Washington State University Extension has recently published the new Straw Removal Calculator Guide on the impacts of straw removal on soil fertility. Straw removal has become a widespread practice in dryland wheat production in the inland Pacific Northwest (IPNW). While straw harvest may provide short-run economic benefits, there are also potential hidden costs associated with straw harvest. The hidden costs include the depletion of soil organic carbon and the removal of nutrients, especially base cations (e.g., K+, Ca++, and Mg++). This publication serves as a guide for our straw removal calculator designed to assist growers in calculating the hidden costs of straw removal in order to make decisions on whether or not it is appropriate to remove straw under various environments and market conditions.
The tool begins by allowing users to enter actual straw yields from their fields or they can estimate straw yield from actual or predicted grain yield. There is also an option to adjust straw yield based on wheat variety as well since different varieties can produce different harvest indices. Once these factors are established, the tool can estimate the amount of N P2O5, S, Zn, B, K2O, Ca, and Mg removed with the straw and assign a value to each. It can then estimate the amount of lime required to replace the cations removed and total cost of fertilizer to replace other macro- and micronutrients. If soil health is of interest, the tool also estimates how much residue is required to stay on-farm to maintain or increase soil organic matter over time.