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Mixing corn hybrids to increase yield

There may be advantages to mixing corn hybrids, but it’s not recommended practice in Manitoba

There are advantages to mixing hybrids, such as lengthening the period of pollen availability to potentially decrease the risk of poor pollination from moisture stress during flowering and promoting cross pollination toward larger kernels and higher grain protein. However, it has not yet been determined whether or not planting them across neighbouring fields offers similar advantages.

As with any practice, there are challenges that need to be met through advances in precision agricultural technologies, but many believe that, one day, mixing hybrids within fields will could become common practice.

Crop stress

According to Dr. Bao-Luo Ma, a crop physiologist with Agriculture and Agri-Food Canada’s Eastern Cereal and Oilseed Research Centre in Ottawa, within every growing season, crops are inevitably exposed to stress, both biotic (stress caused by living creatures like fungus or insects) and abiotic (stress caused by the environment, like cold, heat, crowding, weeds or water or nutrient deficiencies.)

Bao-Luo Ma’s research focuses mainly on corn crop responses to abiotic stress. Theoretically, Bao-Luo Ma sees mixing corn hybrids within a field increasing the diversity and adaptability to both types of stress. “Slightly early or delayed growth stages of one hybrid could help it avoid insect damage, pathogen infestation, effects of drought, flooding, nutrient deficiency, shading, etc. at critical stages of crop development, compared to other hybrids in a mixed-culture or monoculture field,” says Bao-Luo Ma.

“This would result in overall greater grain yields of mixed culture fields than those of the monoculture fields.”

But mixing corn hybrids will not always produce greater yields than would mixing monocultures. “Mixing corn hybrids could often result in the same or even lower yields than monocultures if the conditions weren’t right for mixing cultures or if the wrong hybrids were chosen,” said Bao-Luo Ma.

Bao-Luo Ma advised, first and foremost, knowing your field. Mixing hybrids could be more profitable where there are more differences within the field. “Mixed culture may be more promising in fields with expected large spatial variability, coarse-textured soil, and continuous rain-fed monoculture with a history of higher risk of diseases and insect damages.”

“As well, all hybrids should have high productivity potential with similar plant height, but should have different specific traits.” Some hybrids may be more tolerant to drought, nutrient, crowding or resistant to root or foliar diseases. In a mix, some hybrids may be more suitable for heavy textured soil, have stronger root/stalk strength, or fast dry-down rates — a variety of traits can make mixing hybrids more profitable.

Precision agriculture

As new hybrids become available, it is important to conduct frequent tests to optimize agronomic measures. Testing small areas in many locations before implementing change over the whole farm is very important.

According to Dr. Jiali Shang, who conducts research in remote sensing at AAFC, since the 1950’s, several studies conducted in the U.S. and Canada to evaluate the potential increase in yields of hybrid mixing have shown little or no yield benefit — but, with advances in precision agricultural technologies, mixing hybrids within fields is receiving more attention. “Under the control of precision farming, we’re able to alter the variables of many factors influencing the crop yield and obtain different yield results,” said Shang.

With precision agriculture, it is important that varying hybrid plantings and seeding rates within a field are in accordance with varying soil conditions and properties. “Precision seeding technology, for example, allows for the planting of ‘defensive hybrids’ and ‘high yielding’ hybrids at varying seeding rates, according to the differences in yield potential across a field,” said Dr. Bao-Luo Ma.

By measuring the yield results of mixing crop hybrids using precision farming technologies, farmers and researchers can know what affects the productivity of mixed crop hybrids and ultimately improve the mix.

“Growers should pay attention to kernel shape and maturity of the selected hybrids for mixing culture,” said Bao-Luo Ma. “Planter setting of seeding rates for round shape kernel is different from that of long grain shape hybrids at the same seeding rates.

“Keep in mind that if the difference in anthesis (flower blooming time) or physiological maturity between hybrids in the field is five days or more, kernel moisture content in the mixing could be exceeding the desirable range (below 20 per cent) for combine harvest. This could influence the quality of kernels (broken kernels) and cost of drying.”

More improvements of corn hybrids and the development of agri-technology will help improve productivity, reduce production costs and increase environmental sustainability.

Mixing in Manitoba

Morgan Cott, field agronomist with the Manitoba Corn Growers Association at Carman, Man., is not aware of any farmers in Manitoba who mix hybrids — besides those planting both Bt and non-Bt varieties (which help combat European Corn Borer infestations).

“Mixing varieties would get really tricky, as many have different points of maturity,” said Cott. “Even if you have two varieties with the same specification for corn heat units required, they may not ripen evenly.” This could be especially true for farmers using hybrids from different companies.

Cott advises farmers not to mix varieties that need different heat units, due to the risk of varying maturity.

“At planting, if you have different varieties of different CHUs or not, you may have different types of seed — round versus flat,” says Cott. “At pollination, different varieties may pollinate at different times. At harvest, you’ll find the biggest struggle. A producer following this practice will have to wait until the later variety matures. If he begins harvest when the early variety finishes, the later variety will be too wet and he’ll run into higher drying times and costs.

Assuming the two varieties are the same maturity, there will still likely be different moistures at the same time of harvest. It all depends on the hybrids chosen and how fast/slow they each dry down.”

According to Cott, much work is still needed to improve corn on the Canadian prairies, by way of shortening their maturity times while increasing yields in these varieties.

“We’re extremely lucky here, in Manitoba, to be able to take advantage of all of the advances in corn in the recent past — enabling us to grow a successful crop in the Red River Valley and surrounding areas, pushing outwards in all directions. It won’t be long before you should be able to grow a grain corn crop in southern Manitoba and not run the risk of it being frozen before maturity.”

In 2012, Manitoba had 273,000 acres of grain corn and 75,000 acres of silage corn. In 2013, provincial corn acreage increased to about 342,000 acres of grain corn and 86,000 acres of silage corn. The majority of harvested grain corn is sold to Minnedosa’s Husky Energy plant for ethanol and feed.

This article first appeared in the March 11 issue of Grainews.

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