Corn Stalk Issues/Solutions

Dealing with corn stalks Part 1

After heavy rains/flooding, a common complaint is the movement of corn stalks/residue off fields into surface ditches. The Soil & Water transects shows that about 67% of corn acres are planted to no-till soybeans and only 6-7% of soybean acres are planted to true no-till corn. The corn residue including corn leaves, corn stalks, and corn cobs and chaff may float off any field once it becomes saturated with water. The practice of no-tiling soybeans into corn stalks followed by conventional tilled corn is called rotational tillage.

Farmers have found that there are economic benefits to no-tilling soybeans into corn stalks. It takes less fuel for no-till, the corn residue conserves moisture in a dry summer, reduces weed growth, increases water infiltration, and improves drainage. Environmental benefits of no-till soybeans into corn residue include less soil erosion and sediment losses, less nutrient runoff, and improved soil productivity. Negative side-effects of rotational tillage include corn residue that is slow to decompose and may float away during heavy rainfall events. An understanding of soil ecology is needed to explain why corn stalks are slowly decomposing. Farmers have three tillage production systems to consider: conventional tillage, no-till, and no-till plus cover crops (Ecological or ECO Farming).

In conventional tillage, the soil is disturbed which changes how the soil functions and changes the soil ecology. Tillage is a destructive process that oxidizes the soil organic matter and releases nutrients to the soil. In the short-term, crops benefit from the increased nutrient availability, but long-term, soils lose their structure, get harder and denser and the environmental consequences may be severe. Advantages of tillage include about 0.5 to 1.0 inches of water removed from the soil profile. Soils in the spring tend to warm up faster because it takes 10 times more energy to warm up cold water than it does air. Disadvantage of tillage include decreased soil structure, increased soil compaction, decreased water infiltrate, decreased soil organic matter levels due to excess oxidation, and decreased soil-water storage. Ecologically, a tilled system is dominated by bacteria and the soil functions less efficiently than a healthy soil. Bacteria tend to decompose soluble nutrients and sugars but are not as efficient as fungus at decomposing corn stalks high in lignin.

In no-till systems, the soil is not disturbed; however; the soil is still left bare in the winter. Advantages of this system include increased water infiltration, some improvement in soil organic matter levels, some improvement in soil structure, and some increased soil-water storage capacity which increases yields under dry conditions. The soil is cooler in the summer and may be wetter due to increased surface crop residue. Disadvantages include colder soils in the spring because soils that hold more soil moisture also take more energy to warm up in the spring. In reality, there are very few long-term no-till fields. Most farmers practice rotational tillage where soybeans are no-tilled into corn stalks and then the soybean stubble is chiseled or turbo-tilled in the fall to create a stale seed bed for conventional corn the next year. Turbo-tilling increases soil warming in the spring and increases faster nutrient release. However it also creates a zone of surface compaction which limits water infiltration. To make no-till work efficiently, it takes 5-7 years to transition to long-term no-till and most farmers are not that patient. Ecologically, true long-term no-till soils have a better balance of bacteria and fungus in the soil because fungal populations recover due to less tillage.

The third system is ecological farming or ECO Farming which includes both long-term no-till and cover crops. The advantage of this system is similar to no-till except that the improvements are more dramatic. Increased soil organic matter levels due to increased root turnover and improved soil structure result in decreased soil compaction, increased water infiltration and increased soil-water storage. These soil changes decrease surface water ponding and increase water storage in the soil profile which may decrease flooding potential. With the increased pore space, in the spring, soils tend to be warmer due to increased porosity and higher aeration and live roots keep the soil warmer. Ecologically, the soil is alive with healthy bacteria and fungus populations which decompose high lignin crop residues like corn stalks quicker.

Each system has an impact on how long it takes for corn stalks and corn residues to decompose. In the next article, potential solutions will be discussed to to reduce corn stalks in surface water.

Dealing with Corn Stalks Part 2

This article discusses possible solutions to reducing corn stalks in surface water. An immediate solution is to keep corn stalks firmly attached to the soil at harvest by raising the corn headers. Excess corn residue flowing through the combine gets chewed up and is less likely to be spread evenly and unattached residue may float off the field. New harvest innovations are strippers which strip corn ears and soybean pods from the plant yet leave the stalks firmly attached to the soil.

A farm myth is that GMO (genetically modified organism) corn decomposes slower than NonGMO corn. A study by Dr. Peter Thomison, OSU Corn specialist, shows that there is no difference in the rate of decomposition between GMO and Non-GMO corn. Farmers chop, turbotill, or disk corn stalks to increase decomposition and these practices have no effect on corn stalk decomposition. Chopping, turbo-tilling or disking corn stalks may actually increase the removal of corn residue from the field by decreasing soil attachment, increase surface compaction, decrease water infiltration and increase field flooding.

Corn stalk decomposition is dependent on three major factors: soil temperature, soil moisture, and fungal decomposition. Why are corn stalks so difficult to decompose? There are four major reasons: 1) Conventional fields are dominated by bacteria microbial communities rather than a healthy balanced mix of bacteria and fungus, 2) Soil that are compacted and too wet for optimal decomposition, 3) Farmers may be overusing fungicides which decrease fungus populations, and 4) Late maturing corn harvested late in the year results in lower soil temperatures and decreases the time for corn stalk decomposition. Ecological or ECO Farming systems use fewer fungicides and have a healthy balance of bacteria and fungus to decompose corn stalks rapidly if soil temperatures are warm, soil moisture is adequate, and there is adequate time for decomposition before winter. The real solution is higher soil temperatures and adequate moisture to stimulate fungal populations to decompose quickly the lignin in corn stalks.

A major change that farmers need to adopt is to plant earlier maturing corn and soybeans so that the soil temperature is warmer at harvest for faster corn stalk decomposition. Harvesting early maturing corn and soybeans allows cover crops to be planted in a timely basis in September which allows the crop to become firmly established before winter. Most cover crops need 60 to 90 days of growth before winter. Live covers promote healthy microbial communities and maximize invertebrates (earthworms, beneficial beetles, springtails) for optimal corn stalk decomposition.

OSU research by Dr. Peter Thomison and Ohio Soybean Specialist shows that optimal corn and soybeans yields are related to the timing of soil moisture more so than crop maturity. Early maturing corn planted in early May benefits from timely late May and June rains while corn that begins tasseling in July and August may be hurt by dry or hot soil conditions. There may be a slight advantage to later maturity corn and soybeans due to increased photosynthesis, but this advantage may be small compared to improved weather conditions from early planting, early harvest, and optimal soil conditions.

The benefits of early maturing corn (<102 days) and soybeans (< group 2.0 maturity) are 1) lower crop moisture at harvest (1-3% points), 2) easier dry down (warmer temperatures) due to harvesting in September versus cold air in November/December/January, 3) less chance of wet soil conditions and soil compaction, and 4) possible crop premiums for early harvested corn or soybeans. If the yield is the same or comparable for early and late maturing corn and soybeans, early maturing crops offer many benefits to farmers. Pick the highest yielding early maturing corn and soybean varieties based on current agronomic research to maximize crop yields. Also pick varieties that are disease resistance.

Using ecological or ECO Farming methods increases the microenvironment for maximum crop decomposition. Warmer temperatures and healthy soils have a balance of fungus and bacteria which allow corn stalks and soybean residue to decompose faster than later maturing harvested crops. Increased microbial life along with healthy invertebrates and earthworm populations increases decomposition. If heavy rains occur, the increased water infiltration and increased soil-water storage decreases water runoff and flooding potential, and the cover crops restrict corn stalks from floating away.

Farmers have several options to decrease corn stalks and corn residue from floating off fields. Some options are relatively simple to implement while other options require a long-term management plan to implement. With some changes in farming practices, the incidence of corn stalks/residue in surface ditches may be reduced.