Effects of Crop Rotation and Tillage on Winter Wheat Growth and Yield under Cold Dryland Conditions

To investigate responses of two winter wheat genotypes under different crop management systems (rotation and tillage), a split-split plot experiment was conducted based on a randomized complete block design (RCBD) with three replications during 4 years in Maragheh, Iran. Three crop rotation treatments [vetch-wheat (V-W), chickpea-wheat (C-W), and safflower-wheat (S-W)] were considered in main plots, three tillage treatments (conventional-tillage (CT), minimum-tillage (MT), and no-tillage (NT)) were located in subplots, and two winter dryland wheat genotypes (Baran and Azar2) were allocated in sub-sub plots. Results indicated that soil moisture content in NT was greater than that in MT and CT. The highest relative water content (RWC), normalized difference vegetative index (NDVI), stomatal conductance (gs), and transpiration rate (E) were obtained from the Baran genotype in the V-W rotation under NT. In the last year of the experiment, rainfall productivity in NT treatment improved by 32%, compared to CT. The Baran genotype had higher rainfall productivity in both MT and NT treatments with 0.71 and 0.70 kg m-3, respectively. Crop water requirement was not affected by crop rotation or tillage treatments. Maximum grain yields in V-W, C-W, and S-W rotations were recorded as 2231, 2105, and 1991 kg ha-1, respectively. With increasing soil moisture storage and improving rainfall productivity under full implementation of conservation agriculture components (after 4 years), grain yield of Baran and Azar2 improved in NT compared to that of CT by about 6-9% and 6-14%, respectively. Therefore, the application of V-W rotation with NT in cold dryland areas is recommended for developing of conservation agriculture system.