Effect of phosphate-solubilizing bacteria isolates in acid soil on soybean (glycine max l.) seed yield

Acidic soil is generally poor in macro nutrients, especially phosphoms (P) which is the second major nutrient after nitrogen needed for crop production. The objective of this study was to identify efficient isolates of phosphate solubilizing bacteria (PSB) in acid soils to improve soybean productivity. Two experiments were carried out: one in the greenhouse of ILETRI and the other, a field experiment, in the acid soil of Tanah Laut Two experiments were carried out namely in the greenhouse of Indonesian Legumes and Tuber Crops Research Institute (ILETRI) and the field experiment in acid soil of Tanah Laut, South Kalimantan, Indonesia The treatments were arranged in a split-plot design with three replications. The main plots were the equivalent dose of lime in the form of dolomite: 0; 400; and 800 kg ha(-1) dolomite. Sub plots consisted of two factors: factor 1 was P fertilizer equivalent to 0; 100; and 200 kg SP36 ha(-1), and factor 2 was inoculation of PSB isolates i.e. without inoculation, isolate Lampung-1, isolate Lampung-2 and isolate Lampung-3. The result of the greenhouse study revealed that, isolate Lampung-2 increased seed yield by 18%, and when combined with dolomite equivalent to 800 kg ha(-1 )it increased yield by 40% compared to control (without dolomite and P-solubilizing bacteria). Application of Lampung-2 + 200 kg ha(-1) SP36 gave the highest yield and yield increase of 45% relative to 0 kg ha(-1) SP36 un-inoculated as controls. The increase in yield was supported by an increase in plant P uptake, which was highest in Lampung-2 isolates. The result of the field experiment showed that at fertilization dose of 100 kg ha(-1) SP36, Lampung-2 was able to increase yield by 27% (equivalent to seed yield obtained from 200 kg ha(-1) SP36), followed by Lampung-1 with 18.5%, over the control treatment The present study suggests Lampung-2 biological fertilizer combined with phosphoms fertilizer and dolomite could be recommended for enhancing growth and yield of soybean in acid soils in Indonesia.