Abstract:
In order to investigate the effects of different cultivation technologies on the yield, water and fertilizer utilization efficiency of rapeseed (Brassica napus L.), a 2-factor complete random design experiment was conducted, which included 3 cultivation models (flat cultivation, straw mulching and ridge-furrow rainfall harvesting) and 3 fertilization models (conventional fertilization rate and type, reducing application rate with slow-release fertilizer and no fertilizer). The experiment was carried out in Baoping town of Yunyang county, Chongqing, China. The rapeseed variety was Sanxiayou No.5. The conventional fertilizer was urea (N 46%). The application rate of the conventional fertilizer was 225 kg/hm2 N, 63 kg/hm2 P and 72 kg/hm2 K. The application rate of the slow release fertilizer was 180 kg/hm2 N, 50 kg/hm2 P and 58 kg/hm2 K. In the slow release fertilizer, the N, P and K content were 25%, 7% and 8%, respectively. The experimental plot was 4 m in width and 4 m in length. During the experiments, the precipitation was measured. The plant height, dry matter and root shoot ratio were determined. After harvesting, the pod number, seeds number per plant, 1 000 grain weight and yield were determined too. Protein, oil content and fatty acid were measured. The water consumption and water use efficiency were calculated. The apparent utilization efficiency, agronomic efficiency and physiological efficiency of N, P and K were calculated. The results showed that it was rainy in 2016-2017 and had seasonal drought during the nutritional growth stage in 2017-2018. The yield and its composition values were lower in rainy year than in seasonal dry year. The single water-saving technology had no significant effect on yield increase when seasonal drought occurred. The water-saving and fertilizer saving technology could not only stabilize the yield when there was a lot of rain, but also obtained enough water during drought to increase the yield. The technique of straw mulching plus reducing application rate of slow-release fertilizer and furrow ridge rainwater collection plus reducing application rate of slow-release fertilizer could improve stress resistance at seedling stage of rapeseed, increased the effective pod number per plant and thus improved the yield and maintained the stability of the quality of rapeseed. At the same time, compared with the conventional cultivation under 2 different precipitation conditions, the technique of straw mulching plus reducing application rate of slow-release fertilizer and furrow ridge rainwater collection plus reducing application rate of slow-release fertilizer could reduce the water consumption of rapeseed, increase the water use efficiency by 8%-40%, and increased the fertilizer use efficiency. Considering results of this study and ecological condition in arid field of southwest, we suggested the technique of straw mulching plus reducing application rate of slow-release fertilizer and furrow ridge rainwater collection plus reducing application rate of slow-release fertilizer. The slow-release fertilizer was applied once as base with the application rate of 720 kg/hm2. The technique combined with others such as hole broadcast could effectively relieve the adverse impacts of abnormal climate conditions on the growth and yield of rapeseed to achieve high yield and quality.