Indentiffication Nutrients Limiting Rice Grwoth in Soils of Northeast Thailand under Water-Limiting and Non-Limiting conditions

Abstract

Gllashouse nutrient omission trials are useful in identifying nutrient limitations for plant grwoth in a number of soils under the same environmental counditions. Soils of low fertility are commonly used for production of rinfed lowland rice (Oryza sativa L.), and the crop oftern encounters water stress. Nutrient requirements may be modified when standing water disappears from the field. Two experiments with ricee requirements smay be modiffied when standing water disappears from the field. Two experiments with rice seedlings were conducted in a glasshouse at Ubon Rice Research center, Thailand, to identify the nutrients which limit rice grwoth in soils of Northeast Thailand and to determine whether nutrient limitations are affected by water availability. In Experiment 1, rice was grown on two soils (Roi et and Ubon series) under well-watered and water-limiting conditions and 15 nutrient treatments were imposed. In Experiment 2, sic soils from Notheast Thailand were examined using the same 15 nutrient treatments. The nutrients which clearly limited potassium (K) and sulfur (S) also limited growth, and in one soil zinc (Zn) and boron (B) also limited growth. A shortage of N was the most important limitation for plant grwoth in all soils except one in which P was more important. The low supply of P decreased plant height and leaf area development during early growth; low N supply had a greater effect later during grwoth. The omission of P had a larger detrimental effect on growth when water supply was limited. In the Roi et soil, the omission of S had a large effect on leaf area and total dry matter production only under water stress conditions, but this was not found in the other soils examined. These results from glasshouse studies show tha tthe nutrients limiting rice grwoth depend on soil type and water availability in soils of Northeast Thailand.