Cover crops and nitrogen fertilization effects on soil carbon and nitrogen and tomato yield

Abstract

Cover crops can influence soil properties and crop yield. We examined the influence of legume [hairy vetch (Vicia villosa Roth) and crimson clover (Trifolium incarnatum L.)] and nonlegume [rye (Secale cereale L.)] cover crops and N fertilization (0, 90, and 180 kg N ha−1) on the short- and long-term effects on soil C and N and tomato yield and N uptake. We measured organic C and N (long-term effects), potential C and N mineralization (PCM and PNM) and inorganic N (short-term effects) periodically on a Greenville fine sandy loam (fine-loamy, kaolinitic, thermic, Rhodic Kandiudults) planted with tomato (Lycopersicum esculentum Mill) from April to August in 1996 and 1997 in Georgia USA. Soil C and N concentrations increased early in the growing season with cover crop residue incorporation, but decreased as the residue decomposed. Rye increased organic N and maintained greater levels of organic C and PCM after 3 yr than other treatments. In contrast, hairy vetch and crimson clover increased PNM and inorganic N soon after residue incorporation into the soil and produced tomato yield and N uptake similar to that produced by 90 and 180 kg N ha–1. Nitrogen fertilization increased PNM and inorganic N after split application and tomato yield and N uptake but decreased organic C and N and PCM compared with rye. Compared with 0 kg N ha–1, nonlegume cover crops, such as rye can increase organic C and N and PCM but legume cover crops, such as hairy vetch and crimson clover, can enrich soil N and produce tomato yield and N uptake similar to that produced by 90 and 180 kg N ha−1. Key words: Cover crops, nitrogen fertilization, soil carbon, soil nitrogen, tomato yield