Evaluation of biofertilizers under irrigated and upland soil conditions

Biofertilizers have been claimed as an alternative source of nutrients for plants in order to increase yield and reduce the inorganic fertilizer use by 50%. These are microorganisms-carrying materials which are said to fix atmospheric nitrogen, mobilize and mineralize nutrients in soils, produce growth promoting hormones and serve as biocontrol agent against pest and diseases. The study was undertaken in various sites including Laguna, Isabela, Ausan, Bohol, Ilocos Norte, Negros Occidental, Leyte, Nueva Ecija, Samar, and Camarines Sur in wet and dry seasons to verify the effectiveness of biofertilizers under irrigated and upland ecosystems. It was aimed also to determine the soil and environmental conditions where these biofertilizers may be effective so that appropriate guidelines can be generated for the benefit of the farmers. The experiment consisted of 9 treatments namely control, biofertilizers (Bio N, Vital N, Biocon) applied alone or in combination with inorganic fertilizers wither at 1/2 or full recommended rate. Generally, grain yields and biomass of irrigated and rainfed rice including yield components, such as plant height, tiller count, number of productive tillers, spikelet count, number of filled grains, number of unfilled grains and weight of 100 grains showed no positive effect of biofertilizers. The positive effect of BioCon, Bio N and Vital N on root length of rice at seedling stage may be attributed to the microorganisms producing plant growth hormones, which enhance root growth under 'dapog' seedbed. However, the beneficial effect on root growth was not sustained and reflected on the yield. It is therefore quite evident that biofertilizers evaluated were not effective under anaerobic condition. For corn, yield responses were variable. Some sites showed positive effect of biofertilizers while in some sites they have not contributed to increased crop growth and yield.