It was observed by the authors that the potential deficiency of phosphorus may be widely distributed throughout all paddy fields of Thailand, and that the response of plants to phosphorus deficiency might be different with varieties. Therefore, two varieties, Dawk Mali 3, which shows high phosphorus content, and Muey Nawng 62 M, which has extremely low phosphorus content, were selected and compared under the condition of phosphorus deficiency. A striking difference in growth and yield was found: Muey Nawng 62 M failed to produce any grain, whereas Dawk Mali 3 yielded 1 ton/ha of paddy.
The tracer experiment using ³²P revealed that Dawk Mali 3 is capable of absorbing soil phosphorus much more efficiently than Muey Nawng 62 M. As far as the authors know, such a varietal difference in the response to phosphorus deficiency caused by the difference in the ability of variety to utilize soil phosphorus has not yet been reported in the world.
The authors believe that this finding is very significant in Thailand where phosphorus deficient soil is distributed very widely throughout the country.