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Effectivelyutilizing legume cover crops as an organic source of nitrogen in concord grape

K.E. Bair. 2006.

Abstract

Leguminous cover crops are commonly used as green manures in organic cropping systems because they provide nitrogen (N) to plants. Concord grape (Vitis labruscana Bailey) is well suited for organic production because of low detrimental plant pathogen and insect pest pressure. The objectives of this research are to (i) evaluate the effectiveness of hairy vetch (Vicia villosasubsp. villosa L.) and yellow sweet clover (Melilotus officinalis (L.) Lam.) in providing N to organically grown Concord grape, (ii) synchronize N release from mineralization following incorporation of cover crops with plant N demand and (iii) compare the ability of soluble, more readily available sources of N (blood meal and conventional fertilizer) to legume cover crops in providing N to grape. Field analysis of research and commercial sites was initiated in 2003. Treatments consisted of spring and fall planted cover crops, 112 kg N ha-1 conventional fertilizer and 112 kg N ha-1 blood meal. Cover crops were incorporated in the early spring. Cover crop biomass depended on time of planting and material planted. Large seed size and careful water management were advantageous for cover crop establishment and biomass production. Fall planted covers tended to establish better than those planted in the spring with hairy vetch being more consistent than yellow sweet clover. The yellow sweet clover did, however, show high biomass production potential. Plant Root Simulator (PRS) and soil test NO3-N peaked for legume and fertilizer treatments during the critical plant N demand period from bloom to veraison. Cumulative degree-days to peak NO3-N availability were similar for measured treatments, although peak magnitude varied. Grape yield and quality were different by site and year but not by treatments in the same site and year. Hence, yield was not influenced by treatment. Yield and quality data coupled with leaf tissue N data suggest that cover crops have the potential to provide sufficient plant available N for crop production.