Dynamics of nitrogen under different rotations, tillage systems and residue management in wheat

Iván Vidal1, Jorge Etchevers1 y Anthony Fischer2

The behavior of wheat (Triticum aestivum) in distinct rotations, tillage systems and residue management were quantified, and the mineralization and absorption of nitrogen (N) under different management conditions were measured employing microlysimeters placed in the soil. Three years after establishing treatments tending to make the wheat production system more manageable in a zone with summer rainfall, the incorporation of a legume in the rotation translated, in general, into better yields and better N supplies for the plant. This was explained by the occurence of greater mineralization of N in the soil, both during the crop’s growth period as well as at the moment of seeding as a consequence of the incorporation of residues in the rotation. In almost all cases, wheat cultivated as a monoculture had the lowest grain yield, however, the lowest soil N supply was observed in the corn-wheat rotation. Zero tillage resulted to be good management practice in those years where water was a limiting factor for crop growth, however, no advantage of this practice was observed in normal rainfall years. Conventional tillage always resulted in higher residual N measured at sowing as well as more N mineralized during the cropping period, which occurred to the detriment of N reserves in the soil. The practice of leaving or removing the prior crop residues did not produce any conclusive results, although it is hoped that the benefits will begin to be observed in future years. This practice, as well as zero tillage, however did produce a significant increase in the soil microbial biomass, which is considered as a positive biological indicator of the quality of the soil and the sustainability of the systems.

Keywords: mineralization, zero tillage, cropping system, Triticum aestivum.
1 Universidad de Concepción, Facultad de Agronomía, Depto. de Suelos, Casilla 537, Chillán, Chile. E-mail: ividal@udec.cl
2 Colegio de Postgraduados, Centro de Edafología, Montecillo, México.