RELACIÓN ENTRE EL CULTIVO ANTECESOR Y LA DISPONIBILIDAD NITRÓGENO PARA EL TRIGO EN LA ROTACIÓN.

The effect of preceding crop residue characteristics on N availability for wheat (Triticum aestivum L.) may mask the changes in soil capability to provide N due to management. Preceding crop effects should be taken into account to diagnose N fertility. The aims of this work were to evaluate i) wheat relative (to the maximum obtained in the corresponding experiment and year) yields (RR) and aboveground dry matter (MSR) and N accumulation (NR) in time after different preceding crops, and ii) the relationship between RR, MSR and NR variation and soil organic matter content changes. In two long term crop rotation experiments at Balcarce (on a complex of Typic Argiudoll and Petrocalcic Paleudoll) the variation of RR, MSR and NR along years under cropping with conventional tillage, was analyzed. The preceding crops were potato (Solanum tuberosum L.), soybean (Glycine max L. Merr.), wheat, sunflower (Helianthus annuus L.) and maize (Zea mays L.). All three variables showed a decrease along cropping years, but up to different levels according to which had been the preceding crop. Residue characteristics and/or the way they had been managed before wheat seeding made that RR, MSR and NR after soybean, potato and wheat were higher. On the other hand, wheat RR, MSR, NR after maize were the lowest. These effects were associated with the role of residues on N mineralization-immobilization cycle. In general, the variation in wheat RR, MSR and NR along cropping years was not associated with changes in soil organic matter due to soil management under cropping. The short term effect of preceding crop residues and of its management on N dynamics defined the amount and timing of the availability of N for wheat. This was independently of the effect of the rotation on the capability of the soil to mineralize N due to how the residues intervene on the cycle mineralization-immobilization. [ABSTRACT FROM AUTHOR]