Open Access. Powered by Scholars. Published by Universities.®
- Discipline
- Publication Year
Articles 1 - 15 of 15
Full-Text Articles in Life Sciences
Wheat Growth Monitoring And Yield Estimation Based On Multi-Rotor Unmanned Aerial Vehicle, Zhaopeng Fu, Jie Jang, Yang Gao, Brian Krienke, Meng Wang, Kaitai Zhong, Qiang Cao, Yongchao Tian, Yan Zhu, Weixing Cao, Xiaojun Liu
Wheat Growth Monitoring And Yield Estimation Based On Multi-Rotor Unmanned Aerial Vehicle, Zhaopeng Fu, Jie Jang, Yang Gao, Brian Krienke, Meng Wang, Kaitai Zhong, Qiang Cao, Yongchao Tian, Yan Zhu, Weixing Cao, Xiaojun Liu
Department of Agronomy and Horticulture: Faculty Publications
Leaf area index (LAI) and leaf dry matter (LDM) are important indices of crop growth. Real-time, nondestructive monitoring of crop growth is instructive for the diagnosis of crop growth and prediction of grain yield. Unmanned aerial vehicle (UAV)-based remote sensing is widely used in precision agriculture due to its unique advantages in flexibility and resolution. This study was carried out on wheat trials treated with different nitrogen levels and seeding densities in three regions of Jiangsu Province in 2018–2019. Canopy spectral images were collected by the UAV equipped with a multi-spectral camera during key wheat growth stages. To verify the …
Towards Estimation Of Canopy Foliar Biomass With Spectral Reflectance Measurements, Lingli Wang, E. Raymond Hunt Jr., John J. Qu, Xianjun Hao, Craig S.T. Daughtry
Towards Estimation Of Canopy Foliar Biomass With Spectral Reflectance Measurements, Lingli Wang, E. Raymond Hunt Jr., John J. Qu, Xianjun Hao, Craig S.T. Daughtry
United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications
Canopy foliar biomass, defined as the product of leaf dry matter content and leaf area index, is an important measurement for global biogeochemical cycles. This study explores the potential for retrieving foliar biomass in green canopies using a spectral index, the Normalized Dry Matter Index (NDMI). This narrow-band index is based on absorption at the C–H bond stretch overtone and is correlated with leaf dry matter content in fresh green leaves. PROSPECT and SAIL model simulations suggest that the NDMI at the canopy scale is able to minimize the effects of leaf thickness and leaf water content and to maximize …
Evaluation Of The Modis Lai Product Using Independent Lidar-Derived Lai: A Case Study In Mixed Conifer Forest, Jennifer L.R. Jensen, Karen S. Humes, Andrew T. Hudak, Lee A. Vierling, Eric Delmelle
Evaluation Of The Modis Lai Product Using Independent Lidar-Derived Lai: A Case Study In Mixed Conifer Forest, Jennifer L.R. Jensen, Karen S. Humes, Andrew T. Hudak, Lee A. Vierling, Eric Delmelle
USDA Forest Service / UNL Faculty Publications
This study presents an alternative assessment of the MODIS LAI product for a 58,000 ha evergreen needleleaf forest located in the western Rocky Mountain range in northern Idaho by using lidar data to model (R2=0.86, RMSE=0.76) and map LAI at higher resolution across a large number of MODIS pixels in their entirety. Moderate resolution (30 m) lidar-based LAI estimates were aggregated to the resolution of the 1-km MODIS LAI product and compared to temporally-coincident MODIS retrievals. Differences in the MODIS and lidar-derived values of LAI were grouped and analyzed by several different factors, including MODIS retrieval algorithm, sun/sensor …
Evaluation Of The Intercom Model For Predicting Growth Of Forest Herbs, Zorica S. Popović, J. L. Lindquist
Evaluation Of The Intercom Model For Predicting Growth Of Forest Herbs, Zorica S. Popović, J. L. Lindquist
Department of Agronomy and Horticulture: Faculty Publications
The ecophysiological model INTERCOM was evaluated for its suitability in predicting the growth of perennial forest herbs. A field experiment was conducted to obtain data on photosynthesis and growth parameters of two spring flowering understorey geophytes. Results were used to parameterize the model and its performance was evaluated using the average normalized difference (AE) between predicted and observed biomass and the leaf area index. The model was assumed to provide accurate simulations if the AE was smaller than 0.4. Adjusting the photosynthetic intensity parameters in the model to reflect observed changes in photosynthesis throughout the growing period resulted in the …
Leaf Area Index Simulation In Soybean Grown Under Near-Optimal Conditions, T. D. Setiyono, Albert Weiss, James E. Specht, Kenneth G. Cassman, A. Dobermann
Leaf Area Index Simulation In Soybean Grown Under Near-Optimal Conditions, T. D. Setiyono, Albert Weiss, James E. Specht, Kenneth G. Cassman, A. Dobermann
Department of Agronomy and Horticulture: Faculty Publications
Different approaches have been used to simulate leaf area index (LAI) in soybean (Glycine max L. Merr). Many of these approaches require genotype-specific calibration procedures. Studies modeling LAI dynamics under optimal growth conditions with yields close to the yield potential of soybean have remained scarce. A sink-driven approach was developed and evaluated for LAI simulation in soybean under near-optimal environments. The rate of change in expanding leaf area was simulated using the first derivative of a logistic function accounting for plant population density, air temperature, and water deficit. The rate of change in senescing leaf area was also simulated …
Initial Response Of Evapotranspiration From Tallgrass Prairie Vegetation To Co2 At Subambient To Elevated Concentrations, H. W. Polley, H. B. Johnson, P. A. Fay, J. Sanabria
Initial Response Of Evapotranspiration From Tallgrass Prairie Vegetation To Co2 At Subambient To Elevated Concentrations, H. W. Polley, H. B. Johnson, P. A. Fay, J. Sanabria
United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications
A series of weighing lysimeters in which tallgrass prairie species had been planted were exposed to a subambient to elevated gradient in CO2 in a field chamber. Lysimeters with intact monoliths of three soil types were represented along the CO2 gradient. We used regression analysis to determine how CO2 effects on evapotranspiration per unit of soil surface area (ETsoil) and per unit of leaf area (ETla) depended on variation in leaf area index (LAI) and diurnal changes in environmental variables during the initial 6 weeks of CO2 treatment.
Switchgrass Biomass Simulation At Diverse Sites In The Northern Great Plains Of The U.S., Jim R. Kiniry, Marty R. Schmer, Kenneth P. Vogel, Robert B. Mitchell
Switchgrass Biomass Simulation At Diverse Sites In The Northern Great Plains Of The U.S., Jim R. Kiniry, Marty R. Schmer, Kenneth P. Vogel, Robert B. Mitchell
Department of Agronomy and Horticulture: Faculty Publications
The Agricultural Land Management Alternatives with Numerical Assessment Criteria (ALMANAC) model, originally developed and tested in Texas, needs to be tested for switchgrass (Panicum virgatum L.) simulation in more northerly locations. The Northern Great Plains of the U.S. has regionally adapted native populations of switchgrass and has excellent potential for growing switchgrass as a biofuel crop. The objective of this study was to adjust switchgrass parameters (potential leaf area index (DMLA) and degree days to maturity (PHU)) for northern sites and populations and to validate the model against switchgrass data from diverse sites in this region. Three or 4 …
Comparative Nitrogen Uptake And Distribution In Corn And Velvetleaf (Abutilon Theophrasti), John L. Lindquist, Darren C. Barker, Stevan Z. Knezevic, Alexander R. Martin, Daniel T. Walters
Comparative Nitrogen Uptake And Distribution In Corn And Velvetleaf (Abutilon Theophrasti), John L. Lindquist, Darren C. Barker, Stevan Z. Knezevic, Alexander R. Martin, Daniel T. Walters
Department of Agronomy and Horticulture: Faculty Publications
Weeds compete with crops for light, soil water, and nutrients. Nitrogen (N) is the primary limiting soil nutrient. Forecasting the effects of N on growth, development, and interplant competition requires accurate prediction of N uptake and distribution within plants. Field studies were conducted in 1999 and 2000 to determine the effects of variable N addition on monoculture corn and velvetleaf N uptake, the relationship between plant N concentration ([N]) and total biomass, the fraction of N partitioned to leaves, and predicted N uptake and leaf N content. Cumulative N uptake of both species was generally greater in 2000 than in …
Effect Of Nitrogen Addition On The Comparative Productivity Of Corn And Velvetleaf (Abutilon Theophrasti), Darren C. Barker, Stevan Z. Knezevic, Alex R. Martin, Daniel T. Walters, John L. Lindquist
Effect Of Nitrogen Addition On The Comparative Productivity Of Corn And Velvetleaf (Abutilon Theophrasti), Darren C. Barker, Stevan Z. Knezevic, Alex R. Martin, Daniel T. Walters, John L. Lindquist
Department of Agronomy and Horticulture: Faculty Publications
Weeds that respond more to nitrogen fertilizer than crops may be more competitive under high nitrogen (N) conditions. Therefore, understanding the effects of nitrogen on crop and weed growth and competition is critical. Field experiments were conducted at two locations in 1999 and 2000 to determine the influence of varying levels of N addition on corn and velvetleaf height, leaf area, biomass accumulation, and yield. Nitrogen addition increased corn and velvetleaf height by a maximum of 15 and 68%, respectively. N addition increased corn and velvetleaf maximum leaf area index (LAI) by up to 51 and 90%. Corn and velvetleaf …
Seasonal Leaf Dynamics Across A Tree Density Gradient In A Brazilian Savanna, William A. Hoffman, Edson Rangel Da Silva Jr., Gustavo C. Machado, Sandra J. Bucci, Fabian G. Scholz, Guillermo Goldstein, Frederick C. Meinzer
Seasonal Leaf Dynamics Across A Tree Density Gradient In A Brazilian Savanna, William A. Hoffman, Edson Rangel Da Silva Jr., Gustavo C. Machado, Sandra J. Bucci, Fabian G. Scholz, Guillermo Goldstein, Frederick C. Meinzer
USDA Forest Service / UNL Faculty Publications
Interactions between trees and grasses that influence leaf area index (LAI) have important consequences for savanna ecosystem processes through their controls on water, carbon, and energy fluxes as well as fire regimes. We measured LAI, of the groundlayer (herbaceous and woody plants <1-m tall) and shrub and tree layer (woody plants >1-m tall), in the Brazilian cerrado over a range of tree densities from open shrub savanna to closed woodland through the annual cycle. During the dry season, soil water potential was strongly and positively correlated with grass LAI, and less strongly with tree and shrub LAI. By the end of the dry season, LAI of grasses, groundlayer dicots …
Growth And Yield Of Snap Beans As Affected By Wind Protection And Microclimate Changes Due To Shelterbelts And Planting Dates, Laurie Hodges, Mohd Nazip Suratman, James R. Brandle, Kenneth G. Hubbard
Growth And Yield Of Snap Beans As Affected By Wind Protection And Microclimate Changes Due To Shelterbelts And Planting Dates, Laurie Hodges, Mohd Nazip Suratman, James R. Brandle, Kenneth G. Hubbard
Department of Agronomy and Horticulture: Faculty Publications
The effects of wind protection on growth and total and marketahle yields of snap bean (Phaseolus vulgaris L.) planted at 2-week intervals through the 1994 and 1995 growing seasons were examined. Research was conducted under nonirrigated conditions at the Shelterbelt Research Area, Univ, of Nebraska Agricultural Research and Development Center (ARDC) near Mead. 'Strike' (white-seeded) and 'Rushmore' (dark-seeded) were planted in locations sheltered from wind stress hy tree windbreaks (shelterbelts) and in locations exposed to normal winds using a randomized complete-block design with a split-split plot arrangement of treatments. Air temperature, soil temperature, humidity, wind speed, and wind direction …
Growth Response Of Velvetleaf To Three Postemergence Herbicides, Cheryl A. Murphy, John L. Lindquist
Growth Response Of Velvetleaf To Three Postemergence Herbicides, Cheryl A. Murphy, John L. Lindquist
Department of Agronomy and Horticulture: Faculty Publications
Knowledge of how reduction in the rate of herbicide application or rotation of their mode of action influences weed growth will provide insight into how successful these practices will be in an integrated weed management program. Field experiments were conducted in 1996 and 1997 to quantify velvetleaf growth response to three postemergence herbicides, each with a different mode of action. A monoculture of velvetleaf was treated with halosulfuron, dicamba, and flumiclorac at 0, 0.10, 0.25, 0.50, 0.75, and 1.0 X the labeled rate for weed control in corn. Percent plant mortality increased with rate of application; the greatest mortality occurred …
Performance Of Intercom For Predicting Corn– Velvetleaf Interference Across North-Central United States, John L. Lindquist
Performance Of Intercom For Predicting Corn– Velvetleaf Interference Across North-Central United States, John L. Lindquist
Department of Agronomy and Horticulture: Faculty Publications
Cost-effective weed management requires accurate estimates of yield and the potential yield loss resulting from weed infestations. However, crop yield and the effects of weeds are highly variable across years and locations. Ecophysiological models may be useful for predicting the effects of environment and management on crop and weed growth and competitive ability. Ability of the model INTERCOM to predict corn (Zea mays) growth and yield, velvetleaf (Abutilon theophrasti) interference on corn yield loss, and single-year economic threshold velvetleaf density (Te) was evaluated using 13 data sets collected in four states. Predicted and observed …
Canopy Analysis As A Technique To Characterize Defoliation Intensity On Sandhills Range, M. S. Miller-Goodman, Lowell E. Moser, Steven S. Waller, J. E. Brummer, P. E. Reece
Canopy Analysis As A Technique To Characterize Defoliation Intensity On Sandhills Range, M. S. Miller-Goodman, Lowell E. Moser, Steven S. Waller, J. E. Brummer, P. E. Reece
Department of Agronomy and Horticulture: Faculty Publications
Characterization of relationships between grazing and vegetation responses is difficult. Rapid and accurate measurement of pasture canopy characteristics would help clarify these relationships if canopy changes are directly related to grazing variables. The objectives of this study were (1) to evaluate use of the LI-COR LAI-2000 for quantification of changes in canopy density and architecture in response to defoliation by cattle, (2) to determine if changes in leaf area index (LAI) measured with the LAI-2000 are related to stocking rate, and (3) to determine advantages and drawbacks of the LAI-2000 for monitoring grazing impacts on canopy density and architecture. Leaf …
Spatial Pattern Of Gas Exchange For Montane Moist Meadow Species, Tony Svejcar, Gregg M. Riegel
Spatial Pattern Of Gas Exchange For Montane Moist Meadow Species, Tony Svejcar, Gregg M. Riegel
United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications
Montane moist meadows of western North America are relatively unique in that they are characterized by annual cycles of spring inundation followed by summer drought. Thus, plants adapted to these ecosystems must cope with a wide range of environmental conditions. We compared gas exchange and water relations of upper canopy leaves and leaf area index (LAI) of three dominant montane meadow graminoids growing at both streamside and mid-meadow locations (2.5 and 20.0 m, respectively from the stream edge). The two locations were environmentally very different in spite of their close proximity. The water table at the streamside location was ca. …