Productivity and nitrogen benefits of late-season legume cover crops in organic wheat production

Abstract

When full-season cover crops are used in stockless organic rotations, cash crop production is compromised. Including winter cereals in rotations can widen the growing season window and create a niche for late-season cover crops. We investigated the establishment and biomass production of relay-cropped red clover (Trifolium pratense L.) and sweet clover (Melilotus officinalis L. ‘Norgold’) and double-cropped cowpea (Vigna unguiculata L. ‘Iron and Clay’), hairy vetch (Vicia villosa L.), lentil (Lens culinaris L. ‘Indianhead’), soybean (Glycine max L. ‘Prudence’), pea (Pisum sativum L. ‘40 10’), and oil seed radish (Raphanus sativus L.) as well as wheat response to these crops under reduced tillage (RT) and conventional tillage (CT) at three locations in Manitoba, Canada. Red clover, sweet clover and pea produced from 737 to 4075 and 93 to 1453 and 160 to 2357 kg ha 1of biomass, respectively. All double crops, with the exception of soybean at 2 site years, established successfully under both RT and CT. The presence of cover crops increased wheat N uptake at stem elongation, maturity and yield, even when the biomass production of cover crops was modest. We conclude that late-season cover crops enhance the following wheat yield and facilitate reduced tillage in organic crop production.