Long-term green manure application improves soil K availability in red paddy soil of subtropical China
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SOILS, SEC 1 • SOIL ORGANIC MATTER DYNAMICS AND NUTRIENT CYCLING • RESEARCH ARTICLE
Long-term green manure application improves soil K availability in red paddy soil of subtropical China Yumei Wen 1 & Jinwei You 1 & Jun Zhu 1 & Hongqing Hu 1
&
Jusheng Gao 2 & Jing Huang 2
Received: 26 January 2019 / Accepted: 27 August 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Purpose Potassium (K) in soil minerals is an important factor affecting rice production in red paddy soil of subtropical China under intensive agricultural production. The long-term application of green manure might affect the soil K availability through accumulative effects of microbial activity on K-bearing minerals. This study aims to investigate the effect of green manure applications (GMs) on soil K availability in relation to soil minerals. Materials and methods The soil mineralogy under 36 years of GMs, including milk vetch application (MV), rape application (RA), and ryegrass application (RY), was studied by X-ray diffraction (XRD) measurement, with a winter fallow treatment (WF) as the control. Fast available K (FAK), non-exchangeable K (NEK), and structural K (SK) were extracted with NH4OAc, HNO3, and HF-HClO4 solution, respectively. All the extracted K was determined by flame photometry. The K release or retention was measured by a new method of potassium Q/I curve. Results and discussion The GMs significantly decreased the SK, which was associated with weakened diffraction intensity of feldspar and mica. However, the NEK under GMs increased from 90.9 to 100.1–104.8 mg kg−1 compared with that under WF, which was in line with the higher content of illite under GMs. The soil clays contained much kaolinite and illite, leading to easy leaching of K. The GMs obviously improved K retention in the soil, especially the MV and RY, which could be ascribed to the large amounts of illite with poorly crystallized structure under GMs. Conclusions Long-term GMs, especially MV and RY, can improve the availability of SK and K retention capacity in the soil in relation to soil mineralogy, and thus can be an effective alternative to enhance soil K availability in red paddy soil. Keywords K availability . Red paddy soil . Long-term green manure application . Soil mineralogy
1 Introduction Potassium (K) is an essential plant nutrient and plays a critical role in the photosynthesis, protein synthesis, enzyme activation, and phloem transport of plants (Zhang et al. 2010). The K
Responsible editor: Zhihong Xu * Hongqing Hu [email protected] * Jusheng Gao [email protected] 1
College of Resource and Environment, Huazhong Agricultural University, Wuhan 430070, China
2
Red Soil Experimental Station in Hengyang, Chinese Academy of Agricultural Sciences/National Observation and Research Station of Farmland Ecosystem in Qiyang, Qiyang 426182, China
mainly exists in the forms of exchangeable K (EK), nonexchangeable K (NEK), and structural K (SK) in soil minerals. The SK is derived from primary minerals such as feldspar and mica and a
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