Biological strategies to maximize nitrogen and phosphorus use efficiency in grain sorghum with Trichoderma harzianum

Abstract

Chemical fertilization is essential for increasing yields in various crops, including Sorghum bicolor . Currently, there is increasing interest in sustainable alternatives, such as microbial-based biostimulants. Among the most widely used microorganisms, Trichoderma spp. are well-known plant growth-promoting fungi. The objective of this study was to evaluate biological strategies for reducing fertilizer use in grain sorghum through the application of Trichoderma harzianum combined with varying rates of nitrogen and phosphorus fertilizers. Two experiments were conducted at the State University of Goiás, in Ipameri, Goiás, Brazil. The experimental design was a 4 × 5 factorial arrangement in randomized complete block design with five replications. In the nitrogen experiment, stabilized urea (N45) and conventional urea were applied, with or without T. harzianum , at nitrogen rates of 50, 70, 90, 110, and 130 kg N ha -1 . In the phosphorus experiment, stabilized phosphorus sources (P35) and single superphosphate were applied at rates of 10, 80, 150, 220, and 290 kg P 2 O 5 ha -1 . The evaluated variables included plant height, relative chlorophyll content, days to flowering, stem diameter, fresh stem mass, fresh leaf mass, and dry grain mass. The treatment with stabilized urea (N45) combined with T. harzianum (T 2 ) exhibited higher dry grain mass at the maximum nitrogen rate (130 kg N ha -1 ), which was associated with higher photosynthetic activity, greater consistency of stem diameter growth, and increased leaf mass compared to the conventional urea treatment (T 3 ). In the phosphorus experiment, treatment T 2 (stabilized phosphorus – P35 combined with T. harzianum ) exhibited the highest dry grain mass at 290 kg P 2 O 5 ha -1 . In this case, the increase in grain yield was attributed to higher photosynthetic activity, greater plant height and stem diameter, and increased fresh stem and leaf mass, despite fewer days to flowering, compared with T 3 (single superphosphate).