| For achieving high yield and economic benefits, as well as protecting the environment, it was necessary to clarify the relevant thresholds to optimize application of fertilizer phosphorus (P). Based on the long-term experiments in lower reach of Liaohe River Plain, the thresholds of soil
Olsen-P for yield (TPY) were calculated by linear-linear (LL), linear-plateau (LP) and Mitscherlich type exponential (Exp) models. In addition, the thresholds of soil Olsen-P for leaching (TPL) were determined by soil column leaching experiment. Results showed that the TPY was 12.0 mg·kg-1 and 10.8 mg·kg-1 for maize (Zea mays L.) and soybean (Glycine max), respectively. Furthermore, the TPY was the highest as calculated by the Exp model, whereas the least was obtained with the LP model. The TPLs ranged from 74.6 mg·kg-1 to 82.0 mg·kg-1, with the mean value of 80.2 mg·kg-1. It was recommended that Olsen-P concentration should be maintained within the range from 12.0 mg·kg-1 to 80.2 mg·kg-1 in the target area, in order to sustain crop production and avoid environmental contamination. |