[Phosphorus application effects and input threshold of Chinese cabbage in the oasis irrigation region.]

To resolve the problem of higher application and lower use efficiency of phosphorus fertilizer of Chinese cabbage (Brassica pekinensis), the yield, use efficiency of phosphate fertilizer and soil phosphate balance were examined by a located field trial in Zhangye Observation and Experiment Station of the Agro-ecological Environment in oasis irrigation region from 2011 to 2013. The results showed that the yield increased with the increase of phosphorus fertilization rate from 0 to 112.52 kg P·hm^-2, beyond which there would be no further enhancement. The yield was 5489.1 kg·hm^-2 at 112.52 kg P·hm^-2 treatment. This treatment increased the yield by 13.3%-23.8%, under which the phosphorus use efficiency was 14.2%. Soil Olsen-P and CaCl₂-P were positively correlated. For 111.1 kg P·hm^-2 treatment, the content of soil Olsen-P was 24.22 mg·kg^-1, with no phosphorus leaching and no pollution. At the rate of 60.17 kg P·hm^-2, there was a balance between phosphorus input and output and the phosphate demand of Chinese cabbage being met. In conclusion, the optimal phosphorus threshold was 60.17-112.52 kg·hm^-2 for Chinese cabbage, the amount at which could reduce the risk of phosphorus pollution.