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Peer Review Of Teaching: Et Theory, Deficit Irrigation And Consumptive Use, Derek M. Heeren, Saleh Taghvaeian Jun 2023

Peer Review Of Teaching: Et Theory, Deficit Irrigation And Consumptive Use, Derek M. Heeren, Saleh Taghvaeian

Department of Biological Systems Engineering: Conference Presentations and White Papers

A BSE Peer Review of Teaching was carried out for a graduate level course on Advanced Irrigation Management. This course has been offered for several years; each time improvements are made, but there is always a need for additional improvement. In particular, ET theory, deficit irrigation, and consumptive use are topics that the students struggle to grasp. These topics involve a relatively high level of math for an MS-level (800-level) Agricultural Systems Technology course, and the available materials on these topics either were not well developed or were not a good fit for this class. The primary objective was to …


Soybean Crop Coefficients Under Different Seeding Rates And Full And Limited Irrigation And Rainfed Management, Suat Irmak, Rupinder Sandhu May 2023

Soybean Crop Coefficients Under Different Seeding Rates And Full And Limited Irrigation And Rainfed Management, Suat Irmak, Rupinder Sandhu

Department of Biological Systems Engineering: Papers and Publications

The effects of soybean seeding rates on evapotranspiration (ETc) and grassand alfalfa-reference crop coefficients (Kco and Kcr) were investigated under five seeding rates (185,250, 247,000, 308,750, 370,500 and 432,250 seeds ha-1) (62, 82, 103, 124 and 144% of the recommended seeding rate of 300,000 seeds ha-1 in the experimental region) and different irrigation strategies (i.e. full irrigation treatment [FIT], limited irrigation of 75% FIT and 50% FIT and rainfed treatment). Kco and Kcr values were developed for each soybean growth stage. The seasonal ETc ranged from 460 mm for …


Toward Automated Irrigation Management With Integrated Crop Water Stress Index And Spatial Soil Water Balance, Sandeep Bhatti, Derek M. Heeren, Susan A. O’Shaughnessy, Christopher M. U. Neale, Jacob Larue, Steve Melvin, Eric Wilkening, Geng Bai May 2023

Toward Automated Irrigation Management With Integrated Crop Water Stress Index And Spatial Soil Water Balance, Sandeep Bhatti, Derek M. Heeren, Susan A. O’Shaughnessy, Christopher M. U. Neale, Jacob Larue, Steve Melvin, Eric Wilkening, Geng Bai

Department of Biological Systems Engineering: Papers and Publications

Decision support systems intended for precision irrigation aim at reducing irrigation applications while optimizing crop yield to achieve maximum crop water productivity (CWP). These systems incorporate on-site sensor data, remote sensing inputs, and advanced algorithms with spatial and temporal characteristics to compute precise crop water needs. The availability of variable rate irrigation (VRI) systems enables irrigation applications at a sub-field scale. The combination of an appropriate VRI system along with a precise decision support system would be ideal for improved CWP. The objective of this study was to compare and evaluate two decision support systems in terms of seasonal applied …


Toward Automated Irrigation Management With Integrated Crop Water Stress Index And Spatial Soil Water Balance, Sandeep Bhatti, Derek M. Heeren, Susan A. O’Shaughnessy, Christopher M. U. Neale, Jacob Larue, Steve Melvin, Eric Wilkening, Geng Bai May 2023

Toward Automated Irrigation Management With Integrated Crop Water Stress Index And Spatial Soil Water Balance, Sandeep Bhatti, Derek M. Heeren, Susan A. O’Shaughnessy, Christopher M. U. Neale, Jacob Larue, Steve Melvin, Eric Wilkening, Geng Bai

Department of Biological Systems Engineering: Papers and Publications

Decision support systems intended for precision irrigation aim at reducing irrigation applications while optimizing crop yield to achieve maximum crop water productivity (CWP). These systems incorporate on-site sensor data, remote sensing inputs, and advanced algorithms with spatial and temporal characteristics to compute precise crop water needs. The availability of variable rate irrigation (VRI) systems enables irrigation applications at a sub-field scale. The combination of an appropriate VRI system along with a precise decision support system would be ideal for improved CWP. The objective of this study was to compare and evaluate two decision support systems in terms of seasonal applied …


The Effect Of Relative Humidity On Eddy Covariance Latent Heat Flux Measurements And Its Implication For Partitioning Into Transpiration And Evaporation, Weijie Zhang, Martin Jung, Mirco Migliavacca, Rafael Poyatos, Diego G. Miralles, Tarek S. El-Madany, Marta Galvagno, Arnaud Carrara, Nicola Arriga, Andreas Ibrom, Ivan Mammarella, Dario Papale, Jamie R. Cleverly, Michael Liddell, Georg Wohlfahrt, Christian Markwitz, Matthias Mauder, Eugenie Paul-Limoges, Marius Schmidt, Sebastian Wolf, Christian Brümmer, M. Altaf Arain, Silvano Fares, Tomomichi Kato, Jonas Ardö, Walter Oechel, Chad Hanson, Mika Korkiakoski, Sébastien Biraud, Rainer Steinbrecher, Dave Billesbach, Leonardo Montagnani, William Woodgate, Changliang Shao, Nuno Carvalhais, Markus Reichstein, Jacob A. Nelson Mar 2023

The Effect Of Relative Humidity On Eddy Covariance Latent Heat Flux Measurements And Its Implication For Partitioning Into Transpiration And Evaporation, Weijie Zhang, Martin Jung, Mirco Migliavacca, Rafael Poyatos, Diego G. Miralles, Tarek S. El-Madany, Marta Galvagno, Arnaud Carrara, Nicola Arriga, Andreas Ibrom, Ivan Mammarella, Dario Papale, Jamie R. Cleverly, Michael Liddell, Georg Wohlfahrt, Christian Markwitz, Matthias Mauder, Eugenie Paul-Limoges, Marius Schmidt, Sebastian Wolf, Christian Brümmer, M. Altaf Arain, Silvano Fares, Tomomichi Kato, Jonas Ardö, Walter Oechel, Chad Hanson, Mika Korkiakoski, Sébastien Biraud, Rainer Steinbrecher, Dave Billesbach, Leonardo Montagnani, William Woodgate, Changliang Shao, Nuno Carvalhais, Markus Reichstein, Jacob A. Nelson

Department of Biological Systems Engineering: Papers and Publications

While the eddy covariance (EC) technique is a well-established method for measuring water fluxes (i.e., evaporation or 'evapotranspiration’, ET), the measurement is susceptible to many uncertainties. One such issue is the potential underestimation of ET when relative humidity (RH) is high (>70%), due to low-pass filtering with some EC systems. Yet, this underestimation for different types of EC systems (e.g. open-path or closed-path sensors) has not been characterized for synthesis datasets such as the widely used FLUXNET2015 dataset. Here, we assess the RH-associated underestimation of latent heat fluxes (LE, or ET) from different EC systems for 163 sites in …


The Combined Impact Of Redcedar Encroachment And Climate Change On Water Resources In The Nebraska Sand Hills, Yaser Kishawi, Aaron R. Mittelstet, Zablon Adane, Nawaraj Shrestha, Paolo Nasta Dec 2022

The Combined Impact Of Redcedar Encroachment And Climate Change On Water Resources In The Nebraska Sand Hills, Yaser Kishawi, Aaron R. Mittelstet, Zablon Adane, Nawaraj Shrestha, Paolo Nasta

Department of Biological Systems Engineering: Papers and Publications

The Nebraska Sand Hills (NSH) is considered a major recharge zone for the High Plains Aquifer in the central United States. The uncontrolled expansion of the eastern redcedar (Juniperus Virginiana) under climate warming is posing threats to surface water and groundwater resources. The combined impact of land use and climate change on the water balance in the Upper Middle Loup River watershed (4,954 km2) in the NSH was evaluated by simulating different combination of model scenarios using the Soil Water Assessment Tool (SWAT) model. A total of 222 climate models were ranked according to the aridity …


Dynamics Of Crop Evapotranspiration Of Four Major Crops On A Large Commercial Farm: Case Of The Navajo Agricultural Products Industry, New Mexico, Usa, Koffi Djaman, Komlan Koudahe, Ali T. Mohammed Oct 2022

Dynamics Of Crop Evapotranspiration Of Four Major Crops On A Large Commercial Farm: Case Of The Navajo Agricultural Products Industry, New Mexico, Usa, Koffi Djaman, Komlan Koudahe, Ali T. Mohammed

Department of Biological Systems Engineering: Papers and Publications

Crop evapotranspiration (ETa) is the main source of water loss in farms and watersheds, and with its effects felt at a regional scale, it calls for irrigation professionals and water resource managers to accurately assess water requirements to meet crop water use. On a multi-crop commercial farm, different factors affect cropland allocation, among which crop evapotranspiration is one of the most important factors regarding the seasonally or annually available water resources for irrigation in combination with the in-season effective precipitation. The objective of the present study was to estimate crop evapotranspiration for four major crops grown on the Navajo Agricultural …


Crop Response To Thermal Stress Without Yield Loss In Irrigated Maize And Soybean In Nebraska, Sandeep Bhatti, Derek M. Heeren, Steven R. Evett, Susan A. O'Shaughnessy, Daran Rudnick, Trenton E. Franz, Yufeng Ge, Christopher M.U. Neale Sep 2022

Crop Response To Thermal Stress Without Yield Loss In Irrigated Maize And Soybean In Nebraska, Sandeep Bhatti, Derek M. Heeren, Steven R. Evett, Susan A. O'Shaughnessy, Daran Rudnick, Trenton E. Franz, Yufeng Ge, Christopher M.U. Neale

Department of Biological Systems Engineering: Papers and Publications

Thermal sensing provides rapid and accurate estimation of crop water stress through canopy temperature data. Canopy temperature is highly dependent on the transpiration rate of the leaves. It is usually assumed that any reduction in crop evapotranspiration (ET) leads to crop yield loss. As a result, an increase in canopy temperature due to a decrease in crop ET would indicate crop yield loss. This research evaluated the hypothesis that crop water stress could be detected using canopy temperature measurements (increased leaf temperature) from infrared thermometers (IRTs) before incurring crop yield loss. This would be possible in a narrow range when …


Real-Time Irrigation Scheduling Of Maize Using Degrees Above Non-Stressed (Dans) Index In Semi-Arid Environment, Hope Njuki Nakabuye, Daran Rudnick, Kendall C. Dejonge, Tsz Him Lo, Derek M. Heeren, Xin Qiao, Trenton E. Franz, Abia Katimbo, Jiaming Duan Sep 2022

Real-Time Irrigation Scheduling Of Maize Using Degrees Above Non-Stressed (Dans) Index In Semi-Arid Environment, Hope Njuki Nakabuye, Daran Rudnick, Kendall C. Dejonge, Tsz Him Lo, Derek M. Heeren, Xin Qiao, Trenton E. Franz, Abia Katimbo, Jiaming Duan

Department of Biological Systems Engineering: Papers and Publications

Irrigation scheduling methods have been used to determine the timing and amount of water applied to crops. Scheduling techniques can include measurement of soil water content, quantification of crop water use, and monitoring of crop physiological response to water stress. The aim of this study was to evaluate the performance of a simplified crop canopy temperature measurement (CTM) method as Irrigation Principles. Soil and Water Conservation Engineera technique to schedule irrigation for maize. Specifically, the Degrees Above Non-Stressed (DANS) index, which suggests water stress when canopy temperature exceeds the non-stressed canopy temperature (Tcns), was determined by estimating T …


Evaluating Evapotranspiration Values In Rwanda Using The Fao-56 Pm, Turc, And Hargreaves-Samani Equations, Elizabeth Uwase Apr 2021

Evaluating Evapotranspiration Values In Rwanda Using The Fao-56 Pm, Turc, And Hargreaves-Samani Equations, Elizabeth Uwase

Department of Biological Systems Engineering: Dissertations and Theses

Evapotranspiration (ET) is an important component of the hydrologic cycle and involves exchange of water between the surrounding water bodies, soil, crop surfaces, and the atmosphere. Therefore, this research was aimed at determining ET and its trend across Rwanda using climatic data measured at five sites. Equations were used to calculate ET using extra-terrestrial radiations, solar radiations, evapotranspiration using the FAO-56 guidelines - Turc method (1961) and Hargreaves-Samani (HS) method (1983). The obtained data from the weather stations were analyzed using the two methods and graphs were plotted for visualization. The average monthly reference evapotranspiration for both equations ranges from …


Site-Specific Irrigation Management In A Sub-Humid Climate Using A Spatial Evapotranspiration Model With Satellite And Airborne Imagery, Sandeep Bhatti, Derek M. Heeren, J. Burdette Barker, Christopher M. U. Neale, Wayne Woldt, Mitchell S. Maguire, Daran Rudnick Jan 2020

Site-Specific Irrigation Management In A Sub-Humid Climate Using A Spatial Evapotranspiration Model With Satellite And Airborne Imagery, Sandeep Bhatti, Derek M. Heeren, J. Burdette Barker, Christopher M. U. Neale, Wayne Woldt, Mitchell S. Maguire, Daran Rudnick

Department of Biological Systems Engineering: Papers and Publications

Variable Rate Irrigation (VRI) considers spatial variability in soil and plant characteristics to optimize irrigation management in agricultural fields. The advent of unmanned aircraft systems (UAS) creates an opportunity to utilize high-resolution (spatial and temporal) imagery into irrigation management due to decreasing costs, ease of operation, and reduction of regulatory constraints. This research aimed to evaluate the use of UAS data for VRI, and to quantify the potential of VRI in terms of relative crop and water response. Irrigation treatments were: (1) VRI using Landsat imagery (VRI-L), (2) VRI using UAS imagery (VRI-U), (3) uniform (U), and (4) rainfed (R). …


Actual Evapotranspiration And Crop Coefficients Of Irrigated Lowland Rice (Oryza Sativa L.) Under Semiarid Climate, Koffi Djaman, Daran R. Rudnick, Yonnelle D. Moukoumbi, Abdoulaye Sow, Suat Irmak Jan 2019

Actual Evapotranspiration And Crop Coefficients Of Irrigated Lowland Rice (Oryza Sativa L.) Under Semiarid Climate, Koffi Djaman, Daran R. Rudnick, Yonnelle D. Moukoumbi, Abdoulaye Sow, Suat Irmak

Department of Biological Systems Engineering: Papers and Publications

Lowland irrigated rice is the predominant crop produced in the Senegal River Valley characterized by very low annual rainfall, high temperatures, and low relative humidity. The Senegal River is shared by Senegal, Mali, Mauritania, and Guinea, and serves as the main source of irrigation water for the adopted double rice cropping system. Developing appropriate resource management strategies might be the key factor for the sustainability of rice production in the region. This study aims to estimate rice seasonal evapotranspiration (ETa), irrigation water requirement, and to develop rice growth stage specific crop coefficients (Kc) to improve rice water productivity. Field experiments …


Variable Rate Irrigation Using A Spatial Evapotranspiration Model With Remote Sensing Imagery And Soil Water Content Measurements, Sandeep Bhatti Dec 2018

Variable Rate Irrigation Using A Spatial Evapotranspiration Model With Remote Sensing Imagery And Soil Water Content Measurements, Sandeep Bhatti

Department of Biological Systems Engineering: Dissertations and Theses

Variable rate irrigation may help in intensification of agriculture by producing more yield per unit inputs. Real time spatial information about water balance components is important for designing VRI prescription maps. This work involved use of a spatial evapotranspiration model for studying spatial variability in an agricultural field at the Eastern Nebraska Research and Extension Center near Mead, Nebraska. Imagery from unmanned aerial systems and Landsat were used as input for the spatial evapotranspiration model. Other inputs into the model were soil water content measurements from neutron probes, weather data, crop data, previous irrigation prescriptions, and soil properties for the …


Evaluation Of A Hybrid Reflectance-Based Crop Coefficient And Energy Balance Evapotranspiration Model For Irrigation Management, J. Burdette Barker, Christopher M. U. Neale, Derek M. Heeren, Andrew E. Suyker Apr 2018

Evaluation Of A Hybrid Reflectance-Based Crop Coefficient And Energy Balance Evapotranspiration Model For Irrigation Management, J. Burdette Barker, Christopher M. U. Neale, Derek M. Heeren, Andrew E. Suyker

Department of Biological Systems Engineering: Papers and Publications

Accurate generation of spatial soil water maps is useful for many types of irrigation management. A hybrid remote sensing evapotranspiration (ET) model combining reflectance-based basal crop coefficients (Kcbrf) and a two-source energy balance (TSEB) model was modified and validated for use in real-time irrigation management. We modeled spatial ET for maize and soybean fields in eastern Nebraska for the 2011-2013 growing seasons. We used Landsat 5, 7, and 8 imagery as remote sensing inputs. In the TSEB, we used the Priestly-Taylor (PT) approximation for canopy latent heat flux, as in the original model formulations. We also used the …


Evaluation Of Variable Rate Irrigation Using A Remote-Sensing-Based Model, John Burdette Barker, Derek M. Heeren, Christopher M.U. Neale, Daran Rudnick Jan 2018

Evaluation Of Variable Rate Irrigation Using A Remote-Sensing-Based Model, John Burdette Barker, Derek M. Heeren, Christopher M.U. Neale, Daran Rudnick

Department of Biological Systems Engineering: Papers and Publications

Improvements in soil water balance modeling can be beneficial for optimizing irrigation management to account for spatial variability in soil properties and evapotranspiration (ET). A remote-sensing-based ET and water balance model was tested for irrigation management in an experiment at two University of Nebraska-Lincoln research sites located near Mead and Brule, Nebraska. Both fields included a center pivot equipped with variable rate irrigation (VRI). The study included maize in 2015 and 2016 and soybean in 2016 at Mead, and maize in 2016 at Brule, for a total of 210 plot-years. Four irrigation treatments were applied at Mead, including: VRI based …


Crop Evapotranspiration, Irrigationwater Requirement And Water Productivity Of Maize From Meteorological Data Under Semiarid Climate, Koffi Djaman, Michael O'Neill, Curtis K. Owen, Daniel Smeal, Komlan Koudahe, Margaret West, Samuel Allen, Kevin Lombard, Suat Irmak Jan 2018

Crop Evapotranspiration, Irrigationwater Requirement And Water Productivity Of Maize From Meteorological Data Under Semiarid Climate, Koffi Djaman, Michael O'Neill, Curtis K. Owen, Daniel Smeal, Komlan Koudahe, Margaret West, Samuel Allen, Kevin Lombard, Suat Irmak

Department of Biological Systems Engineering: Papers and Publications

Under the semiarid climate of the Southwest United States, accurate estimation of crop water use is important for water management and planning under conservation agriculture. The objectives of this study were to estimate maize water use and water productivity in the Four Corners region of New Mexico. Maize was grown under full irrigation during the 2011, 2012, 2013, 2014 and 2017 seasons at the Agricultural Science Center at Farmington (NM). Seasonal amounts of applied irrigation varied from 576.6 to 1051.6 mm and averaged 837.7 mm and the total water supply varied from 693.4 to 1140.5 mm. Maize actual evapotranspiration was …


Trend Analysis In Rainfall, Reference Evapotranspiration And Aridity Index In Southern Senegal: Adaptation To The Vulnerability Of Rainfed Rice Cultivation To Climate Change, Komlan Koudahe, Koffi Djaman, Ansoumana Bodian, Suat Irkmak, Mamadou Sall, Lamine Diop, Alpha B. Balde, Daran Rudnick Jan 2017

Trend Analysis In Rainfall, Reference Evapotranspiration And Aridity Index In Southern Senegal: Adaptation To The Vulnerability Of Rainfed Rice Cultivation To Climate Change, Komlan Koudahe, Koffi Djaman, Ansoumana Bodian, Suat Irkmak, Mamadou Sall, Lamine Diop, Alpha B. Balde, Daran Rudnick

Department of Biological Systems Engineering: Papers and Publications

Rainfall and evapotranspiration are two vital elements for food production under rainfed agriculture. This study aims at investigating the combined changes in these variables in the form of aridly index in the southern Senegal. The temporal trends in annual and monthly (from May to October) aridity index, rainfall and evapotranspiration are examined and adaptation strategies to the vulnerability of rainfed rice cultivation to the changes are developed. The results show a significant decreasing trend in annual rainfall at all study locations for the period 1922-2015. When analyzing the trends in sub-periods, there are two clear patterns in the annual rainfall …


Spatial And Temporal Changes In Maize And Soybean Grain Yield, Precipitation Use Efficiency, And Crop Water Productivity In The U.S. Great Plains, Meetpal S. Kukal, S. Irmak Jan 2017

Spatial And Temporal Changes In Maize And Soybean Grain Yield, Precipitation Use Efficiency, And Crop Water Productivity In The U.S. Great Plains, Meetpal S. Kukal, S. Irmak

Department of Biological Systems Engineering: Papers and Publications

Sustainable agricultural utilization of the limited water resources demands improvements in understanding the changes in crop water productivity (CWP) in space and time, which is often presented as a potential solution to relieve the growing pressure on fresh water resources. In addition, crop yield needs to be studied in relation to precipitation received annually and during the growing season for its contribution to reduce irrigation water requirements, which is quantified through precipitation use efficiency (PUE). Hence, systematic quantifications, mapping, and analyses of large-scale CWP and PUE levels are needed. This study aims to quantify long-term (1982-2013) information on grain yield, …


Agroecosystem And Ecosystem Resiliency To Extreme Hydrometeorological And Climate Events, Katherine M. Werner May 2016

Agroecosystem And Ecosystem Resiliency To Extreme Hydrometeorological And Climate Events, Katherine M. Werner

Department of Biological Systems Engineering: Dissertations and Theses

The purpose of this study was to understand how a large-scale representation of agroecosystems and ecosystems respond to extreme hydrometeorological and climate extreme events (EHCE) within the Platte River Basin. The ability for agroecosystems and ecosystems to adapt to a changing and variable climate is vital for global water, energy, and food security. Two model experiments were performed, the first with a time span from 2000 to 2013 in which a dynamic leaf area index (LAI) MODIS15A2 product was implemented. The second experiment ran from 1950 through 2013 used a climatological fixed seasonal cycle calculated as the average from the …


Long-Term Patterns Of Air Temperatures, Daily Temperature Range, Precipitation, Grass-Reference Evapotranspiration And Aridity Index In The Usa Great Plains: Part I. Spatial Trends, Meetpal S. Kukal, Suat Irmak Jan 2016

Long-Term Patterns Of Air Temperatures, Daily Temperature Range, Precipitation, Grass-Reference Evapotranspiration And Aridity Index In The Usa Great Plains: Part I. Spatial Trends, Meetpal S. Kukal, Suat Irmak

Department of Biological Systems Engineering: Papers and Publications

Due to their substantial spatio-temporal behavior, long-term quantification and analyses of important hydrological variables are essential for practical applications in water resources planning, evaluating the water use of agricultural crop production and quantifying crop evapotranspiration patterns and irrigation management vs. hydrologic balance relationships. Observed data at over 800 sites across the Great Plains of USA, comprising of 9 states and 2,307,410 km2 of surface area, which is about 30% of the terrestrial area of the USA, were used to quantify and map large-scale and long-term (1968-2013) spatial trends of air temperatures, daily temperature range (DTR), precipitation, grass-reference evapotranspiration (ET …


Evaluation Of A Hybrid Remote Sensing Evapotranspiration Model For Variable Rate Irrigation Management, J. Burdette Barker, Christopher M. U. Neale, Derek M. Heeren Nov 2015

Evaluation Of A Hybrid Remote Sensing Evapotranspiration Model For Variable Rate Irrigation Management, J. Burdette Barker, Christopher M. U. Neale, Derek M. Heeren

Department of Biological Systems Engineering: Papers and Publications

Accurate generation of spatial irrigation prescriptions is essential for implementation and evaluation of variable rate irrigation (VRI) technology. A hybrid remote sensing evapotranspiration (ET) model was evaluated for use in developing irrigation prescriptions for a VRI center pivot. The model is a combination of a two-source energy balance model and a reflectance based crop coefficient water balance model. Spatial ET and soil water depletion were modeled for a 10 km2 area consisting of rainfed and irrigated maize fields in eastern Nebraska for 2013. Multispectral images from Landsat 8 Operational Land Imager and Thermal Infrared Sensor were used as model …


Vulnerability Of Crops And Native Grasses To Summer Drying In The U.S. Southern Great Plains, Naama Raz-Yaseef, Dave P. Billesbach, Marc L. Fischer, Sebastien C. Biraud, Stacey A. Gunter, James A. Bradford, Margaret S. Torn Jan 2015

Vulnerability Of Crops And Native Grasses To Summer Drying In The U.S. Southern Great Plains, Naama Raz-Yaseef, Dave P. Billesbach, Marc L. Fischer, Sebastien C. Biraud, Stacey A. Gunter, James A. Bradford, Margaret S. Torn

Department of Biological Systems Engineering: Papers and Publications

The Southern Great Plains are characterized by a fine-scale mixture of different land-cover types, predominantly winter-wheat and grazed pasture, with relatively small areas of other crops, native prairie, and switchgrass. Recent droughts and predictions of increased drought in the Southern Great Plains, especially during the summer months, raise concern for these ecosystems. We measured ecosystem carbon and water fluxes with eddy-covariance systems over cultivated cropland for 10 years, and over lightly grazed prairie and new switchgrass fields for 2 years each. Growing-season precipitation showed the strongest control over net carbon uptake for all ecosystems, but with a variable effect: grasses …


Surface Energy Balance, Evapotranspiration, And Surface Coefficients During Non-Growing Season In A Maize-Soybean Cropping System, Lameck O. Odhiambo, Suat Irmak Jan 2015

Surface Energy Balance, Evapotranspiration, And Surface Coefficients During Non-Growing Season In A Maize-Soybean Cropping System, Lameck O. Odhiambo, Suat Irmak

Department of Biological Systems Engineering: Papers and Publications

Surface energy balance components, including actual evapotranspiration (ET), were measured in a reducedtill maize-soybean field in south central Nebraska during three consecutive non-growing seasons (2006/2007, 2007/2008, and 2008/2009). The relative fractions of the energy balance components were compared across the non-growing seasons, and surface coefficients (Kc) were determined as a ratio of measured ET to estimated alfalfa (ETr) and grass (ETo) reference ET (ETref). The non-growing season following a maize crop had 25% to 35% more field surface covered with crop residue as compared to the non-growing seasons following soybean crops. Net …


Integrating Remote Sensing Of Evapotranspiration With Applied Water To Target Potential Water Conservation Projects In Watersheds, Daniel J. Howes, Stuart Styles Nov 2014

Integrating Remote Sensing Of Evapotranspiration With Applied Water To Target Potential Water Conservation Projects In Watersheds, Daniel J. Howes, Stuart Styles

BioResource and Agricultural Engineering

The overall purpose of the project is to develop a methodology for watershed managers to successfully target and release recommendations to growers that could benefit from improved on-farm irrigation management. Initially it was thought that the methodology could rely on remote sensing of actual crop evapotranspiration, effective rainfall estimates, and water application information (pumped volumes and surface water deliveries) to simply evaluate if fields and farms that applied significantly more water than plants needed could be identified. However, it became clear that, in this region specifically, additional information on water quality, crop sensitivity to salinity, and an assumed good irrigation …


Evaluating Net Groundwater Use From Remotely Sensed Evapotranspiration And Water Delivery Information, Daniel J. Howes, Charles M. Burt, Lucas Hoffman Nov 2014

Evaluating Net Groundwater Use From Remotely Sensed Evapotranspiration And Water Delivery Information, Daniel J. Howes, Charles M. Burt, Lucas Hoffman

BioResource and Agricultural Engineering

A detailed, comprehensive, and accurate identification of groundwater aquifer properties will likely never be fully achieved because of the high degree of variability and costs that testing involves. Furthermore, accurate estimates of boundary conditions are essential for groundwater modeling so that investigations of improved management scenarios can be conducted. The lack of key input values at the ground surface boundary limits the ability to accurately assess aquifer dynamics. Of major importance is actual evapotranspiration (water consumption or the loss of water to the atmosphere through transpiration and evaporation). The Irrigation Training and Research Center (ITRC) modified remotely sensed satellite imagery …


Soybean Yield, Evapotranspiration, Water Productivity, And Soil Water Extraction Response To Subsurface Drip Irrigation And Fertigation, Suat Irmak, James E. Specht, Lameck O. Odhiambo, J. M. Rees, K. G. Cassman Jan 2014

Soybean Yield, Evapotranspiration, Water Productivity, And Soil Water Extraction Response To Subsurface Drip Irrigation And Fertigation, Suat Irmak, James E. Specht, Lameck O. Odhiambo, J. M. Rees, K. G. Cassman

Department of Biological Systems Engineering: Papers and Publications

Soybean [Glycine max (L.) Merr.] yield, irrigation water use efficiency (IWUE), crop water use efficiency (CWUE), evapotranspiration water use efficiency (ETWUE), and soil water extraction response to eleven treatments of full, limited, or delayed irrigation versus a rainfed control were investigated using a subsurface drip irrigation (SDI) system at a research site in south-central Nebraska. The SDI system laterals were 0.40 m deep in every other row middle of 0.76 m spaced plant rows. Actual evapotranspiration (ETa) was quantified in all treatments and used to schedule irrigation events on a 100% ETa replacement basis in all but …


Grass Referenced Based Vegetation Coefficients For Estimating Evapostranspiration For A Variery Of Natural Vegetation, Daniel J. Howes, Mariana Pasquet Oct 2013

Grass Referenced Based Vegetation Coefficients For Estimating Evapostranspiration For A Variery Of Natural Vegetation, Daniel J. Howes, Mariana Pasquet

BioResource and Agricultural Engineering

In arid and semi-arid regions, evapotranspiration from vegetation results in the significant utilization of available water. Accurate estimates of evapotranspiration are required for surface and subsurface hydrologic evaluations as well as irrigation district water balance studies. A significant amount of transferable information exists for irrigated agricultural crops through past and current research in the form of grass or alfalfa reference based crop coefficients (Kc) and basal crop coefficients (Kcb). However, transferable evapotranspiration information on natural vegetation is limited. Much of the work was conducted in the early to mid-1900’s and is presented as actual evapotranspiration from the vegetation at the …


Maize Evapotranspiration, Yield Production Functions, Biomass, Grain Yield, Harvest Index, And Yield Response Factors Under Full And Limited Irrigation, Koffi Djaman, Suat Irmak, William R. Rathje, Derrel L. Martin, Dean E. Eisenhauer Jan 2013

Maize Evapotranspiration, Yield Production Functions, Biomass, Grain Yield, Harvest Index, And Yield Response Factors Under Full And Limited Irrigation, Koffi Djaman, Suat Irmak, William R. Rathje, Derrel L. Martin, Dean E. Eisenhauer

Department of Biological Systems Engineering: Papers and Publications

South-central Nebraska is one of the most extensively irrigated areas in the U.S., with over 65,000 active irrigation wells, and maize is the major agronomical crop produced. Maize production in this region requires supplementary irrigation for maximum productivity. Effective on-farm implementation of full and limited irrigation practices for potential improvements of crop productivity requires knowledge of locally developed crop yield response to water functions. In this study, the effects of full and limited irrigation practices on maize (Zea mays L.) plant height, leaf area index (LAI), grain yield and biomass production, actual crop evapotranspiration (ETa), yield production functions, …


Development And Evaluation Of Ordinary Least Squares Regression Models For Predicting Irrigated And Rainfed Maize And Soybean Yields, Vivek Sharma, Daran R. Rudnick, Suat Irmak Jan 2013

Development And Evaluation Of Ordinary Least Squares Regression Models For Predicting Irrigated And Rainfed Maize And Soybean Yields, Vivek Sharma, Daran R. Rudnick, Suat Irmak

Department of Biological Systems Engineering: Papers and Publications

Understanding the relationships between climatic variables and soil physical and chemical properties with crop yields on large scales is critical for evaluating crop productivity to make better assessments of local and regional food security, policy, land and water resource allocation, and management decisions. In this study, ordinary least squares(OLS) regression models were developed to predict irrigated and rainfed maize and soybean yields at the county level as a

function of explanatory variables [precipitation (P), actual crop evapotranspiration (ETa), organic matter content (OMC), cation exchange capacity (CEC), clay content (CC), and available soil water capacity (ASW)] of the dominant soil type …


Evapotranspiration And Surface Energy Balance Of A Common Reed-Dominated Riparian System In The Platte River Basin, Central Nebraska, Isa Kabenge, Suat Irmak, John E. Gilley, George E. Meyer, Stevan Z. Knezevic, Timothy J. Arkebauer, Duane Woodward, Milton Moravek Jan 2013

Evapotranspiration And Surface Energy Balance Of A Common Reed-Dominated Riparian System In The Platte River Basin, Central Nebraska, Isa Kabenge, Suat Irmak, John E. Gilley, George E. Meyer, Stevan Z. Knezevic, Timothy J. Arkebauer, Duane Woodward, Milton Moravek

Department of Biological Systems Engineering: Papers and Publications

Quantifying actual evapotranspiration (ETa) of riparian zones is important for more robust water balance analyses that will enable better planning, managing, and allocating of water resources as well as developing strategies to protect delicate riparian ecosystem functions. The ETa, sensible heat flux (H), net radiation (Rn), soil heat flux (G), meteorological variables (air temperature, Ta; incoming shortwave radiation, Rs; wind speed, u3; relative humidity, RH; vapor pressure deficit, VPD; precipitation, etc.), and albedo were measured on an hourly time step, and leaf area index (LAI) and plant height …