The favourable traits of different varieties and hybrids of maize and soybeans are being exploited in North America by sowing 2 such seed options within the same field – not at the same time but in areas of the field with different seedbed or microclimate conditions.
The potential benefits have led to the development of planters that can switch between 2 seed lots according to a prescription map. Kinze’s 4900 Multi-Hybrid planter (see video at bottom of article) and the vSet Select twin disc metering system developed by Precision Planting have 2 electrically-driven metering discs feeding a single seed tube.
Different varieties or hybrids held in twin tanks can therefore be switched instantly according to the planter’s location in the field.
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Peter Bixel is a grower and SciMax Solutions agronomy leader at the MaxYield co-operative in northern Iowa, United States. After at least 2 years of trials planting 2 corn and soybean hybrids on clients’ fields, he says the planting technology works just fine.
“The big question is how you choose the optimum variety or hybrid combination for zone planting in each field,” he adds. “I’d like to see a lot more detailed information from the seed companies on the performance of different varieties and hybrids in different situations to help with that.”
US breeder Beck’s Hybrids probably has more experience than most of this approach having several years’ trials under its belt with a hybrid classification system designed to help selection across field landscapes.
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It claims to have achieved 74% accuracy in the selection of ‘offensive’ over ‘defensive’ hybrids for highly productive soils, and 82% accuracy choosing a ‘defensive’ hybrid for less productive zones.
Results from multi-hybrid planting depend upon the scale of variability, of course, but advocates see potential for the technique in planting more drought-tolerant cultivars on hill slopes and sandy soils, or in the corners of circle-irrigated fields that get no added moisture.
Other possibilities include planting varieties chosen for robust disease resistance in field environments prone to infection or in areas where access for spraying is difficult, particularly using aircraft.
In our 2015 soybean trials, we got better yields by compensating for differences in soil-pH
Hybrids with a high stress emergence rating could be planted selectively in field areas prone to poor emergence, suggest enthusiasts for the concept, while field margins could benefit from varieties or hybrids with greater insect or weed competition tolerance, or with herbicide resistance traits that allow more effective control of invasive weeds.
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Standing ability or maturity could be used strategically to compensate for soil and environmental factors, and some envisage selective use of seed treatments under a dual planting strategy.
“In our 2015 soybean trials, we got better yields by compensating for differences in soil-pH,” recalls Peter Bixel. “We placed a ‘defensive’ variety in high pH areas where iron chlorosis reduces yields and an offensive variety in lower pH zones.”
“But seed companies need to keep gathering data and interpolating the results, so we can accurately advise clients where they should get better yields and a financial return from using this approach.”