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Meeting the Nitrogen Needs of Processing Tomatoes through Winter Cover Cropping

1991; Wiley; Volume: 4; Issue: 3 Linguagem: Inglês

10.2134/jpa1991.0330

2689-4114

Lydia J. Stivers, Carol Shennan,

Soil Carbon and Nitrogen Dynamics

A field study was initiated in 1986 in Davis, CA, to determine the long-term effects of "winter green manures/cover crops" on N dynamics and soil structural and biological properties in a semi-arid, irrigated cropping system. Results from the first 2 y of the experiment are used to compare the productivity of several legume green manures and to determine if they can provide adequate available soil N to support yields of a subsequent crop of processing tomatoes (Lycopersicon lycopersicum L. Karsten var. lycopersicum) typical for this area. Lana woolly-pod vetch (Vicia dasycarpa Ten.), bell beans (Vicia f aba L.), berseem clover (Trifolium alexandrinum L.), Austrian winter peas (Pisum arvense L.), oats (Avena sauva L.), and an oats and vetch mixture, planted in October and disked under in April, were compared with various levels of ammonium sulfate fertilizer. Lana vetch produced the greatest biomass of the legumes, and fixed the most N (90 lb/acre by February, and 230 lb/acre by March in 1987, as determined by the difference method). Use of green manures, relative to winter fallow, dried out the soil (0–24 in. depth) by an amount equivalent to 0.4 to 0.8 in. of water depending on the cover crop. Tomato yields for the legume cover-cropped plots were as high as those in the fertilizer-treated plots, but the response to applied N was low. Nitrate levels in the top 8 in. of soil in vetch-treated plots remained as high as in the 200 lb N/acre ammonium sulfate fertilizer plots throughout the growing season.