Management Effects on Barley Straw Decomposition, Nitrogen Release, and Crop Production

Abstract

Development of sustainable‐crop production systems depends on identifying effective strategies for the management of postharvest crop residues. The effects of time‐of‐incorporation (autumn‐incorporated [AI] vs. spring‐incorporated [SI] and irrigation (irrigated[Irr] vs. nonirrigated[Nirr]) on barley Hordeum vulgare L. straw decomposition and microbial activity were investigated in relation to soil N availability and crop production over one cropping cycle in Canterbury, New Zealand. Over the winter‐fallow period, the weight loss of AI barley straw averaged 33% as compared with 18% for surface straw of SI treatments. By harvest, nearly all of the difference in mass loss between AI and SI straw (17%) from NIrr treatments could be attributed to decomposition in the fallow period. Irrigation increased straw decomposition during the cropping period by 68% in AI treatment compared with only 37% in SI treatment. The effect of winter‐straw placement on the response of barley straw to summer irrigation was related to the size of the residue‐borne microbial populations at the start of the cropping period. Although relatively little N was released (<5 kg N ha −1 ) from decaying barley straw, cultivation, and incorporation of straw in autumn (AI) did result in greater topsoil (0–25 cm) mineral N levels during the winter period as compared with the SI treatment. Overall, Irr and AI of straw increased the dry matter production and N uptake of the summer barley crop, resulting in a concomitant decrease in soil mineral N levels relative to Nirr SI treatments. The mechanisms that explain this difference in crop response to winter residue management require further investigation.