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Articles 1 - 13 of 13
Full-Text Articles in Physical Sciences and Mathematics
Maize Leaf Appearance Rates: A Synthesis From The United States Corn Belt, Caio L. Dos Santos, Lori J. Abendroth, Jeffrey A. Coulter, Emerson D. Nafziger, Andrew E. Suyker, Jianming Yu, Patrick S. Schnable, Sotirios V. Archontoulis
Maize Leaf Appearance Rates: A Synthesis From The United States Corn Belt, Caio L. Dos Santos, Lori J. Abendroth, Jeffrey A. Coulter, Emerson D. Nafziger, Andrew E. Suyker, Jianming Yu, Patrick S. Schnable, Sotirios V. Archontoulis
School of Natural Resources: Faculty Publications
The relationship between collared leaf number and growing degree days (GDD) is crucial for predicting maize phenology. Biophysical crop models convert GDD accumulation to leaf numbers by using a constant parameter termed phyllochron (°C-day leaf−1) or leaf appearance rate (LAR; leaf oC-day−1). However, such important parameter values are rarely estimated for modern maize hybrids. To fill this gap, we sourced and analyzed experimental datasets from the United States Corn Belt with the objective to (i) determine phyllochron values for two types of models: linear (1-parameter) and bilinear (3-parameters; phase I and II phyllochron, and transition …
Two Source Energy Balance Maize Evapotranspiration Estimates Using Close-Canopy Mobile Infrared Sensors And Upscaling Methods Under Variable Water Stress Conditions, A. Katimbo, D. Rudnick, W. Liang, K. Dejonge, T. Lo, T. Franz, Y. Ge, X. Qiao, H. Kabenge, H. N. Nakabuye
Two Source Energy Balance Maize Evapotranspiration Estimates Using Close-Canopy Mobile Infrared Sensors And Upscaling Methods Under Variable Water Stress Conditions, A. Katimbo, D. Rudnick, W. Liang, K. Dejonge, T. Lo, T. Franz, Y. Ge, X. Qiao, H. Kabenge, H. N. Nakabuye
School of Natural Resources: Faculty Publications
No abstract provided.
Validation Of A Process-Based Agro-Ecosystem Model (Agro-Ibis) For Maize In Xinjiang, Northwest China, Tureniguli Amuti, Geping Luo, Gang Yin, Qi Hu, Elizabeth A. Walter-Shea
Validation Of A Process-Based Agro-Ecosystem Model (Agro-Ibis) For Maize In Xinjiang, Northwest China, Tureniguli Amuti, Geping Luo, Gang Yin, Qi Hu, Elizabeth A. Walter-Shea
School of Natural Resources: Faculty Publications
Agricultural oasis expansion and intensive management practices have occurred in arid and semiarid regions of China during the last few decades. Accordingly, regional carbon and water budgets have been profoundly impacted by agroecosystems in these regions. Therefore, study on the methods used to accurately estimate energy, water, and carbon exchanges is becoming increasingly important. Process-based models can represent the complex processes between land and atmosphere among agricultural ecosystems. However, before the models can be applied they must be validated under different environmental and climatic conditions. In this study, a process-based agricultural ecosystem model (Agro-IBIS) was validated for maize crops using …
Feasibility Analysis Of Using Inverse Modeling For Estimating Field-Scale Evapotranspiration In Maize And Soybean Fields From Soil Water Content Monitoring Networks, Foad Foolad, Trenton E. Franz, Tiejun Wang, Justin Gibson, Ayse Kilic, Richard Allen, Andrew Suyker
Feasibility Analysis Of Using Inverse Modeling For Estimating Field-Scale Evapotranspiration In Maize And Soybean Fields From Soil Water Content Monitoring Networks, Foad Foolad, Trenton E. Franz, Tiejun Wang, Justin Gibson, Ayse Kilic, Richard Allen, Andrew Suyker
School of Natural Resources: Faculty Publications
No abstract provided.
Quantification And Mapping Of Surface Residue Cover For Maize And Soybean Fields In South Central Nebraska, Vivek Sharma, Suat Irmak, Ayse Kilic, Vasudha Sharma, John E. Gilley, George Meyer, Stevan Z. Knezevic, D. B. Marx
Quantification And Mapping Of Surface Residue Cover For Maize And Soybean Fields In South Central Nebraska, Vivek Sharma, Suat Irmak, Ayse Kilic, Vasudha Sharma, John E. Gilley, George Meyer, Stevan Z. Knezevic, D. B. Marx
School of Natural Resources: Faculty Publications
The area cultivated under conservation tillage practices such as no-till and minimal tillage has recently increased in Midwestern states, including Nebraska. This increase, consequently, resulted in changes in some of the impacts of cropping systems on soil, such as enhancing soil and water quality, improving soil structure and infiltration, increasing water use efficiency, and promoting carbon sequestration. However, there are no methods currently available to quantify the percent crop residue cover (CRC) and the area under conservation tillage for maize and soybean at large scales on a continuous basis. This research used Landsat-7 (ETM+) and Landsat-8 (OLI) satellite data to …
Informative Spectral Bands For Remote Green Lai Estimation In C3 And C4 Crops, Oz Kira, Anthony L. Nguy-Robertson, Timothy J. Arkebauer, Raphael Linker, Anatoly A. Gitelson
Informative Spectral Bands For Remote Green Lai Estimation In C3 And C4 Crops, Oz Kira, Anthony L. Nguy-Robertson, Timothy J. Arkebauer, Raphael Linker, Anatoly A. Gitelson
School of Natural Resources: Faculty Publications
Green leaf area index (LAI) provides insight into the productivity, physiological and phenological status of vegetation. Measurement of spectral reflectance offers a fast and nondestructive estimation of green LAI. A number of methods have been used for the estimation of green LAI; however, the specific spectral bands employed varied widely among the methods and data used. Our objectives were (i) to find informative spectral bands retained in three types of methods, neural network (NN), partial least squares (PLS) regression and vegetation indices (VI), for estimating green LAI in maize (a C4 species) and soybean (a C3 species); (ii) to assess …
Modeling Gross Primary Production Of Maize And Soybean Croplands Using Light Quality, Temperature, Water Stress, And Phenology, Anthony L. Nguy-Robertson, Andrew E. Suyker, Xiangming Xiao
Modeling Gross Primary Production Of Maize And Soybean Croplands Using Light Quality, Temperature, Water Stress, And Phenology, Anthony L. Nguy-Robertson, Andrew E. Suyker, Xiangming Xiao
School of Natural Resources: Faculty Publications
Vegetation productivity metrics, such as gross primary production (GPP) may be determined from the efficiency with which light is converted into photosynthates, or light use efficiency (ϵ). Therefore, accurate measurements and modeling of ϵ is important for estimating GPP in each ecosystem. Previous studies have quantified the impacts of biophysical parameters on light use efficiency based GPP models. Here we enhance previous models utilizing four scalars for light quality (i.e., cloudiness), temperature, water stress, and phenology for data collected from both maize and soybean crops at three Nebraska AmeriFlux sites between 2001 and 2012 (maize: 26 field-years; soybean: …
Uncertainty In Simulating Gross Primary Production Of Cropland Ecosystem From Satellite-Based Models, Wenping Yuan, Wenwen Cai, Anthony L. Nguy-Robertson, Huajun Fang, Andrew E. Suyker, Yang Chen, Wenjie Dong, Shuguang Liu, Haicheng Zhang
Uncertainty In Simulating Gross Primary Production Of Cropland Ecosystem From Satellite-Based Models, Wenping Yuan, Wenwen Cai, Anthony L. Nguy-Robertson, Huajun Fang, Andrew E. Suyker, Yang Chen, Wenjie Dong, Shuguang Liu, Haicheng Zhang
School of Natural Resources: Faculty Publications
Accurate estimates of gross primary production (GPP) for croplands are needed to assess carbon cycle and crop yield. Satellite-based models have been developed to monitor spatial and temporal GPP patterns. However, there are still large uncertainties in estimating cropland GPP. This study compares three light use efficiency (LUE) models (MODIS-GPP, EC-LUE, and VPM) with eddy-covariance measurements at three adjacent AmeriFlux crop sites located near Mead, Nebraska, USA. These sites have different croprotation systems (continuous maize vs. maize and soybean rotated annually) and water management practices (irrigation vs. rainfed). The results reveal several major uncertainties in estimating GPP which need to …
Gross Primary Production And Ecosystem Respiration Of Irrigated And Rainfed Maize–Soybean Cropping Systems Over 8 Years, Andrew E. Suyker, Shashi B. Verma
Gross Primary Production And Ecosystem Respiration Of Irrigated And Rainfed Maize–Soybean Cropping Systems Over 8 Years, Andrew E. Suyker, Shashi B. Verma
School of Natural Resources: Faculty Publications
The objective of this study is to examine interannual variability of carbon dioxide exchange and relevant controlling factors in irrigated and rainfed maize–soybean agroecosystems. The mean annual gross primary production (GPP) of irrigated and rainfed maize was 1796 ± 92 g C m−2 y−1 (±standard deviation) and 1536 ± 74 g C m−2 y−1, respectively. Mean annual GPP of soybean (average of irrigated and rainfed crops) was about 56% that of maize. Light use efficiency of maize and soybean during clear sky conditions were 1.96 ± 0.10 and 1.37 ± 0.06 g C MJ−1 …
Comparison And Analysis Of Empirical Equations For Soil Heat Flux For Different Cropping Systems And Irrigation Methods, Ayse Kilic, R. K. Singh, Elizabeth A. Walter-Shea, Shashi Verma, Andrew E. Suyker
Comparison And Analysis Of Empirical Equations For Soil Heat Flux For Different Cropping Systems And Irrigation Methods, Ayse Kilic, R. K. Singh, Elizabeth A. Walter-Shea, Shashi Verma, Andrew E. Suyker
School of Natural Resources: Faculty Publications
We evaluated the performance of four models for estimating soil heat flux density (G) in maize (Zea mays L.) and soybean (Glycine max L.) fields under different irrigation methods (center‐pivot irrigated fields at Mead, Nebraska, and subsurface drip irrigated field at Clay Center, Nebraska) and rainfed conditions at Mead. The model estimates were compared against measurements made during growing seasons of 2003, 2004, and 2005 at Mead and during 2005, 2006, and 2007 at Clay Center. We observed a strong relationship between the G and net radiation (Rn) ratio (G/Rn) and the normalized difference …
Coupling Of Carbon Dioxide And Water Vapor Exchanges Of Irrigated And Rainfed Maize–Soybean Cropping Systems And Water Productivity, Andrew E. Suyker, Shashi B. Verma
Coupling Of Carbon Dioxide And Water Vapor Exchanges Of Irrigated And Rainfed Maize–Soybean Cropping Systems And Water Productivity, Andrew E. Suyker, Shashi B. Verma
School of Natural Resources: Faculty Publications
Continuous measurements of CO2 and water vapor exchanges made in three cropping systems (irrigated continuous maize, irrigated maize–soybean rotation, and rainfed maize–soybean rotation) in eastern Nebraska, USA during 6 years are discussed. Close coupling between seasonal distributions of gross primary production (GPP) and evapotranspiration (ET) were observed in each growing season. Mean growing season totals of GPP in irrigated maize and soybean were 1738 ± 114 and 996 ± 69 g C m−2, respectively (±standard deviation). Corresponding mean values of growing season ET totals were 545 ± 27 and 454 ± 23 mm, respectively. Irrigation affected GPP …
Evapotranspiration Of Irrigated And Rainfed Maize–Soybean Cropping Systems, Andrew E. Suyker, Shashi Verma
Evapotranspiration Of Irrigated And Rainfed Maize–Soybean Cropping Systems, Andrew E. Suyker, Shashi Verma
School of Natural Resources: Faculty Publications
We have been making year-round measurements of mass and energy exchange in three cropping systems: (a) irrigated continuous maize, (b) irrigated maize–soybean rotation, and (c) rainfed maize–soybean rotation in eastern Nebraska since 2001. In this paper, we present results on evapotranspiration (ET) of these crops for the first 5 years of our study. Growing season ET in the irrigated and rainfed maize averaged 548 and 482 mm, respectively. In irrigated and rainfed soybean, the average growing season ET was 452 and 431 mm, respectively. On average, the maize ET was higher than the soybean ET by 18% for irrigated crops …
Test Of An Extended Mathematical Approach To Calculate Maize Leaf Area Index And Leaf Angle Distribution, Elizabeth A. Walter-Shea, Mark A. Mesarch
Test Of An Extended Mathematical Approach To Calculate Maize Leaf Area Index And Leaf Angle Distribution, Elizabeth A. Walter-Shea, Mark A. Mesarch
School of Natural Resources: Faculty Publications
No abstract provided.