Application of Spent Sun Mushroom Substrate in Substitution of Synthetic Fertilizers at Maize Topdressing

Synthetic fertilization can increase maize yields, but also cause environmental impacts, as well as increasing production costs and food security risks. Sun mushroom (Agaricus subrufescens) is an important Brazilian fungus used to generate large amounts of spent mushroom substrate. This residue can be used for maize fertilization, but little is known about its ideal application rates to reduce maize dependence on synthetic fertilizers. Therefore, this study aimed to evaluate the agronomic performance of a maize crop under different combinations of synthetic fertilizers and two different spent mushroom substrate doses. The experiment was carried out in pots and evaluated maize germinate and biometric parameters, as well as soil and leaf chemical characteristics. The results showed that residue application increased maize germination and Emergence Speed Index. Regarding the maize biometric parameters, height, stem diameter, shoot fresh and dry masses, and leaf area were superior for residue with synthetic fertilization at sowing only at higher doses. Moreover, residue with synthetic fertilization at sowing proved to be more relevant for maize growth according to canonical discriminant analysis. In terms of nutrients, the use of spent mushroom substrate increased significantly leaf P, K, and S levels and mainly K content in the soil, justifying non-application at maize topdressing.