There is Value in Wheat Straw!

The value of straw is often a hotly debated question and as wheat harvest approaches it would be a good time to discuss the situation. Straw has value from both the nutrients removed and
the organic matter addition it will return to the soil. Table 4-6, Straw Nutrients, from OMAFRA the Field Crop Agronomy Guide, shows the range of nutrients that straw may contain. Straw nutrient concentration can vary greatly - straw from hard wheat varieties will generally contain less (approximately 2.75 lb/tonne or 1.25 kg/tonne) nitrogen than soft wheat straw (Falk, 2005). Potash concentration varies tremendously in straw, as potash is readily leached from straw by rainfall after maturity. The only accurate way to determine nutrient value is through an analysis.

There is added debate about whether the nitrogen component should be included in the value of straw. The carbon:nitrogen ratio of straw is quite high (80:1), which would require additional nitrogen for breakdown by soil organisms. Thus, many growers do not add nitrogen into the value calculation. Using average nutrient concentrations, straw value can be calculated using the formulas shown in Table 4-6.

Table 4 - 6. Straw Nutrients

The value of the organic matter that straw returns to the soil is much more difficult to calculate. There is no doubt that the organic matter value is extremely significant. Estimates range from at least equal value to the nutrient removal, to estimates that removal of four high-yield straw crops could reduce soil organic matter by 0.1%. This 0.1% organic matter could be capable of holding up to 4.4 cm (1.75 in.) of available water for crop growth. In dry seasons, this amount of water might result in an additional 0.24 t/ha (3.5 bu/acre) of soybeans, or 0.88 t/ha (14 bu/acre) of corn yield. While these are simply mathematical estimates of the organic matter impact, they drive home the point of just how valuable that component can be and something you should consider your straw value.