Effect of split application of phosphorus on the growth of A zolla and low land rice

Abstract

The Azolla pinnata (Vietnam) inoculated in rice field 10 days after transplanting (DAT) at a rate of 500kgha -~fresh biomass along with phosphorus fertilizer application produced a mat on the water surface at 30 DAT. The three split application of phosphorus as 4.4, 2.2 and 2.2 kg P ha ~ applied at 10, 15 and 20 DAT, respectively produced 67% more biomass and 57% more Nitrogen in Azolla than those obtained by applying 8.8 kg P ha -~ at 10 DAT. Whereas, the two splits of phosphorus as 6.6 and 2.2 kg and 4.4 and 4.4 kg P haapplied 10 and 15 DAT, respectively produced 20 and 33% more biomass and 14 and 27% more Nitrogen only. The three split application of phosphorus also increased the grain and straw yields, panicle number and weight, nitrogen concentration and its uptake in rice significantly over application of the entire amount once only. An increase of 10% grain yield and 13% straw yields was observed when 8.8 kg P ha-~ was applied in three splits rather than applied at one time. On the average an increase of 24% grain and 23% straw yields in rice were observed due to AzolIa intercropping and 22% and 16%, respectively due to phosphorus application. The intercropping of Azolla with rice along with phosphorus application also increased the fertility level of soil by increasing the total nitrogen, organic carbon and available phosphorus of soil.