Maintenance of the surface straw and its effect on the soil attributes and the productivity of canavial

Author(s)

Ana Paula Guimarães Santos

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia Agrícola
• Defense date: 2016-10-11

Examining board members

Zigomar Menezes de Souza; Edson Eiji Matsura; Fábio Vale Scarpare; José Luiz Rodrigues Torres; Marcelo Andreotti

• Advisor: Zigomar Menezes de Souza

Abstract

Maintaining sugarcane straw on the soil surface can increase soil carbon stocks, reduce total greenhouse gas emissions, improve the physical and chemical properties of soil, increase its biological activity and enhance in filtration and water storage potential. However, the sugarcane sector has increasingly shifted toward the use of this residue for electricity and 2nd generation ethanol production. Therefore, assessing the amount of sugarcane straw that should be maintained on the soil surface of sugarcane fields is increasingly important to ensure the sustainability of green cane management in São Paulo. Thus, the aim of this study was to evaluate the effect of maintaining different amounts of sugarcane straw on the soil surface and compare the out comes for the physical and chemical attributes, soil carbon stocks and sugarcane yields. The work was conducted in two sugarcane mills located in São Paulo State; Iracema (claysoil ¿Eutrutox soil) and Zilor (sandy soil ¿ Haplutox), located in the cities of Iracemápolis-SP and Quatá-SP, respectively. The experiments were installed in a randomized block design with four replicates. Each plot consisted of 10 sugarcane rows that had a row- spacing of 1.5 m and a length of 10 m. The evaluations consisted of: soil density, soil porosity, least limiting water range and soil-water retention curve, aggregate stability, soil water content and water content variation, soil resistance to penetration, extraction and compartmentalization of nutrient contents in sugarcane, straw decomposition and soil carbon concentration. We concluded that although straw rates of 15 t ha-1gave better carbon and nitrogen contributions for both soil types, the results of nitrogen and sulphur content were better in plots without straw and when it was maintained at rates of 5 t ha-1. Therefore, it is necessary to correct fertilization for nitrogen and sulphate where straw is present on the soil surface. In higher temperature conditions, the remaining dry matter is less and decomposition is accelerated when there is a larger amount of straw. In the second crop year, calcium and nitrogen obtained faster half-life for both of the studied soils. The nutrient degradation within straw showed better results at rates of 15 t ha-1 for both soils. The improvements during the first crop year to the physical attributes of sandy soils shows that straw cover shave a greater potential to mitigate soil compaction when compared to clay soils. This suggests that straw removal for industrial purposes may be more damaging in sandy soils. With respect the maintenance of water in the soil, higher rates of straw showed significant effects on soil water retention at depths ranging from 0.00 to 0.10 m in clay soils. The clay soil showed an increase in average diameter at depths between 0.00 to 0.05 m. However, the increase in soil carbon concentration in depth was more significant for the sandy soil (AU)

• FAPESP's process: 13/02792-1 - Maintenance of surface straw and its effect on soil attributes and yield sugarcane.
• Grantee: Ana Paula Guimarães Santos
• Support Opportunities: Scholarships in Brazil - Doctorate