Cover crops decrease nitrate leaching

Living mass within soil reduces concentration of nitrate

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A recent study at the University of Guelph found cover crops help to reduce nitrate leaching, a threat to the environment.

Masters student Jared Lapierre studied how cover crops help to better control nitrate leaching in two different soil types.

Why it matters: Cover crops are known to help store and contain nutrients by increasing the time roots are in the soil, by increasing the time roots are in the soil, extending the yearly growing season.

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The study took place at the Soil Health Interpretive Centre. Lapierre used the soil column weighing lysimeters to help calculate nitrate leaching by measuring the evapotranspiration, infiltration, precipitation, soil storage and run off of water.

“We have these tank balances which can mediate how much water is going in and out of the lysimeters based on field conditions. This is where we get our drainage amount; the nitrate concentration is derived from our soil samplers,” said Rebecca Johnson, Masters student candidate who presented on behalf of Lapierre during a recent tour at the Elora Research Station.

One system was without cover crops and the other included an oat, cereal rye, radish and crimson clover cover crop incorporation.

Study results showed that soil type played a role in the drainage, but the cover crops did not affect drainage rate.

But when looking at the concentration of nitrate, there was a significant difference in the amount of nitrate that was leached, when comparing cover crops to no cover crops.

Concentration of nitrate vs. drainage in different soil types.
photo: Jared LaPierre’s research

“Overall, the cover crops did reduce the rate of leached nitrate. For silt loam it was 69 per cent reduction in nitrate leaching and for the sandy loam it was a 77 per cent reduction in nitrate leaching.

“The entire winter period, the cover crop in the silt and in the sand was much less with nitrate concentration, which is what we were hoping for in the first place.”

What does this mean?

Soil type plays a larger role than cover crops when it comes to water drainage. Cover crops play a larger role in the concentration of nitrate within the soil solution.

“Nitrate concentration was the main driver in the nitrate leaching and was found to be most prominent at the beginning of November, spring melt and post planting.”

Cover crops reduced the amount of nitrate leaching through the decrease of nitrate concentrations.

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