April showers do bring May flowers – I always find that most of those timeless sayings are true.  But you know what else April showers can bring?  Nutrient loss for the farmers who are trying to grow a productive crop on their fields in the summer.

This is a very big and very complicated problem, but to put it simply, bare fields with no plants in them can be a problem.  All the spring rains rushing through a bare field can pick up nutrients as they make their way to local ditches and springs.  Exposed soil also means more erosion – as those raindrops hit bare soil, they always grab a few particles to take with them.

Farmers can notice top soil loss and nutrient loss when they have bare fields.  Neither of those is good for the future of their crop or the water supply around them.

The solution for some farmers is to plant cover crops.  Cover crops – a variety of plants that can grow in the soil in the fall and very early spring – can take up the nutrients and store them so that they are less susceptible to run-off.  In essence, for a farmer using cover crops, the nutrients are in plant form instead of just free in the ground.

The plants also protect against soil erosion and improve overall soil health.  They can improve organic matter, improve biodiversity, and break up tough soils with roots that dig deep.

Let’s think about it in city terms:

Many of us apply fertilizer to our lawns in the spring and fall.  On average (and this calculation requires increasing the size of a lawn to an acre for the purpose of comparison) a homeowner would apply 130 pounds of nitrogen per acre.  This amount could actually increase depending on the type of grass you have seeded in your yard.

Farmers are, on average, applying 160 pounds per acre, because corn uses more nitrogen than grass.  Everything considered, our application rates are very similar.

Farmers applying nitrogen in the fall into bare soil would be similar to a homeowner applying nitrogen in the dead of winter.  The grass isn’t growing, so it isn’t pulling up any nitrogen and the expensive fertilizer you just applied is more or less lost cash.  The fertilizer would be carried off with rains or snows through the winter.

If farmers apply nitrogen in the fall AND plant a cover crop, the cover crop uses the nitrogen and saves it for the corn to use in the following in the spring.   This is more similar to a homeowner putting down fertilizer for the lawn in the fall when the grass is still growing.

The overall goal for farmers is to apply fertilizers nearest to the time when the corn will be growing and will actually need the nutrients.  But because of weather and infrastructure, it can be too risky to apply all the fertilizer the crop will need in the spring.  In this case, cover crops can be a good management option, helping to minimize nutrient loss during those heavy April showers.

Caroline Wade
Council on Best Management

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