The short answer to the question posed by the title of this article is: “Whenever you want to begin planting corn.” After all, it is your choice, right? The even shorter answer to the question is the typical Extension Specialist answer: “It depends.” The decision about when to begin planting corn depends on your ultimate goal.
- If your goal is to simply check out the operation of the planter or the “fitness” of the field conditions, then go for it.
- If your goal is to begin planting early to rile up the neighbors, then go for it.
- If your goal is to avoid the late planting frustration of last year, then go for it.
- If your goal is to begin planting at the earliest crop insurance date to qualify for replanting payments, then go for it.
Understand that planting early with those goals in mind tends to ignore the possible consequences of unacceptable stand establishment that might occur due to cold soils, frost or freeze injury, or planter furrow soil compaction (especially smeared sidewalls).
- If your goal is to plant when soil conditions are “fit” AND soil temperatures are suitable for rapid germination and emergence and stand establishment, then there are some considerations worth noting.
One of the key factors in setting the stage early for maximum grain yield at harvest is the success or not of the stand establishment process. This includes the success of germination, the success of emergence, and the success of the initial rooting of the young plants from about the 2-leaf collar stage (V2) to about V6. Successful stand establishment requires adequate and uniform seed-to-soil contact at planting, adequate and uniform soil temperature, adequate and uniform soil moisture, absence of soil crusting, absence of planter furrow compaction, and minimal or no soil-borne pests. That’s not asking for much, is it? 😉
Soil temperature, in particular, is a key driver of the success of germination and emergence. It requires approximately 115 Growing Degree Days (GDD) after planting for a corn crop to emerge.
This GDD “threshold” for corn emergence, if you want to call it that, is more consistent if you calculate GDD using soil temperatures rather than air temperatures.
The faster corn germinates and emerges, the fewer number of days the seeds or young seedlings are exposed to other stresses. To put it in a calendar perspective, corn could emerge 7 days after planting if daily AVERAGE soil temperatures were consistently 66-67F (16-17 GDDs per day x 7 days). However, if AVERAGE daily soil temperatures averaged only 55F from planting to emergence (equal to 5 GDD per day), emergence would not occur for about 23 days after planting.
The astute reader will immediately recognize that the odds of cool soils in Indiana are greater in early April than late April. Consequently, I believe caution should be exercised when considering whether to begin planting in early April throughout much of central and northern Indiana.
However, once the calendar moves ahead to about the third week of April, the climatological odds are in our favor that soils will warm up consistently over the coming weeks and so soil temperatures become less of an issue. In fact, most farmers intuitively recognize this fact as evidenced by historical statewide planting progress that indicates that significant planting of corn in Indiana typically begins in that third week of April (USDA-NASS, 2020).
So, like I said at the outset… It’s your choice when to begin planting corn. Make sure you choose wisely.
Related References
Nielsen, R.L. (Bob). 2017. Heat Unit Concepts Related to Corn Development. Corny News Network, Purdue Extension. http://www.kingcorn.org/news/timeless/HeatUnits.html [URL accessed Apr 2020].
Nielsen, R.L. (Bob). 2019. The Planting Date Conundrum for Corn. Corny News Network, Purdue Extension. http://www.kingcorn.org/news/timeless/PltDateCornYld.html. [URL accessed Apr 2020].
USDA-NASS. 2020. Crop Progress. USDA National Agricultural Statistics Service. https://usda.library.cornell.edu/concern/publications/8336h188j [URL accessed Apr 2020].
