Crop & Pest Report

Accessibility


| Share

Tools for Monitoring Weather Impact on Corn Development (07/27/17)

We are slightly more than halfway through the growing season for corn. This allows us to look at how fast corn is developing this season relative to other seasons to make a more informed guess as to when it might mature.

Tools for Monitoring Weather Impact on Corn Development

We are slightly more than halfway through the growing season for corn. This allows us to look at how fast corn is developing this season relative to other seasons to make a more informed guess as to when it might mature. Corn development is strongly correlated with growing degree day (GDD) accumulations. Many seed companies provide information on the number of GDDs required for a hybrid to reach silking and black layer (physiological maturity). NDAWN is an excellent source of information on the status of GDD accumulations. This information is obtained by going to the “Corn GDD” application within NDAWN (on the main page select “Applications” in the left hand column, then select “Corn GDD”). I am in Bismarck this morning, so from the “Corn GDD” application menu, I selected Mandan as the weather station, May 1 as the planting date and indicated I wanted to compare this year’s data with the long-term average. The results of this query indicate that Mandan has accumulated 1300 GDDs, which is 145 GDDs greater than normal. In other words, the season has been warmer than average and the crop will likely mature ahead of normal.

Another tool that I like for its ease of use and because it also predicts dates for key development stages is called “U2U Decision Support Tools - Corn GDD”. It was developed by a team of land grant researchers and is available at https://hprcc.unl.edu/gdd.php . With this tool, you may select your location from a map and then indicate the relative maturity of your hybrid and the planting date. It will generate data on the accumulated GDDs, predict the silking date of your hybrid, and project the most-likely date your crop will reach black layer (including a range of potential dates this will occur). For example, this morning I selected Bismarck as my location, May 1 as the planting date, and indicated that I planted an 85 RM hybrid. The results indicate that this location has accumulated 1274 GDDs (compared to the long-term average of 1193), that the hybrid reached the silking stage on July 16 (compared to the average of July 19), and that it will reach black layer on September 6 (compared to the average of September 15). It also indicates that the potential range of the dates for reaching black layer are between August 17 (the warmest scenario) and never (meaning that during the coldest-case scenario the crop would not accumulate sufficient GDDs prior to freezing to reach black layer). Though the range in outcomes for this theoretical corn crop near Bismarck is quite large, the data does suggest that in this area of the state the crop is developing ahead of average, and that it will likely mature ahead of normal. This is good news, because the sooner the crop matures, the greater the chance will be that it will dry sufficiently so that little to no post-harvest drying will be required.

This year moisture, not temperature, has been the main concern. The “Crop Water Use” application within NDAWN application menu provides us with a means of estimating water use. The input variables needed are the NDAWN weather station, crop, and emergence date. For example, I selected Mandan, corn, and May 20 as an emergence date. The results from this query indicate that the corn crop this season has used 11 inches of water and is running a water deficit of 7.21 inches (water use minus rainfall during the season – it does not account for stored soil moisture). The deficit is 1.78 inches greater than last year, and 2.88 inches greater than the 5-year average. These results suggest that the crop has probably depleted most of the stored soil moisture. A soil that does not restrict root growth can provide 6 to 10 inches of moisture depending on its texture and moisture status in the top 4 feet at the beginning of the season. These results reinforce the fact that the corn crop is in urgent need of rainfall if we are to achieve reasonable yields from what at the moment looks like a very productive corn crop.

Joel Ransom

Extension Agronomist for Cereal Crops

Creative Commons License
Feel free to use and share this content, but please do so under the conditions of our Creative Commons license and our Rules for Use. Thanks.