Effects of tillage and time of sowing on bread wheat, chickpea, barley and lentil grown in rotation in rainfed systems in Syria

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Cropping systems in the drylands of west Asia are characterized by grazing, burning or harvesting of stubbles, multiple cultivations and late sowing, which can limit yields and lead to soil erosion and degradation. There is a lack of information on more conservation-based technologies developed in other countries to address some of these problems, particularly manipulations of tillage and time of sowing. This long-term field experiment was conducted under rainfed conditions at ICARDA near Aleppo in northern Syria to investigate the effects of conventional tillage (CT) and zero tillage (ZT) in combination with early and late times of sowing on the performance (production and profitability) of bread wheat, chickpea, barley and lentil grown in rotation over six years (2006–07 to 2011–12). As expected, the amount and pattern of rainfall was a major driver of crop performance, varying from 222 to 453mm among the growing seasons. The grain yield of crops was often similar under ZT and CT (≈70% of year–crop–time of sowing combinations) and with early and late sowing (≈80% of year–tillage–crop combinations), but there were also many instances when ZT yielded significantly better than CT (≈25%) and early sowing yielded better than late sowing (≈13%). Importantly, over the four years from 2008–09 to 2011–12, the improved crop management system of ZT and early sowing gave higher grain yields than the conventional farmer system of CT sown late in two (13%) of the 16 year×crop combinations, similar yields in 13 (81%) combinations and lower yields for ZT early in one (6%) combination. During this time, the average grain yield increases with ZT and early sowing when compared to CT and late sowing were a significant 332kgha−1 (18%) for wheat, 127kgha−1 (20%) for chickpea and 135kgha−1 (15%) for lentil, and a non-significant 295kgha−1 (12%) for barley. Corresponding increases in gross margins ($US) were 162, 147, 89 and 176 $ha−1 for wheat, chickpea, barley and lentil, respectively. In chickpea, the most profitable treatment was ZT sown late, producing an extra 281kgha−1 and 271 $ha−1 compared to CT sown late. Early sowing improved crop establishment with increased plant densities of 30%, 48% and 29% for wheat, barley and lentil respectively, while ZT increased densities by 19%, 22% and 12% for chickpea, barley and lentil, respectively, when sown early. Other yield components reflected the grain yield responses. The increased grain yields achieved in this study, in combination with lower costs and greater profits, suggest ZT plus early sowing should be evaluated and promoted more widely as an attractive cropping technology for farmers in the Middle East.