化肥优化减施杧果园磷钾养分平衡与环境风险.

[Objective] With a view to providing reference for the management of phosphorus (P) and potassium (K) and environmental assessment in the orchard, the nutrient balance and the environmental risk of P and K in mango orchards under optimized and reduced application of chemical fertilizer were examined.[Method] Seven fertilization treatments were conducted: (i) No fertilization (control, NF), (ii) Sole application of basal organic fertilizer (control, CF), (iii) Constant furrow application of chemical fertilizer (A), (iv) Combined furrow application of organic-inorganic fertilizer (OS), (v) Constant furrow application of integrated water fertilizer (IWF), (vi) 30% Reduced furrow application of water fertilizer (RA), (vii) Combined application of organic-inorganic water fertilizer (OWF) . The surface runoff test was performed on the basis of rainfall simulation experiments, and estimations were made grounded on local meteorological data; The environmental risk assessment test of P and K was carried out in virtue of laboratory tests under simulated conditions to determine the threshold of environmental sensitivity of P and K, thereby dividing the scale; Nutrient balance was utilized to analyze the surplus and deficit of P and K.[Result] The surplus rate of P earned the highest ranking, up to 63.36% (67.04 kg/hhm²), in the constant furrow application of chemical fertilizer (A) ; Maximum K surplus was recorded in the furrow application of chemical fertilizer (A), with a rate of 49.49% (142.96 kg/hhm²) ; The runoff losses of P and K in mango orchards attained to 10.74 kg/hhm² and 8.86 kg/hhm² respectively. The P output and corresponding proportion was ranged as follows: Pruned branches and leaves > surface runoff > litter > harvested fruits, while the sequence of K output and corresponding proportion was: Harvested fruits > prune branches and leaves > litter > surface runoff. The risk threshold of P for a single input was 45.99 kg/hhm², and that of K reached 20.29 kg/hhm². The environmental risk of P in soil was calculated to be 103.78 mg/kg, and that of K arrived at 143.98 mg/kg. The available phosphorus contents of such treatments as A, OS, IWF and OWF exceeded the environmental risk threshold, signaling the phosphorus losses. Similarly, the potassium losses should be noted in that the available potassium contents in OWF and IWF topped the environmental risk threshold. The available potassium content in OS approached the environmental risk threshold, which suggested the potential risk of potassium losses. [Conclusion] (i) Remarkable improvements in the availability of soil potassium and the absorption of potassium by fruit trees can be achieved in virtue of combined application of organic fertilizer. (ii) Measures should be adopted to conserve soil and water in light of the large proportion of phosphorus runoff losses to the phosphorus input in orchards. (iii) Compared with other fertilization treatments, 30% reduced furrow application of water fertilizer (RA) embodies the most balanced input of P and K in general, as well as pockets of improvement. Hence a certain proportion of organic fertilizer instead of chemical fertilizer input is recommended. (iv) It is advisable to keep a single input of P no more than 45.99 kg/hhm² considering the lower demand of mango trees for phosphorus and make K input less than or equal to 20.29 kg/hhm² each time despite the great demand for potassium, and nutrients can be supplied with low amounts and high frequency. [ABSTRACT FROM AUTHOR]