Araya, Yoseph Negusse; De Neve, Stefaan and Hofman, Georges
Nitrogen mineralization from cabbage crop residue and its uptake efficiency by rye grass.
Acta Agriculturae Scandinavica, Section B - Plant Soil Science, 60(1)
Crop residues are an important component of N cycling in the agro-ecosystem. In this study, a loam soil was amended with cabbage residues and the N mineralization from soil organic matter and residues, as well as N uptake by Italian rye grass, were investigated. Four mineral fertilizer-residue combination treatments and two application times were tested in micro-plots. For uncropped micro-plots, application of residue resulted in higher soil mineral N content (43 mg N kg-1, 63 days post application) versus 30.5 mg N kg-1 for an unamended soil. Both bulked dry matter production and N uptake by the rye grass decreased in the order full mineral fertilizer > half mineral fertilizer + half residue > full residue applied 3 weeks before sowing > full residue applied at sowing, but the differences were more pronounced in the N uptake. Shoot N recovery from the applied residue (27.5-31.4%) was much smaller than that from the full fertilizer (70.2%), but was still considerable. Apparent net N mineralization from soil organic matter was significantly depressed in the treatments where mineral fertilizer was added. Cropping also reduced apparent net N mineralization, but this effect was reduced when residues were applied 3 weeks before sowing. Results showed that crop residues play an important role in crop production, in terms of obtaining comparable dry matter production to that of full mineral fertilizer application. Moreover, nitrogen supplied as residue is less liable for loss due to leaching during the growing season. The efficiency of crop uptake to residue-derived nitrogen could be increased by earlier application time.
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