Trouble with Stubble

Trouble with crop residues and stubble is getting worse. Residue management is one of the biggest problems facing no-till farmers today. Crops have more biomass because of better breeding, higher carbon dioxide levels in the atmosphere, plus the increasing use of late season foliar fungicides and insect resistance traits has increased stalk strength and slowed decomposition. Many crops, especially corn, accumulate enough crop residues to cause problems.

Some crop residue is needed to protect soil and prevent erosion during rain events or high winds, but too much residue causes problems when planting, cultivating and can reduce crop germination and growth by preventing seeds from making contact with the soil or through allelopathy. Crop stalk residues can damage equipment and be very tough on expensive tractor tires. Residues also tie up nutrients and provide growing environments for insects and crop diseases.

High production agricultural practices have decreased the population of beneficial microorganisms. Healthy populations of the right microorganisms are needed to decompose crop residues and give a continual release of nutrients throughout the growing season. Beneficial microorganisms also help loosen compacted soils (soil tilth), fix atmospheric nitrogen, produce amino acids, vitamins, plant hormones and other substances for plant growth, and can even breakdown unwanted herbicide residues.

Farmers have been managing crop residues for a long time with deep plowing and burning, but those practices are labor intensive and have significant environmental issues. Farmers also use mechanical shredding. Making crop residues smaller helps, but those residues still contain cellulose and lignin that need specific types of microorganisms to breakdown.

Today, the most common residue management practice is to spray nutrients such as sugars, manure, humates and nitrogen fertilizers directly on crop residues after harvest. The purpose is to feed existing bacteria and fungi so their populations increase. The approach works if you can get enough nutrients to the right locations and the right types of microorganisms are already present. Still, it takes a long time for microbe populations to increase to levels that breakdown aboveground crop residues. Adding the right type of microbes can be very advantageous with today’s tough residues.

GarrCo Products has developed a biological crop residue digester with a highly concentrated formulation, 109 colony forming units/cubic centimeter, with dozens of naturally occurring strains of beneficial microorganisms. Most of the microbes are specifically selected to digest tough crop residues including lignin, hemicellulose and cellulose. The balance is “cafeteria” microbes that produce nutrients to feed the digestion microbes. Tank-mixing a small amount of nitrogen or humic/fulvic acid is not required because the formulation contains both digestive and nutrient producing microbes, but can be useful to kick-start the process late in the fall when time is short before temperatures get too cold for microbial action.

Another benefit observed in field trials is a reduction in volunteer corn. The microbes can act on the seeds of unwanted volunteer corn and weed seeds, reducing their germination. The microbes are selected to digest dead residue and living green tissue is left untouched.

Crop residue management technologies are usually applied by ground equipment with chemicals in the fall after harvest. Nutrients do not move very much so their efficacy depends on the spray covering as much of the residue as possible. In contrast, a biological residue digester can be applied anytime as well as with glyphosate burndown applications. The goal is to give the microbes enough time to digest the crop residues. The longer the microbes have to digest residues the better. The decay is from the inside out so there is brittle residue remaining to protect the soil from wind and water erosion. The remaining corn stalk shells often seem to explode when hit by a tire or planter.

GarrCo is evaluating applications of our biological residue digester aerially before harvest. Pre-harvest applications get the digestion process started early by taking advantage of warmer weather to accelerate microbial activity and the harvesting process to mix and get better coverage on the crop residue. The pre-harvest timing would extend the aerial application season in some areas and increase the number aerially applied acres. Pre-harvest application of GarrCo’s biological residue digester is ideal for aerial application because of the large crop size and the low spray volume needed.

For more information on the next generation in crop residue management, contact John Garr at (765) 395-3441 or


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