Development of maize under different pH values, humidity and presence of Azospirillum brasilense

Abiotic factors play a crucial role in the productivity of agricultural systems, and stress resulting from these factors can significantly restrict crop yields. To address this challenge, the use of tools capable of mitigating adverse effects, such as growth-promoting bacteria, is essential. This study aimed to investigate the growth of maize plants inoculated or not with Azospirillum brasilense, subjected to variations in soil pH and moisture. Two experiments were conducted under controlled conditions, in which maize plants inoculated with A. brasilense were subjected to variations in (i) soil moisture (100, 75, 50, and 25% of field capacity) and (ii) hydrogenic potential (pH 4.5; 5.5; 5.0; 6.0; and 6.5). It was observed that low moisture favored root growth but limited the development of leaves and stems of maize plants at the V4 phenological stage. The increased root development provided by A. brasilense under conditions of water restriction resulted in a reduction in water use efficiency by the leaves. Additionally, more acidic and/or alkaline pH levels also reduced the dry mass of roots and aboveground parts, as well as the carboxylation efficiency of rubisco, but increased water use efficiency (At 25% FC water deficit, WUE increased by 9.5% in rhizobacterium-treated seeds and by 16% in the control). Inoculation with A. brasilense promoted greater development of maize plants, as evidenced by increased volume, root length, and leaf area. Although maize plants showed better initial development without water restriction and in soil with a pH of 5.9, A. brasilense allowed maize plant growth even at pH 5.1, without significant adverse impacts.