The effect of cover crops on the establishment and yield of vining peas and on nitrate leaching

Abstract

SUMMARYExperiments were designed to assess the effects of cover crops, compared with bare stubble, on the establishment and yield of a following crop of vining peas sown in March. The cover crops of winter wheat (to simulate self-sown wheat) or winter rye, and bare stubble, were ploughed in on different dates: 1 December, 1 February or 1 March. Cover crops were destroyed with or without the use of herbicide. The three experiments in 1990/91, 1991/92 and 1992/93 were sited on a free-draining, sandy loam soil at Thornhaugh, Cambridgeshire.The cover crops, sown as soon as possible in September following a winter wheat crop, had low dry matter (DM) production and nitrogen uptake in the dry autumns of 1990 and 1991, but in the third experiment (1992/93), autumn rainfall was higher than the long-term average and DM production and N uptake were greater. Cover crops reduced the overwinter soil mineral nitrogen (SMN) content in all 3 years compared with bare stubble. However, in spring, SMN increased where cover crops had been incorporated, due to the mineralization of the cover crop residues. Rye captured more nitrogen than wheat.Vining pea vigour and maturity at quick-freezing harvest stage were not affected by cover crop, destruction date or method in any of the three seasons.On the light soil, satisfactory seedbeds were achieved after ploughing at all three timings for experiments in 1990/91 and 1992/93 and vining pea yields were not reduced by cover crops or by destruction date or method. However, delayed ploughing in February and March in the 1991/92 experiment resulted in lower vining pea yields compared with ploughing in December. This was due to poor seedbeds after late ploughing rather than cover crop, stubble treatment or method of destruction.