ScienceAsia 19 (1993): 057-072 |doi: 10.2306/scienceasia1513-1874.1993.19.057

LOW-INPUT IMPROVEMENT OF AGRICULTURE OF NORTHEAST THAILAND USING AQUATIC LEGUMES AND PHOSPHATE ROCK
PART 3: RELATIONS BETWEEN P-NUTRITION AND NODULATION UNDER UPLAND CONDITIONS

PONGSIRI PATCHARAPREECHA,^a DUANGSAMORN TAJA^b AND HIDENORI WADA^c

ABSTRACT: Effects of triple superphosphate (TSP) and phosphate rock (PR) on growth of Sesbania rostrata and Aeshynomene afraspera were examined by pot experiments. The plants were cultivated in a sandy soil under upland conditions during the dry season when the temperature was very hlgh. In the initial growth stage, spontaneous nodulation was very poor for both plants, probably due to too high temperature and/or too low humidity. Inoculation of Azorhizobbium caulinodans ORS 571 on the stems of the plants easily induced many stem nodules. This situation revealed close interactions between nodules and P-nutrition. Even before inoculation, growth of S. rostrata was remarkably promoted with TSP but the yellow coloration of the plant indicated that they suffered from N-deficiency. After the inoculation, the plants became green again and it growth was further promoted. On the other hand, PR was somewhat suppressive to S. rostrata before inoculation. After the inoculation, growth of the plant was enhanced in the presence of PR. Similar results were obtained for A. afraspera, though the suppressing effect of PR was more serious for A. afraspera than for S. rostrata. Reasons for the difference is discussed.

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Received June 3, 1992