Comparative effects ofAzolla and blue-green algae in combination with chemical N fertilizer on rice crop

Abstract

FreshAzolla pinnata (Bangkok) and dry blue-green algae dominated byAulosira sp. andGloeotrichia sp. were inoculated separately at the rates of 500 and 10 kg/ha, 10 and 3 days after transplanting, respectively to evaluate their effects in combination with chemical N fertilizer applied at different stages of rice crop. Split application of 30 kg N/ha urea (15 kg basal and 15 kg 45 days after transplanting) showed higher biomass and N accumulation in bothAzolla and blue-green algae than that of applied whole as basal or 15 kg basal plus 15 kg 20 days after transplantation. Application of 30kg N/ha urea in combination withAzolla basal or dual gave the grain yield as obtained by 3 split application of 60 kg N/ha urea, whereas, use ofAzola basal plus dual showed slightly higher grain yield. Blue-green algae dual culture in combination with 30 kg N/ha urea applied as basal or in two split doses produced significantly low grain yield than that of 60 kg N/ha urea. The application of 30 kg N/ha urea as basal or 50% basal plus 50% 20 or 45 days after transplantation in combination withAzolla or blue-green algae dual culture did not show significant difference in grain yield.