Cover crops influencing phosphorus dynamics in different soil management systems

Author(s)

Ianna Bizerra Barros

• Document type: Doctoral Thesis
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 2024-11-05

Examining board members

Paulo Sergio Pavinato; Edson Marcio Mattiello; Leônidas Carrijo Azevedo Melo

• Advisor: Paulo Sergio Pavinato

Abstract

Phosphorus (P) is an essential element for agricultural production. However, the proper management of this nutrient poses one of the greatest challenges in agriculture within tropical regions, where the soils exhibit a high affinity for P. Therefore, the objective of this study is to understand the changes brought about by the use of cover crops and the different soil management practices on the availability of P, through long-term experiments conducted in the Cerrado region. The study evaluated the potential activity of the enzymes beta-glucosidase (BG) and acid phosphatase (ACP), the abundance of the bacterial community (16s rRNA), phosphorus mineralizers (phoC and phoD), the fractions of P, the accumulated productivity of soybean and cotton, total stocks of carbon (TC), nitrogen (TN), and phosphorus (TP), as well as the multifunctionality of the soil ecosystem (MFSE) across three experiments involving two cultivation systems (no-tillage - NT and conventional - CT) and four types of cover crops (fallow, millet, brachiaria, and crotalaria). The use of cover crops increased the activity of the ACP enzyme in the soil and promoted the immobilization of P in their biomass, resulting in a decrease in soil P availability. The NT increased the activities of the enzymes BG and ACP in the surface layer of the soil, however, a reduction in these activities was observed in the deeper layers, when compared to CT. The overall abundance of bacteria (16s rRNA) was higher in the NT, particularly in association with grasses such as brachiaria and millet. The phoD gene was more abundant than phoC in the three analyzed sites. The CT and long-term fallow favored the microbial community associated with the phoC gene, while the cultivation of brachiaria as a cover crop resulted in a significant increase in the abundance of the phoD gene. Grasses contributed to the reduction of P levels in the less labile fractions of the soil. Overall, cover crops, especially Brachiaria, increased soybean and cotton productivity in the long-term. The NT and the use of cover crops also elevated the stocks of TC, TN, and MFSE. In contrast, the fallow exhibited a higher stock of TP in the soil. Our findings indicate that long-term soil conservation systems, such as NT combined with cover crops, are effective in stimulating soil biological activity, promoting the decarbonization of the atmosphere, optimizing nutrient cycling, and improving soil quality, thereby contributing to the productivity of commercial crops and global food security. (AU)

• FAPESP's process: 21/03961-8 - Cover crops affecting phosphorus dynamics in different soil management systems
• Grantee: Ianna Bizerra Barros
• Support Opportunities: Scholarships in Brazil - Doctorate