Ohio State University Extension Fact Sheet

Horticulture and Crop Science

2001 Fyffe Court, Columbus, OH 43210-1096

Topcross® High Oil Corn Production: Management Considerations

AGF-135-97

Peter R. Thomison

High oil corn contains 50 to 100% more oil and higher quality proteins than normal yellow dent corn. High oil corn is attractive as a livestock feed because it has greater energy than normal corn and can replace some of the more expensive sources of fats and proteins. Contract production of high oil corn may help grain producers increase their profits through premiums.

The TOPCROSS® grain production system licensed by DuPont Quality Grains is rapidly gaining popularity as the preferred method of producing high oil corn. The TOPCROSS system may minimize the yield disadvantage associated with conventional high oil corn hybrids, while also enhancing grain nutrient composition.

The TOPCROSS® high oil grain production system involves planting a blend (TC BLEND® seed corn) of two types of corn. One type, representing 90 to 92% of the seed in the blend, is a hybrid that is designated as the "grain parent." The second type, representing 8 to 10% of the seed, is a special "pollinator." The grain parent is a male sterile (produces no pollen) version of an elite hybrid that may be in commercial production. The pollinator is a special line, available from DuPont and licensed to seed companies, that sheds pollen within a TOPCROSS grain production field. The pollen shed from these pollinator plants contain special genes that cause a kernel to produce a much larger than average germ or embryo (commonly called the xenia effect). Since most of the oil and essential amino acids are in the germ, the oil, and thus the energy level, and protein quality of the grain produced by fertilization with these pollinators is enhanced. Pollinator plants contribute little to overall grain yield, but use resources such as soil nutrients, water, and sunlight. Their function is to provide pollen to the male sterile grain parent. Recent Ohio evaluations indicate that TC BLENDS are available with grain yields comparable to normal corn hybrids, and that the oil content of TOPCROSS grain is about 3 percentage points higher than normal dent corn.

DuPont Quality Grains acknowledges in the LIMITATION OF WARRANTY AND LIABILITY statement (printed on each product bag) that there are risks associated with TOPCROSS grain production. Insect and disease injury, hail damage, drought during the period between planting and immediately after pollination, and/or the failure to follow the recommended method of use may result in an insufficient quantity of pollen or missed timing of pollen shed in relation to silking. According to DuPont, these environmental and production factors can adversely influence pollination by either reducing the number of pollen shedding plants, affecting the timing of pollen shed in relation to silking, or reducing the amounts of silks. Although these conditions can also affect normal corn hybrids, they can have a greater impact on TC Blends due to the limited number of pollinator plants.

The objective of this publication is to identify some key management steps that growers should consider when producing TOPCROSS high oil corn. These suggestions are based on university evaluations and observations as well as guidelines from seed companies and DuPont Quality Grains. TOPCROSS high oil corn production is a relatively new cropping system so there is still much to learn about how the system will respond to various production environments across Ohio.

The cultural practices required for successful TOPCROSS high oil corn production are similar to those used to optimize performance of normal yellow dent corns. The major difference between TOPCROSS high oil corn and normal corn production is the need to follow management practices, from planting through storage, that will preserve grain identity in the TOPCROSS system, i.e. prevent reduction in grain oil content. Certain high-yield management practices recommended for use in normal corn production become especially important in TOPCROSS high oil corn production. According to DuPont Quality Grains, growers must use recommended agronomic practices, including the maintenance of good soil fertility and good control of weeds and other pests, to minimize the variability in performance between the two genetically different seed types contained in TC BLEND seed corn. Growers need to give special attention to management practices that will promote the successful performance of the limited number of pollinator plants.

1. Select field sites with high yield potential for TOPCROSS corn production. Plant TC BLENDS on the most fertile, well drained soils to maximize yield and reduce stress. Avoid droughty soils as well as poorly drained soil conditions. If moisture stress reduces or interferes with pollen shed from TC BLEND pollinator plants, grain yields may be significantly reduced. If cold, wet soil conditions result in uneven seedling emergence and plant development, pollination may be adversely affected.

2. Use crop rotations. For best results plant TC BLENDS after soybeans or forage legumes and do not plant after corn. Grain yields of corn following soybeans or forage legumes will typically be about 10% higher than corn following corn. The yield advantage of growing corn in rotation with soybean is often much more pronounced when drought occurs during the growing season. The benefits of growing corn in rotation with soybean vs. growing continuous corn include less disease and insect pressure. The impact of certain weather related stresses and insect feeding may be greater in high oil TC BLENDS than in normal corn given the relatively small number of pollen producing plants. According to DuPont Quality Grains, adverse environmental stresses such as drought prior to pollination, hail damage, or insect pests attacking the two seed components of TC BLEND differently can cause pollen shed to miss the nick with silking and reduce the amount of pollen available at silking. Therefore, rotational benefits may be even more important in TOPCROSS systems by minimizing environmental stress and insect damage of pollinator plants. Crop rotation will also help high oil corn during grain fill by reducing losses to various foliar and stalk rot diseases. Leaf destruction by foliar diseases during grain fill may not only decrease grain yield but also lower grain oil content.

   Recent problems with poor pollination and reduced kernel set in TOPCROSS high oil corn fields in west central Ohio were associated with significant grain yield losses. Silk clipping and root lodging caused by western corn rootworm appeared to be much greater in TOPCROSS fields following corn than in those following soybeans or wheat.

   Using a crop rotation will also minimize volunteer corn which can be a problem in continuous corn. In a TOPCROSS production field following corn, volunteer corn could fertilize the sterile grain parent instead of the TC BLEND pollinator and thereby reduce oil content of the grain and overall oil production.

3. Isolate TC BLEND fields from normal yellow dent corn. Fields planted to TC BLEND seed corn need to be isolated to minimize cross pollination with normal corn and thereby prevent possible reduction in oil content. The minimum isolation distances recommended by seed companies range from 100 to 200 feet. Some companies indicate in their literature that if isolation is not possible, then the first 30 to 40 rows of TC BLEND corn ( i.e. 75 to 100 feet if planting with 30-inch row planter) may be affected by foreign pollen which will lower the oil content of TOPCROSS grain. According to one company, isolation is not necessary. However this company does not recommend planting TC BLEND seed in narrow fields bordered by normal corn since normal corn will lower the oil content of TOPCROSS grain up to 40 feet into the field planted with a TC BLEND. Ohio State research suggests that isolation distances considerably less than 100 feet may be adequate to minimize effects of adjacent normal corn on TOPCROSS grain.

4. Select TC BLENDS best adapted to your growing conditions. Choose a TC BLEND which is best suited to your operation based on maturity, drydown, stalk quality, disease resistance, and yield potential and stability. Since a number of elite normal hybrids are available as TC BLEND grain parents, you should not have to sacrifice agronomic performance when growing TC BLENDS. Although the grain yields of some TC BLENDS may average as much as 15% less than their normal grain parents, other TC BLENDS are available with grain yields comparable to popular normal hybrids. Therefore it's important to consult performance results when selecting TC BLENDS to plant. Check with your seed company representative for test information. Several universities including Ohio State conducted evaluations of TC BLENDS in 1997. Results of this year's Ohio State evaluation, which contained 12 TC BLENDS from seven different seed companies, are available in Extension Fact Sheet AGF-136 1997 High Oil TC BLEND Performance Tests.

5. Prepare a seedbed that will promote uniform seed emergence and crop development. According to DuPont, crusting or cool weather could have different effects on emergence and stand establishment of the two seed components. Seedbed conditions that result in good seed to soil contact and seed furrow closure will help minimize variability in performance between the two seed types contained in a TC BLEND. Some seed companies suggest using conventional tillage to help ensure even emergence and thereby enhance uniform development of the TC BLEND pollinators and normal parents. Using soil insecticides to prevent potential stand losses from early season insect pests, such as cutworms, may help minimize excessive injury to pollinators. Soil insecticides should also be selected with activity against rootworm larvae to minimize corn root damage.

6. Increase seeding rates. DuPont Quality Grains recommends that TC BLEND seed corn be planted with a plateless planter at 2,000 kernels per acre greater density than typical up to a planting rate of 30,000 kernels per acre. Above 30,000 kernels per acre, TC BLEND seed should be planted with a plateless planter at the same rate as normal hybrid seed. The higher seeding rate is recommended to help compensate for the lower grain yields of the pollinator plants. Although most companies don't recommend a specific population, one company recommends targeting a final stand of 28 to 30,000 plants/A; another suggests increasing no-till populations by at least 2000 plants/A. Higher seeding rates in TC BLEND plantings will also result in more pollinators on a per acre basis. However, planting at excessively high rates may increase stress and the likelihood of stalk rot and lodging. To avoid such problems, growers should follow the seeding rate recommended by the seed company for the TC BLEND that they are planting.

   Use of a plateless planter minimizes the possibility of the two types of seed (normal parent vs. pollinator) segregating based on size differences during the planting operation. Proper planter calibration and depth settings for uniform seed distribution and planting depth is a must. Plant at a speed that allows the most uniform distribution of seed. Prior to planting TC BLENDS, clean the planter thoroughly to prevent the planting of any normal seed that might cause pollen contamination at silking.

7. Plant early to optimize oil yields. Planting early will help extend the grain filling period and reduce the likelihood of stress during pollination. However, avoid wet, cold soils which may cause emergence problems. Adjust seeding rates 10 to 15% higher to compensate for higher seedling mortality that often occurs in early plantings especially with reduced tillage. Ohio State research suggests that it is possible to obtain oil levels above 6.5% (dry wt. basis) in TOPCROSS grain with late plantings but that overall oil yields decrease due to lower grain yields. Late season plantings of corn also are more susceptible to foliar diseases like gray leaf spot and certain insect pests like western corn rootworm beetles and second generation European corn borer.

8. Scout fields for potential pest problems throughout the growing season. Early season insect problems like cutworms or slugs which reduce stand or injure young plants could be particularly serious in TC BLENDS if the number of functioning pollinator plants is reduced below the level needed for successful pollination. Similarly excessive pollen feeding and silk clipping by insects such as aphids, rootworm beetles and Japanese beetles could pose a greater threat to TC BLENDS than to normal corn because of the limited number of pollinators. Since there are an increasing number of reports of western corn rootworm damage in corn following soybeans in Illinois and Indiana, crop rotation alone may no longer be an effective deterrent against this specific insect pest in the future. Although the pollinators used in TC BLENDS shed much larger amounts of pollen on a per plant basis than normal corn, this may be inadequate when insect problems are severe under certain environmental conditions. One seed company marketing TC BLEND suggests that growers consider the higher value of TOPCROSS grain when determining economic thresholds for pest control ( i.e. for certain insect pests, the current thresholds for normal corn may not be appropriate with high oil corn); another seed company recommends spraying if there are one or more rootworm beetles per plant. However specific insect thresholds have not yet been established for TC BLENDS.

   Weed pressure should be monitored. Early season weed control is essential to minimize stress caused by weed competition for sunlight, soil nutrients and water.

9. Segregate TOPCROSS grain to preserve its "identity" and maximize oil premiums. Store TOPCROSS grain in separate bins to prevent mixing with normal corn. Also, to minimize contamination with normal grain, clean the combine, augers, trucks, dryers, bins, legs and pits prior to beginning harvest of high oil corn. To reduce grain breakage and maintain quality, adjust combine cylinder speed and clearance during the harvest operation as necessary. Using low-temperature drying will prevent damage to grain from overheating and help maintain grain quality.

TC BLEND® and TOPCROSS® are registered trademarks of DuPont.