CORN
Crop Observation and Recommendation Network

February 25- March 11, 2002
C.O.R.N. 2002-4

In This Issue:

A) Corn Profit Tips-Hybrid Selection, Tillage And Rotation
B) Weed Management In Alfalfa
C) Ten Years Of Subsoiling Research
D) When To Till?

A) Corn Profit Tips-Hybrid Selection, Tillage And Rotation - Thomison and Lentz CORN Questions

Lower commodity prices continue to force growers to critically evaluate production inputs. Over the next four issues of CORN we will highlight a list of proven production practices and reminders to help corn growers increase their net income. Most of these involve cultural practices that can be changed without increasing the cash cost of production. Implementing some of these practices requires a higher level of management but these low or "no-cost" crop production considerations, coupled with superior management, skills can help crop producers survive this period of economic stress.

1. Choose High-Yielding, Adapted Hybrids.
Corn acreage, soil type, tillage practices, desired harvest moisture, and pest problems determine the need for such traits as drydown rate, disease resistance, early plant vigor, plant height, etc. End uses of corn should also be considered. Will the corn be used for grain or silage? Will it be sold directly to the elevator as shelled grain or used on the farm? Capacity to harvest, dry, and store grain should also be considered. The most important factors for hybrid selection are maturity and yield potential. Other characteristics for consideration are stalk quality, drydown, kernel characteristics, and disease and insect resistance.

Select hybrids that have produced consistently high yields across a number of locations and/or years. Hybrids of similar maturity may vary in yield potential by as much as 30 to 40 bu/acre. Choosing a hybrid because it possesses a particular trait, such as big "flex" ears, numerous kernel rows, deep kernels, or upright leaves, does not ensure high yields; instead, look for yield stability across environments.

Consult results of state, company, and county performance trials before purchasing hybrids. Because weather conditions are unpredictable, the most reliable way to select superior hybrids is to consider performance during the past one to two years over a wide range of locations and climatic conditions. When using university performance trials, choose some of the highest yielding hybrids from the two-year, several-location average. Results of on-farm strip tests can be used to choose high-yielding hybrids providing there are 10 or more different locations of the strip tests. Results from single on-farm strip tests should not be used to choose hybrids because they cannot predict hybrid performance across a range of environmental conditions. Nevertheless, such tests can be useful in evaluating various traits, such as stalk and root lodging, green snap, drydown, harvestability (ease of shelling, ear retention, etc.), disease resistance, and staygreen.

Results of the OSU Corn Performance Tests can be accessed on line at: http://www.ag.ohio-state.edu/~perf/. Corn test results are also available from local county Extension offices.

2. Plant Hybrids of Different Maturities.
To reduce damage from diseases and environmental stress at different growth stages (improving the odds of successful pollination) and to spread out harvest time and work-load, plant hybrids having different maturities. Consider spreading hybrid maturity selections between early-, mid-, and full-season hybrids for example, a 25-50-25 maturity planting, with 25 percent in early- to mid-season, 50 percent in mid- to full-season, and 25 percent in full-season. Planting a range of hybrid maturities is probably the simplest and most effective way to diversify and broaden hybrid genetic backgrounds.

3. Perform Tillage Operations Only When Necessary and Under the Proper Soil Conditions.
Deep tillage should only be used when a compacted zone has been identified and soil is relatively dry. Late summer and fall are the best times of year for deep tillage. Avoid working wet soil and reduce secondary tillage passes. Perform secondary tillage operations only when necessary to prepare an adequate seedbed. Shallow compaction created by excessive secondary tillage can reduce crop yields. Cloddy seed beds and soil compaction contribute to uneven stands.

4. Take Advantage of Rotational Benefits.
Corn grown following soybeans will typically yield 1015% higher than corn grown following corn. Rotation benefits are most pronounced following legumes such as soybean or alfalfa, especially in reduced tillage systems on poorly drained soils.

Benefits from growing corn in rotation with soybeans include:

• Better weed control in both crops.
  
• Fewer difficult-to-control weeds.
  
• The opportunity to rotate herbicides as crops are rotated (which means that it is less likely that certain weed species will develop resistance to specific herbicides).
  
• Less opportunity for an increase in insect pests and disease inoculum. (Cash costs are reduced because rootworm insecticide is not needed for first-year corn.)
  
• Lower fertilizer nitrogen use is possible without lowering corn yields.

The spread of gray leaf spot across the Corn Belt in recent years can be directly related to continuous no-till corn production. Given the limited genetic resistance available in most corn hybrids, rotation must be used to manage this disease effectively. Tillage to bury disease inoculum may help reduce the onset of disease, but it carries the risk of greater soil erosion.

Future Topics:
PLANTER MAINTENANCE AND STAND ESTABLISHMENT
NUTRIENT NEEDS
PLANTING DECISIONS

B) Weed Management In Alfalfa - Loux CORN Questions

Alfalfa and other forages compete well with weeds, and proper establishment and management go a long way toward keeping weeds under control. Some general reminders on weed management in forages:

Establishment and seedling year:

• weeds that emerge with the crop are generally most destructive
  
• maintain the forage relatively weed-free for the first 60 days
  
• weeds that emerge beyond the first 60 days will not influence that year's forage yield
  
• later-emerging weeds may still influence forage quality
  
• winter annual weed competition in early spring is most damaging to forages
  
• broadleaf weeds are generally more competitive against legumes than grassy weeds

Established stands - factors that should influence decision to use a herbicide:

• thin or irregular stands do not thicken once weeds are removed. Be sure there are sufficient desirable species to fill in the gaps. A minimum of five alfalfa plants per square foot should be present (another way to look at this is that yield will not be limited by stand if there are at least 55 stems per square foot - stands with 40 to 55 stems can still be productive). Weeds tolerant of the herbicide may invade the space left by more susceptible species, ultimately creating a more severe weed problem.
  
• treat only well-established, vigorous stands with herbicides.
  
• if the forage stand is at least 2 years old and 25 to 30% of the plants are weeds, removing them with an herbicide is of questionable value.
  
• if 50% or more of the plants are weeds, it is time to rotate to a different crop.

At this point in time, winter annuals are the predominant weeds in many forage fields. Examples are chickweed, deadnettle, pennycress, etc., which will increase in size as temperatures increase. In established stands (at least one year old), application of Sencor or Velpar within the next several weeks while alfalfa is still dormant is an excellent strategy for controlling winter annual weeds. These herbicides also have activity on dandelion and curly dock and if used at maximum rates may control some of them. Velpar can be applied to established stands with no more than 2 inches of new growth (take note of the long recrop restrictions before using Velpar), but Sencor must be applied when alfalfa is dormant. Gramoxone is labeled for application to dormant alfalfa (new or established stands - rate is lower on new stands). Gramoxone is more effective on chickweed than on deadnettle or mustards.

Pursuit and Butyrac (2,4-DB) are probably the best options for winter annual control in fields where significant new forage growth has occurred. Raptor is also now labeled for use in alfalfa, but should not be any more effective on winter annuals than Pursuit. Butyrac is weak on chickweed and henbit, but is effective on small weeds in the mustard family (pennycress, shepherd's-purse, mustards). Weeds should be no more than 2 to 3 inches tall, and rosettes should be no more than 2 inches in diameter for best results. Butyrac can be used on established or new stands of alfalfa, clover, and birdsfoot trefoil. Do not use on sweet clover. Butyrac should not injure grasses in the stand, but is not labeled for mixed grass/legume stands except in set-aside land.

Pursuit should be applied when alfalfa is in at least the 2nd trifoliate stage, but before alfalfa growth exceeds 3 inches to allow for adequate spray coverage on weeds. Apply when weeds are 1 to 3 inches tall, or before rosettes exceed 3 inches in diameter. Pursuit is effective on most small winter annual weeds. Pursuit may cause injury to small forage grasses - we do not have data on grass tolerance.

Buctril is less effective for winter annuals than Butyrac and Pursuit, but can be effective on mustards if small (rosettes less than 1 inch in diameter). Alfalfa should have at least 4 trifoliates. Buctril can cause crop leaf burn. Do not apply when temperatures will exceed 70 degrees on the day of and for three days following application.

Select and Poast/Poast Plus can be applied later in the spring when annual grasses are several inches tall. Both herbicides are effective on most annual grasses, but Select is more effective on quackgrass and other perennial grasses.

C) Ten Years Of Subsoiling Research - Reeder CORN Questions

Subsoiling has proven its value in Ohio, especially on Hoytville silty clay loam. In the ten years since we started deep tillage research at the Northwest Branch, OARDC, corn and soybean yields have averaged about 4 to 5 percent higher where we deep tilled, whether the tillage was every two years, or less frequently. Only once, in the dry summer of 1993, did fall subsoiling hurt yields substantially. Usually the yields were the same or better on the subsoiled plots. In 2001 subsoiling increased corn yields 4 percent, but had no effect on soybeans.

Controlled traffic has helped maintain the soil structure improvements in our plots. All machines used on the research farm are fairly light.

Hoytville silty clay loam is a soil that benefits from deep loosening, even if you didn't drive any big machinery over it. We were surprised to find that subsoiling increased yields on soil which has never been abused by heavy machinery. Subsoiling gave as much yield boost on our uncompacted plots as on the ones we intentionally compacted with a 20-ton/axle load.

A two-year research project, comparing five subsoiler designs, on Kokomo silty clay loam in the early 1990s gave yield increases ranging from about 2% to 6%.

D) When To Till? - Beuerlein, Dorrance, Hammond, Lentz, Lipps and Loux CORN Questions

Tillage is one of the largest out-of-pocket expenses used for crop production and often does not generate enough yield to make the tillage profitable. While no-tillage can reduce production cost and increase profits, it also creates problems that producers must solve with proper management of the other inputs and production practices. Some of these problems are colder, wetter soil at planting, more root rot disease, slower emergence and growth, dealing with crop residues and the diseases they contain, etc. There are times when tillage is warranted, and will likely be profitable. Following is partial listing of some of the situations when tillage may be needed:

1. Use tillage when inadequate soil drainage leads to serious yield loss due to root rot diseases, poor stand establishment or late planting.
   
2. Use tillage to bury crop residue and thus reduce pathogen survival that can infect a following crop.
   
3. Use tillage as a prelude to land leveling, rock removal and for the incorporation of soil amendments such as lime or very high rates of fertilizer.
   
4. Use tillage to mitigate compacted soil layers or zones that interfere with water movement into and through the soil which may delay planting, harvesting and other field operations.
   
5. Use tillage to destroy crop residues that harbor insects that can interfere with succeeding crops.

The following table contains the cost to perform various tillage operations and the yield increases needed to pay for those operations.

Table 1. Cost of various tillage operations and the yield increases of Corn, Wheat and Soybean required to pay the cost(s).

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C.O.R.N. is a summary of crop observations, related information, and appropriate recommendations for Ohio Crop Producers and Industry. C.O.R.N. is produced by the Ohio State University Extension Agronomy Team, State Specialists at The Ohio State University and Ohio Agricultural Research and Development Center. C.O.R.N. Questions are directed to State Specialists, Extension Associates, and Agents associated with Ohio State University Extension and the Ohio Agricultural Research and Development Center at The Ohio State University.

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