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Harvest the sun year-round

Keep a crop in the field all year so Mother Nature doesn’t do it for you, filling the gap with weeds.

May 14, 2024

3 Min Read
A wide landscape view of a cover crop field
MORE CARBON: The sun shines on this cover crop field following wheat, meaning more carbon will be captured. Tom J. Bechman

When you think of harvesting sunshine, for many, the first thing that comes to mind is solar panels. There is another way to harvest sunshine. Living plants, including your crops, harvest the sun and turn it into grain and soil carbon.

In Indiana, July and August are the sunniest months, but the sun shines year-round. A common corn-soybean crop rotation in Indiana is typically planted in April or May and harvested in September or October, meaning you have about six months of growing plants in the field.

What about the other six months of the year? If you don’t have a growing plant out there, you are missing the opportunity to harvest the sun and feed your soil biology, leading to less carbon entering the soil.

Importance of soil organic matter

Soil organic matter helps build soil structure, holds soil water, holds plant-available nutrients, and provides food and shelter to soil biology, to name some benefits.

For example, for each percent of soil organic matter, an acre of soil can hold up to 20,000 gallons of water. That could make a significant difference to crops in a long, dry summer.

When you fill the gaps between your cash crops with cover crops or an overwintering crop, sunshine is being harvested year-round. Photosynthesis, which is the process plants use to produce food for themselves, uses the sun to produce sugars. The plant then uses those sugars to produce biomass, including grain and root exudates.

Root exudates are used as food for soil biology and help to build soil organic matter. In early plant stages, around 80% of the sugars produced from photosynthesis are released as root exudates. This is because plants depend on their mutually beneficial relationship with soil biology to gather additional nutrients they need from the soil, and from the soil biology itself.

As the plant continues to grow, around 50% of the sugars produced are used for root exudates until the plant reaches reproductive and grain or pod fill stages. At that point, the plant then focuses the sugars into producing biomass.

Take advantage of free solar energy

Keeping living roots in the soil should be your first goal. If there are living plants performing photosynthesis in the field, root exudates are being produced and soil carbon is being built. Focus on soil health and mitigating yield-limiting factors. A healthy plant will produce the most sugars and provide the best yields.

Also, consider how to get those cover crops planted and growing as quickly as possible. If you can plant the cover crop before the cash crop is harvested, there will be little to no time that the field does not have actively growing roots.

Lastly, make sure to keep the soil covered. Soil cover will reduce soil temperature during hot summer days, so plants avoid stress, and the soil biology remains active and functioning at optimal levels. If the soil temperature gets too hot, both plants and biology will go dormant and shut down.

Remember, if you’re not planting anything, Mother Nature will fill the gap with weeds. Nature is using weeds to provide the soil with growing roots to keep producing sugars and soil carbon. Everyone would much rather plant their own plants than have nature choose for them. Make sure you’re thinking about how to harvest sunshine as you plan for harvest and beyond.

Kautz is the state soil health specialist with the Natural Resources Conservation Service in Indiana. She writes on behalf of the Indiana Conservation Partnership.

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