The standard method used to follow and predict corn growth stages is using growing degree days (GDD). This is a calculation that uses average daily temperatures measure accumulated heat over the growing season. Using GDD works better than days from planting because cool spring temperatures slow early planted corn, while corn planted later in May can have a more linear growth pattern.
For the past three seasons in Georgetown we have followed our research plots and have these values as the average GDD for our area (Table 1). They will be similar to those found in other states, but represent averages and ranges for our region. You may find GDD values on our regional mesonet (DEOS) or through the Climate Smart Ag page at Cornell (edit the site location).
Growing Degree Days (GDD) Average Accumulation to Reach Corn Vegetative and Reproductive Stages.
According to data from the last two years (https://sites.udel.edu/agronomy/2020/09/23/2019-2020-corn-growing-degree-days/), silking and pollination (R1) has occurred between 1320 and 1594 growing degree days, while VT (tasseling) occurs between 1200-1300. In many of our research fields, VT also began to occur in this range last week, followed quickly by silking. Stress during pollination can determine initial pollination and kernel set, so temperature becomes very important. Planting date is an important part of this, as corn growth will follow heat accumulation, so cooler springs will take longer to reach R1 and vice versa. Continue reading
While it may not seem much warmer than it was in 2020, having steady days above 50°F had provided much faster emergence than last year. In 2019 we were getting about 10 growing degree days (GDD) per day, while now we are seeing 15-20. The threshold for emergence is about 100-120 GDD, which we have reached for most fields planted between April 15 and April 22nd (Table 1). In 2020, we had only reached half of that (60-90 statewide) over the same time period.
The standard method used to follow and predict corn growth stages is using growing degree days (GDD). This is a calculation that uses average daily temperatures to measure accumulated heat over the growing season. Most of the GDD values we use are from the Mid-West, so we have followed a few research fields the past two years to compare how DE lines up. We have also included days from planting and light accumulation (pulled from DEOS) to compare other measurement methods (Table 1 – flip phone sideways for best presentation).
Table 1: Following Corn Vegetative Growth Stages (2019-2020)
The preferred soil temperature for corn germination is 50°F, which allows the seed to begin root and shoot growth. When soils fall below this temperature, germination may be limited and seeds may rot in the ground. Many of the weather stations on DEOS (http://www.deos.udel.edu/) have soil temperature as an option, so you can track current conditions. Continue reading