Faba bean (Vicia faba L.) response to tillage and soil residual nitrogen in a continuous rotation with wheat (Triticum aestivum L.) under rainfed Mediterranean conditions

The present field study was undertaken to determine the effects of tillage systems on faba bean (Vicia faba L.) yield over 11 yr and the effects of tillage systems and residual N on faba bean yield, yield components, and N uptake over 4 yr in a wheat (Triticum aestivum L.)-faba bean rotation under rainfed Mediterranean conditions. Tillage treatments included no-tillage and conventional tillage. Nitrogen fertilizer rates were 0, 50, 100, and 150 kg N ha(-1), applied only to wheat. The weather had a marked influence on seed yield, which ranged from 587 to 2964 kg ha(-1). Thousand-seed weight rose with increasing seed yield and seeds per pod, seeds per pod decreased with increasing pods per square meter, and harvest index rose with increasing seeds per pod but decreased with rising pods per square meter. Over the 11-yr study period, the tillage system did not significantly influence seed yield. However, in three rainy years, conventional tillage was more productive than no-tillage. Seed yield, total dry matter, and N uptake were lower at 0 kg N ha(-1), and no significant differences were recorded among other N rates. Total N uptake ranged from 50 to 127 kg N ha(-1) while seed N uptake fluctuated between 34 and 107 kg N ha(-1). Soil nitrate at wheat sowing after faba bean was not affected by the type of tillage system used while the effect of the N rates applied to wheat 2 yr before was very reduced due to N fixed by the faba bean crop.