Potassium requirement of rice crop in Malaysian soils
2002
Choudhury A.T.M.A., Sydney Univ., Ross street Building A03, University of Sydney, NSW 2006 (Australia). Dept. of Agriculture Chemistry and Soil Science | Mohd. Khanif Y. | Aminuddin H. | Zakaria W. (eds.), Putra Malaysia Univ. (UPM), 43400 UPM Serdang, Selangor (Malaysia). Faculty of Agriculture
Investigation conducted at the Muda Irrigation Scheme, Kedah showed that the exchangeable potassium (K) content in rice soils ranged from 0.08 to 0.44 cmol kg-1. Five out of sixteen soils studied were found deficient in K. A follow up adsorption study indicated that K adsorption varies among soils. Maximum K adsorption capacity, calculated from Langmuir equation, is higher in soil with higher pH. Results of a succeeding greenhouse study indicated that total K removal by one rice crop varies from 26 to 95 kg ha-1 depending on rice yield. Rice yield and total K removal by rice crop were higher in soil with higher fertility status. Harvest index of K was 21-25%. This result indicated that returning rice straw into the land will return 75-79% of removed K back to the soil. Even if rice straw is applied in-situ, apparent K balance is negative with the present rate of K fertiliser application in soils with higher rice yield potential. Application of higher rate of K fertiliser is needed in this soils to maintain the soil K status in the long run. Based on this review, it can be concluded that K deficiency exists in Malaysian rice soils, and K adsorption property of soils varies. These should be considered while applying K fertiliser in rice crop. Recycling rice straw can return at lease 75% of removed K back to the soil. Application of higher rate of K fertiliser is needed in soils with higher rice yield potential.
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