Mycorrhizal Fungus-Based Fertilizer Mitigates Salt Stress Damage on Colored-Fiber Cotton in Semi-Arid Salinized Soil of Brazil

In Northeastern Brazil, agricultural cultivation can be limited by excess soil salinity, which poses a challenge to crop production. To mitigate the impacts of salt stress on plants, it is necessary to develop appropriate technologies; the use of organomineral fertilizers based on biological inputs—such as mycorrhizal fungi—stands out among these. The objective of this study was to evaluate the growth, gas exchange, photosynthetic pigment contents, and production components of colored-fiber cotton grown in salinized soil under concentrations of an organomineral fertilizer based on mycorrhizal fungi. The experiment was carried out under field conditions at the Federal University of Campina Grande, Pombal campus, PB, Brazil, using a randomized block design, in a 5 × 4 factorial scheme, referring to five electrical conductivity of the saturation extract (ECse) levels (3.7, 4.9, 6.1, 7.3 and 8.5 dS m−1) and four concentrations of an organomineral fertilizer based on mycorrhizal fungi (FMF = 0—Control; 1.5, 2.5 and 4.5 g L−1). Soil salinity of 5.0 dS m−1 inhibited growth and gas exchange of colored-fiber cotton. The 2.7 g L−1 concentration improved water use efficiency in cotton plants up to 4.9 dS m−1. The application of up to 1.9 g L−1 increased photosynthetic pigment synthesis under ECse levels of up to 5.8 dS m−1. Application of FMF at 2.5 g L−1 increased cotton production at ECse levels up to 5.5 dS m−1. Under the experimental conditions of this study, the use of an organomineral fertilizer based on mycorrhizal fungi proves to be an efficient strategy for producers in arid and semi-arid regions, which are frequently affected by excess soil salinity.