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2014 end of August crop evaluation

Published: Friday, Aug. 29, 2014 5:44 p.m. CDT • Updated: Tuesday, Sept. 2, 2014 2:13 p.m. CDT

As we near September, our 2014 corn and soybean crop appear to be taking a leisurely trip to maturity.

This is in part due to the below normal temperatures in July and the majority of August, coupled with a delayed planting for most northern Illinois farmers.

Utilizing the Illinois State Water Survey Water and Atmospheric Resources monitoring program and inputting May 1 as a planting date with DeKalb as a weather collection site (coincidentally, that data is collected on site at the Northern Illinois Agronomy Research Center) we have reached 2,066 base 50 growing degree units (GDU’S) in Northern Illinois as of Aug. 27. We are only 66 GDUs behind the 11-year average.

The cooler weather has not necessarily been a bad thing for our corn crop. The weather pattern extends the time required for the plant to reach maturity and can provide additional days dedicated to grain fill. I would be interested in hearing from some of our area farmers, but most of the Northern Illinois cornfields I have been in over the last week are in early to mid-dough stage (R4), with a few fields starting to reach dent stage (R5).

Kernel moisture is approximately 70 (R4) and 60 percent (R5) in these respective stages. Research from Purdue University suggests corn in the dough stage requires approximately 36 days to reach physiological maturity. This number can be decreased or increased by above or below average temperatures. Allowing several more days for additional drying from the physiological maturity moisture of 30 percent, it seems likely that very few corn acres will be harvested in Northern Illinois prior to Oct. 1.

Many of the cornfields I have visited have areas that are goose necked to some degree, a result of substantial wind events that have crossed the state. It will be well worth a farmer’s time to check the standability of different hybrids and schedule harvest accordingly, starting with those most likely to lodge.

Because the total number of kernels have been set on the corn ear at this stage, those visiting fields can make preliminary yield estimates.

• In the field, measure off a length of row equal to 1/1000th acre. For 30-inch rows, this equals 17.4 -feet. Row length equal to 1/1000th of an acre = 43560/(row spacing/12)/1000.

• Count and record the number of ears on the plants in the 1/1000th acre of row that you deem harvestable.

• Collect at least three (or more) predetermined ears. For example, grab the fifth,10th and 15th ear. The more ears you choose the greater the reliability you will likely have on your estimated yield.

• Record the number of complete kernel rows per ear and average number of kernels per row. Multiplying the row number by average kernels per row then multiply each ear's row number by its number of kernels per row to calculate the total number of kernels for each ear. Calculate the average number of kernels per ear by summing the values for all the sampled ears and dividing by the number of ears.

• Estimate the yield for each site by multiplying the ear number by the average number of kernels per ear, and this is where it can get a little subjective; some suggest dividing that result by 90 (approximately 90,000 kernels in a bushel of corn). Under excellent growing conditions with very good kernel fill this may underestimate final yield, and you may want to divide the number of kernels by 75-85.

Turning to soybean crops, most are at R6, the full seed stage. Our soybean crop undoubtedly benefited from August rains.

A number of pest issues are showing up in Northern Illinois soybean fields, but because of the stage of maturity of the crop few situations justify further treatments or applications.

After a summer of few pest insects in the soybean field, we are now finding soybean aphids, still in low numbers but certainly increasing. Also western and northern corn rootworm beetles, stink bugs, grasshoppers and a few Japanese beetles all feeding on the leaves.

White mold disease can be found on several varieties at the research center and has been reported in several fields in Northern Illinois. My counterpart in Monmouth, Angie Peltier, is reporting significant Sudden Death Syndrome (SDS) symptoms are showing up in Western Illinois soybean fields, even on supposedly resistant varieties. Symptoms include leaf interveinal chlorosis or necrosis (yellowing or browning) followed by the dropping of leaflets leaving the petiole intact. Scouting soybean fields now will benefit you when selecting varieties with specific disease resistance and tolerance packages in future years.

The Northern Illinois Agronomy Research Center and the University of Illinois Extension encourage farmers to visit their fields one more time, and to have a safe harvest.

Russ Higgins is from the University of Illinois Extension, Northern Illinois Agronomy Research Center.

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