Enhancing Effect of Nitrogen and Phosphorus on Azolla (Azolla microphylly) in Rice Production in Acid Sulphate Soil

Abstract

The experiment was carried out at Pathumthani Rice Research Center in the year 1995/96 to evaluate the effects of 1) Azolla-N and urea-N to rice in acid sulphate soil, and 2) the split application of P on Azolla biomass production. The soil at the experimental site was classified as Sulphic Tropaquepts:isohyperthermic acid in Rangsit Series (RS). To evaluate the effect of P. the Azolla was inoculated 20 days before transplanting and 5 days after transplanting as dual-crop with rice. P was applied as basal or splitted 2 and 4 times at 10 and 5 days intervals, respectively. The results indicated that maximum fresh biomass can be produced with 2 or 4 split application of P. N content and total N production in Azolla was found significantly higher with 4 split applications of P. Azolla doubling time, its biomass production and N content were not affected by its cultivation methods. Split application of P to Azolla result in higher grain yield and total dry-matter production in rice. N-yield (uptake) in rice was found to be increased with increasing number of split applications of P to Azolla.