Sistemas de implantação de soja em áreas de arroz irrigado e efeitos em atributos físicos do solo e em características agronômicas e fisiológicas da planta

Abstract

The lowland areas are predominantly cultivated with irrigated rice. However, the monoculture of rice can to complicate the use of these areas for rice crop. An alternative to this is the use of crop rotation. The crop that may be used in rotation with rice is the soybean. But, some lowland areas present poor drainage, low hydraulic conductivity and compacted layer present in the soil sub-surface, soybean yield is usually limited especially in drought years. Thus, the objective this study was to evaluate the effect of tillage systems and soybean sowing and border irrigation on soil physical and hydraulic properties, oxidative stress in the leaf tissue of plants, root growth and development, nutrients content in leaf tissue of plants and soybeans yield. The experiments were performed in the Experimental Area of the Federal University of Santa Maria, during 2013/14 and 2014/15 growing season in Santa Maria-RS, Brazil and during 2013/14 growing season in Formigueiro, RS. Levels of factor A were: tillage and seeding systems: chisel plough with sowing using a offset double disc; no-till with sowing using a furrow opener upon a raised bed; sowing using a knife runner opener; sowing using a (fluted coulter disc) wavy disc with 12 waves and sowing using a offset double disc. The D factor levels were: irrigated and non-irrigated. The results showed that systems with sowing using knife, sowing on raised bed and chisel plough reduce soil bulk density in the layer from 0.00 to 0.20 m in the sowing row. These systems improve in the soil physical and hydraulic properties such as soil bulk density, total porosity, macroporosity and infiltration capacity and water storage in the soil. Tillage systems with sowing using offset double disc and (fluted coulter disc) wavy disc has less effect of soil bulk density reduction in the soybean sowing row and improvement of soil physical and hydraulic properties. The presence of a compacted layer in the soil sub-surface (layer from 0.07 to 0.15 m) causes oxidative stress in plants in drought seasons. The system using chisel plough and sowing using knife minimize those stresses and provide greater soybean roots growth and development, nodulation and higher grain yield. The border irrigation on soil moisture conditions below 60% of field capacity results in reduced oxidative stress, increased of roots growth and development, providing increase in nodulation and soybeans yield in areas with presence compacted layer in the soil sub-surface.