Baling wheat straw has become a more common practice in the past few years for many reasons, said Fabian Fernandez, University of Illinois Extension specialist in soil fertility and plant nutrition.

While the uses for wheat straw are varied, removing straw has at least one common denominator: exporting nutrients out of the field.

“Knowing how much nutrient is contained in straw is important,” Fernandez said. “It helps producers know the value of the straw, in addition to how much fertilizer is being removed, or in other words, how much fertilizer should be applied back to the field to maintain fertility levels.”

He said the most precise way to determine how much fertilizer is being removed with the straw is to obtain the weight of the bales and to extract a representative sample of the straw. Using that sample, two values must be obtained from a testing lab — moisture content to determine the dry weight of the bale and nutrient content of the sample reported on a dry basis.  

“This approach may not be practical or possible for all producers,” he added.

“If that is the case, then it is possible to estimate the value of straw by following a few simple steps. But keep in mind that this second approach is an estimate and there can be substantial variability depending upon how the straw is processed.”

The first step in the calculation is to determine how much straw is being produced. The best estimates are obtained as a function of plant height and grain yield.