Global project 931012711 · 1982 · agriculture

Worldwide increases in the cost of nitrogen fertilizer have led to renewed interest in biological nitrogen fixation as an alternative fertilizer source. This paper attempts to determine the amount of nitrogen that can be produced through biological fixation in flooded rice fields and examines the ability of biological nitrogen fixation to maintain or increase rice yields. First, the paper reviews three methods of measuring biological nitrogen fixation and nitrogen cycling. Next, a number of studies on nitrogen gains and losses in the rice field are summarized; exogenous and endogenous nitrogen sources, nitrogen sinks, and the nitrogen balance are examined. Experimental evidence is then cited which indicates that farmers can manipulate nitrogen fixers to significantly raise rice yields. A final section discusses limits on the effectiveness of nitrogen fixers in providing nitrogen to rice. The author concludes that while biological nitrogen fixation can provide 100 kg or more of nitrogen per hectare per crop, there is a critical need to identify management practices that will reduce nitrogen losses from rice fields. Included are 136 references (1939-80) and 15 tables of data.

Source: DEC abstract, PN-AAL-834 (1982). The source's own text.