practice of soil NO3-N testing may be extendable to other cole crops with similar N requirements.

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