Short CommunicationA vetch winter cover crop can improve response to nitrogen fertiliser and profitability of no-till maize

Abstract

A high nitrogen (N) fertiliser requirement can be a deterrent to the adoption of conservation agriculture (CA). A field trial was carried out to test whether a high biomass-yielding vetch (Vicia dasycarpa L.) winter cover crop can be used to improve N response and profitability of a subsequent maize (Zea mays L.) crop under no-till and irrigation. There were five N fertilisation treatments (0, 60, 120, 180 and 240 kg ha⁻¹). Maize grain yield after vetch was higher than that after a fallow (no winter cover crop) for most of the cases when the N fertiliser application rate was below 180 kg ha⁻¹. Where no N fertiliser was applied, maize yields after vetch were 4.71 and 7.26 tons ha⁻¹ for the first and second seasons, translating into an N fertiliser replacement value of approximately 90 kg N ha⁻¹. The highest marginal rate of return for vetch over the two maize seasons (399% and 649%) was obtained at a fertiliser rate of 0 kg N ha⁻¹. These data from preliminary CA studies in the Eastern Cape highlight the importance of promoting legume winter cover crops as an entry point to CA, especially for poor maize farmers who cannot afford N fertiliser.

Keywords: conservation agriculture, grazing vetch, maize grain yield, nitrogen fertiliser rate

South African Journal of Plant and Soil 2014, 31(1): 45–48