Effects of potassium fertilization on crops yield, potassium uptake, and soil potassium fertility in rice-oilseed rape cropping systems

ABSTRACT

To determine the impact of K fertilization on crop yields and soil K supplying capacity in rice (Oryza sativa L.) and oilseed rape (Brassica napus L.) rotation, four field experiments were conducted with five K fertilizer rates: 0 (K0), 90–147 (K1), 180–210 (K2), 270–300 (K3) and 336–390 (K4) kg K₂O ha⁻¹ per rotation. Compared with K0, adding K increased the yield of rice and oilseed rape by 4.2–8.9% and 7.5–32.6%, respectively. Potassium fertilization increased K uptake at four sites, whereas yields remained stagnant in K2, K3, and K4 treatments despite increasing K uptake. Continuous K removal decreased soil K supplying capacity. For the 0 to 20 cm and 20 to 40 cm soil depths, the NH₄OAc-K and boiling HNO₃-K at the harvest were decreased in K0 and K1 treatments, whereas it maintained or increased in K2, K3, and K4 treatments, although negative K balances were recorded at all sites. It suggests that application 180–210 kg K₂O ha^–1 in rice-oilseed rape cropping systems improved crop yield and maintained soil potassium fertility.

KEYWORDS:

• Rice-oilseed rape rotation
• soil test K
• K use efficiency
• soil K supplying capacity
• apparent K balance

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], International Potash Institute Co-operation Program and the Fundamental Research Funds for the Central Universities [2662017JC010]. We are grateful to David Clay for the constructive suggestions for improving this manuscript.