Spatial and Temporal Variability of Soil CO2 Flux in Sugarcane Green Harvest Systems

Rose Luiza Moraes Tavares,Gustavo Soares De Souza,José Luiz Rodrigues Torres,Newton La Scala Jr,Zigomar Menezes De Souza,Guilherme Adalberto Ferreira Castioni

doi:10.1590/18069657rbcs20150252

Abstract

The sugarcane green harvest system, characterized by mechanized harvesting and the absence of crop burning, affects soil quality by increasing crop residue on the soil surface after harvest; thus, it contributes to improving the physical, chemical, and microbiological properties and influences the soil carbon content and CO2 flux (FCO2). This study aimed to evaluate the spatial and temporal variability of soil FCO2 in sugarcane green harvest systems. The experiment was conducted in two areas of sugarcane in Sao Paulo, Brazil: the first had a 5-year history of sugarcane green harvest (SG-5) and the second had a longer history of 10 years (SG-10). The temporal FCO2 were evaluated in the dry and rainy periods, and spatial variability in the dry period, and related to soil chemical and physical properties, including organic C porosity, bulk density, soil penetration resistance, mean weight diameter of soil aggregates, clay, P, S, Ca, Mg and Fe. The temporal variability indicated no differences between the dry and rainy periods in SG-10, while in SG-5 soil moisture was increased by 33 % in the rainy period. The spatial variability indicated a different pattern from the temporal one, where FCO2 in SG-10 was correlated with soil temperature, air-filled pore space, total porosity, soil moisture, and the Ca and Mg contents; in the SG-5 area, FCO2 was correlated with soil mean weight diameter of soil aggregates and the sulfur content.

Highlights

IntroductionThe sugarcane green harvest system (characterized by the absence of crop burning, with mechanized harvest and residue deposition on the soil surface, especially leaves and culms), which has replaced the pre-harvest burning method, has increased in use in Brazil since the 1990s due to increased awareness of environmental impacts, such as the increase in gas emissions that cause the greenhouse effect and emissions of particulate matter that have a harmful impact on human health (Arbex et al, 2012; Sisenando et al, 2012)
The sugarcane green harvest system, which has replaced the pre-harvest burning method, has increased in use in Brazil since the 1990s due to increased awareness of environmental impacts, such as the increase in gas emissions that cause the greenhouse effect and emissions of particulate matter that have a harmful impact on human health (Arbex et al, 2012; Sisenando et al, 2012)
Soil FCO2 in SG-10 was more consistent over time and an increase associated with the rainy period was not observed as it was in SG-5 (Figure 3)

Summary

Introduction

The sugarcane green harvest system (characterized by the absence of crop burning, with mechanized harvest and residue deposition on the soil surface, especially leaves and culms), which has replaced the pre-harvest burning method, has increased in use in Brazil since the 1990s due to increased awareness of environmental impacts, such as the increase in gas emissions that cause the greenhouse effect and emissions of particulate matter that have a harmful impact on human health (Arbex et al, 2012; Sisenando et al, 2012). Panosso et al (2009) compared the spatial and temporal variability of soil CO2 emissions in pre-harvest burning with a seven-year green harvest system and found that the CO2 emissions were 39 % higher in the burned plot when compared to the green one. They showed that, with green management, CO2 was more homogeneous when spatial and temporal variability were considered

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Conclusion