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A growing demand for resources has led to the expansion of agricultural areas worldwide. However, land conversion associated with poor soil management might lead to soil physical degradation. We investigated the effects of land conversion on soil physical properties in the Brazilian Cerrado region, under native Cerrado vegetation (NV)—pasture (PA) and NV—cropland (CL) conversion scenarios. Soil physical properties related to compaction, pore size distribution, and structure stability were assessed up to a 30 cm depth. Additionally, carbon levels of soil organic matter fractions (particulate and mineral-associated organic matter) were determined. Our results indicate that the compaction process equivalently reduced the soil porosity in PA and CL. However, soil penetration resistance was higher in PA (~2.5 MPa) than in CL (~1.5 MPa), as well as the stable mean weight diameter of soil aggregates. The highest total and labile organic carbon levels were observed in CL, while the lowest levels of total and labile organic carbon occurred in PA (smaller than in CL). These results suggest that the higher structural stability found in PA was mediated by the predominance of stabilized carbon (a decrease in the proportion of soil labile carbon), causing the gaining of soil strength under negligible soil volume variation (in comparison with CL). Our results suggest that the reduction in the soil porosity by compaction due to PA and CL uses can equivalently reduce macropore space and soil hydraulic functioning, and that soil carbon quality alterations (i.e., labile vs. stabilized fractions) are responsible for the gain in soil strength in long-term degraded PA areas. Future research should focus on understanding the magnitude in which soil organic matter controls soil physical attributes, such as soil strength in these expansion areas, and whether this gain in soil strength limits plant development and compromises productivity in the long term.

The original version of this article was published with a wrong heading by mistake. The correct heading is Original Paper.

Environmental benefits from bioenergy production derived from sugarcane crop residues (straw) can be lost by soil organic matter depletion resulting from excessive straw removal rates from fields. Soil organic carbon stock is the core for sustaining soil health, supporting nutrient cycling, and sequestering carbon dioxide. To find out that how much sugarcane straw can be removed from the field to produce bioenergy without changes in soil C concentrations, we investigated effects of straw removal rates (total, moderate, and no removal of sugarcane straw) on soil carbon and nitrogen fractions in an Oxisol and an Ultisol in southeastern Brazil for two years. Soil C and N fractions were affected by increased rates of straw removal at the second year. In the Oxisol, total straw removal decreased labile and microbial-C by ~30% and soil C stock by 20% compared to no straw removal. No removal decreased microbial-N and total N stock by ~15% and ~20%, respectively. In the Ultisol, no straw removal resulted in increases in C stock by >10% and labile and microbial-C by ~20% related to total straw removal. Total straw removal showed more microbial-N (~10%) and total-N stock (~25%) compared to no straw removal. The moderate straw removal intensity (i.e., 8 to 10 Mg ha−1 of straw) may control the straw-C release to soil by straw decomposition. This study suggests that excessive straw removal rates should be avoided, preventing SOM depletion and consequently, soil health degradation. Moderate straw removal seems to be a promising strategy, but long-term soil C monitoring is fundamental to design more sustainable straw management and bioenergy production systems.

Exploiting native soil phosphorus (P) and the large reservoirs of residual P accumulated over decades of cultivation, namely "legacy P", has great potential to overcome the high demand of P fertilisers in Brazilian cropping systems. Long-term field experiments have shown that a large proportion (> 70%) of the surplus P added via fertilisers remains in the soil, mainly in forms not readily available to crops. An important issue is if the amount of legacy P mobilized from soil is sufficient for the crop nutritional demand and over how long this stored soil P can be effectively 'mined' by crops in a profitable way. Here we mapped the spatial-temporal distribution of legacy P over the past 50 years, and discussed possible agricultural practices that could increase soil legacy P usage by plants in Brazil. Mineral fertiliser and manure applications have resulted in ~ 33.4 Tg of legacy P accumulated in the agricultural soils from 1967 to 2016, with a current annual surplus rate of 1.6 Tg. Following this same rate, soil legacy P may reach up to 106.5 Tg by 2050. Agricultural management practices to enhance soil legacy P usage by crops includes increasing soil pH by liming, crop rotation, double-cropping, inter-season cover crops, no-tillage system and use of modern fertilisers, in addition to more efficient crop varieties and inoculation with P solubilising microorganisms. The adoption of these practices could increase the use efficiency of P, substantially reducing the new input of fertilisers and thus save up to 31.8 Tg of P fertiliser use (US$ 20.8 billion) in the coming decades. Therefore, exploring soil legacy P is imperative to reduce the demand for mineral fertilisers while promoting long-term P sustainability in Brazil.

In Brazilian sugarcane (Saccharum spp.) production systems, the practice of moving harvesting residue from row to inter-row positions (i.e., raking) has increased in response to producer concerns over the potential negative effects of sugarcane straw on crop establishment and stalk yield. Despite increasing adoption among sugarcane farmers, the impacts of straw raking practices on plant growth and yield remain unclear. A 2-yr experiment that included both dry and wet seasons was conducted at two sites in southeastern Brazil to evaluate straw management strategy effects on plant tillering, phytomass accumulation, plant nutritional status, and stalk yield. The experiments were established at the Bom Retiro mill and the Univalem mill. Experimental treatments included raking straw to inter-rows (raked), total straw removal (bare soil), and no straw removal (straw cover). Raked and bare soil treatments improved plant tillering but did not influence final plant population. Straw management had a slight effect on phytomass accumulation. Reduction of phytomass yield was observed from the first to the second ratoon during both seasons at both sites. At Bom Retiro, phytomass yield decreased 37% for stands established during the dry season and 19% for stands established during the wet season. At Univalem, phytomass yield decreased 20% for stands established during the dry season and 30% for stands established during the wet season. Retaining straw in the field (regardless of treatment) increased leaf tissue P content but not stalk yield. Raking straw from row to interrow positions at these locations in southeastern Brazil had no benefit on sugarcane yield but may result in soil compaction and higher production costs over time.

Increasing global demand for biofuel has accelerated land-use change (LUC) in Brazil, primarily through the planting of sugarcane (Saccharum officinarum) to replace degraded pastures. The intensive mechanization associated with this LUC has increased concerns regarding structural quality of Brazilian tropical soils. Through decades of research focusing on identifying sensitive indicators of soil degradation due to land use and management, the Visual Evaluation of Soil Structure (VESS) method has emerged as a simple, fast, reliable and accurate semi-quantitative approach for assessing soil structure changes. VESS integrates soil properties related to size, strength and porosity of aggregates, and root characteristics into a single score (Sq – structural quality) that ranges from 1 (good structural quality) to 5 (poor structural quality). Although the VESS method was developed for temperate soils, it has been used successfully as an indicator of soil and crop management practice effects on structural quality of tropical and subtropical soils. Our objectives were to evaluate soil structural quality changes associated with a LUC sequence (i.e., native vegetation to pasture to sugarcane) at three sites under Oxisols, Alfisols and Ultisols across centralsouthern Brazil using the VESS; and to correlate VESS scores with quantitative measurements of soil physical properties. Average VESS scores were 2.0, 2.7, and 3.1 for native vegetation, pasture, and sugarcane, respectively. Overall the VESS method was able to detect soil structural quality changes under LUC for sugarcane cultivation, indicating a decrease in soil quality from native vegetation through pasture to sugarcane. The VESS scores were significantly correlated with quantitative soil physical property measurements, suggesting VESS is a reliable indicator of soil structural quality in tropical soils. A VESS score Sq = 3.0 seems to be suitable as a guide for management decisions. We conclude that VESS scores provide

Excessive harvest of corn (Zea mays L.) stover for ethanol production has raised concerns regarding negative consequences on soil physical quality. Our objective was to quantify the impact of two tillage practices and three levels of corn stover harvest on near-surface soil physical quality through the Least Limiting Water Range (LLWR). We evaluated no harvest, moderate and high stover harvest treatments within no-tillage and chisel plow plots following seven years of continuous corn production. Forty undisturbed soil samples were taken from the 0–7.5 cm deep layer within each treatment and used to determine water retention curves, soil resistance to penetration and bulk density values (Bd). No-tillage plots had higher average soil bulk density and resistance to penetration values, and were more affected by stover harvest than chisel plow plots. The results confirmed that soil resistance to penetration determined the lower limit of the LLWR regardless of tillage or stover treatment, whereas soil aeration controlled the upper limit only at Bd > 1.45 and Bd > 1.55 Mg m-3 for chisel plow and no-tillage, respectively. The LLWR was smallest for no-tillage with moderate or high corn stover harvest, indicating poor soil physical condition for plant growth, while the largest LLWR occurred with moderate stover harvest and chisel plowing. The introduction of alfalfa (Medicago sativa L.) into an extended rotation with no-tillage improved the LLWR by reducing the potential crop growth restriction due to resistance to penetration. Although bulk density values were only occasionally higher than the critical level (Bd = 1.60 Mg m-3 for chisel plow and Bd = 1.64 Mg m-3 for no-tillage), lower soil structure quality was evident with no-tillage under moderate or high stover harvest and with chisel plowing under high stover removal. The LLWR was more sensitive than available soil water content for detecting tillage and stover harvest effects on soil structural degradation.

High levels of corn (Zea mays L.) stover harvest for ethanol production have raised concerns regarding negative consequences on soil structure and physical quality. Visual soil structure assessment methods have the potential to help address these concerns through simple, straightforward on-farm evaluations. Our objective was to determine if the visual evaluation of soil structure (VESS) approach could detect soil structural quality differences associated with different levels of corn stover harvest and tillage practices. We evaluated no harvest and moderate and high stover harvest levels within no-tillage (NT) and chisel plow (CP) plots following 7 yr of continuous corn. Undisturbed 10- by 20- by 25-cm soil samples were taken using a spade in April 2015. The thickness and structural quality (Sq) scores for the 0- to 5- (top) and 5- to 20-cm (bottom) soil layers were determined, and an overall Sq was computed. The Sq values showed a significant interaction between corn stover harvest and tillage practice. Soil structural quality showed no significant differences between NT and CP systems for either the no- or moderate-harvest treatments, but with a high stover harvest rate, CP structural quality was worse than NT. With NT, both moderate and high rates of stover harvest significantly increased Sq compared to no harvest; in CP, there was no significant difference between the no- and moderate-harvest treatments. Only a high level of stover harvest had an adverse effect on the Sq rating. The VESS approach was sensitive for detecting the effects of corn stover harvest and tillage systems on soil structural quality and should be further evaluated as an integrative, on-farm soil quality/health indicator.

The Soil Management Assessment Framework (SMAF) was developed in the U.S.A. and has been used as a tool for assessing and quantifying changes in soil quality/health (SQ) induced by land uses and agricultural practices in that region and elsewhere throughout the world. An initial study using SMAF in Brazil was recently published, but additional research for a variety of soils and management systems is still needed. Our objective was to use data from five studies in southern Brazil to evaluate the potential of SMAF for assessing diverse land-use and management practices on SQ. The studies examined were: (i) horizontal and vertical distribution of soil properties in a long-term orange orchard; (ii) impacts of long-term land-use change from native vegetation to agricultural crops on soil properties; (iii) effects of short-term tillage on soil properties in a cassava production area; (iv) changes in soil properties due to mineral fertilizer and pig slurry application coupled with soil tillage practices; and (v) row and inter-row sowing effects on soil properties in a long-term no-tillage area. The soils were classified as Oxisols, with clay content ranging from 180 to 800 g kg-1. Six SQ indicators [pH(H2O), P, K, bulk density, organic C, and microbial biomass] were individually scored using SMAF curves and integrated into an overall Soil Quality Index (SQI) focusing on chemical, physical, and biological sectors. The SMAF was sensitive for detecting SQ changes induced by different land uses and management practices within this wide textural range of Brazilian Oxisols. The SMAF scoring curve algorithms properly transformed the indicator values expressed in different units into unitless scores ranging from 0-1, thus enabling the individual indicators to be combined into an overall index for evaluating land-use and management effects on soil functions. Soil sector scores (i.e., chemical, physical, and biological) identify the principal soil limitations and can therefore be u

The Soil Management Assessment Framework (SMAF) was developed to evaluate impacts of land use and management practices on soil quality (SQ), but its suitability for Brazilian tropical soils was unknown. We hypothesized that SMAF would be sensitive enough to detect SQ changes associated with sugarcane (Saccharum officinarum L.) expansion for ethanol production. Field studies were performed at three sites across the south-central region of Brazil, aiming to quantify the impacts of a land use change sequence (i.e., native vegetation–pasture–sugarcane) on SQ. Eight soil indicators were individually scored using SMAF curves developed primarily for North American soils and integrated into an overall Soil Quality Index (SQI) and its chemical, physical, and biological sectors. The SMAF scores were correlated with two other approaches used to assess SQ changes, soil organic C (SOC) stocks and Visual Evaluation of Soil Structure (VESS) scores. Our findings showed that the SMAF was an efficient tool for assessing land use change effects on the SQ of Brazilian tropical soils. The SMAF scoring curves developed using robust algorithms allowed proper assignment of scores for the soil chemical, physical, and biological indicators assessed. The SQI scores were significantly correlated with SOC stocks and VESS scores. Long-term transition from native vegetation to extensive pasture promoted significant decreases in soil chemical, physical, and biological indicators. Overall SQI suggested that soils under native vegetation were functioning at 87% of their potential capacity, while pasture soils were functioning at 70%. Conversions of pasture to sugarcane induced slight improvements in SQ, primarily because of improved soil fertility. Sugarcane soils are functioning at 74% of their potential capacity. Based on this study, management strategies were developed to improve SQ and the sustainability of sugarcane production in Brazil.