Elsevier

Pedosphere

Volume 32, Issue 2, April 2022, Pages 330-338
Pedosphere

Comparison of potential potassium leaching associated with organic and inorganic potassium sources in different arable soils in China

https://doi.org/10.1016/S1002-0160(21)60077-2Get rights and content

ABSTRACT

Potassium (K) leaching is detrimental to the maintenance of sustainable arable soil K fertility, especially in low-K fixation soils. It is not known whether the application of inorganic fertilizers with lower K mobility or crop straw can reduce potential K leaching in low-K fixation arable soils. The potential K leaching of 14 representative arable soils with different K fixation capacities in China was evaluated with or without the addition of K under two rainfall intensities (90 and 225 mm), and then potential K leaching was assessed in relation to five K sources (KCl, K2SO2, KH2PO2, maize (Zea mays L.) straw, and rice (Oryza sativa L.) straw). Without K addition, K leaching mainly occurred in sandy soils at 90 mm of rainfall and in soils with greater organic matter at 225 mm of rainfall. With K addition, the leaching percentage of exogenous K ranged from 0.6% to 11.6% at 90 mm of rainfall and 1.2% to 21.2% at 225 mm of rainfall. The greatest K leaching occurred in soils with fewer K-bearing minerals and lower pH at both rainfall intensities. In most cases, KH2PO2, which has lower K mobility, markedly reduced K leaching in both high- and low-K leaching soils at the two rainfall intensities. Maize and rice straw reduced K leaching only in soils with high K leaching, regardless of rainfall amount, whereas more K was leached in soils with lower K leaching at high rainfall intensity. In conclusion, KH2PO2 and straw should be preferred for reducing K leaching in low-K fixation arable soils.

Section snippets

INTRODUCTION

Potassium (K) has been accepted as an essential nutrient in crop production for many decades (Cakmak, 2010; Römheld and Kirkby, 2010; Zörb et al., 2014). Plant-available K in soil is significantly constrained by two main processes: K fixation into a non-exchangeable form and K leaching out of arable soil (Rees et al., 2013; Islam et al., 2017). Potassium leaching is detrimental for sustainable arable soil K fertility, especially in soils with poor K fixation capacity (Nguyen and Marschner, 2013

Arable soils

The soils tested were collected from: Changsha County (S1) in Hunan Province, Yingtan County (S2) in Jiangxi Province, Qichun (S3) and Qianjiang (S4) counties in Hubei Province, Wuhu City (S5) in Anhui Province, Hailun County (S6) in Honglongjiang Province, Fengqiu County (S7) in Henan Province, Guangde (S8) and Huaining (S9) counties in Anhui Province, Laiyang County (S10) in Shandong Province, Changshu (S11) and Yancheng (S12) counties in Jiangsu Province, Chongqing (S13), and Hengshui County

Exogenous K distribution among different K pools

There were considerable variations in the distribution of exogenous K in different soils. For S1, S3, and S9, applications of K fertilizer distributed higher amounts of water-soluble K (Fig. 1). In contrast, significantly lower levels of water-soluble K occurred in S13 and S14. For S6, S9, and S2, the distribution in exchangeable K of exogenous K accounted for about 70%, 63%, and 62% of total K fertilizer, respectively, and was significantly higher than that in S13, S8, and S12 (Fig. 1).

Key factors affecting K leaching

In this study, the variation in K leaching was lower in soils without K fertilizer addition than in those with K addition, mainly because of lower available K levels (except in S6). Under low rainfall intensity, significantly greater K leaching mainly occurred in the light-textured soils, such as S7 and S10 (Fig. 2a). Furthermore, higher K leaching amounts at this rainfall intensity were mainly observed for soils with high available K, such as S6 and S2 (Fig. 1a). It was likely because the

CONCLUSIONS

Fertilization significantly increased K leaching. High K leaching with exogenous K fertilizer primarily occurred in soils with fewer K-bearing minerals and lower pH regardless of rainfall intensity. High soil organic matter resulted in high K leaching at high rainfall intensities, indicating that the real mechanism of maintaining K in soil was K fixation. Reducing K mobility in soil by the application of KH2PO2 could significantly decrease K leaching for soils with high and low K leaching

ACKNOWLEDGEMENT

This research was supported by the National Key Research and Development Program of China (No. 2018YFD0200901) and the National Natural Science Foundation for Young Scientists of China (No. 41907075).

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