Continuous Corn Effects and Management in Corn Silage
By: Cullen Johnson
Like any good businessman, beef and dairy producers are looking for “the best bang for their buck.” Corn silage is an option these beef/dairymen have to do just that. Overall, feed use of corn silage for beef and dairy has been continually rising, as it provides more tons per acre and thus, increasing profit when fed. According to the U.S. Census of Agriculture, in 2012, 7.2 million acres were grown for corn silage, up 18% from 2007. As we all know, we aren’t making any more land; therefore, to keep up with the increasing demands, more tons must be grown on the same amount of acreage. Although genetics play an important role in increasing yields, soil management is also a key influence to yield, and maintaining that yield for years to come.
Benefits of growing and feeding more corn silage does come at a cost. Soil quality, an indicator of how well the soil will grow a crop (associated with soil organic matter), is slowly declining in all current conventional cropping systems. Crop rotation using perennials, like alfalfa, helps slow the loss of soil quality. Annual crop rotation and continuous corn cropping systems quickly reduce the soil quality. Unfortunately, continuous corn is more likely when growing corn silage, which means soil management will be of great importance. Factors to consider when deciding management practices include, soil characteristics and moisture, insects and disease management, and nutrient availability.
Choosing fields with good tilth and water holding capacity will help reduce the yield penalty associated with growing on corn-after-corn fields. Picking the correct tillage option for continuous corn acreages will assist in maintaining soil quality. Current estimates of average annual soil erosion losses in corn production acreage at 1 pound of soil lost for every pound of corn grain produced, and it’s even higher for corn silage acres. Soil moisture is especially important when in drought conditions. In dry years, corn following corn fields may yield more as the biomass from previous year will help capture moisture that would be lost when following other cropping systems. This can be a disadvantage though in wet years, as crop residue will keep the soil 5 to 10 degrees cooler and significantly wetter than rotated soils.
Biological soil management is also crucial for maintaining soil quality and reducing yield loss. Continuous corn fields typically have more soil insect problems. Pests to consider include armyworms, European and Southern corn borers, flea beetles, cutworms, earworms, and rootworms. Systemic soil insecticides will reduce damage done by some of these insects, but identification of insects will be more useful for targeting specific pests. Corn silage hybrids must also have good disease-tolerance traits in combination with pathogen pesticides for maintaining high silage yields, as diseases will overwinter in the crop residue.
In any cropping system, nutrient availability can be the difference between breaking even and taking a loss. For corn-after-corn fields grown for silage, more frequent nitrogen and potassium applications will be needed than in rotated field. Frequent applications of nitrogen will increase acidity of the soil and require frequent soil tests to determine when lime is needed. Soil tests will also be required to determine if potassium will be needed to be applied, as corn silage can remove around 7.3 pounds of available potassium per ton of silage.
Careful soil management by the grower can potentially mitigate yield reduction by staying attentive to these factors influencing soil quality. As utilization of corn silage increases to meet the demands of the beef and dairy producers, so must our concern for the soils we cultivate crops with. We as an industry must evolve our current corn silage production systems if we are to develop long-term soil health and sustainability. In the meantime, selecting the best soil management practices for the field will help in conserving our precious natural resource while we still have it.