Effectiveness of Bio-N in enhancing growth and yield of rainfed rice

In intensive rice production system, the indigenous N-supply and mineral N in the soil are never sufficient. High leaching losses that result in only about 25-40% recovery of applied N is a major reason. This necessitates the application of high amount of inorganic N-fertilizer to meet the crop’s requirement. However, their high cost that ranges from P895 to more than P1,000 for urea (46-0-0)/bag and from P450 to P670 for ammonium sulfate (21-0-0)/bag are almost unaffordable to ordinary farmers. Hence, farmers usually cut down on their fertilizer usage which often results in lower grain yield. Thus, there is a need for cheaper and environment-friendly alternatives such as the biofertilizer use.

To test the effectiveness of Bio-N inoculant as biofertilizer , Abalos and Duclayan (DMMMSU) assessed its performance when applied to rice alone or in combination with inorganic N-fertilizer (urea) during WS planting (July-October 2004) in rainfed areas of Bulaoan, La Union. Bio-N inoculation was done by sprinkling Bio-N solution (one pack Bio-N mixed in 10 L water) 4 days before hand pulling of seedlings on the seedbed. The Bureau of Soils and Water Management (BSWM) recommended fertilizer rate (RR) of 120-0-0 was considered as basis in the various treatments used for this study.

Findings

• Application of 50% and 75% of the RR + Bio-N resulted in yields comparable with the application of 100% RR. Yields of 3.48 t/ha and 3.67 t/ha were obtained in the 50% and 75% of the RR + Bio-N application, respectively. Plants applied with 100% RR alone gave a yield of 3.76 t/ha. Lower rates (0-25% RR) and Bio-N alone proved to be insufficient to promote optimum growth and yield of rice.
• The most significant effect in terms of yield was obtained in plot treated with 100% RR + Bio-N which gave a yield of 4.52 t/ha.
• Cost and return analysis revealed that highest net income (P16,628.86) and benefit-cost ratio (BCR) of 1.56 were obtained from plants applied with 100% RR + Bio-N. A comparable net income (ranging from P5,502.04 to P9,505.45) and BCR (ranging from 1.21 to 1.45) were obtained from plants applied with 100% RR alone and from 25% to 75% RR + Bio-N treatments.

Since rice performance at 50-75% RR + Bio-N application was relatively similar to rice applied with 100% RR alone, it was apparent that inorganic N-fertilizer use may be reduced to avoid unfavorable soil and other environmental conditions and improve farm productivity.

There is still a need, however, to conduct another trial to further verify and assess the ability of Bio-N to supply the nitrogen requirements of standing rice plant in the rainfed areas.

Source: PCARRD, 2006. Highlights 2005, Los Banos, Laguna.

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