Study of Phosphate Solubilizing Microbe to Reduce the Rate of Inorganic-P Fertilizer on ICM (Integrated Crop Management) and SRI (System of Rice Intensification) Cultivation System

Abstract

Phosphorus (P) fertilizer has an important role in increasing the production of paddy rice (Oryza sativa L.). Application of high rate P fertilizer is not suitable with the availability of P in the soil because most P bounded by Al, Fe and Ca so make it unavailable to plants. This leads to inefficient use of P fertilizers. Utilization of phosphate solubilizing microbes (PSM) is one of the means to increase the availability of P that can be absorbed by plants, thus reducing the use of inorganic-P fertilizer. Therefore, the aims of the experiment were (1) isolating and selecting some phosphate solubilizing microbes, (2 )to test its effectiveness of PSM in increasing the availability P available on cultivation system of ICM and SRI, (3) to know the effect of PSM to reducing rate inorganic-P fertilizer on the growth and yield of rice. The experiment was conducted of two experiment. First experiment was conducted in Soil Biotechnology Laboratory, Department of Soil Science and Land Resources, Faculty of Agriculture, Bogor Agricultural University in October 2011 - April 2012. Second experiment was conducted at Field Experiment Sawah Baru, University Farm, Bogor Agricultural University in May to August 2012. The first experiment was (1) isolating and selecting PSM (phosphate solubilizing bacteria and fungi) from biofertilizers. (2) Phosphate solubilizing index test (PSI) to measure the clear zone around the colony. (3) Test the ability of solubilizing P from insoluble phosphate source (Ca3(PO4)2, AlPO4, FePO4). (4) Antagonistic test to know ability of phosphate solubilizing bacteria and fungi and compatibility both in the growing medium and identified of phosphate solubilizing bacteria and fungi. The second experiment was conducted using a split block design with two factors and three replications. First factor as main factor is cultivations system (ICM and SRI) and second factor as sub plot is Combination of rate inorganic-P fertilizer and PSM namely 100% inorganic-P; 75% inorgaic-P; 75% inorganic-P + Phosphate solubilizing bacteria (PSB); 75% inorganic-P + phosphate solubilizing fungi (PSF); 50% inorgaic-P; 50% inorganic-P + PSB; 50% inorganic-P + PSF; PSB only; PSF only; and PSB + PSF. The results of laboratory experiment obtained isolate of PSB BPFA5 (Pseudomonas aeruginosa) and the isolate of PSF FPFE1 (Aspergillus niger) has high phosphate solubilizing index, with wide of clear zone is 2.29 and 1.22, ability of phosphate solubilizing from P source Ca3(PO4)2 is 259.86 dan 537.26 ppm-P and compatible (non antagonistic) in same medium. Both of these isolates used for inoculation in the field. The result of second experiment in the field showed that treatment of cultivation system produced that number productive of tillers, weight of dry plant ,number of grain per panicle, weight of 1000 grain, yield, and population of phosphate solubilizing microbes higher on SRI cultivation system than ICM cultivation system. Combination of 75% inorganic-P fertilizer + PSM on SRI cultivation system produced number of productive tillers, yield, and uptake P of viii grain higher than other treatments. PSM application (PSB and PSF) increase of yield and nutrient-P uptake of straw and grain.