Corn Off to a Good Start

May 12, 2000
The idea of drought has "settled in," and it looks like we'll continue to hear about the possibility, or even likelihood, that drought is coming. Rain in most parts of Illinois during the past week has turned thoughts away from the threat of dryness, at least temporarily.

If drought does set in, we have probably set the crop up to protect itself about as well as possible. By official estimate, more than 90% of the crop was planted by the beginning of this week. That's about the earliest corn planting that we've ever had in Illinois, though it's about the same as in (I hesitate to say the year) 1988, when 95% of the corn crop was planted by May 10.

While we consider early planting and a rapid start of growth to be helpful in the event that drought later develops, early planting is no guarantee of high yields. In the past 20 years, there have been 8 years when 80% or more of the corn crop was planted by May 10. Six of these were in the 1980s and only two in the 1990s. All 4 years in the 1980s when Illinois corn yield exceeded 130 bushels per acre were years when at least 80% of the crop was planted by May 10. The other two early-planting years that decade, however, were 1980 and 1988, when yields were 93 and 73 bushels per acre, respectively. In the 1990s, the yield was 149 in the early-planting year 1992 but only 129 in 1997, the other early-planting year. So early planting brings no guarantees.

The real positives to the start of the corn-growing season in Illinois this year include early planting, a general lack of heavy rainfall before emergence, warm temperatures recently, and very good planting conditions. Tillage and other trips over the field probably caused minimal compaction due to the fact that soils were drier than usual during April. Stands in most fields are excellent, with few if any drowned-out spots, and uniformity is good. Warmer-than-usual temperatures the past week have caused rapid growth, with the result that many fields planted the first half of April are now in the V3 (three leaf collars visible) stage, and some are at V4.

Few will regret that they planted early this year, as most stands are good regardless of when they were planted. April was cool enough, however, that corn planted in late March or early April and corn planted in late April are not much different in growth stage. Growing degree-day (GDD) accumulations were slow until the last week of April and have been above normal so far in May, so the crop is off to a faster start than normal. It is important that nodal roots get a good start, and it appears that they are doing so in most fields. Where rainfall has been high the past week, roots will not grow very fast deeper in the soil until the soils start to dry out again and oxygen can reach deeper depths in the soil.

GDD accumulation was close to normal (about 200) in April this year, and, in the first third of May at Urbana, we've received about 40% of the average May total, or about 165 GDD. If the temperatures are normal for the next month, we can expect the corn now at V3 to reach about the 7-leaf stage (about knee high) by the end of May, and by the end of June the earliest hybrids should be at or near tasseling. Once corn has been established, it takes about 65 GDD to add a new leaf.

Let's hope that June is as favorable this year as it was in 1999, when temperatures were warm, the rainfall was infrequent but adequate, and corn growth was very rapid. That's probably the best preparation we can hope for in case it turns dry after that.--Emerson D. Nafziger

Author: Emerson Nafziger