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Con el fin de evaluar el efecto de los residuos vegetales sobre la eficiencia de almacenamiento de agua, la dinámica de nitrógeno y azufre disponible durante el barbecho con y sin presencia de malezas, se realizaron 10 ensayos con distintos niveles de residuos (A: 10.000 kg MS ha-1, M: 5.000 kg MS ha-1, B: menor a 2.000 kg MS ha-1) en Haplustoles de las regiones planicie con tosca y planicie medanosa de La Pampa y Sur de Córdoba. En cada tratamiento de residuos se dividieron las parcelas en dos subtratamientos de manejo de malezas: tratamiento con malezas (malezas) y sin malezas (barbecho). Se realizaron determinaciones de: textura, densidad aparente, punto de marchitez permanente, materia orgánica total. Al inicio y al final del barbecho se midió el contenido de agua en el suelo, nitratos (N), azufre de sulfatos solubles y adsorbidos (S) en 0-0,2 m de profundidad. Al comienzo del barbecho todos los sitios presentaron altos contenidos de agua útil (entre 51 y 100%). A pesar de ello, nuestros resultados mostraron que al finalizar el barbecho el nivel de residuos tuvo un efecto positivo en los contenidos de agua con una diferencia entre A y B de 33%. Con presencia de las malezas, no se pudo comprobar una ventaja por parte de los residuos y la diferencia entre A y B fue de 10%. El factor que más influyó en los contenidos de agua fue la presencia de malezas. Los contenidos de N y de S disponible no fueron influenciados por los distintos niveles de residuos, constatándose un mayor efecto de malezas. En el tratamiento con malezas se vería comprometida la siembra del cultivo de girasol por menor disponibilidad de agua y además se afectaría el rendimiento en 200 kg ha-1 por la menor disponibilidad de N y en 600 kg ha-1 por menor disponibilidad de S disponible en el nivel A de residuos.In order to study the effect of crop residues on the efficiency of water storage, available nitrogen and sulphate dynamics during fallow with and without weed presence, ten experiments with different levels of residue (A: 10,000 kg MS ha-1, M: 5,000 kg MS ha-1, B: less than 2,000 kg MS ha-1) were set up in Haplustolls of the tosca and dune plains in La Pampa and south of Córdoba. Each residue treatment was divided into sub-plots with different weed management: without weed control (malezas) and with control (barbecho). Soil texture, bulk density, permanent wilting pint, and organic matter were determined in each site. At the beginning and end of fallow soil water contents, nitrate (N) and soluble and adsorbed sulphates (S) were measured in samples from 0 -0.2m depth. At all sites the water content at the beginning of fallow was high (between 51 and 100% available water). Despite this, our results showed a positive effect of residue level on water contents at the end of fallow, with a mean difference between A and B of 33%. In weed treatments no effect of residue was observed, and the difference between A and B was 10%. Water contents were more strongly affected by the presence of weeds than by residue level. Available N and S contents showed no effect of residue level, but were strongly affected by weed presence. In weed treatments sunflower seeding would be severely limited by lower available water contents, and the expectable yields would be diminished by 200 kg ha-1 or 600 kg ha-1 due to the lower availability of N and S respectively.

In order to study the effect of crop residues on the efficiency of water storage, available nitrogen and sulphate dynamics during fallow with and without weed presence, ten experiments with different levels of residue (A: 10,000 kg MS ha-1, M: 5,000 kg MS ha-1, B: less than 2,000 kg MS ha-1) were set up in Haplustolls of the tosca and dune plains in La Pampa and south of Córdoba. Each residue treatment was divided into sub-plots with different weed management: without weed control (malezas) and with control (barbecho). Soil texture, bulk density, permanent wilting pint, and organic matter were determined in each site. At the beginning and end of fallow soil water contents, nitrate (N) and soluble and adsorbed sulphates (S) were measured in samples from 0 -0.2m depth. At all sites the water content at the beginning of fallow was high (between 51 and 100% available water). Despite this, our results showed a positive effect of residue level on water contents at the end of fallow, with a mean difference between A and B of 33%. In weed treatments no effect of residue was observed, and the difference between A and B was 10%. Water contents were more strongly affected by the presence of weeds than by residue level. Available N and S contents showed no effect of residue level, but were strongly affected by weed presence. In weed treatments sunflower seeding would be severely limited by lower available water contents, and the expectable yields would be diminished by 200 kg ha-1 or 600 kg ha-1 due to the lower availability of N and S respectively. [ABSTRACT FROM AUTHOR]