**Chapter 3**

*Sustainable Crop Production*

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[20] Kitajima S, Kaneko J, Shiroshita T. The variations of cation status in paddy soils and cation absorption by rice plants with the application of potassic fertilizers. J. Journal of the Central Agricultural Experiment Station. 1975;**22**:105-177 (in Japanese with

[21] Sharma S, Chander G, Verma TS, Verma S. Soil potassium fractions in rice-wheat cropping system after twelve years of lantana residue incorporation in a northwest

Himalayan acid Alfisol. Journal of Plant Nutrition. 2013;**36**:1809-1820. DOI: 10.1080/01904167.2013.815202

[22] Yamashita K, Honjo H, Nishida M, Kimura M, Asakawa S. Estimation of microbial biomass potassium in paddy field soil. Soil Science and Plant Nutrition. 2014;**60**:512-519. DOI: 10.1080/00380768.2014.919237

[23] Asakawa S, Yamashita K. Soil microbial biomass as a source of potassium to plants: Soil microbes bear not only nitrogen and phosphorus but also potassium in their bodies. Kagaku to Seibutsu. 2017;**55**:444-445

**40**
