The purpose of tillage is to dry and warm the soil and create a consistent seedbed. However, this breaks down macroaggregate soil structure, and over time, soil becomes compacted. Soil can become “tillage-addicted” in that once natural structure is lost, tillage is needed to briefly increase porosity for seedling establishment. Without tillage, roots and organisms create porous and resilient soil structure. No-till farming involves drilling seed into a residue-covered soil surface. Strip-till farming means that a band only wide enough for the crop seedlings is tilled, so less than 50% of the field is disturbed. Both practices significantly reduce loss of soil to erosion, as surface residue slows water flow and protects soil from wind. Well-structured soil is also less likely to blow or wash away. 

Start planning for reduced or no-till the year before your first no-till planting. Use a combine without a chopper to leave corn stalks upright instead of in a thick mat of residue. You may need extra nitrogen fertilizer in the first years, as soil microbes catch up on the larger carbon inputs from residue. Some Soil and Water Conservation Districts in Minnesota offer cost-share for reduced or no tillage. In addition, many districts have no-till drills available for rent so you don’t have to buy new equipment immediately. See the Upper Midwest Tillage Guide from the University of Minnesota Extension for more details about implementation and impacts of various tillage systems.

Cover crops are crops that grow outside of the summer growing season for row crops, thus keeping the ground covered with living plants for a much longer period each year. Cover crops take advantage of spring and fall growing seasons, retain excess nutrients in the field, and reduce fall and spring erosion. They may be hayed, grazed or marketed, but the primary purpose is to protect and build soil. Having a living root in the soil year-round is important for healthy soil because roots release simple carbon compounds that boost microbial activity and growth. When you only grow summer annuals like corn and soybeans, microbes are starved for fresh food for many months of the year. 

The most common cover crop in Minnesota is winter cereal rye, as it’s hardy enough to be planted late in the fall, survive the winter, and grow in the first warm days of spring. Usually it’s terminated with herbicide prior to cash crop planting. In organic systems, a roller-crimper or tillage is used to kill the rye and make way for corn or soybean planting. Rye is known to be especially good at taking up soil nitrogen in the fall, which prevents the nitrogen from being lost to ground or surface water. Instead, the nitrogen becomes part of rye biomass, eventually decomposing in place and being taken up by future crops.

To learn more about different cover crops, you can start by exploring online decision tools from the NRCS, University of Minnesota, and the Midwest Cover Crops Council (MCCC). The MCCC’s Cover Crop Recipes describe low-risk approaches for beginning cover croppers. UMN and the NRCS also have partial budget tools that can help you consider various costs and benefits. A great way to learn more about managing cover crops is to talk with farmers during a field day, or one-on-one about their own experiences with cover crops. Check with your local Soil and Water Conservation district for information on state and federal cost-share for cover cropping. 
 

Cover crop resources

• UMN Extension cover crops
• Minnesota cover crop research
• UMN cover crops economics spreadsheet
• NRCS Cover Crops Economics Tool
• Midwest Cover Crops Council:
  • Cover Crop Recipes
  • Cover Crop Selector tool
     

A diverse array of plant residues supports a multitude of different soil-dwelling primary consumers (earthworms, fungi and bacteria, and small arthropods called shredders), which in turn support predators such as spiders and ants. Soil organisms are incredibly diverse, and we are still learning how critical they are to soil health by supporting soil functions like nutrient cycling, water filtration and plant pathogen control. However, we know that different plant types (e.g. legumes, grasses, etc) host different pests, provide different types of plant residue to decomposing organisms, and have different root patterns which reach different parts of the soil profile. Together, these functions lead to what’s called the “rotation effect” whereby crops grown in rotation tend to be healthier and have higher yields.

Most Minnesota crop farmers use only corn and soybean in rotation, and could benefit from lengthening and diversifying their rotation. A good rule of thumb is to include warm and cool season grasses and broadleaves in the rotation. For example, corn is a warm-season grass, which could be followed by a cool-season grass/legume cover crop mix, like rye and winter pea. Soy is a warm-season broadleaf, which could be followed by more cool-season cover crops. Other cash crops to include in rotation to break up pest cycles could be wheat, barley or oats (cool-season grasses), alfalfa (cool-season perennial legume), flax (warm-season broadleaf), sunflower (warm-season broadleaf), or emerging winter annuals like pennycress or camelina (cool-season broadleaves). 

A primary focus for all commercial farmers is ensuring that weed growth doesn’t impact crop productivity. The impact of weeds on crops varies by region and field, but herbicide-resistant weeds are emerging throughout Minnesota, so it’s important not to let weeds go to seed. Most commercial growers apply herbicide early in the season and depend on crop plants shading out weeds later in the season. Herbicides are known to change microbial communities, but soil can still be healthy and productive with herbicide application. Organic growers usually depend on mechanical cultivation to remove young weeds. This is detrimental to soil structure, but organic growers can still improve soil health below the zone of cultivation, and work towards reducing weed populations over time.

Cover crops which leave a large amount of residue on the soil can choke out emerging weeds, reducing the need for herbicide application. Different weeds tend to be competitive in a no-till system, so farmers who switch to reduced tillage will need to scout for and control weeds with greater vigilance in early years.

A healthy soil is home to a diverse and abundant invertebrate community. As farmers build soil health, they should see different species of ground beetles, spiders, centipedes, millipedes, and isopods (commonly known as pillbugs) on the soil surface. Additionally, farmers should see earthworms or evidence of earthworms if they search just below the soil surface. It is easy to find evidence of earthworms in the soil. Farmers can look for earthworm casts, which are little piles of soil and mineral particles on the soil surface. They can also simply take a spade full of damp soil and investigate the removed soil for earthworms. Mites, collembolans (commonly known as springtails), and other diminutive decomposers or herbivores will also be part of a healthy system, though they are typically quite small and are difficult to see with the unaided eye.

Living crops provide shelter for some of these invertebrates. Additionally, crop residue, or decomposing plant material, serves as a food source. Invertebrates are an indicator that the soil is habitable. They also speed decomposition by shredding plant material, aerate the soil, and play a role in nutrient cycling.

While managing soil health, the use of Integrated Pest Management (IPM) is a strategy to target crop pests without unnecessarily threatening the invertebrates which are beneficial for the soil and the cropping system as a whole. As defined by the Entomological Society of America, IPM is a science-based approach that combines a variety of techniques to manage pests with the most current methods to improve management, lower costs, and reduce risks to people and the environment.

Cover crops are one way to incorporate more vegetative diversity into the cropping system, which fosters more insect and invertebrate diversity. A diverse invertebrate community can be beneficial because a diverse community may include competitors and natural enemies of pests, such as predators or parasitoids. Providing habitat for a diverse invertebrate community allows for these ecosystem interactions to take place, which may reduce the need for more expensive and disruptive methods of pest control.

In natural systems, plants get nutrients from the microbial transformation of organic material into plant-available nutrients (called mineralization). This is especially important for nitrogen. Crop plants are bred to use large quantities of nitrogen, and modern farming systems use inorganic forms like urea and anhydrous ammonia to make sure the corn or wheat have plenty of nitrogen. By increasing the organic residue inputs to your soil, you can increase the microbial mineralization of nitrogen from organic material. That means less inorganic nitrogen is needed. However, while transitioning to better soil health, you may need to add inorganic N to speed the decomposition process of carbon-rich plant residue like straw or corn stalks. The nitrogen can help microbes build soil organic matter faster. After a few years of adding lots of organic residue, your microbes will be robust enough that you may be able to reduce inorganic nitrogen. Microbial mineralization of nitrogen is difficult to predict, because it depends on temperature and moisture conditions in the soil. Organic nitrogen is the starting material for microbes to mineralize nitrogen, so having high soil organic matter is a good starting point to boosting organic nitrogen mineralization.

Grazing livestock stimulate plant growth, spread their own manure, and promote a range of soil invertebrates which assist in soil organic matter cycling and growth. Studies show that grazing covers or harvesting cover crops for forage gives you some immediate profit, even though you may need to choose different species, planting dates, or planting density. If you do not own or wish to own livestock, look into the MN Cropland Grazing Exchange, which connects crop and livestock farmers to facilitate forage grazing. When grazing cropland, the immediate concerns are for fencing, which can be temporary, and setting up a water supply, which may require daily management if no well is available.