Decision-making on the optimum timing for nitrogen fertilization on sugarcane ratoon

Low efficiency of nitrogen from fertilizers is a major concern worldwide, threatening the sustainability of sugarcane production. The N use efficiency (NUE) by sugarcane can be improved by adopting better fertilizing management practices, reducing environmental impacts. This work evaluated the effects of varying N rates and time of application on stalks and sugar yield in ratoon harvested early in the crop season. The experimental design was a randomized block in a 2 × 4 factorial design and a control (no N) with five replications, including two application times (45 or 90 DAH – days after harvest) and four N rates (50, 100, 150, or 200 kg N ha−1). The time of N fertilizer application promoted differences in stalk yield, as the cumulative yield of two harvests was increased by 8 % (15 Mg ha−1) at 45 DAH when compared to the application at 90 DAH. The application performed at 45 DAH augmented sugar yield by 10 % (2.8 Mg ha−1 of sugar) in relation to 90 DAH. The N rates that promoted the highest sugarcane yield were, respectively, 122 and 144 kg N ha−1 in the first and second crop cycles. The average economical rates obtained for the first and second agricultural cycles were, respectively, 104 and 127 kg N ha−1, demonstrating that the gains by applying high amounts of fertilizers (rates above 150 kg N ha−1) may not cover the investment.

Decision-making on the optimum timing for nitrogen fertilization on sugarcane ratoon

Low efficiency of nitrogen from fertilizers is a major concern worldwide, threatening the sustainability of sugarcane production. The N use efficiency (NUE) by sugarcane can be improved by adopting better fertilizing management practices, reducing environmental impacts. This work evaluated the effects of varying N rates and time of application on stalks and sugar yield in ratoon harvested early in the crop season. The experimental design was a randomized block in a 2 × 4 factorial design and a control (no N) with five replications, including two application times (45 or 90 DAH days after harvest) and four N rates (50, 100, 150, or 200 kg N ha−1). The time of N fertilizer application promoted differences in stalk yield, as the cumulative yield of two harvests was increased by 8 % (15 Mg ha−1) at 45 DAH when compared to the application at 90 DAH. The application performed at 45 DAH augmented sugar yield by 10 % (2.8 Mg ha−1 of sugar) in relation to 90 DAH. The N rates that promoted the highest sugarcane yield were, respectively, 122 and 144 kg N ha−1 in the first and second crop cycles. The average economical rates obtained for the first and second agricultural cycles were, respectively, 104 and 127 kg N ha−1, demonstrating that the gains by applying high amounts of fertilizers (rates above 150 kg N ha−1) may not cover the investment.(AU)

Traditional knowledge and variations in capture techniques used for blue land crab (Cardisoma guanhumi, L. 1825) along the coast of Paraíba, Brazil / Conhecimento tradicional e as diferentes técnicas de captura do caranguejo goiamum (Cardisoma guanhumi, L. 1825) no litoral da Paraíba, Brasil

The Mamanguape estuary, located in the Paraíba State (Brazil), hosts many traditional fishing communities and Amerindian villages whose use of the regional natural resources is fundamental to their cultural and physical survival. The aim was to register the traditional local knowledge about the different fish techniques, the influence of the dynamics of the natural environment on the activities of the blue land crab, and the relationships between the sizes of their dens and the sizes of the animals themselves. The only technique used to capture blue land crab is a trap called ‘mousetrap’. It was recorded different materials such as PET bottles, to build the traps. The fishermen stated that fruits are used as bait as well as sugar-cane and onions. The phases of the moon and the different tides do not significantly influence their activities as the crabs inhabit higher lands beyond the influence of normal tides. The knowledge documented here concerning the blue land crab demonstrated that these shell fish harvesters have a detailed understanding of their environment based on observations and empiricism that allows them to determine which techniques and strategies will increase their chances of capturing their prey and consequently guaranteeing their income.

O estuário do Rio Mamanguape, localizado no Estado da Paraíba (Brasil), é residência de diversas comunidades de pescadores tradicionais e povos indígenas que dependem dos recursos naturais para a sobrevivência física e cultural. O objetivo foi registrar o conhecimento tradicional local sobre as diferentes técnicas de captura do goiamum, a influência dos diferentes fatores ambientais sobre a atividade de captura, e outros fatores diversos como diferença entre machos e fêmeas e o tamanho das tocas. A técnica utilizada que permite a captura é a ratoeira, construída com diferentes materiais. As iscas são frutas, cana-de-açúcar ou cebola. As fases da lua não influenciam diretamente a atividade, já que o goiamum habita áreas acima da preamar. O conhecimento dos catadores registrado neste trabalho mostra um entendimento detalhado do ambiente e do animal, construído em empiricismo e observações, que permite determinar a melhor estratégia e técnica para aumentar o sucesso de captura do goiamum, consequentemente garantindo a renda familiar.

Traditional knowledge and variations in capture techniques used for blue land crab (Cardisoma guanhumi, L. 1825) along the coast of Paraíba, Brazil / Conhecimento tradicional e as diferentes técnicas de captura do caranguejo goiamum (Cardisoma guanhumi, L. 1825) no litoral da Paraíba, Brasil

The Mamanguape estuary, located in the Paraíba State (Brazil), hosts many traditional fishing communities and Amerindian villages whose use of the regional natural resources is fundamental to their cultural and physical survival. The aim was to register the traditional local knowledge about the different fish techniques, the influence of the dynamics of the natural environment on the activities of the blue land crab, and the relationships between the sizes of their dens and the sizes of the animals themselves. The only technique used to capture blue land crab is a trap called ‘mousetrap. It was recorded different materials such as PET bottles, to build the traps. The fishermen stated that fruits are used as bait as well as sugar-cane and onions. The phases of the moon and the different tides do not significantly influence their activities as the crabs inhabit higher lands beyond the influence of normal tides. The knowledge documented here concerning the blue land crab demonstrated that these shell fish harvesters have a detailed understanding of their environment based on observations and empiricism that allows them to determine which techniques and strategies will increase their chances of capturing their prey and consequently guaranteeing their income.(AU)

O estuário do Rio Mamanguape, localizado no Estado da Paraíba (Brasil), é residência de diversas comunidades de pescadores tradicionais e povos indígenas que dependem dos recursos naturais para a sobrevivência física e cultural. O objetivo foi registrar o conhecimento tradicional local sobre as diferentes técnicas de captura do goiamum, a influência dos diferentes fatores ambientais sobre a atividade de captura, e outros fatores diversos como diferença entre machos e fêmeas e o tamanho das tocas. A técnica utilizada que permite a captura é a ratoeira, construída com diferentes materiais. As iscas são frutas, cana-de-açúcar ou cebola. As fases da lua não influenciam diretamente a atividade, já que o goiamum habita áreas acima da preamar. O conhecimento dos catadores registrado neste trabalho mostra um entendimento detalhado do ambiente e do animal, construído em empiricismo e observações, que permite determinar a melhor estratégia e técnica para aumentar o sucesso de captura do goiamum, consequentemente garantindo a renda familiar.(AU)

Carbon fractions and soil fertility affected by tillage and sugarcane residue management an Xanthic Udult / Frações do carbono e fertilidade do solo afetados pelo preparo do solo e manejo da palhada da cana-de-açúcar em Argissolo Amarelo

The gradual change in management practices in sugarcane (Saccharum spp.) production from burning straw to a green harvesting system, as well as the use of minimum soil tillage during field renovation, may affect soil fertility and soil organic matter (SOM) contents. The objectives of this work were to investigate the influence of sugar cane production systems on: (1) soil fertility parameters; (2) on physical carbon fractions; (3) and on humic substance fractions, in a long-term experiment, comparing two soil tillage and two residue management systems an Xanthic Udult, in the coastal tableland region of Espírito Santo State, Brazil. The treatments consisted of plots (conventional tillage (CT) or minimum tillage (MT)) and subplots (residue burned or unburned at harvesting), with five replicates The highest values of Ca2+ + Mg2+ and total organic carbon (TOC) were observed in the MT system in all soil layers, while high values of K+ were observed in the 0.1-0.2 m layer. The CT associated with the burned residue management negatively influenced the TOC values, especially in the 0.1-0.2 and 0.2-0.4 m layers. The carbon in the humin fraction and organic matter associated with minerals were significantly different among the tillage systems; the MT showed higher values than the CT. However, there were no significant differences between the sugarcane residue management treatments. Overall, fractioningthe SOM allowed for a better understanding of tillage and residue management systems effects on thesoil properties.(AU)

A mudança gradual nas práticas de manejo da cana de açúcar (Saccharum spp.) de colheita com queima de palha para o sistema de colheita sem queima, bem como o uso de preparo mínimo do solo durante a renovação do canavial, podem afetar a fertilidade do solo e o conteúdo de matéria orgânica do solo (MOS). Os objetivos específicos foram investigar a influência de sistemas de produção de cana-de-açúcar sobre: (1) os parâmetros de fertilidade do solo; (2) sobre as frações físicas do carbono; (3) e em frações de substâncias húmicas, em um experimento de longa duração, comparando dois tipos de preparo do solo e dois sistemas de manejo da palhada em Argissolo Amarelo, na região tabuleiros costeiros do Espírito Santo, Brasil. Os tratamentos consistiram de parcelas (preparo convencional (PC) e cultivo mínimo (CM)) e subparcelas (palha queimada e não queimada perante a colheita), com cinco repetições. Foram observados os maiores valores de Ca2+ + Mg2+ e carbono orgânico total (COT) no sistema de CM, em todas as camadas do solo, enquanto maiores valores de K+ foram observados na camada de 0,1-0,2 m. O PC associado a colheita com queima da palhada influenciou negativamente os valores de COT, especialmente nas camadas 0,1-0,2 e 0,2-0,4 m. O carbono na fração humina e o carbono associado aos minerais do solo foram significativamente diferentes entre os sistemas de preparo do solo; o CM apresentou valores mais elevados do que o PC. No entanto, não houve diferençassignificativas entre o manejo da palhada da cana-de-açúcar. No geral, o fracionamento da MOS permitiuuma melhor compreensão dos efeitos dos sistemas de preparo do solo e manejo da palhada sobre aspropriedades do solo.(AU)

Agronomic performance of sugarcane cultivated under quantities of sugarcane straw on the soil surface / Desempenho agronômico da cana-de-açúcar cultivada sob diferentes quantidades de palhada da cultura na superfície do solo

Mechanized harvesting has become increasingly common in the sugarcane production system. The sugarcane straw removed by mechanical harvesting could be converted into ethanol or be used to generate electricity by burning the material. At the same time, it is important to determine the amount of biomass that could be removed from the soil surface without damage to the cane crop. The agronomic performance of sugarcane was evaluated by growing the variety RB92579 under different amounts of sugarcane straw on the soil surface, in the first and second years of cane crop growth. An experimental randomized block in a split-plot design was used with four replications. In the first year the plots received five amounts of straw (0.0, 4.5, 9.0, 13.5, and 18 Mg ha-1), and six assessments (60, 120, 180, 240, 300, and 360 days after planting) were made in the subplots. In the second year, the plots received the same amount of straw and four assessments (60, 120, 240, and 540 days after the regrowth) in the subplots. Biometric indexes, components of production, and crop yield were evaluated. The data were submitted to variance analysis and polynomial regression (p < 0.05). Increasing amounts of sugarcane straw deposited on the soil surface reduced the number and diameter of stalks at the beginning of crop establishment and the number of leaves for the first year. The maximum productivity of stalks was achieved by maintaining on the soil surface 9.6 Mg ha-1 of straw in the first year and 4.7 Mg ha-1 of straw in the second year of cane crop production.

A colheita mecanizada está cada vez mais presente no sistema de produção de cana-de-açúcar. A palhada retirada durante a colheita pode ser convertida a etanol ou utilizada para geração de energia elétrica por meio da queima, sendo importante determinar a quantidade desta biomassa que pode ser removida, sem que haja prejuízos à cultura. Objetivou-se avaliar o desempenho agronômico da cana-de-açúcar, variedade RB92579, cultivada sob diferentes quantidades de palhada da cultura na superfície do solo, em cultivo de primeiro e segundo ciclo. Utilizou-se o delineamento experimental em blocos casualizados, com parcelas subdivididas no tempo, com quatro repetições. No primeiro ciclo as parcelas receberam cinco quantidades de palhada (0,0; 4,5; 9,0; 13,5 e 18 Mg ha-1) e seis épocas de avaliação (60, 120, 180, 240, 300, 360 dias após o plantio – DAP), dispostas nas subparcelas. No segundo ciclo, nas parcelas foram depositadas as mesmas quantidades de palhada e nas subparcelas foram dispostas as quatro épocas de avaliação (60, 120, 240 e 540 dias após a rebrota – DAR). Foram avaliadas as características fitométricas, os componentes de produção e a produtividade. Os dados foram submetidos à análise de variância e estudo de regressão polinomial (p < 0,05). O aumento das quantidades de palhada depositadas na superfície do solo reduz o número e o diâmetro do colmo no início do estabelecimento da cultura, e o número de folhas para a cana de primeiro ciclo. A produtividade máxima de colmos é obtida com a manutenção de 9,6 Mg ha-1 de palhada para o primeiro ciclo e 4,7 Mg ha-1 de palhada para o segundo ciclo.

Agronomic performance of sugarcane cultivated under quantities of sugarcane straw on the soil surface / Desempenho agronômico da cana-de-açúcar cultivada sob diferentes quantidades de palhada da cultura na superfície do solo

Mechanized harvesting has become increasingly common in the sugarcane production system. The sugarcane straw removed by mechanical harvesting could be converted into ethanol or be used to generate electricity by burning the material. At the same time, it is important to determine the amount of biomass that could be removed from the soil surface without damage to the cane crop. The agronomic performance of sugarcane was evaluated by growing the variety RB92579 under different amounts of sugarcane straw on the soil surface, in the first and second years of cane crop growth. An experimental randomized block in a split-plot design was used with four replications. In the first year the plots received five amounts of straw (0.0, 4.5, 9.0, 13.5, and 18 Mg ha-1), and six assessments (60, 120, 180, 240, 300, and 360 days after planting) were made in the subplots. In the second year, the plots received the same amount of straw and four assessments (60, 120, 240, and 540 days after the regrowth) in the subplots. Biometric indexes, components of production, and crop yield were evaluated. The data were submitted to variance analysis and polynomial regression (p < 0.05). Increasing amounts of sugarcane straw deposited on the soil surface reduced the number and diameter of stalks at the beginning of crop establishment and the number of leaves for the first year. The maximum productivity of stalks was achieved by maintaining on the soil surface 9.6 Mg ha-1 of straw in the first year and 4.7 Mg ha-1 of straw in the second year of cane crop production.(AU)

A colheita mecanizada está cada vez mais presente no sistema de produção de cana-de-açúcar. A palhada retirada durante a colheita pode ser convertida a etanol ou utilizada para geração de energia elétrica por meio da queima, sendo importante determinar a quantidade desta biomassa que pode ser removida, sem que haja prejuízos à cultura. Objetivou-se avaliar o desempenho agronômico da cana-de-açúcar, variedade RB92579, cultivada sob diferentes quantidades de palhada da cultura na superfície do solo, em cultivo de primeiro e segundo ciclo. Utilizou-se o delineamento experimental em blocos casualizados, com parcelas subdivididas no tempo, com quatro repetições. No primeiro ciclo as parcelas receberam cinco quantidades de palhada (0,0; 4,5; 9,0; 13,5 e 18 Mg ha-1) e seis épocas de avaliação (60, 120, 180, 240, 300, 360 dias após o plantio DAP), dispostas nas subparcelas. No segundo ciclo, nas parcelas foram depositadas as mesmas quantidades de palhada e nas subparcelas foram dispostas as quatro épocas de avaliação (60, 120, 240 e 540 dias após a rebrota DAR). Foram avaliadas as características fitométricas, os componentes de produção e a produtividade. Os dados foram submetidos à análise de variância e estudo de regressão polinomial (p < 0,05). O aumento das quantidades de palhada depositadas na superfície do solo reduz o número e o diâmetro do colmo no início do estabelecimento da cultura, e o número de folhas para a cana de primeiro ciclo. A produtividade máxima de colmos é obtida com a manutenção de 9,6 Mg ha-1 de palhada para o primeiro ciclo e 4,7 Mg ha-1 de palhada para o segundo ciclo.(AU)

Sugarcane trash levels in soil affects the fungi but not bacteria in a short-term field experiment

The sugarcane in Brazil is passing through a management transition that is leading to the abolition of pre-harvest burning. Without burning, large amounts of sugarcane trash is generated, and there is a discussion regarding the utilization of this biomass in the industry versus keeping it in the field to improve soil quality. To study the effects of the trash removal on soil quality, we established an experimental sugarcane plantation with different levels of trash over the soil (0%, 50% and 100% of the original trash deposition) and analyzed the structure of the bacterial and fungal community as the bioindicators of impacts. The soil DNA was extracted, and the microbial community was screened by denaturing gradient gel electrophoresis in two different seasons. Our results suggest that there are no effects from the different levels of trash on the soil chemistry and soil bacterial community. However, the fungal community was significantly impacted, and after twelve months, the community presented different structures among the treatments.(AU)

Changes in soil chemical reactions in response to straw sugar cane and vinasse / Alteração na reação química do solo influenciada pela palha de cana-de-açúcar e vinhaça

Sugarcane harvesting is predominantly mechanical because of environmental restrictions, reduced requirements for manpower, and the quest for improved efficiency. Therefore, large amounts of straw remain available in the soil. Vinasse, a liquid waste, is a main byproduct of the sugar and alcohol industry, in addition to sugarcane straw. Both accumulate in sugarcane fields; however, the effects of their interaction are unclear. In this study, the effects of applications of sugarcane straw and vinasse on the pH and the potassium (K), calcium (Ca), and magnesium (Mg) concentrations of a dystroferric Red Nitosol with a high base saturation were examined. The profiles of soil samples from sugarcane plantations collected at depths of 0-0.05, 0.06-0.10, 0.11-0.20, and 0.21-0.30 m were reproduced in 64 polyvinyl chloride (PVC) columns with dimensions of 0.036 × 0.30 m (diameter × height). The soils were treated with doses of 0, 125, 250, and 500 m3 ha-1 sugarcane vinasse and 0, 3, 6, and 9 t ha-1 sugarcane straw and incubated for 60 days. Following the analysis, by layer, the data were subjected to analysis of variance by partitioning the degrees of freedom into orthogonal polynomials. The pH and the Ca, Mg, and K concentrations increased throughout the soil profile upon vinasse application. An acid-base imbalance was observed in the topsoil layers in association with the high K...(AU)

Devido às restrições ambientais, falta de mão-de-obra e a busca por melhor eficiência, a colheita de cana-de-açúcar tende a ser mecanizada, fazendo com que grande quantidade de palhada esteja disponível no solo. Somada à palha, a vinhaça é o principal resíduo líquido da indústria sucroalcooleira. Ambos são depositados a campo; porém, o efeito da interação entre os mesmos, ainda não está esclarecido. Avaliou-se a influência da aplicação de palha de cana-de-açúcar e vinhaça no pH e nos teores de potássio (K), cálcio (Ca) e magnésio (Mg) em Nitossolo Vermelho distroférrico de alta saturação por bases. Em 64 colunas de PVC de 0,036 × 0,30 m (diâmetro × altura) foram reproduzidos perfis do solo coletados nas profundidades 0-0,05; 0,06-0,10; 0,10-0,20; 0,20-0,30 m, em área de cultivo. Os solos foram tratados com vinhaça, em doses equivalentes a 0, 125, 250 e 500 m3 ha-1 e 0, 3, 6 e 9 t ha-1 de palha de cana-de-açúcar e submetidos à incubação por 60 dias. Após as análises por camada, os dados foram submetidos à análise de variância com desdobramento dos graus de liberdade em polinômios ortogonais. Com a aplicação de vinhaça, houve elevação do pH e dos teores de Ca, Mg e K, com distribuição em todo o perfil. Observou-se desequilíbrio de bases nas camadas superficiais devido à alta saturação de K. A palha de cana-de-açúcar potencializou o efeito da vinhaça em todas as profundidades...(AU)

DESEMPENHO AGRONÔMICO E DIGESTIBILIDADE RUMINAL DE VARIEDADES DE CANA-DE-AÇÚCAR CULTIVADAS SOB IRRIGAÇÃO SUPLEMENTAR

Objetivou-se avaliar as características agronômicas, composição química e digestibilidade ruminal in situ de oito variedades de cana-de-açúcar (CV-4, RB-041443, RB-855035, RB-867515, RB-92579, RB-931011, RB-951541 e RB-962962) cultivados em regime de irrigação suplementar, com vistas a alimentação de bovinos leiteiros. O experimento foi delineado em blocos casualizados com oito tratamentos e três repetições, totalizando 24 parcelas experimentais. As análises biométricas foram realizadas aos 360 dias após o plantio e 360 dias após o corte, onde foram avaliados: comprimento do colmo (CC), diâmetro do colmo (DC), número de folhas verdes (NFV) e área foliar (AF). A produtividade em toneladas de colmos por hectare (TCH) e a concentração de açúcares solúveis em ºbrix foram avaliadas na cana-planta e cana-soca1. Amostras de colmos de cada variedade foram trituradas e pré-secadas em estufa, para determinação de sua composição química: matéria seca (MS), matéria mineral (MM), fibra em detergente neutro (FDN), fibra em detergente ácido (FDA) e lignina (Lig). Para a avaliação da digestibilidade ruminal in situ em 24h da MS e da FDN utilizou-se três vacas da raça Girolando, canuladas no rúmen, com peso médio de 510± 20 kg. Amostras contendo 5 g de matéria pré-seca do colmo e planta inteira da cana-planta foram pesadas em saquinhos de tecido não tecido (TNT) e incubadas no rúmen dos animais. A digestibilidade ruminal da MS foi calculada com o desaparecimento de MS em 24 horas de incubação, proporcionalmente a MS originalmente incubada e calculada o resíduo de MS após 72h de incubação (RES 72h). Os dados foram submetidos à análise de variância pelo teste F e as médias comparadas pelo teste de Tukey a 5% probabilidade, por meio do software estatístico InfoStat 12.0. A TCH da cana-planta não apresentou diferença entre as variedades, com média de 104,20 t ha -1 de colmos. Para a TCH da cana-soca não houve diferença entre os genótipos, com média obtida de 155,8 t ha -1. Não houve diferença entre variedades quanto os valores médios da bromatologia do colmo integral, MS (27,34%), MM (1,52%), FDN (40,62%), FDA (22,28%) e LIG (3,50%). Já a composição química da cana em planta inteira apresentou diferenças (P<0,05) entre variedades, quanto aos teores de MS (27,03%), MM (1,91%), FDN (39,59%), FDA (27,95%) e LIG (4,38%). A DEG MS após 24 horas de incubação para as partes colmo integral não foi diferente entre as variedades, com média de 46,20%, para o componente planta inteira houve diferença estatística (P<0,05) e a variedade com desempenho superior foi a RB92579 (65%) e o menor desempenho foi obtido pelas variedades RB931011 (50%) e RB951541 (50,33%). Os valores de DEG FDN para colmo integral variaram de 18,23 a 25,33% com média de 21,25%, já para a variável planta inteira de 18,6 a 24,3% com média 20,7%, em ambas as partes da cana a DEG FDN não apresentou diferença estatística. Sob irrigação suplementar os oito genótipos de cana-de-açúcar apresentaram similaridade quanto às produtividades de colmos, valores de brix e digestibilidade ruminal in situ 24h da MS e da FDN na cana-planta.

The objective of this study was to evaluate the agronomic characteristics, chemical composition and ruminal digestibility in situ of eight varieties of sugarcane (CV-4, RB-041443, RB-855035, RB-867515, RB-92579, RB-931011, RB -951541 and RB-962962) grown under supplementary irrigation, with a view to feeding dairy cattle. The experiment was designed in randomized blocks with eight treatments and three replications, totaling 24 experimental plots. Biometric analyzes were performed 360 days after planting and 360 days after cutting, where the following were evaluated: stem length (CC), stem diameter (DC), number of green leaves (NFV) and leaf area (AF). The productivity in tons of stalks per hectare (TCH) and the concentration of soluble sugars in ºbrix were evaluated in cane-plant and cane-soca1. Stem samples of each variety were crushed and pre-dried in an oven to determine their chemical composition: dry matter (MS), mineral matter (MM), neutral detergent fiber (NDF), acid detergent fiber (FDA) and lignin (Lig). For the evaluation of ruminal digestibility in situ in 24h of DM and NDF, three Girolando cows, cannulated in the rumen, with an average weight of 510 ± 20 kg were used. Samples containing 5 g of pre-dry stem material and the entire plant of the cane-plant were weighed in bags of non-woven fabric (TNT) and incubated in the rumen of the animals. The ruminal digestibility of DM was calculated with the disappearance of DM in 24 hours of incubation, in proportion to the DM originally incubated and the DM residue after 72h of incubation (RES 72h). The data were submitted to analysis of variance by the F test and the means compared by the Tukey test at 5% probability, using the InfoStat 12.0 statistical software. The TCH of cane-plant did not show any difference between the varieties, with an average of 104.20 t ha -1 of stalks. There was no difference between the genotypes for the TCH of the cane, with an average of 155.8 t ha -1. There was no difference between varieties in terms of the average values of the stem stem bromatology, MS (27.34%), MM (1.52%), NDF (40.62%), FDA (22.28%) and LIG (3 , 50%). The chemical composition of sugarcane in whole plant showed differences (P <0.05) between varieties, in terms of DM (27.03%), MM (1.91%), NDF (39.59%), FDA (27.95%) and LIG (4.38%). The DEG MS after 24 hours of incubation for the whole stem parts was not different between the varieties, with an average of 46.20%, for the whole plant component there was a statistical difference (P <0.05) and the variety with superior performance was a RB92579 (65%) and the lowest performance was obtained by the varieties RB931011 (50%) and RB951541 (50.33%). The values of DEG NDF for whole stem ranged from 18.23 to 25.33% with an average of 21.25%, whereas for the whole plant variable from 18.6 to 24.3% with an average of 20.7%, in both the sugarcane parts the DEG FDN did not present statistical difference. Under supplementary irrigation, the eight sugarcane genotypes showed similarity in stalk productivity, brix values and ruminal digestibility in situ 24h of DM and NDF in plant cane.

Influência de diferentes cultivos e fatores climáticos na ocorrência de crisopídeos em sistema agroecológico / Influence of different crops and climate factors on the occurrence of green lacewings in agroecological system

Os insetos predadores da família Chrysopidae têm sido relatados tanto em ecossistemas naturais como nos agroecossistemas, sejam eles cultivos consorciados ou monocultivos. Porém, são escassas as informações sobre o comportamento das populações desses insetos nos agroecossistemas diversificados, como aqueles de base agroecológica. O presente trabalho teve o objetivo de determinar a riqueza de espécies de crisopídeos e avaliar a influência de diferentes cultivos agrícolas, assim como de fatores climáticos na abundância desses insetos em sistema de produção orgânica diversificada. O estudo foi conduzido de setembro de 2008 a agosto de 2009, por meio de amostragens semanais de adultos de Chrysopidae em áreas do Sistema Integrado de Produção Agroecológica, em Seropédica (RJ), cada qual com um tipo de sistema de cultivo (rotação milho-mucuna/olerícolas, cafeeiros sombreados e rotação cana-de-açúcar/pastagem de braquiária). Um total de 424 espécimes de crisopídeos foi coletado, sendo distribuídos em três espécies: Chrysoperla externa (98,1%), Ceraeochrysa cubana (1,7%) e Ceraeochrysa paraguaria (0,2%). Não houve diferença no número de adultos coletados em função dos diferentes cultivos, embora a análise de correlação evidencie que as rotações com poáceas favoreçam o aumento da sua abundância. A abundância dos crisopídeos foi influenciada pelo clima apenas no sistema de cafeeiros sombreados, sendo correlacionada negativamente com a temperatura média do ar e a com a precipitação pluvial acumulada.(AU)

The green lacewings (Chrysopidae) have been reported in natural ecosystems as well in agroecosystems, intercropping or monocropping. However, the knowledge on their behavior on different agroecosystems is scarce. The present work aimed to determine the diversity of green lacewing species and to evaluate the influence of different agricultural crops, as well as climate factors, on the abundance of these insects in an agroecologically-based organic production system. The study was conducted from September 2008 to August 2009, by performing weekly sampling of Chrysopidae adults in areas of the Integrated Production Agroecological System (SIPA) in Seropédica (RJ), each with one type of cropping system (corn-mucuna rotation/vegetable crops; shaded coffees and sugar cane/brachiaria pasture rotation). A total of 424 adult specimens were collected, belonging to three species: Chrysoperla externa (98.1%), Ceraeochrysa cubana (1.7%) and Ceraeochrysa paraguaria (0.2%). There were no differences on the number of green lacewing adults collected in the crops, although the correlation analysis showed that the crop rotations with grasses favor their abundance. The abundance of green lacewings was also influenced by the climate conditions only in the system of shaded coffees, being negatively correlated with mean air temperature and accumulated rainfall.(AU)

Influência de diferentes cultivos e fatores climáticos na ocorrência de crisopídeos em sistema agroecológico / Influence of different crops and climate factors on the occurrence of green lacewings in agroecological system

Os insetos predadores da família Chrysopidae têm sido relatados tanto em ecossistemas naturais como nos agroecossistemas, sejam eles cultivos consorciados ou monocultivos. Porém, são escassas as informações sobre o comportamento das populações desses insetos nos agroecossistemas diversificados, como aqueles de base agroecológica. O presente trabalho teve o objetivo de determinar a riqueza de espécies de crisopídeos e avaliar a influência de diferentes cultivos agrícolas, assim como de fatores climáticos na abundância desses insetos em sistema de produção orgânica diversificada. O estudo foi conduzido de setembro de 2008 a agosto de 2009, por meio de amostragens semanais de adultos de Chrysopidae em áreas do Sistema Integrado de Produção Agroecológica, em Seropédica (RJ), cada qual com um tipo de sistema de cultivo (rotação milho-mucuna/olerícolas, cafeeiros sombreados e rotação cana-de-açúcar/pastagem de braquiária). Um total de 424 espécimes de crisopídeos foi coletado, sendo distribuídos em três espécies: Chrysoperla externa (98,1%), Ceraeochrysa cubana (1,7%) e Ceraeochrysa paraguaria (0,2%). Não houve diferença no número de adultos coletados em função dos diferentes cultivos, embora a análise de correlação evidencie que as rotações com poáceas favoreçam o aumento da sua abundância. A abundância dos crisopídeos foi influenciada pelo clima apenas no sistema de cafeeiros sombreados, sendo correlacionada negativamente com a temperatura média do ar e a com a precipitação pluvial acumulada.(AU)

The green lacewings (Chrysopidae) have been reported in natural ecosystems as well in agroecosystems, intercropping or monocropping. However, the knowledge on their behavior on different agroecosystems is scarce. The present work aimed to determine the diversity of green lacewing species and to evaluate the influence of different agricultural crops, as well as climate factors, on the abundance of these insects in an agroecologically-based organic production system. The study was conducted from September 2008 to August 2009, by performing weekly sampling of Chrysopidae adults in areas of the Integrated Production Agroecological System (SIPA) in Seropédica (RJ), each with one type of cropping system (corn-mucuna rotation/vegetable crops; shaded coffees and sugar cane/brachiaria pasture rotation). A total of 424 adult specimens were collected, belonging to three species: Chrysoperla externa (98.1%), Ceraeochrysa cubana (1.7%) and Ceraeochrysa paraguaria (0.2%). There were no differences on the number of green lacewing adults collected in the crops, although the correlation analysis showed that the crop rotations with grasses favor their abundance. The abundance of green lacewings was also influenced by the climate conditions only in the system of shaded coffees, being negatively correlated with mean air temperature and accumulated rainfall.(AU)

COMPOSIÇÃO BROMATOLÓGICA, PERFIL FERMENTATIVO E DEGRADABILIDADE IN VITRO DE SILAGEM DE CANA ENERGIA (Saccharum spontaneum)

A cana de açúcar na alimentação animal vem sendo utilizada há muitos anos por pecuarista para suprir a demanda de alimento no período seco do ano. A cana energia surge como uma alternativa promissora, pois apresenta alto rendimento de massa verde ha-1 sendo menos exigente que a convencional. Objetivou-se avaliar a composição bromatológica, o perfil fermentativo e a degradabilidade in vitro de duas cultivares de cana energia submetidas a diferentes aditivos. A pesquisa foi realizada no Campus II da UFG, município de GoiâniaGO, entre outubro de 2016 a novembro de 2018. Utilizou-se os seguintes tratamentos: duas cultivares de cana energia, VG 3 e VG 1126, submetidas a 1% de ureia, 1% de NaOH, 1% de CaO sobre a MV, Lactobacillus plantarum e sem aditivo. Utilizou-se o DIC, em esquema fatorial 2x5 com oito repetições. As canas foram picadas em partículas de 1-2 cm, utilizando a planta inteira. Foi retirada uma porção de 2 kg para análise de MV e posteriormente realizou a inclusão dos aditivos em cada 100 kg de MV e ensilados em baldes plástico medindo 29 cm de diâmetro por 31 cm de altura. No fundo dos baldes colocou areia seca e sombrite para quantificação das perdas por efluentes. A massa verde foi compactada com o auxílio de um bastão de ferro a cada 10 cm até atingir densidade de 500-650 kg/m³. A abertura dos mini silos ocorreu aos 72 dias após a ensilagem. Utilizou-se a parte central do balde para realizar as análises. Foi retirada uma amostra que foi subdividida em três partes: a primeira subamostra foi levada a estufa de ventilação forçada a 55ºC por 72h, visando a determinação da matéria pré seca e posteriormente as amostras foram moídas para realização das análises. Foram determinados os teores de MS, MO, MM, PB, FDN, FDA, EE. As outras subamostras, foram utilizadas para extração do suco com a finalidade de analisar pH, poder Tampão, AGV´s, perdas por gases, efluentes e IRMS, e DIVMS. Os dados foram submetidos à análise de variância e teste de média utilizando Scott Knott a 5% de probabilidade com o auxílio do Software R. Os aditivos influenciaram na composição bromatológica das silagens, sendo que o CaO em ambas cultivares apresentou melhores resultados quanto ao teor de MS, MM, FDN e FDA. A ureia proporcionou o melhor teor de PB nas duas cultivares. Os aditivos promoveram diferenças significativas no perfil fermentativo, as menores perdas por gases ocorreram com a utilização de NaOH e CaO, porém ocasionaram as maiores perdas por efluentes. O CaO foi mais eficiente quanto ao IRMS, bem como no teor de CHO´s em ambas cultivares, mas estes apresentaram os mais elevados valores de pH e poder tampão. Com ureia se obteve o maior teor de N-NH3. Com ureia e CaO obteve os melhores resultados quanto aos teores de AL mas também de AB. Os tratamentos refletiram positivamente na DIVMS, sendo que para a cultivar VG 3, o NaOH e CaO proporcionaram maior teor de FS, enquanto na cultivar VG 1126 foi o tratamento testemunho. A DIVMS foi mais efetiva tanto em 48 ou 72h de fermentação utilizando NaOH e CaO, em ambas as cultivares. A degradação do FDN foi influenciada, sendo que na cultivar VG 3 no tempo de 48h, utilizando LP foi o menos eficiente, enquanto os demais tratamentos não diferiram em 72h. Na cultivar VG 1126, em 48h de degradação utilizando NaOH e CaO apresentou melhores resultados e em 72h o CaO foi o menos eficiente. A utilização de NaOH e CaO nas silagens de cana energia avaliadas se mostraram mais eficientes, tanto no processo de fermentação, melhorias na qualidade da silagem quanto na degradabilidade in vitro.

Sugar cane in animal feed has been used for many years by a cattle rancher to supply the demand for food during the dry season of the year. The "energy cane" emerges as a promising alternative, because it presents high yield of ha-1 green mass being less demanding than conventional. The objective of this study was to evaluate the inorganic composition, fermentation profile and in vitro degradability of two sugar cane cultivars submitted to different additives. The research was carried out at Campus II of UFG, Goiânia-GO, between October 2016 and November 2018. The following treatments were used: two cultivars of sugarcane, VG 3 and VG 1126, submitted to 1% urea , 1% NaOH, 1% CaO on MV, Lactobacillus plantarum and without additive. DIC was used in a 2x5 factorial scheme with eight replicates. The reeds were minced into 1-2 cm particles using the whole plant. A 2 kg portion was removed for MV analysis and afterwards the additives were added to each 100 kg of MV and ensiled in plastic buckets measuring 29 cm in diameter by 31 cm in height. In the bottom of the buckets placed dry sand and sombrite to quantify the losses by effluents. The green mass was compacted with the help of an iron rod every 10 cm until reaching a density of 500-650 kg / m³. The opening of mini silos occurred at 72 days after silage. The central part of the bucket was used to carry out the analyzes. A sample was taken and divided into three parts: the first sub-sample was taken to a forced ventilation oven at 55ºC for 72 hours, to determine the pre-dried matter and the samples were ground to carry out the analyzes. The contents of MS, MO, MM, PB, NDF, FDA, EE were determined. The other subsamples were used to extract the juice for the purpose of analyzing pH, Buffer power, AGVs, gas losses, effluents and IRMS, and IVDMS. The data were submitted to analysis of variance and mean test using Scott Knott at 5% probability with the aid of Software R. The additives influenced the bromatological composition of the silages, and the CaO in both cultivars presented better results as the content of MS, MM, NDF and FDA. Urea yielded the best CP content in both cultivars. The additives promoted significant differences in the fermentation profile, the lower gas losses occurred with the use of NaOH and CaO, but caused the greatest losses by effluents. CaO was more efficient in the IRMS, as well as in the CHO content in both cultivars, but these presented the highest values of pH and buffer power. With urea the highest N-NH 3 content was obtained. With urea and CaO, the best results were obtained for AL but also AB. The treatments showed a positive effect on the IVDMD, and for the VG 3 cultivar, NaOH and CaO provided higher FS content, while in the VG 1126 cultivar it was the control treatment. The IVDMD was more effective both in 48 or 72 hours of fermentation using NaOH and CaO in both cultivars. The degradation of the NDF was influenced, and in the cultivar VG 3 in the time of 48h, using LP was the least efficient, while the other treatments did not differ in 72h. In cultivar VG 1126, in 48h of degradation using NaOH and CaO presented better results and in 72h CaO was the least efficient. The use of NaOH and CaO in the energy cane silages evaluated were more efficient, both in the fermentation process, improvements in silage quality and degradability in vitro.

Otimização do cultivo da microalga Haematococcus pluvialis em sistema mixotrófico e potencial uso na alimentação do camarão Macrobrachium amazonicum

A microalga Haematococcus pluvialis apresenta elevado interesse biotecnológico e comercial devido sua capacidade de síntese de compostos de alto valor e composição nutricional rica em proteínas, aminoácidos e outros compostos. Dentre os entraves em sua produção comercial, a obtenção de elevada biomassa tem sido o foco de diversas pesquisa que buscam otimizar o cultivo desta espécie. O cultivo mixotrófico é uma ferramenta que pode auxiliar na obtenção de elevadas produtividades, no entanto a fonte de carbono utilizada nestes cultivos deve ser adequada e disponibilizada de forma correta para completa absorção. O melaço de cana de açúcar é uma fonte de carbono rica em sacarose e nutrientes podendo ser empregado no cultivo de H. pluvialis, no entanto, requer pré-tratamento antes de seu uso. A hidrólise auxilia na redução das moléculas de sacarose em glicose e frutose, aumentando a disponibilidade de carbono e facilitando sua assimilação. Comparado ao melaço in natura, a hidrolise do melaço demonstrou melhores resultados aumentando a produtividade e alta composição bioquímica. Outra ferramenta importante utilizada na otimização dos cultivos algais em condições mixotróficas é o uso de ciclos de luz, uma vez que a luminosidade está relacionada diretamente ao metabolismo algal auxiliando na assimilação dos nutrientes e do carbono. O período de iluminação fornecida varia de espécie para espécie, podendo ou não ser necessário. Neste estudo e para estas condições de cultivo, foram observados o aumento de biomassa e aumento na composição bioquimica quando a microalga H. pluvialis foi exposta a ciclos de luz e os melhores resultados obtidos foram em ciclo de 20:4 horas (claro/escuro). Quando cultivada em green stage a mcroalga H. pluvialis acumula elevados teores de proteínas e aminoácidos, sendo estes compostos fundamentais na alimentação de diversos organismos aquáticos. O camarão Macrobrachium amazonicum é uma espécie nativa brasileira que apresenta elevado valor social e potencial de produção, no entanto, estudos sobre suas exigências nutricionais ainda são escassos. Em sistemas de produções aquícolas, são fornecidas rações com elevado teor proteico e grande percentagem desta proteína é de origem animal principalmente obtida através da inclusão de farinha de peixe, porém o uso de farinha de peixe eleva o custo de produção destas dietas além de ser uma fonte limitada. Uma alternativa para solução desta problemática seria o uso de proteína de origem vegetal. O uso da biomassa da microalga H. pluvialis na substituição da farinha de peixe em dietas para pós-larvas do camarão M. amazonicum, demonstrou ser uma alternativa eficaz e de palatabilidade uma vez que tais dietas formuladas aumentaram o desempenho zootécnico desta espécie, devido ao alto teor proteico e aminoácidos essenciais para o desenvolvimento do camarão, podendo a farinha de peixe ser substituída totalmente da dieta pela biomassa de H. pluvialis.

The Haematococcus pluvialis microalgae displays high biotechnological and commercial interest due to its capacity to synthesize high nutritional value in protein, amino acids and other compounds. Besides the difficulties in commercial production, the obtaining of high biomass amounts has been the objective of several researches which seek to optimize the production of this species. The mixotrophic culture is a tool which may improve the obtention of higher productivity. However, the carbon source for the cultures have to be adequate and has to be in an available form in order to be completely absorbed. The cane molasse is a carbon source rich in saccharose and nutrients and might be employed in H. pluvialis culture. Nevertheless, it requires a pre-treatment for its use. The hydrolysis promotes the reduction of saccharose molecules into glycose and fructose, improving the carbon availability and assimilation. In comparison to in natura molasses, the hydrolysis improved the results by increasing productivity. Light cycle is another important tool for algae culture in mixotrophic conditions, since light is directly related to the algae metabolism, which improves the carbon and nutrients assimilation. The light interval varies according to species and may or may not be necessary to be employed. In this study, an increase in biomass and biochemical composition was observed when H. pluvialis was exposed to light cycles. The best results were obtained with a 20:4 hours cycle (light/dark). When in green stage culture, the microalgae accumulate higher protein and amino acid contents, which are fundamental for the diet of a wide range of aquatic organisms. The Macrobrachium amazonicum shrimp is a Brazilian native species, which presents high social value and production potential. However, research about its nutritional demands are scarce. The feed employed in aquaculture presents high protein values, usually from animal source. Fishmeal is the most employed source; however, it increases the production cost and is a limited source. The employment of a vegetal-origin protein source may be an alternative to this matter. The use of H. pluvialis biomass as replacement for fishmeal in M. amazonicum post-larvae diet resulted in an effective alternative, both in nutrition and palatability. It improved the zootechnical performance, due to high protein and essential amino acids contents for shrimp growth. Thus, the fishmeal may be completely replaced with H. pluvialis biomass.

Sugarcane straw and the populations of pests and nematodes

The green cane harvesting represented a significant change in sugarcane ecosystem due to the presence of straw left on the soil and to the absence of fire. These two factors may affect the populations of pests and their natural enemies. Among the pests benefit from the green cane harvesting stand out the spittlebug, Mahanarva fimbriolata, the curculionid Sphenophorus levis and sugarcane borer, Diatraea saccharalis. In areas of green cane harvesting, the population of these species grew faster than in areas of burnt cane. On the other hand, there are virtually no records of attacks by lesser cornstalk borers in areas of green cane harvesting. Populations of plant parasitic nematodes and the beetles Migdolus fryanus, very important pests of sugarcane, were apparently not affected by the green cane harvesting. Despite the absence of more consistent information, it appears that populations of ants and the giant borer Telchin licus can increase in green cane areas, due primarily to the difficulty of pest control. The partial or total removal of straw from the field represents an additional change to the ecosystem that could alter the status of pests and nematodes. It is likely that spittlebug, the curculionid S. levis and sugarcane borer populations decrease if a portion of the straw is removed from the field. However, the pest populations in areas where the straw is collected will not return to their original conditions at the time of burnt cane harvesting because the absence of fire will be maintained.

Sugarcane straw and the populations of pests and nematodes

The green cane harvesting represented a significant change in sugarcane ecosystem due to the presence of straw left on the soil and to the absence of fire. These two factors may affect the populations of pests and their natural enemies. Among the pests benefit from the green cane harvesting stand out the spittlebug, Mahanarva fimbriolata, the curculionid Sphenophorus levis and sugarcane borer, Diatraea saccharalis. In areas of green cane harvesting, the population of these species grew faster than in areas of burnt cane. On the other hand, there are virtually no records of attacks by lesser cornstalk borers in areas of green cane harvesting. Populations of plant parasitic nematodes and the beetles Migdolus fryanus, very important pests of sugarcane, were apparently not affected by the green cane harvesting. Despite the absence of more consistent information, it appears that populations of ants and the giant borer Telchin licus can increase in green cane areas, due primarily to the difficulty of pest control. The partial or total removal of straw from the field represents an additional change to the ecosystem that could alter the status of pests and nematodes. It is likely that spittlebug, the curculionid S. levis and sugarcane borer populations decrease if a portion of the straw is removed from the field. However, the pest populations in areas where the straw is collected will not return to their original conditions at the time of burnt cane harvesting because the absence of fire will be maintained.

Contribution of nitrogen from sugarcane harvest residues and urea for crop nutrition

Sugarcane (Saccharum spp.) harvested without burning provides a substantial amount of remains (trash) on soil profiles which can be decomposed and release nutrients contributing to reduce fertilizer needs. The contribution of nitrogen (N) from sugarcane plant residues and fertilizer in sugarcane nutrition was assessed. Plant cane treatments were micro plots of 15N-labeled urea, sugarcane trash and root system; the last two to simulate the previous crop residues incorporated into the soil after crop renewal. For ratoons, N-ammonium nitrate (N-AN) micro plots, 150 kg ha-1 of N-AN and control (0 kg ha-1) were set up to evaluate the contribution of trash in N supply and quantify the effects of N-fertilizer on N-trash mineralization. The N balances derived from each 15N source were calculated after four crops and resulted in: 15N-urea applied at planting, 31 % was recovered by plant cane, 12 % by the following ratoons, 20 % remained in the soil and 37 % was not found in the soil-system (NOC). For crop residues 15N-trash + roots 26 % was recovered by sugarcane, 51 % remained in soil, and 23 % was NOC. N-fertilizer applied to ratoons nearly doubled the amount of N from green harvest residues recovered by sugarcane; 17 vs. 31 %. Water balances and crop evapotranspiration were correlated with 15N-sources recoveries and cumulative N recovery presented a positive correlation with evapotranspiration (2005 to 2009). The 15N balances indicated that crop residues are supplementary sources of N for sugarcane and may contribute to reduce N fertilizer needs since trash is annually added to the soil.

Contribution of nitrogen from sugarcane harvest residues and urea for crop nutrition

Sugarcane (Saccharum spp.) harvested without burning provides a substantial amount of remains (trash) on soil profiles which can be decomposed and release nutrients contributing to reduce fertilizer needs. The contribution of nitrogen (N) from sugarcane plant residues and fertilizer in sugarcane nutrition was assessed. Plant cane treatments were micro plots of 15N-labeled urea, sugarcane trash and root system; the last two to simulate the previous crop residues incorporated into the soil after crop renewal. For ratoons, N-ammonium nitrate (N-AN) micro plots, 150 kg ha-1 of N-AN and control (0 kg ha-1) were set up to evaluate the contribution of trash in N supply and quantify the effects of N-fertilizer on N-trash mineralization. The N balances derived from each 15N source were calculated after four crops and resulted in: 15N-urea applied at planting, 31 % was recovered by plant cane, 12 % by the following ratoons, 20 % remained in the soil and 37 % was not found in the soil-system (NOC). For crop residues 15N-trash + roots 26 % was recovered by sugarcane, 51 % remained in soil, and 23 % was NOC. N-fertilizer applied to ratoons nearly doubled the amount of N from green harvest residues recovered by sugarcane; 17 vs. 31 %. Water balances and crop evapotranspiration were correlated with 15N-sources recoveries and cumulative N recovery presented a positive correlation with evapotranspiration (2005 to 2009). The 15N balances indicated that crop residues are supplementary sources of N for sugarcane and may contribute to reduce N fertilizer needs since trash is annually added to the soil.

Input of sugarcane post-harvest residues into the soil

Sugarcane (Saccharum spp.) crops provide carbon (C) for soil through straw and root system decomposition. Recently, however, sugarcane producers are considering straw to be removed for electricity or second generation ethanol production. To elucidate the role of straw and root system on the carbon supply into the soil, the biomass inputs from sugarcane straw (tops and dry leaves) and from root system (rhizomes and roots) were quantified, and its contribution to provide C to the soil was estimated. Three trials were carried out in the State of Sao Paulo, Brazil, from 2006 to 2009. All sites were cultivated with the variety SP81 3250 under the green sugarcane harvest. Yearly, post-harvest sugarcane residues (tops, dry leaves, roots and rhizomes) were sampled; weighted and dried for the dry mass (DM) production to be estimated. On average, DM root system production was 4.6 Mg ha-1 year-1 (1.5 Mg C ha-1 year-1) and 11.5 Mg ha-1 year-1 (5.1 Mg C ha-1 year-1) of straw. In plant cane, 35 % of the total sugarcane DM was allocated into the root system, declining to 20 % in the third ratoon. The estimate of potential allocation of sugarcane residues to soil organic C was 1.1 t ha-1 year-1; out of which 33 % was from root system and 67 % from straw. The participation of root system should be higher if soil layer is evaluated, a deeper soil layer, if root exudates are accounted and if the period of higher production of roots is considered.

Input of sugarcane post-harvest residues into the soil

Sugarcane (Saccharum spp.) crops provide carbon (C) for soil through straw and root system decomposition. Recently, however, sugarcane producers are considering straw to be removed for electricity or second generation ethanol production. To elucidate the role of straw and root system on the carbon supply into the soil, the biomass inputs from sugarcane straw (tops and dry leaves) and from root system (rhizomes and roots) were quantified, and its contribution to provide C to the soil was estimated. Three trials were carried out in the State of Sao Paulo, Brazil, from 2006 to 2009. All sites were cultivated with the variety SP81 3250 under the green sugarcane harvest. Yearly, post-harvest sugarcane residues (tops, dry leaves, roots and rhizomes) were sampled; weighted and dried for the dry mass (DM) production to be estimated. On average, DM root system production was 4.6 Mg ha-1 year-1 (1.5 Mg C ha-1 year-1) and 11.5 Mg ha-1 year-1 (5.1 Mg C ha-1 year-1) of straw. In plant cane, 35 % of the total sugarcane DM was allocated into the root system, declining to 20 % in the third ratoon. The estimate of potential allocation of sugarcane residues to soil organic C was 1.1 t ha-1 year-1; out of which 33 % was from root system and 67 % from straw. The participation of root system should be higher if soil layer is evaluated, a deeper soil layer, if root exudates are accounted and if the period of higher production of roots is considered.