By Larry Sax, Sax Agricultural Services, Sioux Falls, SD
More factors are influencing farmers to switch from a 50/50 corn-soybean rotation towards more corn-on-corn acres. Whatever the factors are that impact this decision, the resulting question arises. “How do I manage differently for a corn-corn rotation versus a corn-soybean rotation?”
Fertility management. A corn-corn rotation will necessitate an increase in nitrogen applications by 30-45 lbs/acre to account for the soybean nitrogen credit that will not be available. Side dress nitrogen application methods may need to be altered to deal with the additional residue present. Banding a starter fertilizer with the seed or near the seed is very important for seedling vigor. Over fertilization of nitrogen may increase certain disease problems, so do not over apply nitrogen in corn-corn rotations. Soil test levels of potassium must be managed well to avoid potential stalk rot problems. Close attention should also be paid to zinc and sulfur to ensure yield is not lost to deficiencies of these nutrients.
Crop Residue. Another factor impacting management decisions is increased crop residue. Proper management of implement clearance, coulters, and other attachments can easily overcome the challenges of increased residue. In particular care should be given to planter attachments (row cleaners and coulters). These should be adjusted to clear the seedbed of residue while preventing excessive disturbance of the soil. Improper use of coulters and row cleaners may cause “hair pinning” of residue, sidewall compaction or poor seed placement resulting in yield losses.
Insects. Another factor to consider is insect management. If not properly managed, corn rootworm may cause a yield loss of 20 bu./acre or more. Corn rootworm larvae may be controlled through planting CRW corn; using soil applied insecticide; using seed treatment and after planting application of insecticide. The most consistent control has been proven to result from planting CRW Corn or using a quality soil applied insecticide. Row width and availability of planter attachments will impact this decision. (The narrower your row width the more cost effective CRW corn or a seed treatment becomes.) A seed treatment such as Poncho 1250 or Cruiser is better than no protection. The use of one of these corn rootworm control options is not always needed. Proper scouting is needed to determine if a control option should be implemented. Another insect that may cause unexpected problems in a corn-corn rotation with yellow nutsedge present is billbugs. The key to preventing a billbug problem is to control yellow nutsedge.
Plant stand. Final stand is very important in corn production. A corn-corn rotation introduces more factors that may reduce your final stand, thus reducing overall yield. Managing residue, insects, planting depth, and seed bed preparation may require some changes in your operation. Failure to account for these factors in a corn-corn rotation may possibly reduce stand and can cause yield losses of 2-10 bushels/ acre. Check actual planting rates and depth control more frequently in corn-corn rotations.
Weed control. Weed control will most likely be the least impacted aspect of switching from a corn-soybean to a corn-corn rotation. A farmer will need to be aware of a typical increase in foxtail pressure, later emerging broadleaf weeds, and volunteer corn. The availability of Roundup Ready Corn; Liberty Link Corn; and IR/IT Corn allows farmers to rotate herbicide tolerant hybrids in the field, resulting in better control of volunteer corn plants. Do not underestimate yield loss from volunteer corn. It can be as high as 5-10 bushel/acre, or more in worse case scenarios. Volunteer corn may be reduced by using Corn Borer Bt corn and closely adjusting combine settings.
Disease. The unnoticed culprit in many corn-corn rotations is leaf and stalk disease. Diseases of special concern in a corn-corn rotation are stalk rots (diplodia, fusarium, and giberella) and leaf/stalk diseases (anthracnose and grey leaf spot). Corn residue from the previous year’s crop provides the means of infection. Conducive weather conditions facilitate spread within the field and result in significant yield reduction. The main line of defense against these diseases is hybrid selection. Corn fields should be monitored to inventory diseases that are present and hybrid selection should be made to account for the potential impact of these diseases. One disease that needs more attention than merely hybrid selection is grey leaf spot. Grey leaf spot is more prevalent in corn-corn rotations and may cause significant yield loss in certain weather scenarios. Fields with a history of grey leaf spot should be monitored closely and timely treatment decisions made when necessary. Remember over application of nitrogen may increase severity of diseases such as grey leaf spot, corn rust, and common smut.
Hybrid selection. When selecting hybrids for corn-corn rotations consideration should be given to select hybrids with better ratings for leaf diseases, stalk diseases, emergence, roots, and stalk strength. Do not sacrifice yield potential for these traits, but be sure to choose hybrids with stronger agronomics for corn-corn rotations.
By the way, you will need more bin space/acre!