Calculating Crop and Ethanol Yields and Irrigation Needs in Four Easy Steps

Estimating crop yields based on available water in semi-arid regions has been made easier using a special calculator computer program developed by an Agricultural Research Service (ARS) scientist.

The device, called the MultiCalculator CD, was developed by agronomist David Nielsen at the ARS Central Great Plains Research Station in Akron, Colorado.

The MultiCalculator uses three simple downloadable Excel spreadsheets.

In four steps, the yield calculator predicts non-irrigated crop yields--a vital factor in the semi-arid central plains.

First, farmers estimate how much available soil water their fields have. Farmers can tab to a table on a different screen that helps them make this estimate, giving multiplication factors for various soil types. For example, farmers on the predominant soil type in the area, silty loam, would multiply the depth of their wet soil by 2.2 to get the number of inches of soil water available for the crop at planting time.

In the next three steps, farmers choose a crop, a location, and guess the percentage of average precipitation they expect during the growing season.

The computer instantly shows the yields they can expect. The yield calculator does this for 18 crops, including cereal grains, seed legumes, oilseeds and forages.

The water calculator also works in reverse--in five steps--beginning with the farmer choosing a crop, then the target yield. It tells how much irrigation water will be needed to achieve the target yield.

In addition, the calculator will also tell farmers how many gallons of irrigation water they will need for each gallon of ethanol produced from the corn they grow.

The calculations are derived from data from long-term ARS research at Akron, which showed a linear relationship between crop yields and seasonal crop water use.

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Chicken Litter Good Fertilizer

Chicken litter -- a mixture of chicken manure and sawdust or other bedding material -- is a valuable fertilizer with newfound advantages over conventional fertilizers.

Some cotton farmers in the Mississippi area are switching to chicken litter and away from standard inorganic, synthetic fertilizers. Others are interested in the possible economic benefits of using chicken litter, but are reluctant to switch without the numbers to back up their decision.

A recent Agricultural Research Service study by agronomist Haile Tewolde and colleagues provides those numbers.

Farmers know that chicken litter, an organic fertilizer, is a better soil conditioner than synthetic fertilizers, but have never had a way to assign a number to the value of that benefit. But previous studies only considered the economic value of the nitrogen, phosphorus and potassium in chicken litter, compared to that in synthetic fertilizers.

In the new study, Tewolde and colleagues figured the litter's value as a soil conditioner as an extra $17 per ton of litter. They calculated this by balancing the price tag of the nutrients in litter with its resulting higher yields, a reflection of its soil conditioning benefits. They found that cotton yields peaked 12 percent higher with organic fertilizers, compared to peak yields with synthetic fertilizers. With all benefits factored in, they found that chicken litter has a value of about $78 a ton, compared to $61 a ton when figured by the traditional method.

The economic analyses also showed that farmers could further increase their profits by using less of either fertilizer than currently used for maximum yields -- which is also good news for the environment.

Source: Agricultural Research Service, USDA

• Farm Supply
• Fertilizers and Compost
• Cotton Plant, Lubbock, Panhandle, Texas