Abiotic Soil Health Indicators that Respond to Sustainable Management Practices in Sugarcane Cultivation

Abstract

Soil quality (SQ) assessments are fundamental to design more sustainable land uses and management practices. However, SQ is a complex concept and there is not a universal approach to evaluate SQ across different conditions of climate, soil, and cropping system. Large-scale sugarcane production in Brazil is predominantly based on conventional tillage and high mechanization intensity, leading to SQ degradation. Thus through this study, we aim to assess the impact of sustainable management practices, including cover crops and less intensive tillage systems, in relation to the conventional system, using a soil quality index composed of abiotic indicators. Additionally, we developed a decision tree model to predict SQ using a minimum set of variables. The study was conducted in the municipality of Ibitinga, São Paulo, Brazil. The experimental design used was in strips, with four cover crops and three tillage systems. We evaluated three sugarcane cultivation cycles (2015/16, 2016/17, and 2017/18 crops). To calculate the SQ index, we selected five abiotic indicators: macroporosity, potassium content, calcium content, bulk density, and mean weight-diameter of soil aggregates. Based on our SQ index, our findings indicated that the soil quality was driven by the production cycle of sugarcane. Although a reduction of soil quality occurs between the plant cane and first ratoon cane cycles, from the second ratoon cane there is a trend of the gradual restoration of soil quality due to the recovery of both the soil’s physical and chemical attributes. Our study also demonstrated that the cultivation of sunn hemp and millet as cover crops, during the implementation of sugarcane plantation, enhanced soil quality. Due to the advantages provided by the use of these two cover crops, we encourage more detailed and long-term studies, aiming to test the efficiency of intercropping involving sunn hemp and millet during the re-planting of sugarcane.

Heavy Metals and Microbial Activity in Alluvial Soils Affected by Different Land-Uses

“…In this study, generally soil microbial biomass and enzymatic activity was usually and significantly higher under crop rotation than sugarcane monoculture possibly due to the existence of decomposable organic materials in soils available for microbiological utilization and enzymatic reactions (Freitas et al 2017;Carvalho et al, 2018). Associating some soil physicochemical properties under sugarcane monoculture agricultural systems and crop rotation, the main differences to explain this direction are lower content of SOM, lack of various sources of organic substrates on soil microbial biomass, lower plant diversity and lowest organic inputs following sugarcane residues burning in sugarcane fields (Novak et al 2017;Farhate, et al, 2020;Melo et al, 2020). The FDA activity was significantly and positively correlated with soil properties including SOM, SOC and CEC.…”

“…The heavy metal concentrations in sugarcane juice followed the trend Ni ˂ Pb ˂ Cr ˂ Cd (Table 5). The contents of cadmium, chromium, nickel and lead in sugarcane juice have been found at levels above their permissible limits indicating a potential concern for people who eat large amounts of cane in these areas (Yadav et al, 2010;Kamau, 2016;Farhate, et al, 2020;Wang et al, 2020). Recorded very high values of the coefficient variance CVs indicated that the content of the heavy metals varied substantially in both fields under different agricultural systems.…”

Soil physical change and sugarcane stalk yield induced by cover crop and soil tillage

“…The soil was classified as Ultisols [Udults] (USDA, 2014) and as Argissolo Vermelho Distrófico típico according to the Brazilian Soil Classification System (Santos et al, 2018), with sandy loam texture for the 0.00-0.20 m layer and sandy clay loam for the deeper layers (Farhate et al, 2020). The land use capacity class was classified as Class IIIe (Lepsch et al, 2015).…”

“…Conservation practices, such as no-tillage or minimal tillage systems, characterized by the absence or minimal soil mobilization associated with crop residue retention and crop rotation (i.e., mainly with cover crops), are promising strategies to mitigate soil degradation in sugarcane field (Tenelli et al, 2019;Farhate et al, 2020), as widely reported in grain crops (Palm et al, 2014;Blanco-Canqui and Ruis, 2018). More recently, cover crops have been shown as a good option for C inputs in the soil (Poeplau et al, 2015), enhancing soil aggregation and structure (Nascente et al, 2015;Reeves, 2018), reducing erosion, thus providing a favorable environment for the plant growth (Blanco-Canqui et al, 2015;Alvarez et al, 2017).…”

“…Several studies highlight the importance of monitoring physical quality throughout the sugarcane cultivation cycle, either by a general index of soil's physical quality (Cherubin et al, 2016;Vischi Filho et al, 2017;Farhate et al, 2020) or by individual changes in physical properties (Castioni et al, 2018;Barbosa et al, 2019;Awe et al, 2020). The bulk density, porosity, and soil resistance to penetration are physical properties sensitive to changes induced by management practices and have been often used to characterize the soil compaction in agricultural areas (Nawaz et al, 2013;Vischi Filho et al, 2017).…”