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.

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.

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