The fate of nitrogen from incorporated cover crop and green manure residues

Liz Baggs, C. A. Watson, R. M. Rees

Research output: Contribution to journalArticlepeer-review

Abstract

Nitrogen retention and release following the incorporation of cover crops and green manures were examined in field trials in NE Scotland. These treatments reduced the amounts of nitrate-N by between 10-20 kg ha-1 thereby lowering the potential for leaching and gaseous N losses. However, uptake of N by overwintering crops was low, reflecting the short day-lengths and low soil temperatures associated with this part of Britain. Vegetation that had regenerated naturally was as effective as sown cover crops at taking up N over winter and in returning N to the soil for the following crop. Incorporation of residues generally resulted in lower mineralisation rates and reduced N2O emissions than the cultivation of bare ground, indicating a temporary immobilisation of soil N following incorporation. Emissions from incorporated cover crops ranged from 23-44 g N2O-N ha-1 over 19 days, compared with 61 g N2O-N ha-1 emitted from bare ground. Emissions from incorporated green manures ranged from 409-580 g N2O-N ha-1 over 53 days with 462 g N2O-N ha-1 emitted from bare ground. Significant positive correlations between N2O and soil NO3- after incorporation (r=0.8-0.9; P<0.001 and r=0.1-0.4; P<0.05 for cover crops and green manures, respectively) suggest that this N2O was mainly produced during nitrification. There was no significant effect of either cover cropping or green manuring on the N content or yield of the subsequent oats crop, suggesting that N was not sufficiently limiting in this soil for any benefits to become apparent immediately. However, benefits of increased sustainability as a result of increased organic matter concentrations may be seen in long-term organic rotations, and such systems warrant investigation.

Original languageEnglish
Pages (from-to)153-163
Number of pages11
JournalNutrient Cycling in Agroecosystems
Volume56
Issue number2
DOIs
Publication statusPublished - 1 Jan 2000

Keywords

  • Available N
  • Cover crop
  • Crop uptake
  • Green manure
  • Incorporation
  • NO

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