Soil properties and crop yield under different tillage methods for rapeseed cultivation in paddy fields

A two-year research was conducted to investigate the effect of different tillage methods on some soil physical characteristics and crop yield in rapeseed cultivation after rice harvesting. Five tillage treatments including: (i) using rotavator, once to depth of 10-15 cm (T1), (ii) using rotavator, twice to depth of 10-15 cm (T2), (iii) using moldboard plow to depth of 25 cm + rotavator, once to depth of 10-15 cm (T3), (iv) no-till planting through removing rice stubbles from plots (T4), and (v) no-till planting without removing rice stubbles from plots (T5), were evaluated under randomized complete block design (RCBD) in three replications. The biannual results revealed that the effect of tillage methods was significant (p<0.01) on soil bulk density, surface residues after tillage, dry mass of weeds, seed germination, and grain yield. T2 and T3 made considerable reduction in soil bulk density compared to other treatments for the 15- to 30-cm tillage depths. In T1, T2, T3, and T4, surface residues after tillage decreased in comparison with T5 by up to 35.37, 50.71, 69.92, and 75.75%, respectively. Having 71.48 g m-2, T5 had the maximum dry mass of weeds while T3 had the minimum one with 37.50 g m-2. Means comparison represented that in T2 and T3, seed germination reached the shortest length of 6.4 days in average. The highest and lowest grain yields were acquired in T3 (1,571 kg ha-1) and T5 (1,339 kg ha-1), respectively. Statistically, there was no significant difference between T1 (1,432 kg ha-1) and T2 (1,537 kg ha-1) compared with T3 in terms of grain yield.