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Plant diversity enhances soil health

Tom J. Bechman various cool-season broadleaves and cool-season grasses grown in cover crop plots in Allen County, Ind.
INCREASE DIVERSITY: These various cool-season broadleaves and cool-season grasses grown in cover crop plots in Allen County, Ind., after wheat harvest illustrate how farmers can increase plant diversity.
Salute Soil Health: Here are the different types of plants that would best help your soils.

Soil health is talked about everywhere. How do you achieve it?

There are four basic principles involved in the concept of soil health:

  • limiting soil disturbance
  • keeping soil covered with living plants or residue
  • plant diversity
  • keeping a living root growing as much of the year as possible

Let’s focus on plant diversity. It’s based on the concept that most plants are in one of four primary groups: warm-season grasses, cool-season grasses, warm-season broadleaves or cool-season broadleaves. Ideally, all these groups will be included somewhere in your crop rotation or as a cover crop. It’s even better if more than one type is growing at the same time. Plants are healthier when they’re in a diverse mix and provide support to each other, as well as competition.

A diverse mix of plants is mimicking nature. If you look at a forest or prairie, it’s made up of many different types of plants growing together, not a monoculture of one species.

Plants thriving at different temperatures also ensures something is always growing and capturing sunlight. As the plant converts sunlight into sugars, it absorbs carbon from the air in the form of carbon dioxide. This carbon is then transferred into the soil through root exudates.

These exudates not only help plants communicate, but also feed soil microbiology and help build organic matter. Each plant species releases a different exudate, so they interact with different types of soil life. Diversity above ground equals diversity below ground, leading to a more complete and functional soil food web.

Achieve plant diversity

In a typical Midwest corn-soybean rotation, corn is a warm-season grass and soybean is a warm-season broadleaf. Changing your crop rotation to add wheat or another small grain every few years, on even a small percentage of your operation, not only would add diversity to your cash crop by adding a cool-season grass, but also would give you a large window of opportunity to use a diverse cover crop after wheat.

Implementing cover crops is probably the easiest way to fit some diversity into your normal crop rotation. Common fall cover crops such as barley, cereal rye or annual ryegrass are cool-season grasses. Radishes, turnips, winter peas and clovers are cool-season broadleaves that are commonly included in fall cover crop mixes. In the summer after wheat harvest, both warm-season grasses, such as sorghum-sudangrass and millet; and warm-season broadleaves, such as sunflower, cow pea and sunn hemp, can be included in the mix. They’ll have plenty of time for good growth before it gets too cold. If you have livestock in your system, this is a great way to build diversity as well as provide additional high-quality forage.

Building diversity into your cropping system will lead to increased nutrient cycling and organic matter levels as the soil food web begins to fully function. It takes time to achieve a well-balanced and diverse system, but eventually it will pay off in big ways.

As soil function increases, you’ll see a larger return on investment in the form of nutrient credits, better water-holding capacity, and increased soil structure and stability. Each of these has a positive effect on crop health and benefits your bottom line.

Kautz is a district conservationist with the Natural Resources Conservation Service. She writes on behalf of the Indiana Conservation Partnership.

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