Soil CO2 emission and its relation to soil properties in sugarcane areas under Slash-and-burn and Green harvest

Abstract

Soil CO2 emission (FCO2) has been related to soil properties that are strongly influenced by agricultural management. The objective of this work was to study FCO2 and its relation to soil properties in adjacent areas cropped with sugarcane managed with Slash-and-burn (SB) and Green (G) harvest. FCO2 was significantly higher (p < 0.01; 2.74 mu mol m(-2) s(-1) in SB and 2.07 mu mol m(-2) s(-1) in G) in SB. Total emission in the 70-day period after harvest was also higher in the SB plot (729 g CO2 m(-2)) when compared to the G (557 g CO2 m(-2)) plot. Organic matter content and carbon stock (0-25 cm) were 13% and 20% higher in SB, respectively, when compared to G. Other soil properties that presented significant difference between plots were pH, available phosphorus, sum of bases, cation exchange capacity, texture, and humification index of soil organic matter. The SB plot presented higher spatial variations in the majority of the soil properties, including FCO2, when compared to the G plot. Principal component analysis sustains the distinction of two groups, G soil samples and SB soil samples, separately. Regression analysis was able to explain up to 75% and 45% of the FCO2 spatial variability in SB and G harvested areas, respectively, and indicates that the humification index of soil organic matter, and its interaction with soil bulk density, is an important factor not just to differentiate emissions in each plot. Linear correlation between humification and FCO2 in each management system shows a positive correlation (p < 0.10) in the G area and negative correlation (p < 0.05) in the SB area. In addition, the interaction between humification index and bulk density relates better than others properties with soil CO2 emission, with this property being the most important to understand the emission variability in the Slash-and-burn area. (C) 2010 Elsevier B.V. All rights reserved.