Other Civil and Environmental Engineering Commons^™

The Assessment Of Water Resources In Ungauged Catchments In Rwanda, O. P. Abimbola, J. Wenninger, R. Venneker, Aaron R. Mittelstet

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Study region: Rwanda is a landlocked country in Africa with precipitation ranging from 800 mm yr−1 in the east to 1500 mm yr−1 in high-altitude regions in the north and west. Study focus: Streamflow estimation is an important task that is required in water resource assessments due to its importance in planning, decision-making and economic development. In this study, streamflow characteristics of ungauged catchments in Rwanda were calculated using a regionalization approach based on climate similarity and stepwise multiple-regression analysis. One climatic homogeneous region was identified and datasets of nine gauged stations and general available catchment characteristics were …

A Geospatial Variable Rate Irrigation Control Scenario Evaluation Methodology Based On Mining Root Zone Available Water Capacity, K. A. Miller, Joe Luck, Derek M. Heeren, T. Lo, Derrel Martin, J. B. Barker

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Increasing concern for sustainable water use has the agriculture industry working toward higher efficiency in use of irrigation water. Recent advancements have improved the capabilities of center pivot irrigation systems to vary water application depths across the field, a technology known as variable rate irrigation (VRI). The goal of this study was to provide a geospatial method for potential VRI technology adopters to evaluate control scenarios and potential water savings using freely available datasets. Root zone available water capacity (R) was estimated spatially across two case study fields using the Natural Resources Conservation Service Gridded Soil Survey Geographic Database. The …

The Effect Of Single-Handed Lifting Tasks On The Activation Of The Neck-Shoulder Shared Musculature, Mohamed R. Amar, David Cochran, Jeffrey Woldstad

Department of Agricultural and Biological Systems Engineering: Faculty Publications

The use of the hand in lifting has been linked to occupational injuries of the neck and shoulder. This research is aimed at examining the effect of work-related factors on the major neck-shoulder shared musculature activity on both sides of the cervical spine for a right-handed lifting task. Subjects lifted different weights from 20 different locations produced by the interaction of varying heights, reach distance, and angles simulating the work done by assembly line workers. All lifting tasks were done by the right hand. Bilateral electromyography data of major shared musculature (upper trapezius, sternocleidomastoid, and levator scapula) were collected using …

Regulation-Structured Dynamic Metabolic Model Provides A Potential Mechanism For Delayed Enzyme Response In Denitrification Process, Hyun-Seob Song, Dennis G. Thomas, James C. Stegen, Minjing Li, Chongxuan Liu, Xuehang Song, Xingyuan Chen, Jim K. Fredrickson, John M. Zachara, Timothy D. Scheibe

Department of Agricultural and Biological Systems Engineering: Faculty Publications

In a recent study of denitrification dynamics in hyporheic zone sediments, we observed a significant time lag (up to several days) in enzymatic response to the changes in substrate concentration. To explore an underlying mechanism and understand the interactive dynamics between enzymes and nutrients, we developed a trait-based model that associates a community’s traits with functional enzymes, instead of typically used species guilds (or functional guilds). This enzyme-based formulation allows to collectively describe biogeochemical functions of microbial communities without directly parameterizing the dynamics of species guilds, therefore being scalable to complex communities. As a key component of modeling, we accounted …

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 Agricultural and Biological Systems Engineering: Faculty 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 …

Performance Of Twelve Mass Transfer Based Reference Evapotranspiration Models Under Humid Climate, Koffi Djaman, Komlan Koudahe, Mamadou Sall, Isa Kabenge, Daran Rudnick, Suat Irkmak

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Reference evapotranspiration is very important parameter in the hydrological, agricultural and environmental studies and is accurately estimated by the FAO Penman-Monteith equation (FAO-PM) under different climatic conditions. However, due to data requirement of the FAO-PM equation, there is a need to investigate the applicability of alternative ETo equations under limited data. The objectives of this study were to evaluate twelve mass transfer based reference evapotranspiration equations and determine the impact of ETo equation on long term water management sustainability in Tanzania and Kenya. The results showed that the Albrecht, Brockamp-Wenner, Dalto, Meyer, Rohwer and Oudin ETo equations systematically overestimated the …

Runoff Water Quality Characteristics Following Swine Slurry Application Under Broadcast And Injected Conditions, Nicole R. Schuster, Shannon L. Bartelt-Hunt, Lisa M. Durso, John E. Gilley, Xu Li, David B. Marx, Amy M. Schmidt, Daniel D. Snow

Department of Agricultural and Biological Systems Engineering: Faculty Publications

This study was conducted to measure the effects of swine slurry application method, time following slurry application, and runoff rate on selected water quality characteristics. Slurry from a commercial swine operation was broadcast or injected on field plots at a rate required to meet annual nitrogen requirements for corn. Rainfall simulation tests were conducted at five varying periods following slurry application. During each study period, three simulated rainfall events, separated by 24 h intervals, were applied for 30 min duration at an intensity of approximately 70 mm h^-1. Following the third rainfall simulation event, inflow was applied at …

Large Co2 And Ch4 Emissions From Polygonal Tundra During Spring Thaw In Northern Alaska, Naama Raz-Yaseef, Margaret S. Torn, Yuxin Wu, David P. Billesbach, Anna K. Liljedahl, Timothy J. Kneafsey, Vladimir E. Romanovsky, David R. Cook, Stan D. Wullschleger

Department of Agricultural and Biological Systems Engineering: Faculty Publications

The few prethaw observations of tundra carbon fluxes suggest that there may be large spring releases, but little is known about the scale and underlying mechanisms of this phenomenon. To address these questions, we combined ecosystem eddy flux measurements from two towers near Barrow, Alaska, with mechanistic soil-core thawing experiment. During a 2 week period prior to snowmelt in 2014, large fluxes were measured, reducing net summer uptake of CO₂ by 46% and adding 6% to cumulative CH₄ emissions. Emission pulses were linked to unique rain-on-snow events enhancing soil cracking. Controlled laboratory experiment revealed that as surface ice …

Multiple Drivers Of Seasonal Change In Pri: Implications For Photosynthesis 1. Leaf Level, Anatoly A. Gitelson, John A. Gamon, Alexei E. Solovchenko

Department of Agricultural and Biological Systems Engineering: Faculty Publications

The goal of this study was to explore the relationships between the photochemical reflectance index (PRI) at the leaf level and pigment pools, focusing on the constitutive role of pigments in influencing PRI over seasonal or ontogenetic time frames. The purpose was to re-evaluate the role of PRI as an indicator of seasonally shifting pigment (chlorophyll, carotenoid and anthocyanin) contents, and hence photosynthetic activity, across a range of tree and crop species. We studied natural vegetation — three tree species (maple, chestnut and beech) and two managed irrigated and rain-fed crop species (maize and soybean), contrasting in photosynthetic pathway and …

Multiple Drivers Of Seasonal Change In Pri: Implications For Photosynthesis 2. Stand Level, Anatoly A. Gitelson, John A. Gamon, Alexei E. Solovchenko

Department of Agricultural and Biological Systems Engineering: Faculty Publications

The goal of this study was to explore the relationships between stand-level photochemical reflectance index (PRI) and canopy structure/ pigment pools, as well as light use efficiency (LUE) of photosynthetically active vegetation focusing on seasonal or ontogenetic time frames. PRI was originally designed as a means of assessing the xanthophyll cycle and LUE over short (e.g. diurnal) time frames, and few studies have explored the drivers of PRI over longer, seasonal time frames, particularly in crops having different photosynthetic pathways or canopy structures. Consequently, our purpose was to understand and quantify the drivers of PRI responses over seasonal time scales …

Soil Water Content Monitoring For Irrigation Management: A Geostatistical Analysis, J. Burdette Barker, Trenton E. Franz, Derek M. Heeren, Christopher M.U. Neale, Joe D. Luck

Department of Agricultural and Biological Systems Engineering: Faculty Publications

With the increasing attention to site-specific or variable rate irrigation management, it is helpful to reconsider the quantity and placement of soil water monitoring locations in this context. Volumetric soil water content (θ_v) was monitored using a neutron probe (NP) at 72 locations in a center pivot irrigated field in eastern Nebraska. Variance reduction and temporal stability analyses were performed on θ_v from shallow (∼top 46 cm) and full profile (∼122 cm) readings for four monitoring cycles in the 2015 growing season and 2016 preseason. Eleven additional cycles were included for a subset of the data for …

Fuel Consumption Models For Tractor Test Reports, Michael F. Kocher, Bryan J. Smith, Roger M. Hoy, Jeffrey C. Woldstad, Santosh Pitla

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Five models for estimating fuel consumption for agricultural tractors with partial drawbar loads were compared. Data were collected from eight John Deere tractors, JD 7230R (e23), 7250R (e23), 7270R (e23), 7290R (e23), 8320R (16 speed), 7290R (IVT), 8345RT (IVT), 8370R (IVT), on the drawbar test track at the Nebraska Tractor Test Lab. The tractors were tested with seven load levels per speed at three different travel speeds as close as possible to 7.5, 10, and 13 km h-1. The IVT tractors were operated in auto mode, and the geared tractors were shifted up three gears and throttled back to the …

A Novel Diffuse Fraction-Based Two-Leaf Light Use Efficiency Model: An Application Quantifying Photosynthetic Seasonality Across 20 Ameriflux Flux Tower Sites, Hao Yan, Shao-Qiang Wang, Kai-Liang Yu, Bin Wang, Qin Yu, Gil Bohrer, Dave P. Billesbach, Rosvel Bracho, Faiz Rahman

Department of Agricultural and Biological Systems Engineering: Faculty Publications

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Diffuse radiation can increase canopy light use efficiency (LUE). This creates the need to differentiate the effects of direct and diffuse radiation when simulating terrestrial gross primary production (GPP). Here, we present a novel GPP model, the diffuse-fraction-based two-leaf model (DTEC), which includes the leaf response to direct and diffuse radiation, and treats maximum LUE for shaded leaves (ε_msh defined as a power function of the diffuse fraction (D_f)) and sunlit leaves (ε_msu defined as a constant) separately. An Amazonian rainforest site (KM67) was used to calibrate the model by simulating the linear relationship between …

Moving Integrated Weed Management From Low Level To A Truly Integrated And Highly Specific Weed Management System Using Advanced Technologies, S. L. Young, S. K. Pitla, F. K. Van Evert, J. K. Schueller, F. J. Pierce

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Integrated weed management (IWM) is one of the most commonly referred to approaches for sustainable and effective weed control in agriculture, yet it is not widely practiced, likely because current IWM systems fail to meet performance expectations of growers. The effectiveness and value of IWM systems should increase with increasing application specificity and true integration made possible with contemporary advances in technology, information systems and decision support. IWM systems can be classified based on their degree of application specificity and level of integration of tactics. In the application specificity pathway, a tactic is applied at a range of scales, from …

Optical Probing Of Gastrocnemius In Patients With Peripheral Artery Disease Characterizes Myopathic Biochemical Alterations And Correlates With Stage Of Disease, Ryan A. Becker, Kim Cluff, Nithyanandhi Duraisamy, Hootan Mehraein, Hussam Farhoud, Tracie Collins, George P. Casale, Iraklis I. Pipinos, Jeyamkondan Subbiah

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Peripheral artery disease (PAD) is a condition caused by atherosclerotic blockages in the arteries supplying the lower limbs and is characterized by ischemia of the leg, progressive myopathy, and increased risk of limb loss. The affected leg muscles undergo significant changes of their biochemistry and metabolism including variations in the levels of many key proteins, lipids, and nucleotides. The mechanisms behind these changes are poorly understood. The objective of this study was to correlate the severity of the PAD disease stage and associated hemodynamic limitation (determined by the ankle brachial index, ABI) in the legs of the patients with alterations …

Creation Of An Injectable In Situ Gelling Native Extracellular Matrix For Nucleus Pulposus Tissue Engineering, Rebecca A. Wachs, Ella N. Hoogenboezem, Hammad I. Huda, Shangjing Xin, Stacy L. Porvasnik, Christine E. Schmidt

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Background Context: Disc degeneration is the leading cause of low back pain and is often characterized by a loss of disc height, resulting from cleavage of chondroitin sulfate proteoglycans (CSPGs) present in the nucleus pulposus. Intact CSPGs are critical to water retention and maintenance of the nucleus osmotic pressure. Decellularization of healthy nucleus pulposus tissue has the potential to serve as an ideal matrix for tissue engineering of the disc because of the presence of native disc proteins and CSPGs. Injectable in situ gelling matrices are the most viable therapeutic option to prevent damage to the anulus fibrosus and future …

Tractor Power Take-Off Torque Measurement And Data Acquisition System, James Bw Roeber, Santosh Pitla, Roger M. Hoy, Joe D. Luck, Michael F. Kocher

Department of Agricultural and Biological Systems Engineering: Faculty Publications

With the mechanization of agricultural operations, agricultural machinery management has become an extensive research field. Sizing tractors and implements to provide the most efficient power transfer has become an ongoing process with advances in technology. Utilization of the rotational power transferred through gear trains from the tractor engine to the power take-off (PTO) shaft is one of the most efficient methods of power transfer to an implement. This research used commercially available torque sensors that were installed on a tractor PTO shaft for measuring the torque delivered to an implement. The torque sensor was calibrated using the Nebraska Tractor Test …

Chitosan-Zein Nano-In-Microparticles Capable Of Mediating In Vivo Transgene Expression Following Oral Delivery, Eric Farris, Deborah M. Brown, Amanda Ramer-Tait, Angela K. Pannier

Department of Agricultural and Biological Systems Engineering: Faculty Publications

The oral route is an attractive delivery route for the administration of DNA-based therapeutics, specifically for applications in gene therapy and DNA vaccination. However, oral DNA delivery is complicated by the harsh and variable conditions encountered throughout gastrointestinal (GI) transit, leading to degradation of the delivery vector and DNA cargo, and subsequent inefficient delivery to target cells. In this work, we demonstrate the development and optimization of a hybrid-dual particulate delivery system consisting of two natural biomaterials, zein (ZN) and chitosan (CS), to mediate oral DNA delivery. Chitosan-Zein Nano-in-Microparticles (CS-ZN-NIMs), consisting of core Chitosan/DNA nanoparticles (CS/DNA NPs) prepared by ionic …

A Case Study Of Field-Scale Maize Irrigation Patterns In Western Nebraska: Implications For Water Managers And Recommendations For Hyper-Resolution Land Surface Modeling, Justin P. Gibson, Trenton E. Franz, Tiejun Wang, John Gates, Patricio Grassini, Haishun Yang, Dean E. Eisenhauer

Department of Agricultural and Biological Systems Engineering: Faculty Publications

In many agricultural regions, the human use of water for irrigation is often ignored or poorly represented in land surface models (LSMs) and operational forecasts. Because irrigation increases soil moisture, feedback on the surface energy balance, rainfall recycling, and atmospheric dynamics is not represented and may lead to reduced model skill. In this work, we describe four plausible and relatively simple irrigation routines that can be coupled to the next generation of hyper-resolution LSMs operating at scales of 1 km or less. The irrigation output from the four routines (crop model, precipitation delayed, evapotranspiration replacement, and vadose zone model) is …

Crop Classification And Lai Estimation Using Original And Resolution-Reduced Images From Two Consumer-Grade Cameras, Jian Zhang, Chenghai Yang, Biquan Zhao, Huaibo Song, Wesley Clint Hoffmann, Yeyin Shi, Dongyan Zhang, Guozhong Zhang

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Consumer-grade cameras are being increasingly used for remote sensing applications in recent years. However, the performance of this type of cameras has not been systematically tested and well documented in the literature. The objective of this research was to evaluate the performance of original and resolution-reduced images taken from two consumer-grade cameras, a RGB camera and a modified near-infrared (NIR) camera, for crop identification and leaf area index (LAI) estimation. Airborne RGB and NIR images taken over a 6.5-square-km cropping area were mosaicked and aligned to create a four-band mosaic with a spatial resolution of 0.4 m. The spatial resolution …

Nanoparticle For Targeting Brain Tumors And Delivery Of O6 - Benzylguanine, University Of Washington, Seattle

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Nanoparticle having a crosslinked chitosan - polyethylene oxide oligomer copolymer coating to which O⁶ - benzylgua nine is covalently coupled , compositions that include the nanoparticle , and methods for using the nanoparticle to treat brain cancers .

Evaluation Of Valiantzas’ Simplified Forms Of The Fao-56 Penman-Monteith Reference Evapotranspiration Model In A Humid Climate, Koffi Djaman, Daran Rudnick, Valere C. Mel, Denis Mutiibwa, Lamine Diop, Mamadou Sall, Isa Kabenge, Ansoumana Bodian, Hossein Tabari, Suat Irmak

Department of Agricultural and Biological Systems Engineering: Faculty Publications

The unavailability of some meteorological variables, especially solar radiation and wind speed, is the main constraint for reference evapotranspiration (ETo) estimation using the standard United Nations Food and Agriculture Organization (FAO) Penman–Monteith (FAO-PM) equation in most developing countries. The application of ETo methods with fewer input requirements is necessary under limited climatic data conditions. The FAO-PM method under limited data conditions and nine of Valiantzas’ equations were evaluated for daily ETo estimation in a humid climate in Uganda. The FAO-PM method with missing relative humidity data performed very well across Uganda, whereas using the long-term local wind speed average values …

Crop Canopy Sensor Orientation For Late Season Nitrogen Determination In Corn, T. M. Shaver, Greg Kruger, Daran Rudnick

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Increasing nitrogen use efficiency (NUE) in irrigated corn production is of great importance to overall agricultural sustainability. Studies have shown that crop canopy sensors can aid in this pursuit as they allow for the determination of nitrogen (N) requirements in split applications later in the growing season. Fertigation can also increase NUE as many split applications can be conducted. If crop canopy sensors could be used to direct N fertigation rates, overall NUE may be increased even further. However, in some cases, N differences may need to be determined later in the growing season after corn has tasseled, which can …

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 Agricultural and Biological Systems Engineering: Faculty 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, …

In Vitro Porcine Blastocyst Development In Three-Dimensional Alginate Hydrogels, Jeremy R. Miles, Taylor D. Laughlin, Catherine Sargus-Patino, Angela K. Pannier

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Appropriate embryonic and fetal development significantly impact pregnancy success and, therefore, the efficiency of swine production. The pre-implantation period of porcine pregnancy is characterized by several developmental hallmarks, which are initiated by the dramatic morphological change that occurs as pig blastocysts elongate from spherical to filamentous blastocysts. Deficiencies in blastocyst elongation contribute to approximately 20% of embryonic loss, and have a direct influence on within-litter birth weight variation. Although factors identified within the uterine environment may play a role in blastocyst elongation, little is known about the exact mechanisms by which porcine (or other species’) blastocysts initiate and progress through …

Laboratory And Full Boom-Based Investigation Of Nozzle Setup Error Effects On Flow, Pressure, And Spray Pattern Distribution, Shane H. Forney, Joe D. Luck, Michael F. Kocher, Santosh Pitla

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Pesticide application is an integral part of crop production, and ground-based agricultural boom sprayers are used extensively to apply pesticides to the crop canopy or soil surface across millions of acres in the United States. Efficient application is necessary to minimize costs and limit adverse environmental impacts. The goals of this study were to provide quantified measurements on the effects of nozzle setup errors on spray pattern uniformity and evaluate how laboratory patternator-based simulations would compare to measurements on a full spray boom. More specific objectives were to determine the effects of factors such as nozzle lateral angle, nozzle spacing, …

Tractor Power Take-Off Torque Measurement And Data Acquisition System, James B. W. Roeber, Santosh K. Pitla, R. M. Hoy, J. D. Luck, Michael F. Kocher

Department of Agricultural and Biological Systems Engineering: Faculty Publications

With the mechanization of agricultural operations, agricultural machinery management has become an extensive research field. Sizing tractors and implements to provide the most efficient power transfer has become an ongoing process with advances in technology. Utilization of the rotational power transferred through gear trains from the tractor engine to the power take-off (PTO) shaft is one of the most efficient methods of power transfer to an implement. This research used commercially available torque sensors that were installed on a tractor PTO shaft for measuring the torque delivered to an implement. The torque sensor was calibrated using the Nebraska Tractor Test …

Laboratory And Full Boom-Based Investigation Of Nozzle Setup Error Effects On Flow, Pressure, And Spray Pattern Distribution, S. H. Forney, J. D. Luck, Michael F. Kocher, Santosh K. Pitla

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Pesticide application is an integral part of crop production, and ground-based agricultural boom sprayers are used extensively to apply pesticides to the crop canopy or soil surface across millions of acres in the United States. Efficient application is necessary to minimize costs and limit adverse environmental impacts. The goals of this study were to provide quantified measurements on the effects of nozzle setup errors on spray pattern uniformity and evaluate how laboratory patternator-based simulations would compare to measurements on a full spray boom. More specific objectives were to determine the effects of factors such as nozzle lateral angle, nozzle spacing, …

Modeling Streambank Erosion On Composite Streambanks On A Watershed Scale, A. R. Mittelstet, D. E. Storm, G. A. Fox, P. M. Allen

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Streambanks can be a significant source of sediment and phosphorus to aquatic ecosystems. Although the streambank-erosion routine in the Soil and Water Assessment Tool (SWAT) has improved in recent versions, the recently developed routine in SWAT 2012 has undergone limited testing, and the lack of site or watershed specific streambank data increases the uncertainty in the streambank-erosion predictions. There were two primary objectives of this research: (1) modify and test the 2012 SWAT streambank-erosion routine on composite streambanks, and (2) compare SWAT default and field-measured channel parameters and assess their influence on predicted streambank erosion. Three modifications were made to …

Quantifying An Aquifer Nitrate Budget And Future Nitrate Discharge Using Field Data From Streambeds And Well Nests, Troy E. Gilmore, David P. Genereux, Kathleen M. Farrell, Helena Mitasova

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Novel groundwater sampling (age, flux, and nitrate) carried out beneath a streambed and in wells was used to estimate (1) the current rate of change of nitrate storage, dS_NO3 /dt, in a contaminated unconfined aquifer, and (2) future [NO₃^–]_FWM (the flow-weighted mean nitrate concentration in groundwater discharge) and f_NO3 (the nitrate flux from aquifer to stream). Estimates of dS_NO3 /dt suggested that at the time of sampling (2013) the nitrate storage in the aquifer was decreasing at an annual rate (mean = –9 mmol/m²yr) equal …