Agronomy Guide For Field Crops – Corn – Hybrid Selection

 

 

Corn development is driven primarily by temperature, especially during the planting-to-silking period. Unlike soybeans, day length has little effect on the rate at which corn develops. The Ontario crop heat unit system has been developed to calculate the impact of temperature on corn development. Ontario crop heat units (CHUs) are calculated based on daily maximum and minimum temperatures and allow for a numerical rating of growing seasons, geographical locations and corn hybrids. This system allows producers to select hybrids that have a high probability of reaching maturity before a killing frost occurs.

 

 

CHU calculations require a start date, a formula for calculating CHU based on daily temperatures and an end date. Starting in 2009, Ontario began recording CHU on May 1, regardless of location or temperatures experienced up to that date. The CHU system uses a calculation to arrive at a daily CHU total and employs the following trigger to mark the season end: when average temperature falls below 12°C, or the first occurrence of -2°C. The current CHU system and map (sometimes referred to as CHU-M1 because of the May 1 start date) are based on data from the 1971–2000 time period.

 

Other jurisdictions use different systems for quantifying the effect of temperature on corn development and for rating corn hybrid maturity. Unfortunately, these systems are unique, and true mathematical conversions from one to the other are not possible. Table 1–7, Approximate conversions between three systems of measuring heat accumulation in a growing season provides values to assist in making reasonable comparisons between the different systems.

 

It takes approximately 75–80 crop heat units to produce each corn leaf. Therefore, at temperatures of 30°C during the day and 20°C at night, there is one new leaf every 2–3 days. At 20°C during the day and 10°C at night, one new leaf appears every 5–6 days.

Video: Evolution of Beef Cattle Farming

The Clear Conversations podcast took to the road for a special episode recorded in Nashville during CattleCon, bringing listeners straight into the heart of the cattle industry. Host Tracy Sellers welcomed rancher Steve Wooten of Beatty Canyon Ranch in Colorado for a wide-ranging discussion that blended family history and sustainability, particularly as it relates to the future of beef production.

Sustainability emerged as a central theme of the conversation, a word that Wooten acknowledges can mean very different things depending on who you ask. For him, sustainability starts with the soil. Healthy soil produces healthy grass, which supports efficient cattle capable of producing year after year with minimal external inputs. It’s an approach that equally considers vegetation, animal efficiency, and long-term profitability.

That philosophy aligned naturally with Wooten’s involvement in the U.S. Roundtable for Sustainable Beef, where he served as a representative for the Colorado Cattlemen’s Association. The roundtable brings together the entire beef supply chain—from producers to retailers—along with universities, NGOs, and allied industries. Its goal is not regulation, Wooten emphasized, but collaboration, shared learning, and continuous improvement.