Fate of nitrogen from a blue-green alga in a flooded rice soil

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Abstract
Uptake of 15N from a blue-green alga (Nostoc sp.) by rice (Oryza sativa) was studied in pot and field experiments. Availability of UN from blue-green algae incorporated into the soil ranged between 23 and 28% for the first crop and between 27 and 36% for the first and second crops. Surface application of the algal material reduced 15N availability to 14-23% for the first crop and 21-27% for the first and second crops. The pot experiment demonstrated that for the first crop algal 15N was less available than ammonium sulfate, but for two crops, its availability was very similar to that of ammonium sulfate. After two crops, 57% of 15N from blue-green algae and 30-40% of 15N from ammonium sulfate remained in the soil.