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Brazil stands out among the countries with the largest area under native vegetation (NV) in the world, as well as a country with a growing population. Despite this fact, the country still does not have an indicator to compile both vegetation and population aspects at national and regional scales. Thus, through this study is proposed to use NV per capita as an indicator of occupation and development processes for the Brazilian territory. This socio-environmental metric can fill the knowledge gap about the aforementioned processes, it is easily calculated and applied throughout Brazil. The indicator is the quotient between native vegetation area and the number of inhabitants of a given municipality. Data were obtained biennially (from 2010 to 2020) in more than 5000 Brazilian municipalities. We found that NV per capita reflects the Brazil's occupation and development processes, although it does not always show changes in land use. In this sense, there are still 5.3 billion hectares of NV among which 91% of this vegetation per inhabitant occurs in Brazilian center-north. Overall, NV ranged from 2.9 to 2.5 ha per capita in the last decade. In addition, NV per capita shows up as an indicator useful to understand both regional and municipal economic traits. On a regional scale, the North showed a negative relationship between NV per inhabitant and Gross Domestic Product (GDP) per capita. Similar pattern was observed for the Southeastern region (ρ = −0.27*). The results demonstrated the importance of indicators able to frame environmental and socioeconomic aspects of a wide dimension country, such as Brazil. The indicator proposed herein (i.e., NV per capita) also can be used to compare with others from countries elsewhere, once the parameters are easily obtained. This comparison may increase Brazil's competitive opportunities in the socio-environmental field. [ABSTRACT FROM AUTHOR]

The total or partial removal of sugarcane (Saccharum spp. L.) straw for bioenergy production may deplete soil quality and consequently affect negatively crop yield. Plants with lower yield potential may present lower concentration of leaf-tissue nutrients, which in turn changes light reflectance of canopy in different wavelengths. Therefore, vegetation indexes, such as the normalized difference vegetation index (NDVI) associated with concentration of leaf-tissue nutrients could be a useful tool for monitoring potential sugarcane yield changes under straw management. Two sites in São Paulo state, Brazil were utilized to evaluate the potential of NDVI for monitoring sugarcane yield changes imposed by different straw removal rates. The treatments were established with 0%, 25%, 50%, and 100% straw removal. The data used for the NDVI calculation was obtained using satellite images (CBERS-4) and hyperspectral sensor (FieldSpec Spectroradiometer, Malvern Panalytical, Almelo, Netherlands). Besides sugarcane yield, the concentration of the leaf-tissue nutrients (N, P, K, Ca, and S) were also determined. The NDVI efficiently predicted sugarcane yield under different rates of straw removal, with the highest performance achieved with NDVI derived from satellite images than hyperspectral sensor. In addition, leaf-tissue N and P concentrations were also important parameters to compose the prediction models of sugarcane yield. A prediction model approach based on data of NDVI and leaf-tissue nutrient concentrations may help the Brazilian sugarcane sector to monitor crop yield changes in areas intensively managed for bioenergy production. [ABSTRACT FROM AUTHOR]

Large amounts of straw are remained in the sugarcane fields after the crop to be mechanically harvested. Straw is pointed out as a feedstock to attend high bioenergy production demand. However, either indiscriminate straw removal or high amount of straw kept on the field may impair several soil functions and thereafter decreases plant tillering and crop yield. Better nutrients cycling and soil physical protection due to Leguminosae species grown within the sugarcane renewal period may offset implications of straw managements across the crop cycles. Thus, does Crotalaria sp. grow within the sugarcane renewal period can offset the undesirable implications of unsustainable straw management on soil and crop yield? To address this research question, a two-year experiment was carried out in Quirinópolis, Chapadão do Céu, Iracemápolis and Quatá, first two sites are in Goiás state, while the other sites are in São Paulo state, Brazil. Soil and plant parameters under straw retention rates (i.e., 0%, 50% and 100% of straw retention) were assessed. This management was coupled with fallow (F) and Crotalaria sp. (CR) grown within the sugarcane renewal period. Soil parameters evaluated included, carbon (C) and nitrogen (N) stocks, while stalk yield was plant parameters assessed. The straw retention implications on soil and plant were site-specific. Carbon and N stocks in the upper 0.4 m soil layer were, respectively, 3.5 and 3.1 time higher at the fine-textured soil than the stocks of those elements at the coarse-textured soil. Regardless of Crotalaria sp. grown, stalk yield increased (ranged from 3 to 16 Mg ha−1) under total straw retention rate for most sites, while in the coolest site 50% and 100% straw retention reduced stalk yield in 13 and 14 Mg ha−1, respectively. In addition, Crotalaria sp. grown within the sugarcane renewal period does not seem able to avoid reduction on soil N availability due to straw retention along the ratoon cycles. Overall, straw removal for bioenergy should be judiciously performed, according to local edaphoclimatic conditions. • Stalk yield was increased due to straw retention in the most sites. • Sugarcane straw retention reduces plant tillering and yield in the coolest site. • Crotalaria sp. promotes the soil nutrient cycling (mainly K and P). • Straw retention increases C sequestrated and stocks. • Crotalaria sp. grown in the sugarcane renewal period increases soil N. [ABSTRACT FROM AUTHOR]

A new method of sugarcane establishment using pre-sprouted seedlings (PSS) is under development in Brazil, requiring lower amounts of vegetative material as compared to the conventional method using billets (1–2 versus 12–20 Mg ha−1). The hypotheses set up herein were: i) the sugarcane fields established with PSS achieve similar yields as compared to fields established conventionally and ii) since PSS has lower nutrition reserve as compared to the nutrients reserve within the billets, the nutritional demand of sugarcane may change according to the method of crop establishment. To test the hypothesis, three field trials were carried out within the main periods of sugarcane establishment in Southeast Brazil (fall, winter and spring), varying in fertilization practices. Treatments included conventional planting method with standard fertilization, New method without and under standard fertilization, named from here on as Conv., New method 1 and New method 2, respectively. In both systems, furrows were opened 1.5 m apart m. between rows. Conv. planting method was done with 12–15 buds m−1, while both New methods were done with pre-sprouted seedlings spaced 0.5 m apart within the line. Measurements included tillering, plant nutritional status, stalk yield and stalk quality parameters over three crop cycles (cane-plant, first and second ratoon). Whereas Conv. method improved plant tillering in specific evaluation periods, both New methods lead to similar milleable plants at harvest time in the three crop seasons. Within all crop cycles, plant nutritional status was similar under all planting methods, even without fertilization for the new method 1. More interestingly, regardless of the crop cycle and season in which the trial was set up, under the New method the stalk yields and total recoverable sugars content were similar to the same parameters evaluated for crop established trough Conv. planting method. Based on this long-term study, crop establishment though pre-sprouted seedlings (New method adoption) can be highlighted as a promising opportunity to increase feedstock for ethanol production to attend the increased ethanol demand forecasted for the upcoming years. • Sugarcane planting with pre-sprouted seedlings (PSS) is under development in Brazil. • Conv. sugarcane planting method requires much higher stalk seeds (12–20 Mg ha−1) than crop planting with PSS (1–2 Mg ha−1). • Sugarcane plantation with PSS increases feedstock amount devoted to other uses in the mills. • Stalk yield and raw material's technological quality were similar under both planting methods. • The N, P and K fertilization done at planting little affects plant nutritional status and crop yield. [ABSTRACT FROM AUTHOR]

• Legume cover crop (rotation system) replaces 60 kg ha-1 of synthetic N at sugarcane planting. • Rotation system adoption increases stalk yield by 20 Mg ha-1 over two ratoon cycles. • The N requirement is reduced by 12.5% for each Mg of stalks harvested under rotation system. • Rotation system adoption may enhance sustainability of sugarcane-based bioenergy. Planting cover crops as a strategy to enhance soil quality has been long adopted in several agroecosystem worldwide. Among the cover crops, some legume species are must chosen due to their abilities to fix atmospheric nitrogen (N) into the soil, which increases soil N availability for the cash crop planted subsequently. Our hypothesis was that planting a legume within the sugarcane (Saccharum spp.) renewal period can be adopted as a strategy to supply the N required for the sugarcane at planting. The hypothesis was tested through an experiment set up within Southeast Brazil into two adjacent areas: in an area sunn hemp (Crotalaria junceae L.) was planted within the sugarcane renewal period (rotation system), whereas the another area was left in fallow (fallow system). Five N-fertilizer rates: 0, 130, 260, 390, and 520 kg N ha-1 were arranged in a randomized block design with four replications within both systems. The N amounts were divided throughout the plant cane, first and second ratoons cycles. Plant parameters evaluated included: tillering, stalk yield and stalk industrial quality. The N content on leaves as well as the inorganic N dynamic on soil were also evaluated. Overall, sunn hemp cropped within the sugarcane renewal period potentially replaces 60 kg ha-1 of N at sugarcane planting. Moreover, the rotation system enhanced stalk yield in 20 Mg ha-1 over both ratoon cycles, whereas the N amount required for each Mg of stalk harvested is reduced by 12.5%, indicating augmented the nitrogen recovering (NUE). The sucrose content and sugar yield are both enhanced under rotation system. However, soil N inorganic dynamic, the N content on leaves and amounts removed on plant components were little sensitive to the rotation system. Our findings highlight the rotation system as a feasible alternative to replace part of the N required by the sugarcane, which improves the NUE for the crop. Conclusions from this study indicate that legume rotation system adoption increases the sustainability of bioenergy from sugarcane by reducing the dependency on synthetic N fertilizers. [ABSTRACT FROM AUTHOR]