The wet weather pattern we have been stuck in for the last 5-6 weeks continues. As of writing this article, I have not seen a planted corn field yet, and don’t expect any will be planted this week with fields being wet and more rain forecasted for Wednesday or Thursday. However the wind is blowing today and temperatures are near 80 degrees, so maybe it won’t take too long to dry up. The good news is that soil temperatures should be plenty warm once fields dry and are ready to plant. Most years by now we have some corn planted and some years we have a substantial amount planted and already emerged. Typically we like to get corn planted in March in South Arkansas and March to Mid-April in North Arkansas. With the weather delays in planting, the questions about how much yield is being lost from late planting have started.
In my opinion we have not lost any yield potential yet and would not expect to lose any yield potential on irrigated fields until late April in South Arkansas and early May as we go north in the state. Can we raise 200+ bu/acre corn planted in March, April, or early May? The answer is yes to all those scenarios as we have done it in past years. Of course getting conducive weather during the growing season and implementing good management practices is needed to achieve high yields regardless of planting date. The table below is a summary of corn planting date trials that I have conducted from 2008-2013 showing estimated corn yield potential based on planting dates for Keiser (Northeast AR), Marianna (East-Central AR), and Rohwer (Southeast AR) using Bt hybrids. The ability to plant relatively late and still make optimum yields may surprise some, but with good production practices and irrigation this can be achieved.
Refuge (non-Bt) corn should be planted as soon as feasible. At Marianna, where corn borers levels were highest in my planting date trials, yields of non-Bt corn tended to decline more than Bt corn when planted after Mid-April. These trials were not sprayed with any insecticides to control corn borers. In areas where corn borer levels are very low, typically we do not see a yield difference between Bt and non-Bt corn.
What impact does a later planting date have on corn growth and development? – ie how much later is harvest going to be from an April planting than a March planting? Not much. Corn growth is driven by heat units and we typically accumulate heat units much more rapidly in April planted corn than from early or Mid-March plantings. Early planted corn tends to take 2 or more weeks to emerge, while April planted corn usually emerges quicker because of warmer soil temperatures. The table below is from a planting date trial at Marianna, AR that I conducted in 2013 and shows the impact of planting date on silking date and maturity date. In this trial, as well as other trials, April planted corn typically may only be delayed a week in maturity compared to corn that was planted several weeks earlier. Of course this can vary year to year is based strictly on heat unit accumulation. Planting early or late it takes the same number of heat units to get to maturity.
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