Field Inoculation of Cereals Grain Crops with Azospirillum Brasilense in the Pampas, Argentina.

The beneficial effects of inoculating with Azospirillum brasilense on the early growth and productivity of cereals crops have been widely described. But, the extensive use under regular production systems is limited because of scarce documented field applied trials. The objective of this study was to quantify the response of cereals grain crops to the on-seed inoculation with a liquid formulation containing A. brasilense INTA Az-39 strain under regular dryland extensive production systems from the pampas, Argentina. The study was performed between 2002 and 2011 evaluating treated and non-treated wheat (Trititicum aestivum L.) and corn (Zea mays L.) crops in 512 and 209 experimental sites, respectively. In general, the crops treated with A. brasilense showed a greater vegetative growth with a greater shoot dry matter accumulation and also a greater number of grains at harvest. No significant differences on single grain weight were described between the treatments. The grain yield response to the A.brasilense treatment was greater than 50 kg ha^-1, in more than 72 % and 82 % of the wheat and corn sites, respectively. Averaged over all the production seasons, the on-seed inoculation increased wheat and corn grain yields by 244 kg ha^-1 and 514 kg ha^-1, respectively. These effects were independent of the crop management practices (N and P fertilization, on-seed fungicide treatments, etc.) and production areas within the Pampas. We conclude that the use of this liquid formulation providing A.brasilense contributes increasing the grain cereals production in the pampas region of Argentina.