Plant Growth-Promoting Organisms and Straw Removal in Sugarcane Cultivation

Plant growth-promoting microorganisms have been widely used in agriculture to sustainably increase productivity. Beneficial bacteria and fungi, such as Bacillus subtilis, Trichoderma spp., and Azospirillum brasilense, play essential roles in enhancing plant health, improving nutrient uptake, and suppressing pathogens. However, the interactions between these microorganisms and management practices, such as straw removal and different irrigation systems, remain poorly understood—especially in terms of their impact on soil carbon sequestration.

This study aimed to evaluate the effects of straw removal and irrigation systems on the community of growth-promoting microorganisms in sugarcane cultivation areas in the Goianésia region, Goiás, Brazil. The experiment followed a completely randomized design in a 3 × 3 factorial scheme (three irrigation systems: sprinkler, center pivot, and rainfed × three straw management regimes: no removal, one-year removal, and two-year removal), with four replicates. Soil samples were collected at a depth of 0–20 cm and used for quantification of Bacillus subtilis, Trichoderma spp., and Azospirillum brasilense through microbiological culture and molecular analysis. Soil physical and chemical properties were also analyzed.

The results showed that plots with two years of straw removal had higher abundances of Bacillus subtilis (6.8 × 10⁵ CFU/g soil) and Trichoderma spp. (4.1 × 10⁵ CFU/g soil) compared to no-removal plots (3.2 × 10⁵ and 2.5 × 10⁵ CFU/g, respectively). Center pivot irrigation favored the development of Azospirillum brasilense, with mean values of 7.4 × 10⁵ CFU/g soil, significantly higher than in other irrigation systems. The presence of these microorganisms was correlated with reduced pathogen populations and increased nitrogen and phosphorus availability in the soil.

It is concluded that prolonged straw removal favors the proliferation of beneficial microorganisms, although it may compromise soil carbon sequestration. Irrigation systems directly influence the microbial composition, with center pivot irrigation being more favorable for Azospirillum brasilense. Integrated management strategies that consider soil microbiology are essential to optimize agricultural productivity and environmental sustainability.