Precision management influences productivity and nutrients availability in dryland cropping system

Authors: Mikha, Maysoon; Mankin, Kyle; KHAN, SHAHBAZ - Colorado State University; Barnard, David

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/17/2024
Publication Date: 9/9/2024
Citation: Mikha, M.M., Mankin, K.R., Khan, S.B., Barnard, D.M. 2024. Precision management influences productivity and nutrients availability in dryland cropping system. Agronomy Journal. 116(6):3325-3343. https://doi.org/10.1002/agj2.21686.
DOI: https://doi.org/10.1002/agj2.21686

Interpretive Summary: Dryland farmers use cropping and nutrient management decisions to deal with the risk of poor weather. When these decisions are tailored to specific field conditions, it is called precision management (PM). The goal is not just to increase yields but also to minimize inputs to improve net profits. We evaluated one such PM approach in a dryland farming system. We compared an aspirational (ASP) no-till system with three crops in four years (winter wheat, corn, millet, fallow/flex) to a business-as-usual (BAU) reduced tillage system with two crops in four years (wheat, fallow). The ASP system also divided the field into three PM zones that received either low, medium, or high nitrogen (N) rates. We found that winter wheat yields were the same or larger using ASP compared to BAU even while adding a third crop every four years. Within the ASP system, wheat, corn, and millet yield increased from low- to medium- to high-PM zones in response to greater applied N, but only during years with more rain. Yield responded not only to in-season rainfall but also to rainfall distribution in the growing season. The low soil organic matter accumulation combined with nutrient removal by the harvested crops reduced soil nutrients. The more diverse and intensive ASP crop rotation with in-field nutrient management was able to maintain or improve crop yields, which should lead to increased farmer profits compared to the conventional BAU cropping system.

Technical Abstract: Precision management (PM) aims to reduce inputs while increasing land productivity and economical return and enhancing cropping system resiliency to climate change. This study evaluated how climate (precipitation) and management influenced yields and soil nutrients in a dryland agricultural system. We compared an “aspirational” (ASP) system (no-till, 4-year rotation of winter wheat [Triticum aestivum L.], corn [Zea mays L.], proso millet [Panicum miliaceum L.], and fallow/flex) to a traditional “business-as-usual” (BAU) system (reduced tillage, 2-year rotation of winter wheat and fallow: W–F). Phases of each rotation were included yearly throughout the study period (2018–2022) with three replications. The ASP system incorporated PM by dividing each ASP field into three zones (high-, medium-, and low-PM) according to prior yield and topography. Nitrogen was applied at high, medium, or low application rates within those zones. Under favorable precipitation, wheat, corn, and millet yields responded to PM treatments, with yields increasing proportional to N addition. Years with low in-season precipitation had a significant reduction in wheat and corn yields (2020 and 2022) and complete millet yield failures (2020 and 2021). Low soil organic matter accumulation (0.1%–0.5%) and a reduction in soil macro- and micronutrient status suggested that soil nutrient additions are needed to prevent soil-nutrient degradation. The ASP treatment added a third crop every 4 years and did so without significantly decreasing wheat yield following fallow. The ASP management shows promise as an alternative to BAU in the Great Plains dryland production region.