Interação da correção da acidez do solo com nitrogênio no acúmulo de carbono estável no solo

• Ano de defesa: 2024
• Autor(a) principal: Andrade, Maria Gabriela de Oliveira [UNESP]
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Estadual Paulista (Unesp)
• Palavras-chave em Português: Nitrogen fertilization; Soil aggregates; Liming; Glycine max L; Zea mays L.; Adubação nitrogenada; Agregados de solo; Calagem
• Link de acesso: https://hdl.handle.net/11449/258438

The effect of the direct seeding system on the accumulation of carbon (C) in the soil is well known. The amount of labile C in the soil is related to the quantity and quality of straw in the system. However, the accumulation of stable C, linked to soil minerals, is more interesting due to its greater resilience. It is known that conservation production systems improve soil aggregation and that smaller aggregates accumulate stable C, which, in turn, depends on the nitrogen (N) present in the system and the presence of cationic bridges. Although the effect of each of these factors is known, little is known about the interaction between them. The objective was to study the effect of applying limestone and agricultural gypsum, associated or not with nitrogen fertilization, on soil aggregation, accumulation of C and humic substances, relating the accumulation of stable C with the classes of aggregates in a production system with soybeans and corn intercropped with Tanzania grass, in the second harvest. The field experiment was installed in Botucatu-SP, in 2016, and the data presented are from 2020 to 2022. The treatments were: control (without application of limestone and gypsum), limestone, and limestone + gypsum, with combined doses of N of 0, 80, 160, and 240 kg ha-1, applied annually to corn. Soybeans were grown in the spring/summer and corn in the fall/winter of each year. The combination of limestone, gypsum, and nitrogen fertilizer led to a 13% higher total C stock and a 20% higher total N stock in the 0-60 cm soil profile compared to the control. Liming + N reduced fulvic acids (FA) and humic acids (HA), but the application of gypsum mitigated this negative effect. The application of lime, gypsum, and N increased humin levels, mainly on the soil surface. Thus, the best strategy to increase C storage and stabilization in humid tropical soils in double soybean-corn cultivation was the combined use of limestone, gypsum, and nitrogen fertilizer applied to corn, achieving greater C storage in larger aggregates. The application of limestone and gypsum resulted in lower carbon mineralization compared to the control under N deficiency. N mineralization was greater when limestone + gypsum was applied together with N. Liming and nitrogen fertilization significantly increased nitrate levels in the soil, with no differences between liming and liming + plaster. Greater microbial activity, carbon mineralization, and nitrification were observed when N was applied to the soil. Furthermore, it was observed that the application of liming and liming + gypsum played a substantial role in the processes involving C mineralization in soils, with greater effects on smaller aggregates. Liming management and gypsum application can extend these benefits to deeper soil layers, resulting in increased soil fertility in subsurface layers. Soil management using limestone + gypsum proved to be a promising practice in increasing the productivity of soybeans and corn. Grains, especially at a lower dose of N (80 kg ha-1) or in the absence of nitrogen fertilizer. This result demonstrates the positive impact of liming and gypsum management on the N-use efficiency of crops, thus reducing dependence on nitrogen fertilization in acidic soils. Productivity gains were directly linked to the physical (greater stability and diameter of aggregates) and chemical (pH and macronutrient content) improvements in the soil provided by limestone + gypsum management. Therefore, it is concluded that the synergism of soil correction practices with liming, gypsum, and nitrogen fertilization applied to second-crop corn intercropped with forage species resulted in greater grain productivity, increased soil fertility, C sequestration, and storage, especially in larger aggregates.