Ag Instructor Vic Martin: Cover Crops and Kansas

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Great Bend Tribune
Published September 27, 2020

The Drought Monitor shows little change from last week, however, the dry/droughty areas will likely expand west from the Colorado border counties with the forecast for the week involving little or no rain and the above normal temperatures of the last few days.  As of this report, our area is still not even listed as abnormally dry regarding soil moisture, in great part due to the cool temperatures.  The forecast is pretty ideal for drying down and harvesting fall crops over this week if the forecast holds.  The six to ten day outlook (September 30 to October 4) indicates well-below normal precipitation and temperatures for the region.  Looking out eight to fourteen days (October 2 to 8) indicates more of the same.  A good forecast for bringing in the fall harvest and planting the 2021 wheat crop but less than ideal precipitation.

For decades, especially in the western part of Kansas, fallow was practiced to try and store enough moisture in the soil for the next crop, typically wheat or grain sorghum.  Fallow is simply defined as leaving the soil for at least one growing season and commonly practiced in areas receiving less than twenty inches or less of precipitation.  In some cases, ground was keep devoid of vegetation for a year or even longer.  Before the advent of effective herbicides this was done with tillage.  While effective when done properly, multiple tillage passes were necessary and each one dried the soil.  With the advent of effective herbicides, chemical control was possible and tillage could be eliminated.  Again multiple trips were required and it could be expensive.  Many producers more recently would use a combination of these two practices.  While fallow could save moisture if properly managed, even the best fallow systems would only save at most 30 – 35% of the precipitation received.  Other problems included wind and water erosion on bare soil and a decrease in soil organic matter levels.  Several things occurred that started to change people’s thinking about fallow and if there was a better solution.  And not just for traditional fallow areas but across the country, even in higher rainfall areas.

  • Soil organic matter level decreases, especially under conventional tillage resulting in increased fertilizer costs, poorer soil structure, decreased soil water holding capacity, and increased wind and water erosion.
  • For those in low rainfall areas, except under conditions of extreme drought, only capturing around one-third of the precipitation while leaving the ground bare for up to a year or longer didn’t make sense economically.  What could be done to make that period useful and improve the soil.
  • Decreasing and/or eliminating tillage for erosion control and soil water conservation increased in popularity but it takes time to develop a good no-till soil chemically and structurally.  What could be done to speed up the process towards mature no-till fields?
  • Wanting to minimize tillage, for reasons previously mentioned, meant more reliance on chemical weed control.  This led to the herbicide resistance issues making headlines for well over three decades.  What could be done to maintain soil surface cover, minimize and hopefully eliminate tillage, and control weed?

Next week:  how cover crops seek to address these, the benefits, and the potential pitfalls.

Part II – The Good
Published October 4, 2020

The Drought Monitor, after an extended period of no precipitation and some unseasonably warm temperatures, now shows almost all of Kansas, including our area, as abnormally dry. Not bad for drying down summer crops for harvest but not good news for wheat establishment. The six to ten day outlook (October 7 to 11) indicates well-below normal precipitation and well-above temperatures for the region. Looking out eight to fourteen days (October 9 to 15) indicates more of the same. A good forecast for bringing in the fall harvest and planting the 2021 wheat crop but less than ideal for wheat establishment.

Last week we discussed the reasons why fallow was developed, its potential benefits, the potential problems, and the increased interest in cover crops. Today, a brief discussion of what a cover crop is and its potential benefits.

  • SARE (Sustainable Agriculture Research and Education), part of the USDA, defines a cover crops as “A cover crop is a plant that is used primarily to slow erosion, improve soil health, enhance water availability, smother weeds, help control pests and diseases, increase biodiversity and bring a host of other benefits to your farm.” In English, a cover crop “covers” the soil to help prevent wind and water erosion. It improves soil health by improving soil structure and providing organic matter for soil microorganisms allowing them to produce stable organic matter and providing essential nutrients. They further improve soil health by providing a more stable soil environment in terms of temperature and moisture. By providing organic matter, they improve the water holding capacity of the soil. By covering the soil, they can smother out weeds. And finally, a well-designed cover crop helps decrease disease and insect pressure.
  • What qualifies as a cover crop? Really anything planted to cover the soil qualifies. However, a good cover crop should help address any specific concerns of the grower. For example, if you want to provide nitrogen to the soil, you would select a legume such as a pea, vetch, or clover. Is your primary objective to cover the soil and protect it from erosion and smother out weeds? Are you looking to increase organic matter to improve nutrient and water holding capacities? Likely, a producer is looking for a combination of these factors.
  • An easy way to look at types of cover crops is legumes vs. non-legumes. We mentioned types of legumes previously. The benefit here is that under the proper conditions the can fix over 100 lb/acre of atmospheric nitrogen. Non-legumes include cereal grains such as wheat and rye while broadleaf species range from buckwheat to brassicas and forage radishes. There are even tillage radishes designed to break up compacted layers of soil. The non-legumes are better when you want a great deal of ground cover to protect the soil surface, suppress weeds, and add larger amounts of organic matter to the soil as rapidly as possible.
  • The cover crop selected is a function of the previously discussed considerations along with cost, the environment, length of production. Typically, it is recommended to plant several species to maximize the benefits.

Part III – The Challenge
Published October 11, 2020

The Drought Monitor, after a continuing period of no precipitation and some unseasonably warm temperatures, most all of Kansas, including our area, as abnormally dry and expanding. Great for harvest but not good news for wheat establishment. The six to ten day outlook (October 14 to 19) indicates below normal precipitation and somewhat above normal temperatures for this half of the state while Eastern Kansas should be normal. Looking out eight to fourteen days (October 16 to 22) indicates below normal temperatures and precipitation. The cooler temperatures aren’t bad for wheat establishment but the moisture is needed. Cooler temperatures will at least stress the wheat less.

The last two weeks we discussed the problems with fallow for moisture conservation in drier areas – wind and water erosion, decreases in organic matter, the inability to conserve more than one-third of the precipitation, etc. Next the potential benefits of cover crops were described – decreased erosion, increased organic matter content leading to improved water and nutrient holding capacity, improved weed control, etc. Today, nothing is without challenges and as any producer knows, one-size doesn’t fit all. So what are these challenges?

  • The most effective cover crops include legumes and a diverse plant population. This is fairly practical in higher rainfall areas such as eastern Kansas. However, in lower rainfall areas, less than 20 inches of precipitation per year, options including legumes such as clover and vetch become much riskier. Grass cover crops are still options, rye, wheat, oats, etc., but the benefits.
  • Cost is also an issue as the most beneficial cover crops including legumes can be pretty pricey. The cost has to be weighed against the benefits. Under good growing conditions, the cost may be offset by the added nitrogen. Other cover crops such as rye, oats, and wheat are relatively cheap and while not as immediately beneficial as legumes, do help. Also, there are cost sharing programs with the USDA than can help.
  • This may seem obvious, but lack of rainfall is typically the major challenge for dryland crops in Western Kansas. Right now, establishing a cover crop could be difficult at best. Or a well-established cover crop, if precipitation is lacking say late winter into spring, can deplete soil moisture needed to establish the crop for harvest.
  • Especially for legume cover crops, it is best to allow them as much growth as possible to maximize benefits. This relates to the previous bullet point. And the benefits of added nitrogen are more quickly realized if the soil is tilled and it’s preferable to leave the soil undisturbed and terminate the cover crop chemically.
  • Some lenders and/or landlords question the expense and not doing anything with the cover crop (this is slowly changing). This is often addressed through haying or, even more typically, grazing. While fine, this walks a line of whether it is still a cover crop. However, most agencies understand and go along.

This isn’t to downplay or dismiss the potential benefits of cover crops but as any producer will tell you, nothing going on out in their fields is without risk.

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