Cropping and Soil Management Effects on the
Dynamics of Crop Residue Derived-N on the
Coarse Textured Soils in Southern Ontario
Researcher: R. Paul Voroney, Dept. Land Resource Science,
University of Guelph, Principal Researcher. Cooperating with Agriculture
- To study the fate of the nitrogen in plant residue (N) and measure
soil organic matter dynamics in a coarse-textured soil cropped to
tobacco-fall rye, continuous corn and to wheat-soybeans using conventional
and zero-till soil management techniques.
- This research will result in the generation of extremely important,
new information about the nature of the dynamics of the soil organic
matter and the maintenance of soil structure in these coarse-textured
soils. The knowledge obtained will compliment the N leaching studies
in progress at Delhi and will form the basis of developing a N soil
test on these soils.
Stability is shown to be greater in the zerotill system. Return times
of invertebrate communities were shorter in the zerotill system and
deflection away from ground state was less in zerotill. Three conceptual
models are provided to explain this result, using past history of disturbance
and the successional state of the two communities. Previous disturbance
"prepares" the zerotill community for the disturbance of plowing and
it is able to respond quickly. The pasture community is not similarly
prepared because it has not been disturbed recently and consequently
takes longer to recover.
It has been recommended to farmers that it is best to no-till the
soil for four to five years and then plow it up and start over again.
However, the soil quality indicators of pore continuity, water infiltration
rate and number of earthworms do not support this recommendation. Saturated
hydraulic conductivity and dry bulk density were significantly higher
in zerotill unplowed soil than in plowed soil. This indicates that there
is a much higher pore continuity in the unplowed soil. Plowing the soil
decreased water infiltration in zerotill soil 100 days after plowing
and earthworm numbers did not return by 142 days after plowing. It appears
that plowing zerotill soil is not beneficial.
The zerotill system does not have low stability or low diversity
in this study. These findings question previous recommendations about
the need to increase diversity and/or stability in agroecosystems. If
future studies provide evidence that agroecosystems are stable, then
this whole area of agroecology may have to be rethought. It may be possible
that pest outbreaks and damage are not due to ecosystem instability,
but rather single population instability.
Tuesday, May 10, 2011 12:49:23 PM