The Kill Date as a Management Tool for Cover Cropping SuccessReportar como inadecuado

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Integrating cover crops CC in rotations provides multiple ecological services, but it must be ensured that management does not increase pre-emptive competition with the subsequent crop. This experiment was conducted to study the effect of kill date on: i CC growth and N content; ii the chemical composition of residues; iii soil inorganic N and potentially mineralizable N; and iv soil water content. Treatments were fallow and a CC mixture of barley Hordeum vulgare L. and vetch Vicia sativa L. sown in October and killed on two different dates in spring. Above-ground biomass and chemical composition of CC were determined at harvest, and ground cover was monitored based on digital image analysis. Soil mineral N was determined before sowing and after killing the CC, and potentially mineralizable N was measured by aerobic incubation at the end of the experiment. Soil water content was monitored daily to a depth of 1.1 m using capacitance sensors. Under the present conditions of high N availability, delaying kill date increased barley above-ground biomass and N uptake from deep soil layers; little differences were observed in vetch. Postponing kill date increased the C-N ratio and the fiber content of plant residues. Ground cover reached >80% by the first kill date ∼1250°C days. Kill date was a means to control soil inorganic N by balancing the N retained in the residue and soil, and showed promise for mitigating N losses. The early kill date decreased the risk of water and N pre-emptive competition by reducing soil depletion, preserving rain harvested between kill dates and allowing more time for N release in spring. The soil potentially mineralizable N was enhanced by the CC and kill date delay. Therefore kill date is a crucial management variable for maximizing the CC benefits in agricultural systems.

Autor: María Alonso-Ayuso, José Luis Gabriel, Miguel Quemada



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