Organic transition in dual‐purpose wheat systems: Agronomic performance and soil nitrogen dynamics

Abstract

AbstractThe Southern Great Plains (SGP) region of the United States is widely known for its dryland dual‐purpose winter wheat (Triticum aestivum L.) cropping systems—integrated systems that provide both livestock grazing and grain production. Few of these systems are organic, however, and no relevant research had been conducted on this topic. A large‐scale (41 ha) systems research study was conducted for 3 yr (2018–2021) to compare a transitional organic dual‐purpose wheat system with a conventional one, with system management components customized to the ecological region. Organic wheat yield was 20% lower than conventional in the first season of organic transition, but there was no yield difference by the third year. The yield improvement in the organic system may be attributed to N fixation by a legume‐based cash crop the previous winter season, exogenous nutrients from application of composted manure, and appropriate wheat cultivar selection. Because of limited moisture, relying on annual establishment of summer cover crops to fix N and deliver other ecosystem services in the organic system was not feasible in most years. Grain protein concentration (GPC) of the transitional organic wheat ranged from 91 to 103 g kg−1, below the 120 g kg−1 threshold for a food market organic price premium. More intensive N management, including in‐season application of a more available form of N that is organic approved, could be an effective strategy to increase GPC. This proof‐of‐concept study shows that organic dual‐purpose wheat systems can be a viable enterprise in the SGP, though additional research is needed to address challenges identified herein.