Developing Bradyrhizobium Japonicum Mixed Pellet Fertilizer And Its Application In Heilongjiang Province

To meet the technical requirement of mechanized sowing and seed-coating with bactericide in soybean production, we conducted a series of tests to develop Bradyrhizobium japonicum mixed pellet fertilizer and the corresponding application methods were investigated.Some efficient rhizobial strains like NK246, 316, etc were screened specially adapted to the soil-type and soybean cultivars in Heilongjiang province. It was showed that application of the rhizobia together with K-dissolving bacteria and P-dissolving bacteria can increase soybean yield. A mutual benefit effect was found when the rhizobia were applied with microelement molybdenum, cobalt and tungsten. Three formulas of efficient multi-strain fertilizers which mainly composed of B. japonicum were developed.The working flow, key techniques and parameters for manufacturing mixed pellet fertilizer were finished. Two new techniques were innovated, (1) 2-step pellet-forming by squeezing it in mould first and rolling it in a tray later; and (2) drying the pellet at low temperature by baking it along the wind first and drying it against the wind later. Some key technique parameter, such as suitable wind temperature (72℃~77℃), pellet temperature (lower than 45℃), drying time (not exceed 16 minutes), etc, were established.The effect of mixed pellet fertilizer on the useful bacteria number in soil, root nodule distribution and soybean yield was investigated in comparison with the traditional seed inoculation method with rhizobial powder. A new technique was developed to put mixed pellet fertilizer into seed layer and found to increase soybean yield by 8.5%~12.3% and to save chemical fertilizer by 20% in albic soil and 30%~40% in meadow black soil respectively in four years.In 2001~2004, 1408.8 ton of such mixed pellet fertilizer had been manufactured and applied in fields with total area of 40250 hm2. The application of mixed pellet fertilizer greatly increased soybean yield and decreased chemical fertilizer input, therefore, helped to protect the soil environment and produce "green soybean". The new fertilizer can be mixed with chemical fertilizers and be applied by machines. It was evaluated as a new high technical product in Heilongjiang province in 2004. No similar product was reported in the published literatures.