By Aaron Saeugling

In December our thoughts turn to evaluating the past season and the triumphs and challenges of producing crops and livestock. In southwest Iowa, we saw how the growing season can go from feast to famine in just a few miles depending on where and when it rained. But a quick summary is that our 2017 corn and soybean crops turned out better than expected.

The biggest challenge for 2018 is the market impact of a large supply of grain. When crop prices are low, we often look for ways to save input costs rather than look for how to be more efficient. Attempting to reduce or at least hold the line on production costs, some farmers are reluctant to try planting cover crops.

Some hesitate to spend money on cover crop seed, plant the cover crop and then kill it in spring with herbicide before planting corn and soybeans. True, it costs money to put a cover crop in your crop rotation. But there are rewards, too. Such as improved soil health, erosion control, preventing nutrient loss, increased infiltration of rainfall and other related benefits.

Yes, cover crops can work in Iowa
Cover crops are a topic we continue to get questions on from farmers. The concept is not new in today’s rural Iowa landscape, and planting cover crops is possible on almost every farm.

Like all farming operations, management of cover crops varies based on climate, soil, economics and field history. We need to focus on our own management style and the impact we wish to leave on the environment.

I could write a book on the challenges of raising cover crops and that wouldn’t change the fact that  using cover crops in a crop rotation can work in Iowa, despite the challenges. We need to look at the impact below the ground to understand how to maximize the growth potential above.

Cover crops do provide some quick and effective soil health benefits not seen immediately, and they also provide long-term benefits that pay big dividends.

Think about the other farming practices we use heavily in Iowa to increase long-term profitability. Tile drainage increases land value and productivity. Why do we use tile?  Simple: to remove excess water where we don’t want it.

Cover crops increase infiltration and reduce soil erosion. Terraces reduce soil erosion and maintain productivity on sloping fields.

Cover crops provide a living mulch to prevent erosion and maintain soil organic matter, and in the longer term, build organic matter. Herbicide applications in spring reduce weed competition; cover crops can also help suppress weeds.

Benefits of covers add up
A living cover in the spring can reduce germination of winter annual weeds and suppress early weed growth in the spring. In northern Iowa where fall seeding is more challenging, we may look to a spring cover crop to manage late-season waterhemp control.

Kansas State University weed scientists in 2015 looked at planting a spring oats and peas mix to suppress Palmer amaranth. They were successful in reducing Palmer’s germination and growth. For more information, see bit.ly/covers-weedcontrol.

The impacts of tillage on soil are well-documented. Tillage is proven to have a detrimental effect on long-term soil structure. We use tillage for short-term gains in crop residue management and to create a warmer soil temperature for planting corn and soybeans in spring. And as we saw in areas that didn’t get needed rainfall last summer, cover crops allow better infiltration of water into the soil to provide the benefit of relief from mid- to late-season moisture stress.

Good mix with livestock
Covers can provide additional land base for livestock operations. With pasture acres on a steady decline in Iowa we struggle to find acres available to hold livestock during the winter and early-spring time frame when cow-calf producers look for areas to keep cows where they can calve.

Fields planted to fall cover crops are where cows can gain some supplemental grazing and have wide-open areas to help manage potential scour outbreaks.

We can debate the issue of cornstalk grazing and the impact on the land. However, one issue that’s clear is cows put back all the nutrients they consume; it’s in the value of manure returned to the land.

Grazing cornstalks also helps reduce the cost of volunteer corn control in those fields planted to soybeans the following spring. And grazing removes crop residue. Fall tillage in most areas of Iowa is used in part to reduce residue.

With high grain yields and high crop residue loads in most fields, cows can help reduce the amount of residue in the field, making it more manageable for planting. 

The amount of crop residue in fields is not getting any less and the amount of tillage, horsepower and labor we use to manage it has a cost. Herbicides are not as effective on some weeds as they used to be. Therefore, we are now spending more on herbicides and seed genetics to manage weeds in our fields.

We continue to search for ways to build organic matter and soil health with products from a jug. We may consider cover crops from a bag. We are experts in planting things from a bag!  

Time for management
This column wasn’t written to give a step-by-step plan to plant cover crops and explain how to do it. We already know how to incorporate cover crops onto the Iowa landscape.  Now, we need to make management decisions to evaluate our own individual operation and figure out which farms or portions of a farm can benefit from cover crops. Don’t think of covers as an all-or-nothing proposition.

Consider a focused approach. In the wet spot this fall that had waterhemp escapes, plant a cover. In the field area where you loaded semi-trucks, plant a cover. Where runoff from a neighbor cuts a gully, plant a cover. These are all small areas where cover crops would make a big difference.

Purpose of this column on cover crops is to help you re-evaluate the other benefits from cover crops and impact on yield. Your local Iowa State University Extension field agronomist is happy to answer any questions you or your landlords may have regarding cover crops.

Saeugling is the ISU Extension field agronomist covering southwest Iowa. You can contact him at [email protected].