Soybean [Glycine max (L.) Merrill] inoculation and reinoculation are essential to guarantee the maximization of the biological N2 fixation process. Most inoculants commercialized for soybean in Brazil are peat-based, but there are doubts about the dose of peat inoculant which should be recommended, specially under stressing conditions or in areas previously inoculated. Therefore, for the central region of Brazil, the recommendation is 1.000 g of inoculant/50 kg of seeds, with a sugar cane solution as adhesive. However, in this study it was shown that the maximum dose of peat inoculant adhered to the seeds ranges between 500 g to 600 g/50 kg seeds. The use of higher doses will thus result in peat accumulated in the sowing machine. Under sterile greenhouse conditions, the dose of 250 g of peat inoculation was sufficient to allow a good nodulation and nitrogen fixation, but in pots containing non-sterile soil or under field conditions, the best results were obtained with the dose of 500 g. In general, reinoculation with 500 g of peat inoculant (10(8) cells/g) with a sugar cane solution as adhesive, under field conditions, increased yield and total N in grains.
Bradyrhizobium; inoculation; nodulation; seed treatment