Microstructure of pampean soils cultivated under no-till. The battle between biology and machines.

HÉCTOR MORRÁS; FILIPE BEHRENDS KRAEMER; BEATRIZ BONEL; CARINA ALVAREZ; PATRICIA LILIA FERNÁNDEZ; MARIO GUILLERMO CASTIGLIONI; EMILIANO BRESSAN; MIGUEL TABOADA; LUCAS MORETTI; EDUARDO FAVRET

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Congreso; XXV Congreso Aapresid. 7mo Congreso Mundial de Agricultura de Conservación.; 2017

AAPRESID

Microstructure of pampean soils cultivated under no-till. The battle between biology and machines. No-till cultivation (NT) modifies various physical, chemical and biological soil properties in comparison to both natural and ploughed soils. These modifications are related to changes in the organization of solid components and are traduced on soil morphology. This contribution synthesizes numerous works carried out using micromorphological and micromorphometric techniques to characterize the microstructure of the surface horizon of different Mollisols of the northern Pampa cultivated under NT. The studied cases covered soils with different cropping sequences, in different sectors within the plots and at different times during the agricultural cycle. Comparative studies were also carried out with ploughed soils and non-cultivated soils.Results obtained show that under NT a typical microstructure develops, characterized by a marked anisotropy resulting in the differentiation of thin microhorizons in the first centimeters of the A horizon. These microhorizons may have different degrees of development, different morphology of aggregates, as well as different type, proportion and orientation of pores. Based on these variants, four NT microstructural models have been distinguished, which are highly variable and dynamic in time and space.These studies clearly show that the microstructure of the surface horizon of soils under NT is the synthetic and dynamic result of two opposing forces: the mechanical pressures arising from machinery traffic on the one hand, and biological activity on the other. The compression produced by the traffic leads to the development of the laminar and densified models. On the contrary, the increase of the biological activity and particularly of the soil fauna leads to a destruction of the structures derived from mechanical stresses, giving rise to the biodisturbed and biobuilded models according to the intensity of those biological actions. Particularly relevant were studies comparing situations with greater intensification and rotation with cereals, versus situations with predominance of soybean in the agricultural cycles. In spite of the increase of machinery traffic in intensified plots, a greater activity of the fauna has shown to counteract effectively the compressive effect produced by traffic. These results suggest that it is possible to improve soil properties and to achieve the sustainability of the system by integrating NT with management practices promoting the increase of biological activity