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Résumé :
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Plant-soil relationships in the surface soil layer affect other processes in agroecosystems, including crop productivity, nitrate leaching and plant-pest interactions. This study investigated the effect of altering surface soil dynamics, using a winter cover crop rotation, on biotic and abiotic characteristics of the soil profile. Two cover crop treatments, phacelia and Merced rye (Phacelia tanacetifolia cv. 'Phaci', and Secale cereale cv. 'Merced'), with a fallow control, were planted in November after harvest of a broccoli crop on a commercial farm site, and were incorporated using reduced tillage techniques the following March. Changes in plant and soil N pools throughout the profile were described, emphasizing nitrate (NO3--N) leaching during winter, and N availability during the subsequent broccoli crop. Changes in other aspects of the ecosystem, such as plant-pest interactions and plant disease incidence, were monitored after cover crop incorporation. The on-farm economic costs of cover cropping were calculated.
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