Anderson Farms began using a modified Growing Degree-Day system for scheduling sweet corn planting in 1995. First, we were a little skeptical and tempted not to trust the method, but using GDD resulted in a more uniform season. Also, the roadside stand was continually full with premium sweet corn, and we estimate a slight increase in profits. We did not have to shop any extra crops out of state or take a lower price for them.
The most crucial, but also most simple, aspect of the GDD system is recording the minimum and maximum temperature for each day. To do this, Anderson Farms purchased an automatic air and soil thermometer that records and stores the temperatures for each day. This machine costs approximately $1,000, depending on where you purchase it. Chris stops in the field to jot down the maximum and minimum temperatures from the previous day. It takes only a few minutes a day to do this. Then we simply wait until enough heat units have accumulated to make the next planting.
Anderson Farms has one variation on their system of GDD. Instead of recording air temperature, they use the maximum and minimum from the soil. This may be even more accurate than using air temperatures. The standard GDD method involves calculating the number of heat units needed during the harvest period and then making another planting. We, however, calculate the number of heat units required from germination during the planting period (approximately 100, depending on the corn variety) and then make another planting. Our feeling is that once the seeds germinate, all the plants are subjected to the same weather conditions, and, thus will all probably mature in sequence. The variation on the system probably allows them to make a couple of extra plantings per season. You may consider doing the same with your own plantings or experiment with what works best for your farm.
If you are reluctant to try this system because of the price of the soil and air thermometer, consider that using this system could save you the loss of an entire planting. Hence, the first acre of corn you save (approximately $3,000) will more than make up for the cost of the machine. The thermometer also has many other uses. We have used the thermometer to identify near frost conditions late in the season. We were able to precisely measure temperatures and start irrigation to avoid freezes, thereby extending our field tomato season by two weeks this past season.
Overall, we are very pleased with the GDD system. Though it does take some getting used to, having a continuous supply of corn without backups and gaps is worth the change in your practices. We were anxious about changing our system at first, especially when using GDD told us not to plant for a whole week. We were tempted to go out in the field and plant a little more. Yet, we both stand by this method. It allows us to be more precise in planting corn.
Also see article: Scheduling Sweet Corn Plantings
Chris Anderson, David Anderson
- Anderson Farm, Wethersfield, CT, and
Richard A. Ashley, University of Connecticut
Originally published in Proceedings. 1997 New England Vegetable and Berry Conference and Trade Show. December 16-18, 1997. Sturbridge Host Hotel, Sturbridge, Massachusetts. Pg.119-123.
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