By Trudy Kelly Forsythe
Last year saw a change in focus for the Ontario Corn Committee’s (OCC) corn hybrid performance trials. Traditionally conducted each year to compare hybrids for yield potential in various regions in Ontario, the initiative now involves standard performance testing as well as testing the response of leading hybrids to an intensively managed, or high input, system. The goal is to develop hybrid-specific management in corn.
“Growers are asking for hybrid-specific management information,” says David Hooker, a field crop agronomist at the University of Guelph. “Since the OCC’s primary objective is to test hybrid performance for growers, it made sense that the OCC would lead research efforts to test hybrids in a high-input system with co-operation and sponsorship of seed companies.”
Researchers have been exploring genotype-environment-management interactions for several years in corn, soybean and wheat. Several years ago they discovered a synergy between nitrogen rate and fungicide applications in wheat, where the yield response to increased nitrogen rate and the addition of a fungicide was greater than the additive effect of the two inputs independently.
“The response to both nitrogen and fungicide response depends on the wheat variety,” Hooker says. “For example, if a wheat variety is susceptible to leaf disease and if the environment is favourable for disease development, there is a good chance it would be responsive to both fungicide and nitrogen.”
Researchers have been investigating similar synergies in corn and have noticed that the response to nitrogen, increased population and fungicide at tasseling stage (VT) – the three inputs with the most impact on yields – can depend on the hybrid.
To conduct their experiments, researchers installed intensive trials on eight field locations representing four crop heat units (CHU) maturity zones. This means the same set of hybrids were installed on two locations per heat unit zone, Hooker explains. “The hybrids selected for each zone were selected by the sponsoring seed companies with assistance from the OCC.”
The researchers compared hybrid performance at each location using standard agronomic practice (32,000 plants per acre with a nitrogen rate according to the Ontario Nitrogen Calculator and no VT fungicide), to the combination of higher plant populations (37,000 plants per acre), a higher nitrogen rate (approximately 50 pounds per acre) and with the application of a fungicide at VT.
“Overall, hybrids responded economically to the intensive management package at seven of eight field locations,” Hooker says. “The average yield response across hybrids varied between nine and 34 bushels per acre, depending on location.
“Approximately 16 bushels per acre were needed to break even economically,” he adds. “However, the top hybrid responders varied between 22 and 54 bushels per acre, depending on the location. Some hybrids did not respond to the intensive management package; it had zero yield response.”
Another finding was an increase in harvest moisture up to 2.5 per cent with the application of the intensive package on some hybrids. There was also a tremendous hybrid-specific response to leaf disease severity, especially at field locations with favourable environments for disease development.
“Hybrid-specific responses to leaf disease were expected,” Hooker says. “Hybrids tended to respond more to the intensive package, mostly due to fungicide, if they were more susceptible to leaf disease infection.”
High grain yields were associated with stay green traits late in the season. This may be attributed to a combination of genetic factors responsible for the stay green trait, disease control by fungicide, and nitrogen uptake and use within the plant.
“Yield response to the intensive management package did not depend on the CHU rating of the hybrid,” Hooker says. “Early maturing hybrids tended to have lower stay green ratings during the late grain fill phase and lower yields, which is not new.”
Since some hybrids responded differently at one location versus another, the researchers concluded that more than two locations are required to measure hybrid stability in yield with or without intensive inputs.
“The results must be repeatable,” Hooker says. “The best hybrid decisions are made from multi-year data.”
Information on hybrid-specific responses to intensive management will help improve hybrid selection decisions and the understanding of hybrid interactions with crop inputs by environment.
“Hybrids that yield much higher with more management or inputs may be considered as racehorse hybrids,” Hooker says. He adds it is likely that no more than 10 per cent of hybrids available are true racehorses. “These hybrids would have different economic responses to management inputs than non-racehorse hybrids.”
At the same time, some hybrids may be identified as top yielders without additional inputs. In this case, it would be highly useful for growers to identify hybrids that would not require additional inputs – and costs – to achieve top yields.
“Top yields of these hybrids would be produced from a strong genetic package, with less reliance on nitrogen fertilizer, fungicides to control disease and lower optimal plant populations,” Hooker says.
Moving forward, the OCC will assist seed companies with hybrid selection and installation of more trials in 2016.