Responses of potato (Solanum tuberosum L.) to green manure cover crops and nitrogen fertilization rates

This study compared the effects of common vetch (Vicia sativa L.), faba bean (Vicia faba L.), and winter wheat (Triticum aestivum L.; control) cover crop green manures in combination with four rates of nitrogen (N) on tuber yield and quality of three potato varieties (Marfona, Hermes and Agria) during 2-years (2004-2005). Results over years were combined for final analysis. Above-ground dry matter for common vetch and faba bean green manure crops were 2,300 and 2,587 kg ha(-1), respectively. Mean root dry matter yield of faba bean (285 kg ha(-1)) was higher than common vetch (120 kg ha(-1)). Nitrogen (N) yields of common vetch and faba bean green manure crops were 49 and 58 kg N ha(-1) for above-ground and 2.0 and 5.0 kg N ha(-1) for root dry matter, respectively. Averaged over all nitrogen fertilizer rates, potato plants grown in plots following common vetch and faba bean green manure cover crops produced 12.7% and 15.0% more tuber yield ha(-1), respectively, compared with plants in the winter wheat plots. Potatoes following green manure legume cover crops produced approximately 36% to 38% higher tuber yields compared with potatoes grown following winter wheat when no nitrogen fertilizer was applied. Differences between tubers yields following cover crops decreased as N rates increased. Results over combined 2-years indicated that the economically optimum N rate (EONR) was an average of 30 kg N ha(-1) lower for potato following green manure legume cover crops compared with potato following winter wheat cover crop.