Assessing a sustainable sugarcane production system in Tucumán, Argentina: Part 1: Dynamics of sugarcane harvest residue (trash) decomposition Evaluación de un sistema sustentable de producción de ca a de azúcar en Tucumán, R. Argentina. Parte I: Dinámica de la descomposición del residuo de la cosecha en verde de la ca a de azúcar

The elimination of burning practices in sugarcane harvest has led to more sustainable productive systems, with lower impact on the environment and on communities. The present paper is part of a study in which two sugarcane management systems were compared: (a) one with sugarcane harvest residue kept on the ground (trash blanketing); and (b) one without trash blanketing (burnt residue). Cultivar LCP 85-384 was planted in macro-plots in a commercial field in Albarracín, Tucumán, Argentina. A split-plot experimental design with three replications was used. Each plot had five 30 m-long rows. Two crop cycles (2006/2007 and 2007/2008), i.e. second and third ratoon, were evaluated. From the end of harvest onwards, residue amount (dry matter/ha) and residue C/N relationship were determined periodically. At the beginning and at the end of each crop cycle, residue P and K contents were assessed. Residue left after harvest amounted to 12 and 16 tons of dry matter per hectare in the first and second evaluated crop cycles, respectively, but decreased significantly throughout these periods. Residue C/N relationship was over 100 in both crop cycles (117 and 101, respectively), but decreased significantly in their course. Reductions in both sugarcane residue and C/N relationship were correlated with days after harvest and accumulated thermal time (∑ mean daily air temperature). Trash initial C concentration was similar in both crop cycles and amounted to approximately 45%, whereas initial N concentration differed (0.4% and 0.6% in second and third ratoon, respectively). Residue decomposition contributed 3800 to 5700 kg of C, 7 to 50 kg of N and 45 to 40 kg of K per ha to the agro-ecosystem in both crop cycles studied. La eliminación de la quema durante la cosecha de la ca a de azúcar llevó a la implementación de sistemas productivos más sustentables, con menos impacto ambiental y más amigables con las poblaciones vecinas. El presente trabajo forma parte de un estudio donde se compararon dos sistemas de producción de ca a de azúcar: a) manteniendo la cobertura de residuos de cosecha (RAC) sobre el suelo y b) sin cobertura de residuos de cosecha (residuo quemado). Se establecieron macroparcelas en un lote comercial implantado con el cultivar LCP 85-384, en la localidad de Albarracín, Tucumán, República Argentina. El dise o experimental fue de parcelas divididas con tres repeticiones; cada parcela estuvo formada por cinco surcos de 30 m. Las evaluaciones se hicieron en dos ciclos agrícolas: 2006/2007 y 2007/2008 (segunda y tercera soca). A partir de la cosecha, se determin