Soil Organic Matter Management: The Roles of Residue Quality in C Sequestration and N Supply - Sustainable Management of Soil Organic Matter - page 140

Fig. 3.5.4. CO 2 emission from soil in the weeks after sowing spring barley in 1997.

hour after ploughing for spring barley. N 2 O emissions, monitored on the
no-tillage treatment using automatic chambers, ranked with the fertilizer
N levels. We also monitored N 2 O emissions using manual chambers
distributed throughout the experimental area. These showed marked
spatial variability in emissions, which was associated with differences in
hydrology resulting from both the treatments and the topography of the
experimental site.

Conclusions

The residual N value from long-term, low-input grass-clover swards to
subsequent arable crops was lower than the residual N value from
moderately fertilized grass swards. This was probably due to the lower N
content of the macroorganic matter (roots, etc.) in the grass-clover swards
before cultivation. In the first year after ploughing out of long-term grass
swards, less nitrate leached from winter cereals than from spring cereal
stubble. In subsequent years, there was no significant difference between
spring- and winter-sown crops.