Wednesday, April 24, 2013

Corn Planting and Fluctuating Temperatures

Chad Lee, Extension Agronomist, University of Kentucky

Corn planting is a little behind in 2013, but that does not mean that we will have low yields. Corn planting was behind in 2011 and 2009, but overall statewide average yields were excellent both years. Corn planting was way ahead in 2012 and overall state yields were some of the worst in recent history.

An excellent article was written about the planting date conundrum in Indiana. Here in Kentucky, we see a similar conundrum. Recently, I asked producers across the state to send me planting date and corn yield data from their operations. They sent me corn planting dates and yields from 2003 through 2012 (Figure 1). The data would indicate that the best planting dates for Kentucky would be from about the last week of April through the third week in May. Who is going to believe that?!

Since 2012 was extremely early for planting and extremely poor for yields, we examined the data from 2003 through 2011 (Figure 2). The first thing to notice about the data from 2003 through 2011 is that the correlation between planting date and yield is very week, suggesting that there may be no relationship between planting date and yield for this data set. If there is a correlation, it would suggest that corn should be planted in May for Kentucky. Again, who is going to believe that?!

Corn planting dates and yields from producer fields in Kentucky from 2003 through 2012.

Corn planting dates and yields from producer fields in Kentucky from 2003 through 2011.

Perhaps the point with this exercise is that we do not need to be in as big of a rush as we think we do to finish corn planting.

Soil temperatures have fluctuated quite a bit over the last month. For Caldwell County in western Kentucky, soil temperatures ranged from 50 F to over 70 F (10 to over 21 C). Soil temperatures above 50 F are generally favorable for corn germination and emergence. But, Warren County soil temperatures ranged from about 45 F to 65 F (7 to 18 C), which is not ideal for germination and emergence. During that same period, air temperatures dipped as low as 27 F (-3 C) and frost-like conditions occurred over the previous weekend. Forecasts project air temperatures below 40 F (4.4 C) later this week. Depending the duration of those temperatures, soil temperatures in the upper 2 inches could decrease as well.

Corn planted the past week or so should begin emerge in about 7 to 14 days. If the young germinating plant experiences fluctuations in soil temperatures, it could deform the mesocotyl development, resulting in "corkscrew corn". Scouting planted fields for germination and emergence would be wise this season. Deformed plants most likely are not the fault of any seed company, or any chemical, but the result of the fluctuating temperatures.
Twisted mesocotyl or "corkscrew" corn most likely
resulting from fluctuating soil temperatures. 

We fully expect producers to plant corn as long as the sun shines and the soil moisture is suitable, because the calendar says it is time to plant corn. However, the experience of recent seasons suggests that we should not worry if corn is planted later than we would prefer.

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