Effect of phosphorus fertilization on yield and phosphorus use efficiency of winter oilseed rape (Brassica napus L.) with two different cropping intensities in the middle and lower reaches of Yangtze River.

摘要

Winter oilseed rape is the most important oil crop in China and it is mainly located in the Yangtze River, which has two cropping intensities (intensity 1: two crops per year, intensity 2: three crops per year). In order to evaluate the effects of phosphorus (P) fertilization and P use efficiency on seed yield of winter oilseed rape (Brassica napus L.) with the two different cropping intensities, 30 experiments were conducted from 2008-2009 in the middle and lower reaches of Yangtze River of China. Phosphorus fertilization significantly increased the seed yield of oilseed rape, the average increase rates of intensity 1 and intensity 2 were 23.8% and 43.5%, respectively. The average seed yields of Anhui, Hubei, and Zhejiang provinces which belonged to intensity 1 were 2598, 2603, and 2417 kg ha-1, respectively, but the seed yields of Hunan and Jiangxi provinces which belonged to intensity 2 were 1809 and 1248 kg ha-1, respectively. Similar to seed yield, P accumulation and P use efficiencies were significantly higher in intensity 1 than in intensity 2, the average P use efficiencies of intensity 1 and intensity 2 were 5.4 and 4.5 kg.kg-1 (AE), 28.2 and 17.0 kg.kg-1 (PFP), 19.4% and 10.4% (RE), respectively. There was no significant difference in soil Olsen P content between two intensities, and soil Olsen P 25 mg kg-1 was the critical P value for oilseed rape production in both cropping intensities. This study demonstrated that P fertilization is indispensable to oilseed rape production, while soil status was not the reason for the difference of P use efficiency between the two cropping intensities. It indicated that P management strategies for oilseed rape production should be adapted to different cropping intensities.