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Steve Groff plants corn into a cover crop plot Steve Groff
NO FERTILIZER, NO PROBLEM: Steve Groff plants corn into a cover crop plot where he has studied the effects of cover crop use on fertilizer inputs. One of the hidden benefits of cover crops, he says, is the reduced need for fertilizer.

3 ways cover crops can reduce need for fertilizer

Growing Healthy Soil: In general, there is a point of diminishing returns when it comes to chemical fertilizers.

Although I try not to pitch cover crops as a magic bullet for cost saving, the truth is that the answer to the question, "Do cover crops pay?" is a resounding "Yes!"

Often, we tend to focus on where they pay off in profit with increased yields. But one of the most overlooked benefits of cover crops is in savings on inputs, such as fertilizer.

Understanding this dynamic and utilizing it is complex. It depends a lot on a field's cropping history, its existing soil health index, crop rotations and the level of biological diversity you've been able to achieve.

I've done controlled testing on my own farm for decades. Here are three ways I have found that you can save on fertilizer use with cover crops:

1. Saving nutrients. In general, your soil will have residual nutrients hanging out in the top 24 inches, such as nitrates.

With bare soil and nothing growing, this useful nitrogen will tend to leave, leaching out through groundwater and runoff. However, lots of plants can forage this nitrogen and turn it into biomass that can re-release more effectively when you need it.

Radishes, cereal rye and oats do particularly well at capturing the nitrogen you paid for to be released for next year's crop. The timing of the release is affected by the maturity of the cover crop when it is terminated or winter-killed.

2. Adding nutrients. Other crops, particularly legumes such as hairy vetch, crimson clover and winter peas, add nitrogen of their own into the soil.

Getting the right mix and sequence of cover crops ahead of your cash crop can put you ahead of the game with needed fertilizer, which can easily offset the cost of the cover crops. Under ideal conditions, a good legume can provide well over 100 pounds of nitrogen.

Even though nitrogen prices are reasonable right now, they will rise again at some point in the future, which will make legumes even more important.

3. The "biology effect." I can't tell you that I understand everything beneficial that goes on in the soil when you use cover crops, but I can tell you it works.

Soil seems to like it when a lot of different plants are grown. This diversity leads to synergy and benefits that are hard to pin down, but also hard to argue with.

One significant example for me is a study on my own farm where I went with no added nitrogen for four years. Cover crops alone accounted for a 25% yield boost.

I'm not recommending zero nitrogen, but I did this research to see the effects my cover crops had.

Takeaways

In general, what I've found is that there is a point of diminishing return when it comes to chemical fertilizers. You may be using more than you need to in the first place without seeing additional yields.

Cover crops can help you make more of the nutrients you add, meaning you use less of them in the first place. Or, stated another way, cover crops make fertilizer more efficient.

The Coach's Closer

Cover crops can indeed lower your fertilizer needs. But it requires astute management and careful observation to achieve that benefit. Do a few test strips and learn how much fertilize you can reduce on your farm!

Groff is a cover crop pioneer and innovator who farms in the Chesapeake Bay Watershed. Check out his website, stevegroff.com.
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