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LSP Report LS7017

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 Canada, Delhi

Funding: $22,300

Objectives

  1. 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.

Expected Benefits

  1. 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.

Summary of Research Results

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.

 

 

 

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Created: 03-23-1996
Last Revised: Tuesday, May 10, 2011 12:49:23 PM