Assessment of Mineralized Nitrogen During Maize Growth Succeeding Different Winter Cover Crops in the Mediterranean Environment

Understanding soil nitrogen (N) dynamics is essential to find alternative N sources and improve N use efficiency in agriculture.

The aim of this study was to assess N mineralization rates from residues of winter cover crops, during maize crop season, under Mediterranean conditions.

A field experiment was carried out from May to September in central Portugal, with four replications, two sowing dates of cover crops (15/10/2011 and 29/11/2011) and three cover crops residues (balansa clover, ryegrass and yellow lupine) that were incorporated in the soil. Plots were cropped with local maize and net N mineralization was measured during the crop cycle, using soil cylinders placed inside micro-perforated polyethylene bags.

Early sowing of the cover crops residues increased the NH₄⁺ and NO₃^- contents in the soil. Yellow lupine residue had the highest rate of daily N mineralization (0.71 mg N kg^-1 day^-1). For all treatments, the highest mineralization rate was found in the last incubation period, ranging between 0.78 mg N kg^-1 day^-1 and 1.84 mg N kg^-1 day^-1, both for balansa clover, from the second and the first sowing date, respectively.

The present study suggests that, under Mediterranean field conditions, cover crops residue of Italian ryegrass, balansa clover and yellow lupin can be used as a nitrogen source namely for sustainable maize crops.