Soil Quality Indexing Strategies for Evaluating Sugarcane Expansion in Brazil

Abstract

Increasing demand for biofuel has intensified land-use change (LUC) for sugarcane (Saccharum officinarum) expansion in Brazil. Assessments of soil quality (SQ) response to this LUC are essential for quantifying and monitoring sustainability of sugarcane production over time. Since there is not a universal methodology for assessing SQ, we conducted a field-study at three sites within the largest sugarcane-producing region of Brazil to develop a SQ index (SQI). The most common LUC scenario (i.e., native vegetation to pasture to sugarcane) was evaluated using six SQI strategies with varying complexities. Thirty eight soil indicators were included in the total dataset. Two minimum datasets were selected: one using principal component analysis (7 indicators) and the other based on expert opinion (5 indicators). Non-linear scoring curves were used to interpret the indicator values. Weighted and non-weighted additive methods were used to combine individual indicator scores into an overall SQI. Long-term conversion from native vegetation to extensive pasture significantly decreased overall SQ. In contrast, conversion from pasture to sugarcane had no significant impact on overall SQ at the regional scale, but site-specific responses were found. In general, sugarcane production improved chemical attributes (i.e., higher macronutrient levels and lower soil acidity); however it has negative effects on physical and biological attributes (i.e., higher soil compaction and structural degradation as well as lower soil organic carbon (SOC), abundance and diversity of macrofauna and microbial activity). Overall, we found that simple, user-friendly strategies were as effective as more complex ones for identifying SQ changes. Therefore, as a protocol for SQ assessments in Brazilian sugarcane areas, we recommend using a small number of indicators (e.g., pH, P, K, Visual Evaluation of Soil Structure -VESS scores and SOC concentration) and proportional weighting to reflect chemical, physical and biological processes within the soil. Our SQ evaluations also suggest that current approaches for expanding Brazilian sugarcane production by converting degraded pasture land to cropland can be a sustainable strategy for meeting increasing biofuel demand. However, management practices that alleviate negative impacts on soil physical and biological indicators must be prioritized within sugarcane producing areas to prevent unintentional SQ degradation over time.

Practices for rehabilitating bauxite‐mined areas and an integrative approach to monitor soil quality

“…These effects would affect the CEC provided by functional groups of SOM and reduce enzymes activity (Table S1). Such results are consistent with the strong influence of SOM on biological processes occurring in the soil and ultimately would boost plant growth (Cherubin et al, ; Lal, ). Thus, the recovery of SOM during the early stages of land reclamation in mined areas also should impact positively on other soil quality indicators (e.g., LOC, BD, and AcP), which are critical to achieve self‐sustaining systems (Chaudhuri, McDonald, Skousen, & Pena‐Yewtukhiw, ; Hu, Niu, Zeng, & Wang, ).…”

Reducing Amazon Deforestation through Agricultural Intensification in the Cerrado for Advancing Food Security and Mitigating Climate Change

“…The rates of C emissions from cutting and burning of tropical forest in the Amazon obtained in this study (Figure 2) are similar to those of 58 to 102 Mg ha −1 reported by Kauffman et al [43] and 100 to 200 Mg ha −1 by Dias-Filho et al [44]. In addition, conversion of native vegetation to agroecosystems adversely affects numerous other ecosystem services such as sustaining agronomic production, maintaining freshwater supply and soil quality, regulating climate and air quality, ameliorating infectious diseases and preserving biodiversity [45][46][47][48].…”

Soil microstructure alterations induced by land use change for sugarcane expansion in Brazil

“…The growing interest in biofuels has resulted in a new demand for arable land for bioenergy crop production. Land use change (LUC) is one of the greatest threats to soil quality (Bonilla‐Bedoya, López‐Ulloa, Vanwalleghem, & Herrera‐Machuca, ; Cherubin, Karlen, Cerri, et al., ), as it can have significant impacts on soil biodiversity (Franco et al., ), carbon storage (Mello et al., ) and ecosystem services (Foley et al., ). Brazil is the world’s largest sugarcane producer with 8.59 million ha of cultivation area and production of 29 Mt of sugar and 33 billion L of ethanol (CONAB, ).…”