Uptake and economic value of macro- and micro-nutrient minerals in wheat residue

Authors: Adams, Curtis; Rogers, Christopher; MARSHALL, JULIET - University Of Idaho; HATZENBUEHLER, PATRICK - University Of Idaho; WALSH, OLGA - University Of Idaho; THURGOOD, GARRETT - University Of Idaho; DARI, BISWANATH - North Carolina A&t State University; LOOMIS, GRANT - University Of Idaho; Tarkalson, David

Submitted to: Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/8/2024
Publication Date: 8/15/2024
Citation: Adams, C.B., Rogers, C.W., Marshall, J., Hatzenbuehler, P., Walsh, O., Thurgood, G., Dari, B., Loomis, G., Tarkalson, D.D. 2024. Uptake and economic value of macro- and micro-nutrient minerals in wheat residue. Agronomy Journal. 14(8). https://doi.org/10.3390/agronomy14081795.
DOI: https://doi.org/10.3390/agronomy14081795

Interpretive Summary: Grain is the primary product of wheat production, but straw is another. Following grain harvest, wheat producers face the choice to retain or remove straw from the cropping system. Increasingly, producers are selling wheat straw to increase their profitability for uses such as animal bedding, mushroom production, and building material. But there are benefits to retaining straw in the cropping system, instead of harvesting and selling it. One of these benefits includes preservation and recycling of mineral nutrients contained in the straw, though the nutrient value of straw is understudied and poorly understood. Therefore, the primary objective of this research was to quantify mineral nutrient (N, P, K, Mg, Ca, S, Mn, Fe, Zn, Cu) content per unit production area (kg or g ha-1) and determine the economic value (US $ ha-1) of those nutrients in terms of fertilizer replacement costs, should the straw be harvested. Field studies were conducted across Southern Idaho in the U.S. to gather data. To make the straw mineral content data more accessible, linear functions were developed describing relationships between wheat grain yield (widely measured) and nutrient contents in straw and grain. These functions will allow users to simply estimate straw mineral contents using just grain yield information for their own systems. Economic analysis indicated that the value of four key nutrients (N, P, K, and S) contained in straw was substantial. For example, in a high-yielding wheat crop (9 Mg ha-1) the economic value of N, P, K, and S contained in the straw (not considering nutrients in grain) was approximately equal to the entire nutrient management budget to grow the crop. This means that the economic value of nutrients in straw is likely to exceed the economic gain from selling the straw. Persistent removal of nutrients from agronomic systems through straw harvest will affect soil nutrient availability in the short- and long-term, and the magnitude and timeframe of these changes will depend on the cropping system and soil. Wheat producers should consider the tradeoff between immediate gains of straw sale and the multifaceted benefits of straw retention, including savings on future nutrient costs.

Technical Abstract: Wheat (Triticum aestivum, L.) producers have the choice to retain or remove residue from the cropping system following grain harvest. Wheat residue is increasingly sold to increase operational profitability. But there are several benefits to retaining residue, including recycling of mineral nutrients contained therein, though this is understudied. Therefore, the primary objectives of this research were to evaluate factors affecting wheat residue nutrient uptake, develop simple tools to estimate nutrient amount in residue, and estimate the economic value of those nutrients. This was accomplished by analyzing a large and diverse dataset that included wheat residue biomass, residue nutrient concentrations, and grain yield. Results showed that wheat residue contained a significant amount of nutrients, but was particularly concentrated in K. Production environment had the most substantial effect on residue mineral uptake, due to site differences in yield and soil nutrient availability. To enable simple estimation of residue nutrient uptake beyond this dataset, tools are presented herein that require as little as grain yield for input. Economic analysis showed the substantial monetary value of residue nutrients. For example, in a high-yielding wheat crop (9 Mg ha-1), the replacement value of just residue N, P, K, and S was similar to the entire fertilizer budget to grow the crop (~$211 vs. $205 ha-1), not considering residue micronutrients or any nutrients in grain. In making residue management decisions, wheat producers should consider the tradeoff between immediate economic gains of residue sale and the multifaceted benefits of residue retention, including savings on future nutrient costs.