What to Expect from Later than Normal Corn Planting

One of the current corn research initiatives at Mississippi State University is a project evaluating corn productivity to later than normal planting dates, particularly when grown with irrigation.

These are preliminary research results from five Bt (corn borer) hybrids grown in irrigated culture in 2009 and 2010 at Mississippi State University (Starkville, MS) and the MSU Delta Research and Extension Center (Stoneville, MS).   Corn produced optimal grain yields until May 1 and dropped surprisingly moderately through May, until declining quickly in June.   These results show considerable promise for producers who have had planting delayed by frequent rainfall or suffered stand failure or catastrophic damage to a young crop, particularly in northern Missisissippi counties. 

Corn response to planting dates when grown in irrigated culture in Mississippi.

A similar study was also conducted in 2010 grown in dryland culture at Mississippi State University in Starkville, MS.  In contrast to the studies grown with irrigation, grain productivity declined more substantially with planting dates extending into late May.  This shows the high importance of sufficient moisture to corn productivity, particularly in late plantings.

Optimal corn planting dates and response trends associated with late plantings are expected to be likely 7-14 days later in northernmost Mississippi counties, compared to the research conducted near the Highway 82 latitude noted above.

These responses are highly dependent upon selection of superior-adapted corn hybrids which can tolerate high temperatures prevalent during the summer.   Therefore, I strongly suggest picking proven late-maturing hybrids which have performed well in dryland, or extreme drought stress environments; even if you intend to fully irrigate your late-planted crop.  The Bt corn hybrids evaluated in the studies above include:  Pioneer 33N58, Pioneer 31G96, Pioneer 31P42, NK N82V and DEKALB DKC68-06.  For more information regarding corn hybrid selection in Mississippi, you may contact a MSU Extension Service agent or see  https://www.mississippi-crops.com/wp-content/uploads/2011/01/CornShortList2011.pdf. 

Resist the natural temptation to plant early-maturing corn hybrids when planting late in order to “make up” for lost time.  Early corn genetics are bred for much milder climates, and although they may perform well when planted early, they must endure extreme heat and humidity when planted late.  This can contribute to poor performance or failure.

Bt insect protection is also particularly helpful for late-planted corn, because corn borers, armyworms and earworms are more likely to infest corn in high numbers and cause heavy crop damage, compared to normal planting dates.  However, Bt refuge requirements still apply.

If you chose to plant corn later than normal, I suggest reducing seeding rate, since grain yield potential is less than normal.  Furthermore, warm temperatures associated with May planting enhance seedling establishment and produce taller, leafier plants, which greatly increase moisture demand, but intercept plenty of light to optimize photosynthesis.  Thus, fewer plants are needed to make to most of this situation.

Another potential pitfall associated with late corn plantings is Southern rust infection.  Southern rust is an aggressive disease which often infects Mississippi corn late in July, but normally doesn’t reduce yield much, because corn is nearly physiologically mature.  However, late-planted corn is much more vulnerable, because it may not mature until September.  Furthermore, corn genetics generally have little resistance to Southern rust.  Thus, you should plan to closely scout the crop and plan to apply fungicide, if disease threatens.  Since corn’s reproductive growth stages span about 60 days and this is an aggressive disease, a single “automatic” fungicide application at tassel stage will not likely provide favorable results.  Frequent field scouting and potentially multiple fungicide applications are essential to moderate heavy Southern rust infection.