Resumo -O objetivo deste trabalho foi avaliar o efeito de diferentes quantidades de palhada sobre o sistema radicular e a produtividade da cana-de-açúcar (Saccharum officinarum), de primeira e segunda soqueiras, em Latossolo Vermelho eutroférrico. Seis tratamentos foram avaliados: 0, 5 (25%), 10 (50%), 15 (75%) e 20 Mg ha -1 (100%) de palhada e cana-queimada, na primeira e segunda soqueiras. Utilizou-se a cana-de-açúcar 'SP80-1816'. Avaliou-se a massa de raízes a 0,45 e 0,75 m de distância da linha de plantio, até 0,60 m de profundidade. Na primeira soqueira, os tratamentos com 50, 75 e 100% de palhada proporcionaram maior massa radicular até 0,20 m de profundidade, em comparação aos tratamentos cana-queimada, 0 e 5 Mg ha -1 (25%) de palhada. Os tratamentos com 50 e 75% de palhada proporcionaram produtividades 43% maiores do que a da cana-queimada (110 Mg ha -1 ). O tratamento com 10 Mg ha -1 (50%) foi suficiente para proporcionar aumento da massa radicular e da produtividade da cana-de-açúcar. O sistema radicular e a produtividade da cana-de-açúcar são favorecidos pela mudança do sistema de colheita de cana-queimada para o de cana sob palhada.Termos para indexação: Saccharum officinarum, biomassa, cana crua, colheita mecanizada, enraizamento, manejo da palhada, produção agrícola. Root system and productivity of sugarcane ratoon associated to different quantities of strawAbstract -The objective of this work was to evaluate the effect of different amounts of straw on the root system and productivity of sugarcane (Saccharum officinarum), of first and second ratoons, in an Oxisol. Six treatments were evaluated: 0, 5 (25%), 10 (50%), 15 (75%), and 20 Mg ha -1 (100%) straw and burned sugarcane of the first and second ratoons. 'SP80-1816' sugarcane was used. Root mass at 0.45 and 0.75 m away from the row, and up to 0.60 m deep was evaluated. In the first ratoon, treatments with 50, 75 and 100% straw provided greater root mass up to 0.20-m depth, in comparison to treatments of burned sugarcane, and 0 and 5 Mg ha -1 (25%) straw. The treatments with 50 and 75% straw had 43% higher yields than burned sugarcane (110 Mg ha -1 ). The treatment with 10 Mg ha -1 straw (50%) was sufficient to provide increased root mass and productivity of sugarcane. The root system and the productivity of sugarcane are favored by the change of burned-sugarcane harvesting system to sugarcane under straw.

Sugarcane straw mulch left in the field after its mechanical harvest has become very valuable raw material for second generation ethanol and bioelectricity production. However, little information is available on how much straw mulch is needed to be left in the field so that agricultural productivity is not affected and high sustainability is provided for the bioenergy production system. The objective of this work was to evaluate the productivity and industrial quality of sugarcane after five years of cultivation when different amount of straw mulch is removed from the field. The experiment was installed in clay texture Eutroferric Red Latosol (Oxisol). Six treatments were evaluated: 0%, 25% (5 t ha −1), 50% (10 t ha −1), 75% (15 t ha −1), 100% (20 t ha −1) of straw mulch and burnt cane harvesting (where 100% of the straw mulch was burned). Evaluated parameters included sugarcane productivity (tons/hectare) and its industrial quality (Pol, soluble solids (°Brix), apparent purity and total sugars (TS)). Productivity was calculated at the end of the cycle whereas industrial quality parameters were evaluated during three phases i.e. 180, 240 and 350 days after cutting (DAC). Straw mulch of 50 and 75% were statistically at par with each other but resulted in higher sugarcane production with 47% more productivity as compared to 0 and 25% of straw mulch as well as burned cane harvesting. Straw mulch didn't affect the industrial quality; however, higher sugar production was supported by higher agricultural productivity, under low moisture condition. It is possible to remove 50% of straw mulch from the field for the production of second generation ethanol or bioelectricity, without any damage to the crop.

Due to mechanical harvesting large amount of straw is left in the field which implicates modification throughout the agriculture environment. This straw is beneficial for both soil and plant. However, there is no information about the sufficient quantity which can be used to achieve such effects and also whether it can be used in other sectors like electricity and ethanol production. Therefore, a research was designed with the objective to evaluate the effect of different amounts of straw on the development and productivity of sugarcane during the first and second ratoons. Treatments used in the experiment included: burned cane, 0%, 25%, 50%, 75% and 100% (20 t ha −1) of sugarcane straw left on the soil surface. The tested variables included leaf area index (LAI), number, diameter, length and production of stems. Plants were evaluated at 60, 120, 180, 240 and 370 days after harvest (DAH) for the first ratoon and at 60, 120, 180, 240 and 270 DAH for the second ratoon. Replacing burned cane harvest system for soil management with straw promotes the development and productivity of sugarcane ratoons. Field managements with burned cane, total removal of the straw, or keeping 25% of straw result in low number of tillers, leaf area index, stem diameter and productivity of sugarcane ratoons, under water stress conditions. Whereas keeping 50% of straw mulch is enough to improve the growth and yield of sugarcane with drought occurrences, while the remaining 50% can be used for second generation of ethanol production or electricity without damaging the crop yield.

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Mechanical harvesting leaves in its wake a considerable amount of straw in the field, which can be effectively utilized to improve the soil condition and sugarcane yield. However, there is no specific information as to the quantity of straw mulch required to achieve such effects and as to whether it can be used in other sectors for bioelectricity and ethanol production. The aim of this research was to evaluate the effect of removing different amounts of straw from the field and its impact on the yield and industrial quality of sugarcane ratoons. The experiment was carried out on Rhodic soil where six treatments were evaluated including 0 %, 25 % (5 Mg ha-1), 50 % (10 Mg ha-1), 75 % (15 Mg ha-1), 100 % (20 Mg ha-1) straw on the soil surface and burned sugarcane (where 100 % of the straw was burned). The influence on yield and industrial quality was calculated using total soluble solids, Pol (Apparent sucrose content), apparent purity, total sugars, reducing sugars and fiber. Shifting the harvesting system from burned cane to growing under straw mulch improved crop yield as well as favoring sugar contents during water deficit conditions. The straw left on the soil did not affect industrial quality in any way during the trials; however, under drought conditions, treatments with 50 and 75 % of straw resulted in a 76 % higher yield compared to burned sugarcane, and 29 % more than the 0 %, 25 % to 100 % treatments of straw mulch thus favoring higher sugar production. The removal of 50 % of the straw caused no damage to the sugarcane crop.

Occurrence of weeds in sugarcane crop according to levels of straw over the soil was studied. Experiment was carried out during two annual cycles. Treatments were 0 % (no straw); 25, 50, 75 and 100% (i.e., 5, 10, 15 and 20 t/ha of straw, respectively); and straw burned over the soil. Floristic analysis of weed species was achieved. Percent area occupied by weeds was assessed visually and regression analysis between weeds and amount of straw mulch was performed. Floristic analysis characterized 19 weed species, from eight botanical families: Amaranthaceae, Asteraceae, Commelinaceae, Convolvulaceae, Euphorbiaceae, Poaceae, Portulacaceae and Solanaceae. Highest richness of species was observed for Asteraceae and Poaceae, with seven and four species, respectively. Higher frequency was found for Amaranthus hybridus, A. viridis and Physalis angulata (85% of samples) for first annual crop cycle; and A. hybridus, Bidens pilosa and Cenchrus echinatus predominated (83% of samples) in second cycle. A. hybridus was the most frequent species in both cycles. The highest density of weeds was observed in treatments with straw burned. Application of 75 and 100% straw showed highest suppression for low and high density of weeds, respectively. Increasing level of straw leads correspondent weed control. That information is vital to orientate decision which amount will deposit over the soil since in recent years the straw is also demanded for alternative sources of energy, as thermal or second generation bio-ethanol.

RESUMOO resedá-nacional (Physocalymma scaberrimum Pohl.) é uma espécie nativa do Brasil que apresenta grande potencial para uso no paisagismo e em reflorestamento, além da madeira ser empregada na marcenaria de luxo. O objetivo deste trabalho foi avaliar o efeito de diferentes substratos e concentrações de ácido indolbutírico (AIB) na estaquia de resedá-nacional. O delineamento experimental foi o inteiramente casualizado, com cinco repetições em arranjo fatorial 3 x 3, sendo os fatores: tipos de substratos (areia de granulação média; casca de arroz carbonizada e vermiculita de granulação média) e concentrações de AIB (0; 1.000 e 2.000 mg L -1 ), em parcelas compostas por dez estacas. Após 104 dias da instalação do experimento, foram avaliadas as seguintes variáveis: sobrevivência das estacas; retenção foliar; porcentagem de estacas com calos não enraizadas; estacas enraizadas; número de raízes por estaca; comprimento de raízes por estaca e massa seca das raízes por estaca. Não foram observadas diferenças quanto ao enraizamento em relação à aplicação de AIB, obtendo-se, em média, 23,5%. Entre os substratos, embora as estacas enraizadas em areia e casca de arroz carbonizada tenham apresentado maior retenção foliar, todos os substratos testados podem ser utilizados. Palavras-chave: estacas; enraizamento; regulador de crescimento; auxina. ABSTRACTThe Brazilian rose wood is a native species from Brazil that has great potential for use in landscaping and reforestation, in addition to its use in luxury furniture. The objective of this work was to evaluate the effect of different substrates and concentrations of indole butyric acid (IBA) in the cutting of Brazilian resedá.

Resumo -O objetivo deste trabalho foi avaliar o efeito de diferentes quantidades de palhada sobre os índices biométricos e fisiológicos e sobre a produtividade da cana-de-açúcar, no primeiro ciclo de cultivo (cana-planta) da variedade SP 801816. Cinco tratamentos -com 0, 25, 50, 75 e 100% de palhada -foram avaliados aos 60, 180, 270 e 350 dias após o plantio. Determinaram-se os seguintes índices biométricos: área foliar, número de folhas, massa de matéria fresca e número de perfilhos. Os índices fisiológicos foram: índice de área foliar (IAF), taxa de crescimento da cultura (TCC) e taxa de crescimento relativo (TCR). Observou-se efeito significativo da palhada em todas as variáveis. Os tratamentos com 100, 75 e 50% de palhada proporcionaram os maiores valores de IAF, TCC, TCR e número de perfilhos, e os tratamentos com 50 e 75%, as maiores produtividades. A manutenção da palhada em superfície não foi prejudicial ao desenvolvimento da cultura. A retirada total ou a manutenção de 25% da palhada resultaram nas menores produtividades. A retirada de 50% da palhada não causa prejuizos à cultura.Termos para indexação: Saccharum, análise de crescimento, cana crua, produção, resíduo agrícola. Productivity and biometric and physiological indices of sugarcane grown under different amounts of strawAbstract -The objective of this work was to evaluate the effect of different amounts of straw mulch on the biometric and physiological indices and on the yield of the sugarcane variety SP 801816, in the first crop cycle (plant cane). Five treatments -with 0, 25, 50, 75, and 100% straw mulch -were evaluated at 60, 180, 270, and 350 days after planting. The following biometric indices were determined: leaf area, number of leaves, fresh matter weight, and number of tillers. The physiological indices were: leaf area index (LAI), crop growth rate (CGR), and relative growth rate (RGR). A significant effect of straw mulch was observed on all variables. Treatments with 100, 75, and 50% straw provided the highest values for LAI, CGR, RGR, and number of tillers, and the treatments with 50 and 75% straw provided the highest yields. Keeping straw mulch at the soil surface had no effect detrimental to sugarcane development. Total removal or straw kept at 25% resulted in the lowest yields. Removal of 50% straw can be done without harming the crop.