Straight from the Horse's Mouth

Duane A. Lienemann, UNL Extension Educator, Webster County July 31, 2009 Edition I was sitting in this same chair exactly one week ago experiencing a .70 inch rain which was the most significant moisture that we have had since early this spring. That was nice, but we are still very dry. It seems that there is a cap setting right on top of the bulk of Webster County, western Nuckolls County and Southeast Franklin County and a bit of southern Adams County. We are at about 50% of normal precipitation for this area and of course have varying degrees of dryness with the worst just north of the Kansas border and progressing slightly less dry as you go north. No matter what, we are dry and our crops are on the verge of a critical point of their very existence in dryland conditions. Irrigated farms have experienced an abnormally extensive season already. Some producers have told me they have made more rotations of their pivots and made more runs with gravity already this year as they do in a total irrigation year affecting input costs. As I write this, we are in a thunderstorm watch and believe me it is really needed, especially in light that the forecast for the next couple of weeks is normal temperatures in the mid to high 90’s. Why do I say normal? It is because we have been considerably below normal for most of July. I have had several people and even some news media ask me about the affect of a cooler July on our crops so I have decided to center this week’s discussion on just that very topic, and hopefully by the time I finish I will be hearing the sound of raindrops on my roof. We have been getting these little teasers of .10 or so and those actually have kept our hopes and our crops going. What we have not had is a good soaking rain. What we have had is cool weather for July. Let’s look at this a little bit and perhaps some ramifications. Earlier this week the USDA reported that temperatures in Nebraska averaged 7 degrees below normal and ranged from highs in the low 90’s to lows in the 40’s for July. We even had area county fairs that were held in 70’s-80’s degree which is unheard of. I remember more 100 degree fair days than 80 degree ones. Record lows were reported in numerous areas. I would say that hits what we have been experiencing in South Central Nebraska pretty much right on the money. The good news is that cooler weather reduces stress on humans, cows, pigs and other farm animals and saves on air-conditioning bills. Even better news for area producers living in the “abnormally dry” area is that the cool weather has probably saved our crops from an early demise. Even as the ground has dried and cracked in this dry spell this summer, there has been a savior. These cool temperatures we experienced in July have kept plants from withering away and becoming a statistic for insurance companies. It also been good for pollination, as one of the biggest enemies of pollination is extreme hot and dry weather. Now let’s look at a side that I don’t want to even think about, but with the weirdness of this year so far, I guess we better think about the potential effect of cool weather during the summer. In a normal July, corn farmers don’t even think about the date of the first killing frost in the fall. But this is not a normal year. When July mornings feel chilly, farmers begin to worry about corn growth. Below-normal temperatures dominated the July weather reports. Corn plant maturity depends on accumulated exposure to heat, unlike the soybean plant, which depends on day length to trigger maturity. Heat units in corn are called “growing degree days” or GDDs. Each corn variety has its own requirement of accumulated degree days. In a normal July, when daily average temperatures range from 85 degrees to 100 degrees, a corn plant accumulates 30 GDD’s each day. On some days this July we’ve gained only 12-20 GDDs, or less than two thirds of normal. That isn’t bad for a few days, because corn plants can make up the difference with hot August days. But if a big deficit accumulates, it would take a very hot August to average out. Heaven knows we don’t desire that. What if we have a cool August coupled with the cool July we just experienced? Actually most crops generally look healthy now, especially the irrigated fields, but some plants are behind schedule. Cool weather and lack of moisture have combined to put our crops behind in maturity. Those GDD’s I spoke of earlier determine the maturity of crops. We only have so many growing days until we are in the threat of an early frost which could happen this year, the way things have been going. Someone told me that they had already heard the locusts sing, which usually indicates a particular time until the first freeze if you take stock in folk lore. Corn hit by freezing weather before it matures will have reduced yields. The plant dies and the kernels on the cob stop filling. Corn that has just pollinated or not yet pollinated by this time is at greatest risk. As a rule, it takes 60 days from silk set to harvest. Producers will need to look at their corn and see where it is at this point. It’s not possible to know what the weather will do for the rest of the growing season. A cool July doesn’t mean an early freeze. A cool July doesn’t even mean a cool August. But it is something to ruminate about. The greatest risk is that early frosts or freezes will cut yields or reduce the quality of what is harvested. Official weather records confirm that it's as cool as you think this month. It's a mixed bag while the low temperatures may deprice corn of the heat it needs to mature, avoiding heat stress could help pollination, which is necessary to form each kernel of corn on an ear. But if slow development of the crop increases, the likelihood that farmers won't have time to harvest before sharply colder weather damages the plants becomes more real. If we get an early frost, and our plants are not mature, it could cut yields, and that of course hits the bottom line! The preceding information comes from the research and personal observations of the writer which may or may not reflect the views of UNL or UNL Extension. For more further information on these or other topics contact D. A. Lienemann, UNL Extension Educator for Webster County in Red Cloud, (402) 746-3417 or email to: dlienemann2@unl.edu