Abstract
Inoculation of corn with diazotrophic bacteria reduces the need for nitrogen fertilization and mitigates environmental contamination risks due to the bacteria’s biological nitrogen-fixation capacity. The aim of the present study was to evaluate the effect of corn seed inoculation with Azospirillum brasilense under different nitrogen levels and post-grazing residual heights. The experiment was performed in two growing seasons and conducted in an integrated crop-livestock system for the 2014/15 and 2015/16. A factorial randomized block experimental design with sub-divided plots and three factors. The main plots varied in post-grazing residual height (0.10, 0.20, 0.30 m, continuous grazing, or no grazing), the subplots varied in inoculation (with or without seed inoculation), and the sub-subplots varied in nitrogen level (0, 75, 150, 225, or 300 kg ha -1 of N). The higher post-grazing residual height associated an A. brasilense and nitrogen fertilization resulted in increased corn biomass and production and yield. At the 300 kg dose of N, the highest grain yield was obtained under different post-grazing heights (10.15 Mg ha -1 ) and in the absence of the bacterium (10.00 Mg ha -1 ). Azospirillum brasilense helps plant growth and yield but does not replace the effect of N fertilization.
Highlights
Corn (Zea mays L.) is the most produced cereal worldwide, ahead of important commodities such as wheat, rice, and soybean
For the quantitative analysis of dry weight accumulation under the different N levels (Figure 2a) in the 2014/15 harvest, treatment M30 with 300 kg N ha-1 was 6% higher than the remaining treatments (20.32 Mg DW). This may be due to the improvement of physicochemical soil conditions and nutrient cycling because forage dry weight accumulation and root growth are higher with low grazing intensity (Barth Neto et al, 2013)
Higher soil cover at the end of the grazing period resulted in higher corn plant growth and grain yield
Summary
Corn (Zea mays L.) is the most produced cereal worldwide, ahead of important commodities such as wheat, rice, and soybean. A total 959.79 million tons of corn were produced in the 2015/16 harvest, with 70 million tons produced in Brazil, making Brazil the world’s third largest corn producer (USDA, 2016) This production is associated with the high demand for corn for human and animal food, especially for birds, cattle, and pigs (Purwanto & Minardi, 2015). The need to increase grain yield and production has led to the development of new technologies that constitute alternatives for grain production, such as integrated crop-livestock systems (ICL). These systems combine the production of grains, such as corn, with pastures, taking advantage of their mutual benefits (Sandini et al, 2011). The addition of large amounts of plant residues to the soil surface improves the physicochemical (Mendonça et al, 2013) and biological soil quality (Santos, Fontaneli, Spera, & Dreon, 2011)
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