Cropping systems under water-limited conditions: effects of rotation and nitrogen management on yield, resource use efficiency, profitability, and soil properties

Sustaining agricultural productivity in water-limited regions such as the Central Great Plains requires cropping systems that balance yield, resource-use efficiency, and economic viability. This thesis integrates results from field studies conducted at different temporal scales, location and under different water-management conditions to evaluate how crop rotation diversity, cover crop integration, and nitrogen management strategies influence productivity, water-use efficiency (WUE), nitrogen-use efficiency (NUE), soil properties, and economic performance. A long-term field experiment conducted from 2014 to 2024 under limited irrigation in south-central Nebraska evaluated five corn-based rotations: continuous corn (C), corn-sorghum (C-Sg), corn-soybean (C-Sb), corn-wheat (C-W), and corn-corn-wheat (C-C-W), using glucose equivalent yield (GE), WUE, NUE, and partial net return as integrative performance metrics. Continuous corn achieved the highest system-level productivity and partial net return but exhibited lower NUE due to higher nitrogen inputs. In contrast, C-Sb achieved the highest NUE but at the expense of productivity and WUE. Corn-wheat consistently underperformed across agronomic and economic indicators. C-Sg and C-C-W, provided balanced trade-offs among yield, efficiency, and profitability, highlighting how rotation design has trade‑offs among productivity, resource‑use efficiency, and short‑term economic performance under limited irrigation. Soil responses to crop rotation were evaluated during Phase I (2015 to 2021): across rotations, total soil carbon and nitrogen stocks to 120 cm were not significantly altered, indicating that detectable changes in soil C and N pools may require longer observation periods. However, surface soil pH reflected cumulative nitrogen management history, with greater acidification in corn-intensive rotations. Mineral nitrogen patterns supported this interpretation, while other soil chemical and physical properties showed limited rotation effects. Phase II (2022 to 2024) introduced a split-plot cover crop treatment to evaluate impacts on system productivity, WUE, and NUE. Despite two years of below normal rainfall, the inclusion of cover crops did not affect system productivity (expressed as glucose equivalent yield per hectare), WUE, or NUE in any rotation, demonstrating that cover crops can be integrated into limited irrigation systems without short-term performance penalties. A complementary four year rainfed study in Kansas evaluated contrasting nitrogen management strategies in wheat. An integrated “progressive” 4R nitrogen approach (optimizing rate, timing, placement, and source) maintained grain yield while reducing nitrogen inputs and improving NUE compared with a conventional single application strategy. Soil moisture and in-season nitrate dynamics were not significantly affected. Overall, this thesis demonstrates that no single management strategy optimizes all performance metrics. While continuous monoculture systems may maximize short-term returns, diversified crop rotations, cover crop integration, and improved nitrogen management offer more resilient pathways by enhancing resource use efficiency without sacrificing productivity. These findings support the adoption of integrated, systems-based approaches to improve the sustainability of cropping systems in the water limited environments of the Central Great Plains.

Author dc:creator

• Garcia Helguera, Maria Paula

• Cover crops
• Nitrogen use efficiency
• Crop rotation
• Limited irrigation
• Soil carbon
• Water use efficiency

Language dc:language.iso

en_US

Handle dc:identifier.uri

https://hdl.handle.net/2097/47293

OAI identifier oai:identifier

oai:krex.k-state.edu:2097/47293