Grazing Green Manures Boosts Soil Nitrogen Levels

Aug 17, 2010 | Corporate Member News

Research conducted by the University of Manitoba has found grazing green manure crops tends to boost the amount of nitrogen available in the soil for subsequent crops.

Green manures are typically planted to improve soil fertility.

In 2009 the University of Manitoba established field trials at Carman to evaluate the potential of several green manure crops for grazing, the effect of grazing green manures on soil nutrient dynamics and on subsequent crop yields.

Joanne Thiessen Martens, a research technician with the Faculty of Agricultural and Food Sciences, says so far the trials have shown grazing green manure crops seems to increase the amount of available soil nitrogen in the fall.

Says Joanne Thiessen Martens-University of Manitoba:

We know that the animal takes off a little bit of the nitrogen in its body.

It’s about 10 to 15 percent so we have 80 to 90 percent of the nitrogen going back on the land but it’s going back in a form that’s highly available to plants and it results in a lot of available nitrogen sitting in the soil at the end of the growing season.

I think it makes us realize how we can perhaps manipulate the nitrogen cycle a little bit using livestock.

Where we were doing this, we were in a high nitrogen environment so we didn’t actually want that much nitrogen in the soil but, for example, in a low fertility environment you could use grazing to sort of kickstart that system, add some immediately available nitrogen to the system.

You get your plants and your soil microorganisms really going and then that can improve the productivity of the system longer term.

Thiessen Martens notes an additional trial is being added this year to look at how to deal with the large amounts of available nitrogen by using non-legume catch crops including barley and oilseed radish that would take up that available nitrogen, prevent it from being lost through leaching and then release it again to the following crop. 

For UniversityNews.Org, I’m Bruce Cochrane.

*University News is a presentation of the University of Manitoba’s Faculty of Agricultural & Food Sciences, to learn more click here.

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