Alterations in soil physical and hydraulic properties under sugarcane straw removal management: basis for assessment of ecosystem services related to water flow regulation and erosion control

• Autor(a) principal: Carvalho, Martha Lustosa
• Data de Publicação: 2021
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Biblioteca Digital de Teses e Dissertações da USP
• Texto Completo: https://www.teses.usp.br/teses/disponiveis/11/11140/tde-15092021-151602/
• topic: Cobertura do solo; Crop residue management; Funções do solo; Manejo de resíduos culturais; Qualidade do solo; Soil cover; Soil functions; Soil health

Removing sugarcane (Saccharum officinarum L.) straw to use as an industrial feedstock is a growing practice in Brazilian sugar mills. Straw can be used to produce cellulosic ethanol and bioelectricity and can generate significant income. However, straw contributes to the regulation of various soil processes and functions and consequently has a relevant role in supporting the provision of ecosystem services, such as water flow regulation and erosion control. Removing straw from the field may cause negative impacts on the provision of these services. Therefore, the challenge lies in seeking the balance between the agri-environmental and economic implications to establish a straw management strategy that maintains the sustainability of the crop in the long run. In this dissertation were evaluated the effects of straw removal on soil structural and functional quality, and the soil\'s capacity to provide ecosystem services related to water flow regulation and erosion control. The evaluations were done in a six-year experiment in Iracemápolis - SP with four levels of straw removal: total (TR), high (HR), low (LR), and no removal (NR). Using disturbed and undisturbed samples from four soil depths and field evaluations the following indicators were determined: soil bulk density, water infiltration and runoff, hydraulic conductivity, available water capacity, Visual Evaluation of Soil Structure (VESS), and porous space via soil micromorphology. These selected indicators were used to study the mechanisms by which straw removal influences soil functions, and were integrated into two soil-related ecosystem services provision indexes (ISES) to examine the soil\'s capacity to provide water flow regulation and erosion control. In Chapter 1, which examines the provision of the water flow regulation service, the results indicate that the maintenance of straw does not minimize the physical degradation of the soil by compaction caused by field traffic. Soil bulk density, macroporosity, and available water capacity showed critical values for plant growth, and water flow regulation indexes indicate low service provision for all treatments. In Chapter 2, which examines the provision of the erosion control service, TR showed a decrease in total carbon, and VESS scores and total area of pores values indicate structural degradation in all treatments, but the (ISES) were all above 70%, which suggests that straw removal had a low-to-moderate impact on the erosion control service for this soil with high structural stability. Therefore, we concluded that at the end of the sugarcane cycle the straw did not mitigate the degradation caused by machine traffic, had little effect on the indicators evaluated, and consequently also little impact on the evaluated services. Moderate straw removal may be an opportunity to increase bioenergy production, however, removal management should be planned considering the roles of straw associated with other ecosystem services such as nutrient cycling, carbon sequestration, and conservation of soil organisms.