Dynamic behavior of plant nutrients in upland soil in Northeast Thailand
1993
Yoshioka, S. | Nonglak Vibulsuk | Chairoj Wongwiwatchai
30 series of upland soils in the northeast were collected in 1985 and their chemical and physical properties were analyzed. In low and middle or high terraces, most soil series showed a sand or sandy texture, while there were more clayey soils in the flood plain or in areas subject to erosion. Corn cultivartion was carried out in pot experiments to study the soil productivity of three upland soils. They showed very low nitrogen, relatively high potassium and all except one had poor phosphorus resources. The nitrogen utilization rate in sandy soils was lower than that in clayey soils. Investigations to determine water runoff and soil loss in sandy soils and clayey soils was found that the amounts were rather smaller in sandy soils than in clayey soils. But the leaching of nitrogen, potassium and magnesium in sandy soils filled into eslon tubes was quicker than in clayey soils. The nutrient movement in Warin soils was studied by using a lysimeter. Considerable amounts of exchangeable bases were leached out, as well as nitrate and chloride ions. Nitrate leached out in mulching plots and compost plots was slightly higher than in non-mulched plots. Double amounts of fertilizer caused more nutrient loss by leaching, but the growth and yield of plants were worse than in the plots where normal fertilizer was applied with the incorporation of mulching or compost. Depending on the amount of leaching, the nitrate content in the soil accumulated much more in the subsoil than in the surface soil.
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