Abstract

CIVEIRA, Gabriela  and  RODRIGUEZ, Mónica Beatríz. Residual and leached nitrogen in soil plant zeolite systems. Cienc. suelo [online]. 2011, vol.29, n.2, pp.285-294. ISSN 1850-2067.

The N use efficiency in agroecosystems is considered low mainly because of N losses by processes such as nitrate leaching. These losses could be mitigated by incorporating natural zeolites to the N fertilizer formulations. The main objective of this study was to evaluate the effect of natural zeolites additions to formulations with N fertilizers on the contents of residual N and leached N in a soil under maize crop. The hypothesis of this study was that zeolite addition to N fertilizer could reduce the residual and leached N levels but could also affect the plant N availability. A greenhouse experiment was conducted under controlled conditions from February to April 2009. Corn was planted (Zea mays L.) in pots which were maintained at field capacity. Zeolite and nitrogen fertilizer (Urea [(NH₂)₂CO], solid granules, 46-0-0) were added together as a dry physical mixture, at the beginning of the experiment. The treatments were T: control, Z1: 120 kg ha^-1 zeolite, Z2: 200 kg ha^-1 zeolite, N: 200 kg N ha^-1, NZ1: 120 kg ha^-1 zeolite + 200 kg N ha^-1, NZ2: 200 kg ha^-1 zeolite + 200 kg N ha^-1. At the maize silking (R1 stage,) soil samples were taken to determine the residual N (NO₃-N and N-NH₄) and plant samples were obtained to measure dry matter (DM) and N absorbed by the plant. The N use efficiency (NUE) was also evaluated in each treatment. Finally, a forced leaching was applied in all treatments. The results showed that the application of N fertilizer with lower rates of zeolites (NZ1) significantly increased the N absorbed by maize, dry matter and NUE compared to the N treatment. These results can be explained by the favourable effect of the zeolites on nitrogen mineralization and soil water retention. The higher absorbed N levels in NZ1 corresponded with a significant residual N decrease compared to the N treatment while the leached N remained the same. Nevertheless, when the applied zeolites rate was higher (NZ2), the absorbed N by maize was similar to the N treatment while the leached N increased significantly compared to the N and NZ1 treatments, thus showing a late release of N to the soil solution. These results suggest that the synchronization between the pattern of N release from the soil-fertilizer-zeolite system and the N absorption by maize depended on the zeolite rate. While in NZ1 such synchronization improved the performance of the nitrogen fertilizer, in the NZ2 treatment the retained N by the zeolites was not available to maize, being detected as leached N at the end of the experiment.

Keywords : Natural zeolites; Nitrate leaching; Residual nitrate; Nitrogen use efficiency.

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