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We evaluated the effects of soil organic matter amendments on crop growth and yield over a three-year period. In Spring, 1990, we added 3.8 cm of spent mushroom compost and 1.3 cm of well-rotted horse manure to the top 0.2 m of selected plots in a 0.4 ha field. Other plots received recommended amounts of synthetic NPK. Total yield and yield of No. 1 grade tomatoes were 25% and 67% greater, respectively, in the amended plots than in the conventional plots the first year. In 1991, we no-till planted three varieties of sweet corn into this field. The conventional plots received either 75% or 100% of recommended N. Previously amended plots received no further N. Sweet corn production was 46-200% greater in amended plots, depending on variety. In 1992 following moldboard plowing, we planted snap beans followed by broccoli or cabbage. Conventional plots received the recommended amount of N (in 100% N plots from 1991) or no N (in 75% N plots from 1991) while plots amended in 1990 received no further N. Yields of snap beans were comparable in all three treatments. Broccoli heads had greater diameters in plots that had been amended. Cabbage from the amended plots were more mature based on growth stage. The beneficial effect of this initial amendment has continued for three growing seasons. This observation suggests that while the initial cost of organic soil amendments may be higher than synthetic fertilizer for the first year, comparable or greater yields may be expected allowing this approach to be cost-effective over a three-year period.

During the initial season of implementation, four tomato production systems differing in soil management, pest control practices, and level of inputs, such as labor, materials, and management intensity were evaluated. These systems were CON, a low input (no mulch, no trellising, overhead irrigation, preplant fertilization, scheduled pest control), conventional agrichemical system; BLD, a high input [straw mulch, trellising, trickle irrigation, compost fertility amendment, integrated pest management (IPM)], ecologically-oriented system that emphasized the building up of soil organic matter levels and used no agrichemicals to supply fertility or for pest control; BLD+, a system similar to BLD, except that agrichemical pesticides were used; and ICM, a high input system (black polyethylene mulch, trellising, trickle irrigation, fertigation, IPM pest control) that used agrichemicals to supply fertility and for pest control. Soil characteristics and fertility levels in the BLD and BLD+ systems were modified with extensive amendments of spent mushroom compost and well-rotted cattle manure. Levels of agrichemical NPK calculated to meet current crop needs were supplied to the CON and ICM systems, with 75% of fertility in the ICM system supplied through the trickle irrigation lines (fertigation). The BLD system had a greater soil water holding capacity and sharply reduced irrigation requirements. During a wet period, fruit cracking and evidence of water-mold root rot were significantly higher in the ICM system than the BLD and CON systems. Defoliation by Alternaria solani was greatest in the BLD system and least in the ICM system. The BLD and ICM systems resulted in a 1 week earlier peak yield compared to the CON system. The yield of No. 1 fruit was 55% to 60% greater in the BLD+ system than the other three systems, which were comparable in yield. Net return was highest in the BLD+ system, although the benefit/cost ratio was greatest in the CON system. This multidisciplinary study has identified important differences in the performance of diverse production systems during the unique transitional season.