RESPOSTA DA CULTURA DA SOJA À COINOCULAÇÃO COM BRADYRHIZOBIUM JAPONICUM E PSEUDOMONAS FLUORESCENS.

Abstract

The use of plant growth promoting bacteria (PGPB), in addition to being a sustainable and economical technique, has shown potential to improve nutrient availability and increase soybean yield. The first study aimed to evaluate agronomic efficiency and phosphorus solubilization through Bradyrhizobium japonicum and a product to be registered Pseudomonas fluorescens (ATCC13525) in soybean, at seed and leaf-spray inoculation. Four experiments with soybean (2020/21 crop) were installed in the following locations in the State of Goiás: Experimental Area of the Goiano Federal Institute, in Rio Verde, Bela Vista Farm, in Indiara, Bauzinho Farm, in Rio Verde, and Cachoeira Farm, in Doverlândia. The B. japonicum was inoculated in the seed of all treatments. It was tested three phosphate fertilization doses: 0, 50, and 100% of recommended P dose, with and without P. fluorescens, at seed treatment and leaf-spray inoculation. The inoculation with P. fluorescens and B. japonicum increases nitrogen (N) content in grains and total N. The P content in dry mass, grains and total are increased using P. fluorescens and B. japonicum, confirming the ability to solubilize phosphates. Inoculation with P. fluorescens and B. japonicum is efficient for increasing shoot dry mass and productivity, then it can be used as a sustainable soybean management technology. Leaf-spray was more efficient than inoculation in seed treatment and can be used as an alternative mode of application. The results demonstrated that the product under test (P. fluorescens - ATCC13525) can be used associated with B. japonicum, in ST or leaf-spray, resulting in increases of agronomic parameters and soybean yield. The second study evaluated the performance of plants inoculated and co-inoculated with PGPB, as well as the effects of the application of nitrogen (N) and protective cellular additives on the soybean productivity. The experiment happened in two crop (2018/2019 and 2019/2020) in random blocks with the following treatments (with 4 repetitions): T1: control (no inoculants or nitrogen-based fertilizers); T2: 200 kg N ha-1; T3: Bradyrhizobium japonicum; T4: B. japonicum + protective additive; T5: Azospirillum brasilense; T6: A. brasilense + protective additive; T7: Pseudomonas fluorescens; T8: P. fluorescens + protective additive; T9: B. japonicum + A. brasilense + P. fluorescens, and T10: B. japonicum + A. brasilense + P. fluorescens + protective additive. It was evaluated the shoot dry mass; the number and dry mass of nodules; N content of dry mass and grain; N total and yield. The results indicate that use of nitrogen fertilizers harm soybean nodulation, harming the BNF and does not result in productivity increases. The inoculation with PGPB is essential for the adequate assimilation of N by the plant, in addition to supporting an increase in productivity, while also improving the N levels of the soybean. The protective additives applied to the inoculants did not influence either nodulation or BNF.