Potassium management effects on quantity/intensity relationship of soil potassium under rice-oilseed rape rotation system

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Abstract
Quantity–intensity curves were used to evaluate the dynamics of soil potassium (K) at different soil depths under different K management. The equilibrium concentration ratio of K (CR0) increased with increasing K concentration. K fertilization and straw return increased soil K supplying capacity by increasing CR0, non-specific available K (-∆K0) and equilibrium K (CK0). The CR0 increase 107%, 392% and 577% at the 0–20 cm layer and 55%, 102% and 131% at the 20–40 cm layer, respectively, under K fertilization, straw return and the interaction of them. The CK0 and -∆K0 at the 0–20 cm layer significantly increased after K fertilization and straw return. The labile K varied from 0.11 to 0.19 cmol kg−1, contributed 85.3% to 107.6% of NH4OAc extracted K. Soil K potential buffering capacity showed significant differences in soil depths, while little difference was observed under different K management. Th e exchangeable K was meaningless for guiding K application when minimum exchangeable K took up 85.9% to 99.0% of equilibrium exchangeable K. Our results showed K fertilization and straw return was the optimal management to enhance soil K supplying capacity, especially at the 0–20 cm layer. Abbreviations: N: nitrogen; P: phosphorus; K: potassium; RS: straw; Q/I: quantity/intensity; CR0: equilibrium concentration ratio of K; KL: labile K; non-specifically available K: -∆K0; PBCK: potential buffering capacity; EK0: equilibrium exchangeable K; CK0: equilibrium solution K; α: magnitude of conversion of added K to exchangeable pool; β: conversion of added K to non-exchangeable K pool; Emin: minimum exchangeable K.
Funding Information
  • National Natural Science Foundation of China (41571284)
  • National Key Research and Development Program of China (2016YFD0200108)

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