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Prairie Farmer - October 2007

A Combine that Fits

Garrett Stoerger
Department of Agricultural and Consumer Economics
University of Illinois at Urbana-Champaign

If you were fortunate enough to make it to this year's Farm Progress Show, you experienced nearly every color paint that has ever landed on a piece of farm equipment.

So if you left the show feeling like your head was spinning from information overload, it's alright. This month, we are going to step back and examine the most expensive piece of iron on your farm: your combine.

Having too big of a combine is like owning a 15-passenger van for a family of three. And the same goes for having too small of a combine.

There are several components to consider when selecting the combine that best suits your operation. To aid has developed a spreadsheet tool.

The Machinery Economics tool can perform an array of calculations, including determining harvest efficiency. Like all of the FAST spreadsheets, this tool can be downloaded for free on the farmdoc Web site.

Punch in the numbers

The Excel-based spreadsheet is user friendly and only requires a few basic inputs regarding the field's size and yield, as well as some combine specifications. In turn, the program will report:

• How many acres per round the combine is achieving
• Corresponding bushels harvested
• Amount of time it takes to complete one round with and without the use of a grain cart
• Number of acres and total bushels the combine will harvest per hour

The example on this page illustrates the combine's efficiency when harvesting corn. Additionally, the benefit of using a grain cart becomes apparent when comparing the number of acres one can cover unloading on the go vs. stopping at the truck.

The second part to the harvest efficiency worksheet is ensuring your grain hauling capabilities match your combine's production. On the lower half of the sheet, you can input your current grain-hauling capacity, round-trip time to unload the truck, whether or not you plan to use a grain cart and what its capacity is.

In return, you'll get your grain hauling capacity per hour, your harvesting capacity from the previous section, and thus determine your grain hauling efficiency. The tool will estimate approximately how many acres you can harvest before your trucks will no longer keep up with in-field production. In some cases, you will have plenty of grain-hauling potential, and the model will report “never” for an answer.

The harvest efficiency section of the Machinery Economics tool is a wonderful resource to use when trying to find the balance between combines, grain carts and trucks. In some cases, an eight-row head on a combine could be just as effi cient as a 12-row head if you are unable to make a complete round before unloading or have an insufficient level of grain transportation. Before you purchase your next piece of machinery, take a look at your farm's harvest efficiency to determine the best fit for your operation.

Stoerger is FAST coordinator with University of Illinois Extension.