Effects of green manure storage and incorporation methods on nitrogen release and N2O emissions after soil application

Summary

More efficient use of green manure-derived nitrogen (N) may improve crop yields and reduce environmental impacts in stockless organic arable farming. In this 3-month incubation study, we tested a new strategy where green manure leys are harvested and preserved until the following spring either as compost mixed with straw (grass-clover:straw, 4:1, w:w) or as silage of harvested ley biomass. Grass-clover compost or silage was soil-incorporated by either simulated ploughing (green manure placed at 15 cm depth) or harrowing (green manure mixed into the upper 5-cm soil horizon) in order to assess treatment effects on net release of plant-available N, nitrous oxide (N2O) fluxes, and soil respiration. Grass-clover silage provided the highest net N release with similar results for the two incorporation methods. Up to one third of the total N content in silage became plant-available during the three months. In contrast, no net N release was observed for the composted grass-clover and straw mixture. In fact, soil incorporation of compost by harrowing caused temporal immobilization of soil mineral N. Silage incorporated by ploughing gave rise to increased N2O effluxes, corresponding to 0.3 % of applied total N. Possibly N2O production via denitrification was stimulated by oxygen-limited conditions near the decomposing silage. In contrast, compost incorporated by harrowing caused downwards N2O fluxes, presumably an effect of reduced mineral N availability in this treatment. Overall, our study revealed that ensiled grass-clover was the best fertilizer product, and that N2O emissions may be reduced by incorporating green manures using harrowing instead of ploughing.

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• Effects of green manure storage and incorporation methods on nitrogen release and N2O emissions after soil application. (deposited 13 Jan 2014 13:11) [Currently Displayed]
  • Effects of green manure storage and incorporation methods on nitrogen release and N2O emissions after soil application. (deposited 21 Feb 2014 10:45)
    • Effects of green manure storage and incorporation methods on nitrogen release and N2O emissions after soil application. (deposited 04 Aug 2014 12:39)
      • Effects of green manure storage and incorporation methods on nitrogen release and N2O emissions after soil application. (deposited 03 Nov 2014 14:20)