The LTAR Cropland Common Experiment at Platte River/High Plains Aquifer.

The Platte River/High Plains Aquifer (PR/HPA) region is characterized by cropland, pastures, and grasslands that are faced with changing climatic conditions and agricultural intensification. The PR/HPA Long-Term Agroecosystem Research (LTAR) site is located in Eastern Nebraska with the goal of improving resilience, sustainability, and profitability of agroecosystems through enhancing ecosystem services and environmental quality, developing strategies for efficient agricultural production, and mitigating and adapting to climate change. To meet this goal, a common experiment and five ancillary experiments have been developed to evaluate prevailing regional practices in grain crop production systems compared to alternative practices in rainfed and irrigated systems.

The LTAR Grazing Land Common Experiment at Platte River High Plains Aquifer.

The Long-Term Agroecosystem Research (LTAR) network of the United States Department of Agriculture (USDA) consists presently of 18 sites within the contiguous United States that are managed by the Agricultural Research Service (ARS) and its partners. The LTAR network focuses on developing national strategies for more efficient, resilient, and profitable agricultural production systems, improved environmental quality, and enhanced rural prosperity. The Platte River High Plains Aquifer (PRHPA) LTAR site is managed jointly by the University of Nebraska-Lincoln (UNL) and USDA-ARS and is one of the LTAR sites that conduct research on both integrated cropping and grazing systems.

Effect of Biomass Water Dynamics in Cosmic-Ray Neutron Sensor Observations: A Long-Term Analysis of Maize-Soybean Rotation in Nebraska.

Precise soil water content (SWC) measurement is crucial for effective water resource management. This study utilizes the Cosmic-Ray Neutron Sensor (CRNS) for area-averaged SWC measurements, emphasizing the need to consider all hydrogen sources, including time-variable plant biomass and water content. Near Mead, Nebraska, three field sites (CSP1, CSP2, and CSP3) growing a maize-soybean rotation were monitored for 5 (CSP1 and CSP2) and 13 (CSP3) years.

Evapotranspiration adjustment for irrigated maize-soybean rotation systems in Nebraska, USA.

Irrigation water requirements are commonly estimated based on the estimated crop evapotranspiration (ET) as determined by the reference evapotranspiration (ETr) and crop coefficient (K). Recent studies show that, at high evaporative demand (high ETr), K tends to decrease, creating an inverse ETr-K relationship. The focus of this long-term study is to, if at high atmosphere demand, there is the same inverse ETr-K relationship in Nebraska, USA, one of the most intensely irrigated regions in the world, and as a result, propose an adjustment to the Kc-ETr approach.

Sustainable irrigation based on co-regulation of soil water supply and atmospheric evaporative demand.

Irrigation is an important adaptation to reduce crop yield loss due to water stress from both soil water deficit (low soil moisture) and atmospheric aridity (high vapor pressure deficit, VPD). Traditionally, irrigation has primarily focused on soil water deficit. Observational evidence demonstrates that stomatal conductance is co-regulated by soil moisture and VPD from water supply and demand aspects.

Joint control of terrestrial gross primary productivity by plant phenology and physiology.

Terrestrial gross primary productivity (GPP) varies greatly over time and space. A better understanding of this variability is necessary for more accurate predictions of the future climate-carbon cycle feedback. Recent studies have suggested that variability in GPP is driven by a broad range of biotic and abiotic factors operating mainly through changes in vegetation phenology and physiological processes.

Productivity, absorbed photosynthetically active radiation, and light use efficiency in crops: implications for remote sensing of crop primary production.

Vegetation productivity metrics such as gross primary production (GPP) at the canopy scale are greatly affected by the efficiency of using absorbed radiation for photosynthesis, or light use efficiency (LUE). Thus, close investigation of the relationships between canopy GPP and photosynthetically active radiation absorbed by vegetation is the basis for quantification of LUE. We used multiyear observations over irrigated and rainfed contrasting C3 (soybean) and C4 (maize) crops having different physiology, leaf structure, and canopy architecture to establish the relationships between canopy GPP and radiation absorbed by vegetation and quantify LUE.