Corn Research

Improving corn hybrid management through replant decisions and clarifying hybrid by fungicide interactions
Dr. David Hooker, University of Guelph, Ridgetown Campus

REPLANT STUDY
The impact of 2008 data into the project confirms that differences in yield response to combinations of hybrid, planting date, and population are significant enough to warrant changes to the current recommendations for replanting decisions in the OMAFRA Publication 811.

Briefly, all nine site-years (Ridgetown, Exeter, and Elora from 2006 to 2008) were planted on a timely basis to achieve early planting, mid planting, and late planting environments. It was determined from this study that lower populations (12,000 and 18,000 plants per acre) tended to yield higher than the current recommendations in Publication 811, which is based on US Corn Belt data.

This may imply fewer decisions to replant and a significant cost savings. This study confirms a trend for higher corn yields with the combination of mid to late planting at low populations compared to the current recommendations based on the US at the two southern locations.

In contrast, corn yields were slightly lower than expected for mid planting, and significantly lower than expected for the late planting in the shorter season area at Elora. This contrast was especially evident in 2008 when Corn Heat Unit accumulation was normal or slightly less than normal. These trends indicate that replant decisions are not economically feasible for short growing season areas.

Differential responses to hybrid characteristics will be investigated for each planting date and population combination. This information will lead to a novel web-based replant calculator based on Ontario data and available to producers on gocorn.net following the 2009 crop.

FOLIAR FUNGICIDE PROJECT
Trial locations were installed at three locations in 2008 to investigate hybrid response to HEADLINE fungicide, and to identify factors responsible for larger yield gains in some hybrids compared to others.

Overall, there was a consistent 0.80 tonnes per hectare yield response with an application of HEADLINE between VT and R2 stages of development when averaged across hybrids. More interesting however, the response to HEADLINE depended on the hybrid, with some hybrids producing no response while others consistently produced up to 1.7 tonnes per hectare (27 bushels per acre) more grain with
HEADLINE compared to the no foliar fungicide application.

All hybrids were rated for disease incidence severity of mainly Northern Leaf Blight, Common Rust, and Grey Leaf Spot before application and two more times after application in the month of August. Hybrid differences in both incidence and severity of some leaf diseases were observed before and after the foliar spray application but there was little evidence to describe any relationship between the hybrid response to yield potential, hybrid maturity or control of leaf diseases. These results indicate that the choice of hybrid is a major factor in the response to HEADLINE (and possibly other fungicides) even when disease pressure is low. The development of a predictive tool for foliar fungicide application decisions must include the effect of hybrids.

This project will be repeated in 2009 with the same hybrids, which will provide some indication whether the stability of responsive/non-responsive hybrids across different environments.