farmgate: Second Year Corn? Third Year Corn?
The combine is in the machine shed. Fall tillage is about finished where you’re planning corn for 2008, but you are not quite done with anhydrous ammonia application. You have worked in some flexibility for switching acreage between corn and soybeans, depending on the price structure over the winter. While most of the decisions are rather cut and dried based on costs and prices, some of your decisions have a lot of gray area because of problems with corn after corn after corn……
The debate is interesting and fun to listen to. University agronomists have numbers to prove there is a yield drag on corn following corn. Farmers have numbers to prove there is no yield drag on corn following corn. There may still be some uncertainty where you line up, so let’s explore some of the risks and work on ways to reduce the potential problems. Corn King Bob Nielsen at Purdue and several colleagues including plant pathologists Bill Johnson and Greg Shaner, along with entomologist Christian Krupke have compiled a how-to guide on mitigating the risks of corn following corn.
Nielsen observes there has been a large amount of fall tillage, which means 2008 corn acres, and with the increased corn acreage in 2007, many farmers will be shifting to a continuous corn cropping system, and he says from an agronomic perspective, such a system is “fraught with hazards.”
1) Nitrogen fertility issues. Optimum rates are 30-50 lbs per acre higher for corn following corn than for corn following soybeans, but yields may be 7-10% lower. He says with higher N prices, corn budgets must be adjusted upward and compared to alternatives. He says sidedressing will require more time and that means height issues will occur. Nielsen says high clearance applicators can be used to lengthen the application window.
2) P & K fertility issues. Corn removes more phosphorus and less potassium than soybeans. Nielsen and colleagues say second year corn will have a negligible effect on P & K fertility levels, but over a number of years, P & K levels need to be monitored and adjusted as needed.
3) Stand establishment issues. Continuous corn produces a build up of stalks and rootballs, which create problems in getting a good stand. Seed placement, germination, and emergence can all be problems and that exposes seed to insects and diseases. Select hybrids with superior seedling vigor and bury the stalk residue where possible. Use row cleaners on no-till planters. Don’t plant too early where soil temperatures are not optimal. Starter nitrogen fertilizers and soil applied insecticides may help.
4) Disease management. Corn residue harbors diseases such as gray leaf spot and northern corn leaf blight, and second year corn can be susceptible. If your hybrid is susceptible, then consider a foliar fungicide, however don’t expect a yield increase unless the fungus is present and the chemical is successful in neutralizing it. Consider burying the stalk residue where possible.
5) Insect management. Corn rootworm is spreading throughout the Cornbelt and should be addressed where it has a history. Where excessive residue exists, seedlings will take longer to emerge and rootworms can overtake slowly emerging seedlings. Excessive residue and winter annual weeds can also attract moths that will lay eggs for cutworms and armyworms. Over large areas with continuous corn, corn borer moths will have more opportunities to lay eggs that will survive. To address the problems, the judicious use of soil applied insecticides or transgenic hybrids are options. Fields should be scouted to justify the use of rescue treatments.
6) Hybrid selection. Hybrids should be chosen that demonstrate consistent performance across multiple environments, including soils and weather. Most Land Grant Universities have websites with variety performance information. Once you have chosen candidates for your operation, look for hybrids that have disease resistance, stalk strength, stalk and root health, seedling vigor, and overall stress tolerance.
7) Weed management. Continuous corn limits the weed control options compared to corn/soybean rotation, and that means some broadleaves and grasses may become problems. Soil applied herbicides should be used at full rates, and post emergent herbicides should be applied before weeds are more than 6 inches tall. A combination of the two will give the best overall performance.
8) Glyphosate resistance. With the increasing populations of weeds that have resistance to glyphosate, alternating weed control programs should be considered in continuous corn. Tillage and soil applied herbicides have also been shown to be valuable alternatives.
9) Harvest season issues. With more acreage, harvest is extended and increases the demands on machinery, transportation, drying and storage. As the unharvested crop remains in the field, losses will increase and disease will become a problem. To overcome the challenges, choose hybrids that have good stalk strength and plant health. Harvest priorities should be given to fields that are rapidly deteriorating in quality.
10) Bottom line. The decisions to switch from a corn/soybean rotation to continuous corn should be made with care and attention to economics and agronomics. The agronomic risks of second year corn can sometimes outweigh the economic benefits.
Summary:
With higher commodity prices and increased market volatility, many producers will make cropping decisions well beyond the typical Cornbelt rotations. If continuous corn is one of those decisions, it will be accompanied by numerous agronomic challenges that must be addressed, such as fertility, insect, weed and disease management, hybrid selection and harvest challenges. While there are economic advantages that may be gained with an increase in corn acreage, it will require higher production costs and more intense management.
Posted by Stu Ellis on November 6, 2007 12:17 AM to farmgate