부산대학교 도서관

This study investigate the potential contribution of nitrogen fixation by indigenous cyanobacteria to rice production in the rice fields of Valencia (Spain). N₂-fixing cyanobacteria abundance and N₂ fixation decreased with increasing amounts of fertilizers. Grain yield increased with increasing amounts of fertilizers up to 70 kg N ha⁻¹. No further increase was observed with 140 kg N ha⁻¹. Soil N was the main source of N for rice, only 8-14% of the total N incorporated by plants derived from ¹⁵N fertilizer. Recovery of applied ¹⁵N-ammonium sulphate by the soil-plant system was lower than 50%. Losses were attributed to ammonia volatilization, since only 0.3-1% of applied N was lost by denitrification. Recovery of ¹⁵N from labeled cyanobacteria by the soil-plant system was higher than that from chemical fertilizers. Cyanobacterial N was available to rice plant even at the tillering stage, 20 days after N application.