Growth and Nitrogen Production Rates of Azolla ( Azolla microphylla ) as Affected by Its Cultivation Methods : An Economic Perspective in Rice Cultivation in Thailand

Abstract

A statistically designed experiment of randomized complete block ( RCBD ) with four treatments was conducted during the year 1995/96 in acid sulphate soil of the central plain of Thailand to evaluate the effects of methods of Azolla cultivation on its growth rate, N production rate and rice production. The results showed that Azolla growth rate was not affected by cultivation methods used. But, N production and its production rate were significantly differed between the cultivation methods used. Azolla grown as a monocrop 20 days before transplanting was found superior in N production rate compared to that of N rate produced by dual cropped Azolla. The grain yield production per kg Azolla-N applied resulted in higher rate of grain production as compared with monocroped Azolla in addition to urea–N on rice when Azolla–N alone was applied to rice. The grain production per kg Azolla-N was found higher when Azolla was applied along with urea-N to rice grown as a dual crop compared to that of Azolla grown as a monocrop and incorporated at transplanting along with the urea-N application to rice. The efficiency of urea-N in grain production was increased when Azolla and urea–N were applied together to the rice crop. The Azolla grown as a dual crop with rice produced economically higher yield compared to that of other cultivation practices used.