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

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; R_S: straw; Q/I: quantity/intensity; CR₀: equilibrium concentration ratio of K; K_L: labile K; non-specifically available K: -∆K₀; PBC^K: 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; E_min: minimum exchangeable K.

KEYWORDS:

• Soil fertility
• nutrient balance
• straw return

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research was supported by National Natural Science Foundation of China (41571284), National Key Research and Development Program of China (2016YFD0200108), and International Potash Institute Co-operation Program.