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Sugarcane (Saccharum officinarum L.) straw is a promising feedstock for bioelectricity and cellulosic ethanol in Brazil, but some straw is also needed to sustain nutrient cycling and crop yields. A literature review and two field studies were conducted to quantify above-ground macronutrient accumulation by sugarcane. Five straw removal scenarios using different amounts of biomass and nutrient composition data of top (green) and bottom (dry) leaves were constructed to estimate fertilizer requirements associated with straw removal in central southern Brazil. Calculated straw removal for five scenarios (S1 to S5) was 3.5, 7, 3, 6, and 12 Mg ha−1, respectively. By removing 12 Mg ha−1 of straw (S5), the potential N, P, K, Ca, Mg, and S removal was 69, 7, 92, 45, 16, and 14 kg ha−1, respectively. It represents a nutrient (NPK) replacement cost of US$ 90.00 ha−1 or US$ 7.60 per Mg of removed straw. The scenario analysis shows that less-impacting strategies are those that maintain top leaves in the field and harvesting only bottom leaves (S1 and S2), whereas total removal (S5) could double NPK-fertilizer consumption in sugarcane fields by 2050. Our findings provide stakeholder guidelines for improved straw management, establish an economic value for accumulated plant nutrients, and promote both socio-economic and environmental benefits of more sustainable bioenergy production in Brazil. [ABSTRACT FROM AUTHOR]

• The Soil Management Assessment Framework (SMAF) detected soil health changes induced by straw removal in sugarcane areas. • Sandy and clayey soils were functioning at 41–56% and 67–86% of their full potential, respectively. • Intensive straw removal rates induced soil health degradation. • Healthier soils were associated with higher sugarcane stalk yields. • Soil health assessments are crucial to design sustainable straw management in Brazil. Sugarcane straw removal is a promising strategy to increase bioenergy production in Brazil. However, if straw removal is not properly managed, it may lead to soil health degradation, thus threatening sustainability of the entire bioenergy production system. In this context, a comprehensive assessment was conducted in 12 field experiments located in central-southern Brazil, the world's largest sugarcane-producing region, to investigate the impacts of straw removal scenarios on soil health, using the Soil Management Assessment Framework (SMAF). Two groups of experiments were arranged in this study, consisting of three (no–NR; moderate–MR; and total removal–TR) and four straw removal treatments (NR; low–LR; high–HR; and TR). Soil samples were collected (0–10 and 10−20 cm) to evaluate a selected set of soil health indicators (i.e., pH, available phosphorus, exchangeable potassium, bulk density and soil organic carbon). Indicators were individually scored and then integrated into an overall Soil Health Index (SHI) and its chemical, physical, and biological components. Datasets were analyzed by site, experiment groups and soil texture (clayey and sandy soils) and the relationships among straw removal, soil health, and sugarcane yield were also investigated. Our findings showed that soil health responses to straw removal were properly detected by SMAF scoring curves. Based on SHI, sandy and clayey soils were functioning at 41–56% and 67–86% of their full potential, respectively. Soil health degradation was mostly induced by TR and HR, while LR and MR resulted in minimal detrimental effects on a short-term basis compared with NR. However, sandy soils were more prone to soil health degradation, indicating that straw removal should be avoided on those soils. For clayey soils, decline in soil health was driven by physical degradation. Healthier soils were associated with higher sugarcane stalk yields, and physical degradation was the main driver for crop yield losses. Conclusions drawn from this study suggest that comprehensive soil health assessments by integrating chemical, physical and biological indicators are fundamental to design more sustainable straw management and bioenergy production systems in Brazil. [ABSTRACT FROM AUTHOR]

There is growing interest in sugarcane straw removal from the field to use as raw material for bioenergy production. In contrast, sugarcane straw removal may have negative implications for many soil ecosystem services and subsequent plant growth. A two-year experiment was conducted at Bom Retiro and Univalem mills within the dry and wet seasons for assessing the impact of straw rates removal on plant production. The experimental design was randomized blocks with five treatments proportional to 0, 25, 50, 75 and 100% of straw removal. Plant parameters evaluated included: tillering, phytomass accumulation, stalk yield and stalk industrial quality. Straw removal increased plant tillering at Bom Retiro mill in both seasons and within dry season at Univalem mill, however the plant population at the end of each ratoon cycle was not affected by straw management. Phytomass yield across each ratoon cycle was fit to a sigmoidal model (R 2 ≥ 0.92, p < 0.05). Time necessary for plant completes its lag-phase is higher at the treatments applied in the dry season, whereas there was no time-pattern for plants to complete the linear and stationary growth phases. Moderate amounts of straw: 4–9 Mg ha −1 (dry base) on soil surface enhanced stalk yield. Different rates of straw removal did not affect stalk industrial quality. Overall, partial straw removal, at least in the short-term, could be a win–win situation, sustaining sugarcane yields and providing feedstock for bioelectricity cogeneration and/or 2G-ethanol production. [ABSTRACT FROM AUTHOR]