Influência da intensidade do tráfego e de sistemas de manejo nas propriedades físicas do solo e nas culturas de soja e girassol

Abstract

Soil compaction can be caused by animal trampling in systems integration-crop-livestock and by the intensive use of machinery in agriculture. The farm tractor traffic can change the physical and hydraulic properties of the soil and compromise agricultural sustainability. The search for alternatives for biodiesel production and crop rotation has provided the growth of sunflower and soybeans crop areas, however, soil compaction can limit the production of these species. Thus, the aim of this research is to evaluate the effects of tractor traffic and tillage system on physical and hydraulic soil properties and on agronomic performance of sunflower and soybean crops. The study was conducted in an Oxisol on the experimental farm of UNIGRAN – Centro Universitário da Grande Dourados, in Dourados – MS. It was adopted an experimental design in randomized blocks in 4 x 4 factorial scheme, with four levels of tractor traffic (control, a traffic, three traffics and six traffics) with for different levels of handling (control, harrowing, subsoiling three months after compaction induction and subsoiling seven months after compaction induction) with three replications. The physical and hydraulic properties of the soil evaluated in the research are: density, macro and micro porosity, S index and rate of water infiltration into the soil. The agronomic characteristics of sunflower measured in the research were: diameter of the glomerulus and stem, plant height, leaf area index, chlorophyll content, , dry weight, root length, area and diameter, root anatomical features, achenes productivity and oil content. The agronomic characteristics of soybean measured in the research were: productivity, leaf area index, plant height, photosynthetic active photons flow density, transpiration rate, stomatal conductance, chlorophyll content, anatomical and morphological characteristics of the root system , soybean grains productivity and oil content. The results showed that tractor traffic lead to an increase in the density of the soil until the 0.10m later and reduced water availability in the soil. The S index showed that tractor traffic reduces soil physical quality and infiltration rate. The tractor traffic reduced productivity, oil content and leaf area of sunflower, it also reduced the surface area and root diameter in the superficial layers but increased root length in deeper layers. The subsoiling led to an increase in leaf area index of sunflower and handling led to an increase in root growth in all segments studied. Traffic reduced leaf area, chlorophyll content and also reduced the productivity, root length and area of soybean in the superficial layer. The tractor traffic causes changes in morphological characteristics of soybean root in the subsurface layers, it changes the anatomical aspect of soybean root making it flat. The subsoiling when performed earlier promotes an increase in root length and in the surface area in subsurface layers.