It seems that the roller coaster weather pattern continues in Arkansas, but hopefully we are moving in the right direction. High temperatures are forecasted to be in the 60’s to near 70 the next few days. Along with very windy conditions, wet fields are likely to dry fairly quickly. Although air temperatures are warming, soil temperatures are still cool. Last week most soil temperature reports were still in the mid 40’s, which is below the minimum of 50 degrees needed for corn germination to occur.
Corn planting started in parts of Southeast Arkansas last week on a somewhat limited basis before the rainfall over the weekend shutdown everything down. With warming temperatures and winds rapidly drying fields, planters will soon be running.
Below are some thoughts on corn planting dates, seeding rates, and planting depth for irrigated corn in Arkansas:
If you asked producers when to plant corn, the resounding answer would be early. There are a lot of advantages to early planted corn including potentially higher yield, less insect and foliar disease pressure and earlier harvest. Very early planted corn does have some drawbacks including ability to get a stand some years, how uniform plant emergence is, blackbird feeding of newly planted fields, and risk for freeze damage.
In 2013, we had several fields that were planted into cold soils (~45 degrees) in early/Mid-March and we had a stretch of weather where soil temperatures did not increase greatly. Resulting corn in many instances took 28 days to emerge and stands were less than optimal and emergence of plants was erratic. In the end this corn yielded well, but corn that was planted later, that ended up with better more uniform stands had higher yields.
We have just completed 6-years of planting date studies on irrigated corn that were conducted at Rohwer, Marianna, and Keiser. When evaluating only Bt hybrids, maximum yield potentials were maintained through the month of April even in South Arkansas. From these studies it was clear that there is a relatively wide window that we can plant irrigated corn and maximize yields. Waiting for optimum planting conditions to get the desired plant population that emerges uniformly is more important than planting date when you are discussing March and April plantings. If corn planting is delayed into May, that is generally when we see yields start to decline because of planting date.
Seeding Rates/Plant Populations
Over time plant populations for maximum yield in irrigated corn have been increasing. Most producers are targeting a final plant population of 32-34K plants/acre with slight variations between “fixed” or “flex” ear hybrids. In our work we have not seen a great deal of differences in hybrid response to plant population, although there are a few hybrids out there that are likely exceptions to that rule. In general a final plant population of 32-34K plants/acre is enough to maximize yields in irrigated fields. Under good planting and emergence conditions 95% emergence should be expected, so I generally increase seeding rates 5% to reach my target plant populations.
We have not seen much difference in response to plant population whether the corn was planted in single 38 inch wide rows, twin 38 inch wide rows or single 30 inch wide rows. The figure was from a plant population trial from a few years ago on single 38 inch wide rows. Having a plant population higher than 34K generally is not going to increase yields, but will increase seed costs and increase late season lodging potential.
Raised Bed Preparation/Planting Depths:
Much of our corn is planted on raised beds for furrow irrigation. Raised beds can provide good surface water drainage and help the soil warm up and dry out quicker for planting. Planting on beds also can create problems. In past years when heavy rains occurred after planting, beds eroded down to some degree, especially on lighter textured soils. If the seed was planted only marginally deep enough, then we can have problems with root development when the effective planting depth after the rains is too shallow. Figure 1 depicts a plant with an effective planting depth of about 1.25 inches, marginally deep enough. Figure 2 depicts corn with an effective planting depth of about 0.5 inch and notice no nodal root development. This shallow planted corn eventually fell over died.
Twin row planted fields need to have a wide flat bed to plant on. Since both rows are typically on the edge of the bed anyway, it is very important to get both rows up on the bed and planted a full 2 inches deep to avoid problems.
Please contact your local county extension agent in Arkansas or the author by email at email@example.com, or by phone at 501-749-6207 if you have questions or comments regarding this newsletter.