Northwest Iowa Crop Update Newsletter by Todd Vagts ISU Extension Crops Specialist Counties Served:  Carroll, Calhoun, Crawford, Ida, Monona, Pocahontas and Sac.
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Volume 2, Number 25

Northwest IA Crop Update, September 16, 2002
(Word Document)

Introduction
Harvest has begun in some early maturing (seed) corn and soybean fields.  Before we know it, much of the area’s crop will be out of the field and in grain bins.  Soybean harvest and storage can often be a challenge because of the way the plant and pods mature and dry down.  Identifying key stages in the maturity and dry-down process can help to schedule harvest activities.   Remember that soybeans need to be at 13% moisture or less for safe storage.  For those that have yield monitors in combines, the information generated by the devices is no good unless the yield monitor is properly calibrated.  Spend the extra time to get the device working properly so that you will trust the data this winter in your management decisions.

Growing Degree Day Accumulation and Crop Development
The area picked up 99 degree days last week, a much more normal accumulation when compared to the previous week (Figure 1).  Degree-day accumulation will continue to slow as the next 7-day total is predicted to be 71.  According to degree-day accumulations, much of the corn and soybean crop has advanced past the physiological maturity mark.  I’ve noticed a few fields of both corn and beans that have bean taken out of the field.  (Physiological maturity is the point in which maximum dry weight accumulation has occurred in the grain.)    Total degree day accumulation remains on track with last year’s accumulation for this calendar date and is still well above (200 DD) the 12-year average.

Determining soybean maturity
Determining when soybeans are mature (both physiological and harvest maturity) helps to schedule harvest operations and reduces in-field harvest losses.  Physiological maturity is when the soybean has accumulated its maximum dry weight.  The growth stage classification is R7 - R8.

With an indeterminate soybean, all pods will not reach physiological maturity at the same time.  There is a period of about two to three weeks from the time the 1st pod reaches physiological maturity to the last pod reaching physiological maturity.  The average seed moisture at the time the pod is physiologically mature is 55%.  When all pods on the soybean plant have reached physiological maturity, the average seed moisture for the plant is usually around 44%.

Two main indicators can be used to determine when individual pods reach this stage. 

ü      Pod Color: A short time prior to seed shrinkage, the pods will begin to lose their green color and will take on a yellowish cast.  When the pod is completely free of green, the seeds inside have already started to shrink.  

ü      Seed Shrinkage: Once the seed has attained its maximum dry weight and size, it will begin to shrink.  Upon shrinking, the seed will become less associated with the white membrane surrounding the seed.  Eventually, the membrane will no longer cling to the seed and will stay with the pod wall when split open.

Harvest maturity indicates when all beans on the soybean plant are ready to be harvested.  This is usually when the average seed moisture is 13%.  Harvest maturity is usually reached about one to two weeks after the entire plant has reached physiological maturity, depending on temperature and humidity.  Timely harvest of a mature field will help minimize losses due to shattering and decreased seed quality.

On-farm storage of soybeans
Storage of soybeans on-farm requires some special considerations when compared to corn.  As with most grains, when moisture is too high, spoilage and reduced germination will result.  High oil content of the soybean makes them more susceptible to spoilage than corn; therefore soybeans need to be about two points dryer than corn for proper storage.  For winter storage, store commercial soybeans at 13 percent moisture or less.  Soybeans with less than 15 percent moisture can be dried with bin fans. 

Aerate the stored soybeans to maintain grain temperature at 35 to 40 degrees F in winter and 40 to 60 degrees F in summer.  Check the bins regularly for heating or spoilage.  When drying soybeans in high or low temperature dryers, be careful.  Soybeans are fragile and can be damaged by air that is too hot or too dry, as well as by rough handling.  Soybeans have about 25 percent less airflow resistance than shelled corn; fans sized for corn drying will produce greater airflow through soybeans.  Greater airflow means faster drying.

Calibrate your yield monitor correctly
University of Nebraska Engineer Paul Jasa recommends proper calibration of yield monitors.  When properly calibrated, a yield monitor can be a valuable tool to gather information about crop production, providing on-the-go estimates of yield and grain moisture content. Jasa further explains that a yield monitor consists of several sensors and a small computer to integrate, display, and save the information. On most yield monitors, the grain flow through the combine is estimated by measuring the force the grain exerts on a sensor at the top of the clean grain elevator. The greater the grain flow, the greater the force or displacement measured. The area harvested is determined from the measured travel speed and the known width of cut. Grain moisture content is also measured so that the grain yield can be corrected to a standard moisture content and estimated on a per acre basis.

Proper calibration involves weighing the grain in a load using a scale and measuring the moisture content with a standard moisture tester. These numbers are entered into the yield monitor's computer, allowing the computer to assign mass flow rates and moisture contents to the millivolt readings sensed. This calibration must be performed separately for each crop. A Checklist for Yield Monitor Operation and

Calibration can be found at the Ohio State University web site at http://precisionag.osu.edu/library/ymonitor.html.  Jasa’s full article in the University of Nebraska September 14, 2001 Cropwatch can be accessed online at http://cropwatch.unl.edu/

Plants and Intellectual Property Rights (Ray Massey, University of MO)
There have been several developments in intellectual property rights related to plants over the last 2 years. The article at this web address (http://ipm.missouri.edu/ipcm/archives/v12n22/ipmltr6.htm) briefly notes the current laws regarding plants and intellectual property rights and recent court cases, along with their implications.