ABSTRACT Conventional tillage and intensive machinery traffic are the major causes of physical soil degradation in sugarcane fields. This study evaluates the impact of adopting conservation management practices during sugarcane planting on soil physical properties and stalk yield of sugarcane in the municipality of Ibitinga, state of São Paulo, Brazil. The experimental design (split-block) included four cover crops and three soil tillage systems, with three repetitions. For comparison purposes, a control treatment was also included (without cover crop and under conventional tillage). Sampling for soil physical analysis was performed in three layers that coincide with soil horizons A (0.00-0.20 m), AB (0.20-0.30 m), and Bt (0.30-0.70 m), during cane-plant and first sugarcane ratoon cycles. The results showed that cultivation of sunn hemp associated with deep subsoiling induced high stalk yield of sugarcane in both production cycles, cane plant (116 Mg ha -1 ) and first ratoon (114 Mg ha -1 ), with a net gain of 11 and 9 Mg ha -1 compared with the control treatment, respectively. However, these results were not sufficient to induce significant differences in sugarcane yield. Nonetheless, the use of sunn hemp and millet, associated with subsoiling (at 0.40 or 0.70 m depth) during sugarcane planting, are promising management strategies to sustain better soil’s physical quality when compared to traditional management, conventional soil tillage without cover crops and/or cash crop, as peanuts, that increase the risks of soil compaction and physical degradation.

ABSTRACT: The Random Forest algorithm is a data mining technique used for classifying attributes in order of importance to explain the variation in an attribute-target, as soil CO2 flux. This study aimed to identify prediction of soil CO2 flux variables in management systems of sugarcane through the machine-learning algorithm called Random Forest. Two different management areas of sugarcane in the state of São Paulo, Brazil, were selected: burned and green. In each area, we assembled a sampling grid with 81 georeferenced points to assess soil CO2 flux through automated portable soil gas chamber with measuring spectroscopy in the infrared during the dry season of 2011 and the rainy season of 2012. In addition, we sampled the soil to evaluate physical, chemical, and microbiological attributes. For data interpretation, we used the Random Forest algorithm, based on the combination of predicted decision trees (machine learning algorithms) in which every tree depends on the values of a random vector sampled independently with the same distribution to all the trees of the forest. The results indicated that clay content in the soil was the most important attribute to explain the CO2 flux in the areas studied during the evaluated period. The use of the Random Forest algorithm originated a model with a good fit (R2 = 0.80) for predicted and observed values.

ABSTRACT: The use of data mining is a promising alternative to predict soil respiration from correlated variables. Our objective was to build a model using variable selection and decision tree induction to predict different levels of soil respiration, taking into account physical, chemical and microbiological variables of soil as well as precipitation in renewal of sugarcane areas. The original dataset was composed of 19 variables (18 independent variables and one dependent (or response) variable). The variable-target refers to soil respiration as the target classification. Due to a large number of variables, a procedure for variable selection was conducted to remove those with low correlation with the variable-target. For that purpose, four approaches of variable selection were evaluated: no variable selection, correlation-based feature selection (CFS), chisquare method (χ2) and Wrapper. To classify soil respiration, we used the decision tree induction technique available in the Weka software package. Our results showed that data mining techniques allow the development of a model for soil respiration classification with accuracy of 81 %, resulting in a knowledge base composed of 27 rules for prediction of soil respiration. In particular, the wrapper method for variable selection identified a subset of only five variables out of 18 available in the original dataset, and they had the following order of influence in determining soil respiration: soil temperature > precipitation > macroporosity > soil moisture > potential acidity.

RESUMO O sistema de colheita mecanizado da cana-de-açúcar têm substituido o sistema de queima do canavial devido a preocupações ambientais como a emissão de partículas durante a queima e diversos malefícios ao solo. O impacto dessa prática no potencial de produção de gases do efeito estufa (GEE) no solo ainda demanda estudo. Assim, o presente trabalho quantificou a produção potencial, em 1 g de solo, de gases do efeito estufa em três sistemas de manejo de cana-de-açúcar. As áreas avaliadas foram: uma com histórico de queima do canavial antes da colheita (B) e outras com duas com sistemas de manejo de “cana crua” em dois períodos de implantação - 5 (G-5) e 10 anos (G-10). Um experimento de incubação em laboratório foi montado para avaliar os potenciais de produção de dióxido de carbono (CO2), óxido nitroso (N2O) e metano (CH4) em de 1g de amostras de solo nos diferentes sistemas de manejo de cana-de-açúcar. Os resultados deste estudo demonstram que os sistemas de manejo de cana-de-açúcar apresentaram impacto na produção potencial de CO2 no solo. Além disso, quando dividiu-se os resultados de gases oriundos de áreas convexas e concavas, observou-se diferenças nos padrões de CO2 entre as áreas B e G-10, with greater emission in the G-10 area, possivelmente devido a presença de palhada na superífice do solo.

ABSTRACT Mechanized sugarcane harvest is replacing the historic practice of field burning, due to environmental concerns of the particulate and emissions during burning. However, the impact of these practices on soil greenhouse gas (GHG) production potential is not fully known. Thus, the present work quantified the potential production, in 1 g of soil, of greenhouse gases (GHG) in three systems of sugarcane management. The systems were: area with a history of burning sugarcane before harvest (B) and another with two systems of management of “green sugarcane” in two periods of implantation - 5 (G-5) and 10 years (G-10). A laboratory incubation experiment was used to assess the production potentials of carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) in 1g of soil samples by the different sugarcane management systems. The results of this study demonstrate that the sugarcane management systems had an impact on the potential production of CO2 in the soil. In addition, when the results of gases were divided from convex and concave areas, differences in CO2 patterns between areas B and G-10 were observed, with greater emission in the G-10 area, probably due the residue on the soil surface.

ABSTRACT: In addition to improving sustainability in cropping systems, the use of a spring and winter crop rotation system may be a viable option for mitigating soil CO2 emissions (ECO2). This study aimed to determine short-term ECO2 as affected by crop rotations and soil management over one soybean cycle in two no-till experiments, and to assess the soybean yields with the lowest ECO2. Two experiments were carried out in fall-winter as follows: i) triticale and sunflower were grown in Typic Rhodudalf (TR), and ii) ruzigrass, grain sorghum, and ruzigrass + grain sorghum were grown in Rhodic Hapludox (RH). In the spring, pearl millet, sunn hemp, and forage sorghum were grown in both experiments. In addition, in TR a fallow treatment was also applied in the spring. Soybean was grown every year in the summer, and ECO2 were recorded during the growing period. The average ECO2 was 0.58 and 0.84 g m2 h–1 with accumulated ECO2 of 5,268 and 7,813 kg ha–1 C-CO2 in TR and RH, respectively. Sunn hemp, when compared to pearl millet, resulted in lower ECO2 by up to 12 % and an increase in soybean yield of 9% in TR. In RH, under the winter crop Ruzigrazz+Sorghum, ECO2 were lower by 17%, although with the same soybean yield. Soil moisture and N content of crop residues are the main drivers of ECO2 and soil clay content seems to play an important role in ECO2 that is worthy of further studies. In conclusion, sunn hemp in crop rotation may be utilized to mitigate ECO2 and improve soybean yield.

RESUMO As práticas de manejo utilizadas na cultura da cana-de-açúcar (cana crua - CC e cana queimada - CQ) interferem na dinâmica dos atributos e expressão magnética do solo. Foi estudado o potencial da suscetibilidade magnética como indicador de qualidade do solo em áreas sob cultivo de cana-de-açúcar. O experimento localiza-se em uma área limítrofe de material de origem, entre o Basalto do Grupo São Bento, Formação Serra Geral, e o Arenito do Grupo Bauru, Formação Adamantina. Foram coletadas 20 amostras de solo em dois sistemas de manejo (com e sem queima da cana-de-açúcar para colheita) na profundidade de 0,0-0,2 m. O solo foi classificado como Latossolo Vermelho Eutroférrico, textura muito argilosa. Foram avaliados os atributos químicos, físicos, emissão de CO2 e a suscetibilidade magnética (SM) do solo na terra fina seca ao ar (SMTFSA), fração total sand (SMAT) e fração argila (SMARG). A assinatura magnética expressa pela suscetibilidade magnética foi eficaz na identificação de mudanças nas características físicas, químicas e mineralógicas de Latossolos sob sistemas de colheita da cana-de-açúcar com e sem queima. As informações geradas neste trabalho podem balizar futuros estudos sobre a gênese de minerais com expressão magnética em ambientes e expostos a presença de fogo.

ABSTRACT Sugarcane management practices (unburned cane - UC and burned cane - BC) interfere with dynamics of soil magnetic properties. This study focused on determining the potential of magnetic susceptibility as soil quality indicator in areas under sugarcane cultivation. The experiment area is on the limit between basalt from São Bento Group, Serra Geral Formation, and sandstone from Bauru Group - Adamantina Formation. Twenty soil samples were collected from two management areas (burned and unburned sugarcane prior to harvest) at a depth range of 0.0-0.2 m. Local soil was classified as eutroferric Red Latosol (Oxisol), with highly clayey texture. Chemical and physical properties, CO2 emissions and magnetic susceptibility (MS) in air-dried fine earth (MSADFE), total sand fraction (MSTS) and clay fraction (MSCF). The magnetic signature from MS was effective in identifying changes of physical, chemical and mineralogical traits in Latosols under burned and unburned sugarcane crop. The information provided here can guide further studies on the genesis of minerals with magnetic expression in environments and exposed to fire burning.

ABSTRACT The harvesting system of green sugarcane, characterized by mechanized harvesting and no crop burning, affects soil quality by increasing the remaining straw left on the soil surface after harvesting, thus, contributing to the improvement of physical, chemical, and microbiological soil attributes, influencing CO2 fluxes. This study aimed to evaluate CO2 fluxes and their relation to soil properties in sugarcane crops under different harvesting managements: burned (B), Green harvesting for 5 years (G-5) and Green harvesting for ten years (G-10). For this, a 1 ha sampling grid with 30 points was installed in each area, all located in the Northeast of São Paulo State, Brazil. In each point, CO2 fluxes were measured and the soil was sampled to analyze the microbial biomass, physical (soil moisture and temperature, mean weight diameter, bulk density, clay, macroporosity and microporosity) and chemical characterization (pH, organic C, base saturation and P). The CO2 fluxes were divided into four quantitative criteria: high, moderate, low and very low from the Statistical Division (mean, first quartile, median and third quartile) and the other data were classified according this criterion. The Principal Component Analysis (PCA) was used to identify the main soil attributes that influence CO2 fluxes. The results showed that G-10 CO2 fluxes were 28 and 41 % higher than those in the G-5 and B treatments, respectively. The PCA analysis showed that macroporosity was the main soil attribute that influenced the high CO2 fluxes.

ABSTRACT The sugarcane green harvest system, characterized by mechanized harvesting and the absence of crop burning, affects soil quality by increasing crop residue on the soil surface after harvest; thus, it contributes to improving the physical, chemical, and microbiological properties and influences the soil carbon content and CO2 flux (FCO2). This study aimed to evaluate the spatial and temporal variability of soil FCO2 in sugarcane green harvest systems. The experiment was conducted in two areas of sugarcane in São Paulo, Brazil: the first had a 5-year history of sugarcane green harvest (SG-5) and the second had a longer history of 10 years (SG-10). The temporal FCO2 were evaluated in the dry and rainy periods, and spatial variability in the dry period, and related to soil chemical and physical properties, including organic C porosity, bulk density, soil penetration resistance, mean weight diameter of soil aggregates, clay, P, S, Ca, Mg and Fe. The temporal variability indicated no differences between the dry and rainy periods in SG-10, while in SG-5 soil moisture was increased by 33 % in the rainy period. The spatial variability indicated a different pattern from the temporal one, where FCO2 in SG-10 was correlated with soil temperature, air-filled pore space, total porosity, soil moisture, and the Ca and Mg contents; in the SG-5 area, FCO2 was correlated with soil mean weight diameter of soil aggregates and the sulfur content.

RESUMO: Este trabalho teve por objetivo avaliar a sensibilidade de isolados dos fungos Metarhizium anisopliae (Metsch.) Sorok. e Beauveria bassiana (Bals). Vuill. ao efeito das radiações solar e ultravioleta e da temperatura. Conídios dos isolados foram expostos, por vários períodos, aos raios de um simulador solar em diversas irradiâncias e a uma lâmpada de raios ultravioleta germicida. Os conídios do isolado de M. anisopliae foram também expostos às temperaturas de 19,5; 24,2 e 31,0ºC, e os do isolado de B. bassiana a 19,4; 20,8 e 28,3ºC, e 18,7; 23,8 e 30,9ºC. Avaliou-se a germinação de conídios pelo teste de viabilidade. Os isolados dos fungos se mostraram bastantes sensíveis aos raios do simulador solar e aos raios ultravioleta. A germinação de ambos sofreu significativa redução a partir de 30 minutos de exposição à radiação do simulador solar. O efeito mais severo foi evidenciado pelo isolado de B. bassiana, com grande redução da germinação dos conídios em todas as irradiâncias testadas. A sensibilidade à radiação ultravioleta também foi grande, pois ocorreu acentuada redução da germinação dos conídios do isolado de M. anisopliae (38,2%) e de B. bassiana (65%) já aos 30 segundos de exposição. A temperatura afetou a viabilidade de ambos os fungos. Temperaturas entre 23,8 e 31ºC favoreceram a germinação dos conídios, enquanto temperaturas próximas de 20ºC dificultaram a germinação.

ABSTRACT: This study aimed to access the sensibility of isolates of the fungus Metarhizium anisopliae (Metsch.) Sorok. and Beauveria bassiana (Bals.) Vuill. to the effect of solar and ultraviolet radiation and temperature. Conidia were exposed for various periods to the rays from a solar simulator at various irradiances, and to light germicidal ultraviolet rays. Conidia of the isolate of M. anisopliae were also exposed to temperatures of 19.5, 24.2 and 31.0ºC and the isolate of B. bassiana to 19.4, 20.8 and 28.3ºC, and also to 18.7, 23.8 and 30.9ºC. The germination of conidia was evaluated by the viability test. The fungal isolates showed to be very sensitive to the solar simulator and ultraviolet rays. Germination of both was significantly decreased starting from 30 minutes of exposure to the rays of the solar simulator. The most severe effect was evidenced by the isolate of B. bassiana with great reduction in conidia germination in all the tested irradiances. Sensitivity to ultraviolet radiation was also great, showing a marked reduction in the germination of M. anisopliae (38.2%) and B. bassiana (65%) conidia after 30 seconds of exposure. The temperature affected the viability of both fungi. Temperatures ranging of 23.8 to 31ºC favor the germination of conidia while temperatures around 20ºC constrained germination.

ABSTRACTSoil CO2 emissions (fCO2) in agricultural areas have been widely studied in global climate change research, but its characterization and quantification are restricted to small areas. Because spatial and time variability affect emissions, tools need to be developed to predict fCO2 for large areas. This study aimed to investigate soil magnetic susceptibility (MS) and its correlation with fCO2 in an agricultural environment. The experiment was carried out on a Typic Eutrudox located in Guariba-SP, Brazil. Results showed that there was negative spatial correlation between fCO2 and the magnetic susceptibility of Air Dried Soil (MSADS) up to 34.3 m distant. However, the fCO2 had no significant correlation with MSADS, magnetic susceptibility of sand (MSSAND) nor clay (MSCLAY). However, MSADS could be a supplemental mean of identifying regions of high fCO2 potential over large areas.

O preparo mecânico do solo é uma das práticas agrícolas que contribuem para o aumento da perda de carbono via emissão de CO2 do solo (FCO2). Com este trabalho objetivou-se investigar o efeito de três sistemas de preparo do solo na FCO2, temperatura e umidade do solo em área de reforma da cultura de cana-de-açúcar. A área experimental foi constituída de três parcelas, cada uma recebendo um dos preparos do solo: preparo convencional (PC), subsolagem convencional (SC) e subsolagem localizada (SL). A FCO2, temperatura e a umidade do solo foram avaliadas durante o período total de 17 dias. A FCO2 foi maior no preparo PC (0,75 g CO2 m-2 h-1). A temperatura do solo não diferiu (p > 0,05) entre as subsolagens: SL (26,2 ºC) e SC (25,9 ºC). A umidade do solo foi maior na SL (24%), seguida pela SC (21,8%) e preparo PC (18,3%). Apenas no preparo PC foi observada correlação significativa (r = –0,71; p < 0,05) entre FCO2 e a temperatura do solo. O preparo PC apresentou emissão total (2.864,3 kg CO2 ha-1), superior às emissões nas subsolagens: SC (1.970,9 kg CO2 ha-1) e SL (1.707,7 kg CO2 ha-1). A conversão do sistema de preparo PC para a SL diminuiu as emissões de CO2 do solo, reduzindo a contribuição da agricultura para o aumento dos gases de efeito estufa na atmosfera.

Soil tillage is one of the agricultural practices that may contribute to increase the loss of carbon through emission of CO2 (FCO2). The aim of this study was to investigate the effect of three soil tillage systems on FCO2, soil temperature and soil moisture in a sugarcane area under reform. The experimental area consisted of three tillage plots: conventional tillage (CT), conventional subsoiling (CS), and localized subsoiling (LS). FCO2, soil temperature and soil moisture were measured over a period of 17 days. FCO2 showed the highest value in CT (0.75 g CO2 m-2 h-1). Soil temperature presented no significant difference (p > 0.05) between LS (26.2 °C) and CS (25.9 °C). Soil moisture was higher in LS (24%), followed by CS (21.8%) and CT (18.3%). A significant correlation (r= ‒0.71; p < 0.05) between FCO2 and soil temperature was observed only in CT. The conventional tillage presented a total emission (2,864.3 kg CO2 ha-1) higher than the emissions observed in CS (1,970.9 kg CO2 ha-1) and LS (1,707.7 kg CO2 ha-1). The conversion from CT to LS decreased soil CO2 emissions, reducing the contribution of agriculture in increasing the concentration of greenhouse gases in the atmosphere.

Soil CO2 emission (FCO2) is one of the main sources of carbon release into the atmosphere. Moreover, FCO2 is related to soil attributes governing the transfer of gases from soil to the atmosphere. This study aimed firstly to describe the spatial variability of hematite (Hm), goethite (Gt), iron extracted with sodium dithionite-citrate-bicarbonate (Fed) contents, soil CO2 emission (FCO2) and free-water porosity (FWP) and secondly, to develop statistical models to predict the above mentioned factors in an Oxisol cultivated under manual harvesting of sugarcane (Saccharumspp.) in southeastern Brazil. The study was conducted on an irregular 50 m × 50 m grid containing 89 points, each 0.5-10 m apart. The 0-0.1 m soil layer at each sampling point was used to assess soil FCO2, moisture and total pore volume. The results were subjected to descriptive statistical and geostatistical analyses using auto- and cross-semivariograms. All soil attributes exhibited a spatial dependence structure and the experimental semivariograms fitted spherical and exponential models. The Gt content was the individual attribute that exhibited the highest linear and spatial correlation, especially with FCO2. We were able to use diffuse reflectance spectroscopy to map large areas, which allows for easy identification and estimation of soil attributes such as FCO2 and FWP. Geostatistical techniques faciltate the interpretation of spatial relationships between soil respiration and the examined properties.

A emissão de CO2 do solo (FCO2) em áreas agrícolas é resultante da interação de diversos fatores, sendo alterada pela prática de manejos do solo e da cultura, além das condições edafoclimáticas locais. Neste estudo, objetivou-se quantificar a FCO2 em função da calagem e posição da aplicação (antiga linha e entrelinha) da cultura da laranja em área de conversão para a cultura da cana-de-açúcar, no município de Frutal-MG. Os tratamentos avaliados foram: Linha/CC (linha com aplicação de calcário); Entrelinha/CC (entrelinha com aplicação de calcário); Linha/SC (linha sem aplicação de calcário), e Entrelinha/SC (entrelinha sem aplicação de calcário). FCO2, temperatura do solo (Ts) e umidade do solo (Us) foram avaliadas durante 12 dias. O maior valor médio da FCO2 ao longo do período de estudo foi observado no tratamento Linha/CC (9,63 µmol m-2 s-1); e o menor, no tratamento Entrelinha/CC (5,92 µmol m-2 s-1), segundo teste de Tukey. A FCO2 foi negativamente correlacionada à Us na Linha/CC (r = - 0,56; p < 0,05) e na Linha/SC (r = - 0,66; p < 0,05). Entre a FCO2 e a Ts, verificou-se correlação positiva e significativa na Linha/CC (r = 0,76; p < 0,001), na Linha/SC (r = 0,89; p < 0,001) e na Entrelinha/SC (r = 0,66; p < 0,05). Observou-se que a calagem e a posição de aplicação (linha e entrelinha) influenciaram nas emissões de CO2 do solo.

The soil CO2 emission (FCO2) in agricultural areas is resulting from the interaction of several factors, as amended by the practice of soil management practices and crop, in addition to the local edaphoclimatic conditions. In this study, we aimed to quantify FCO2 influenced by liming and application position (row and interrow old) of the orange crop in conversion area for cultivation of sugar cane in the municipality of Frutal-MG. The treatments evaluated were: Row/CC (row with lime application), Interrow/CC (interrow with application of lime), Row/SC (row without liming) and Interrow/SC (interrow without liming). FCO2, temperature (Ts) and soil moisture (Us) were evaluated over 12 days. The highest average value of FCO2 over the study period was observed in the treatment Row/CC (9.63 µmol m-2 s-1) and the lowest in Interrow/CC (5.92 µmol m-2 s-1) according to the Tukey test. The FCO2 was negatively correlated with Us in Row/CC (r = - 0.56, p < 0.05) and in Row/SC (r = - 0.66, p < 0.05). It was also observed a significant and positive correlation between FCO2 and Ts in Row/CC (r = 0.76, p < 0.001), Row/SC (r = 0.89, p < 0.001) and in Interrow/SC (r = 0.66, p < 0.05). It was observed that liming and position of application (row and interrow) influenced the soil CO2 emissions.

Melhores condições de trabalho, produção sustentável e competitividade levaram a mudanças substanciais no sistema de colheita de cana-de-açúcar. Tais mudanças alteraram uma série de atributos do solo, incluindo os óxidos de ferro e a matéria orgânica, assim como alguns atributos químicos como a capacidade máxima de adsorção de P no solo. O objetivo deste trabalho foi caracterizar a relação entre óxidos de ferro e a qualidade da matéria orgânica nos sistemas de colheita de cana-de-açúcar. Para este fim, duas parcelas de 1 ha em áreas colhidas mecanicamente e manualmente foram utilizadas para obter amostras de solo da camada de 0,00-0,25 m em 126 pontos diferentes. Os resultados das análises mineralógicas, químicas e físicas foram submetidos às análises da estatística descritiva, com teste de comparação de médias, estatísticas multivariadas e análises de componentes principais. A aplicação da estatística multivariada possibilitou a divisão de todos os atributos estudados de acordo com o sistema de colheita: colheita manual com a queima dos resíduos da cana e colheita mecanizada sem queima. O sistema de colheita mecânica promoveu condições pedoambientais, que conduzem a mudanças na cristalinidade dos óxidos de ferro, no aumento no grau de humificação da matéria orgânica e na diminuição relativa de adsorção de P nessa área, em relação ao sistema de cana queimada.

Improvements in working conditions, sustainable production, and competitiveness have led to substantial changes in sugarcane harvesting systems. Such changes have altered a number of soil properties, including iron oxides and organic matter, as well as some chemical properties, such as the maximum P adsorption capacity of the soil. The aim of this study was to characterize the relationship between iron oxides and the quality of organic matter in sugarcane harvesting systems. For that purpose, two 1 ha plots in mechanically and manually harvested fields were used to obtain soil samples from the 0.00-0.25 m soil layer at 126 different points. The mineralogical, chemical, and physical results were subjected to descriptive statistical analyses, such as the mean comparison test, as well as to multivariate statistical and principal component analyses. Multivariate tests allowed soil properties to be classified in two different groups according to the harvesting method: manual harvest with the burning of residual cane, and mechanical harvest without burning. The mechanical harvesting system was found to enhance pedoenvironmental conditions, leading to changes in the crystallinity of iron oxides, an increase in the humification of organic matter, and a relative decrease in phosphorus adsorption in this area compared to the manual harvesting system.

O solo é um dos principais compartimentos de carbono no ecossistema terrestre, capaz de armazenar quantidades expressivas desse elemento e, portanto, a compreensão dos fatores que contribuem para as perdas de CO2 em solos agrícolas é fundamental para determinar estratégias de redução das emissões desse gás e ajudar a mitigar o efeito estufa. O objetivo deste estudo foi investigar o efeito do preparo do solo e da deposição de resíduos da cultura da cana-de-açúcar na emissão de CO2, temperatura e umidade do solo, durante a reforma do canavial, ao longo de um período de 15 dias. Os manejos avaliados foram: sem preparo do solo e mantendo os resíduos da colheita sobre a superfície do solo (SPCR); sem preparo do solo e sem resíduo (SPSR) e com preparo do solo e sem resíduo (CPSR). A menor média de emissão de CO2 do solo (FCO2) foi observada no manejo SPCR (2,16 µmol m-2 s-1), quando comparado aos manejos SPSR (2,90 µmol m-2 s-1) e CPSR (3,22 µmol m-2 s-1), indicando que as maiores umidades e menores variações da temperatura do solo, observadas em SPCR, foram os fatores responsáveis por tal diminuição. Durante o período de estudo, a menor média diária da FCO2 foi registrada em SPCR (1,28 µmol m-2 s-1) e a maior em CPSR (6,08 µmol m-2 s-1), após a ocorrência de chuvas. A menor perda de C-CO2 do solo foi observada no manejo SPCR (367 kg ha-1 de C-CO2), diferindo significativamente (p<0,05) dos manejos: SPSR (502 kg ha-1 de C-CO2) e CPSR (535 kg ha-1 de C-CO2). A umidade do solo foi a variável que apresentou valores mais diferenciados entre os manejos, sendo positivamente correlacionada (r = 0,55; p<0,05) com as variações temporais da emissão de CO2 nos manejos SPCR e CPSR. Em adição, a temperatura do solo diferiu (p<0,05) somente no manejo SPCR (24 ºC), quando comparada aos manejos SPSR (26 ºC) e CPSR (26,5 ºC), sugerindo que, para as condições deste estudo, o resíduo da cana-de-açúcar retido sobre a superfície propiciou uma temperatura do solo, em média, 2 ºC mais amena.

The soil is one of the main C pools in terrestrial ecosystem, capable of storing significant C amounts. Therefore, understanding the factors that contribute to the loss of CO2 from agricultural soils is critical to determine strategies reducing emissions of this gas and help mitigate the greenhouse effect. The purpose of this study was to investigate the effect of soil tillage and sugarcane trash on CO2 emissions, temperature and soil moisture during sugarcane (re)planting, over a study period of 15 days. The following managements were evaluated: no-tillage with crop residues left on the soil surface (NTR); without tillage and without residue (NTNR) and tillage with no residue (TNR). The average soil CO2 emission (FCO2) was lowest in NTR (2.16 µmol m-2 s-1), compared to the managements NTNR (2.90 µmol m-2 s-1) and TNR (3.22 µmol m-2 s-1), indicating that the higher moisture and lower soil temperature variations observed in NTR were responsible for this decrease. During the study period, the lowest daily average FCO2 was recorded in NTR (1.28 µmol m-2 s-1), and the highest in TNR (6.08 µmol m-2 s-1), after rainfall. A loss of soil CO2 was lowest from the management NTR (367 kg ha-1 of CO2-C) and differing significantly (p<0.05) from the managements NTNR (502 kg ha-1 of CO2-C) and TNR (535 kg ha-1 of CO2-C). Soil moisture was the variable that differed most managements and was positively correlated (r = 0.55, p<0.05) with the temporal variations of CO2 emission from NTR and TNR. In addition, the soil temperature differed (p<0.05) only in management NTR (24 °C) compared to NTNR (26 °C) and TNR (26.5 °C), suggesting that under the conditions of this study, sugarcane trash left on the surface induced an average rise in the of soil temperature of 2 ºC.