Open Access. Powered by Scholars. Published by Universities.®

1984

Discipline
Institution
Keyword
Publication
Publication Type

Articles 1 - 30 of 48

Full-Text Articles in Fresh Water Studies

Benthic Diatom Community Dynamics In The Colorado River: Interactive Effects Of Periodic Dessication And Current Regime, Christopher Gerard Peterson Dec 1984

Benthic Diatom Community Dynamics In The Colorado River: Interactive Effects Of Periodic Dessication And Current Regime, Christopher Gerard Peterson

Publications (WR)

The response to periodic desiccation of periphyton communities developed in eddy environments or in areas exposed to variable, direct current was examined. Algal communities were incubated on clay tiles for between 2 and 12 weeks in the Colorado River, directly below Hoover Dam from October, 1983 - January, 1984. Mean daily discharge from the dam decreased over this period. To assess the influence of these discharge changes on community dynamics, samples collected over the first 12 weeks of the investigation were compared to samples of the same age collected over the final 8 weeks.

The small diatom taxon Achnahthes spp …


A Proposal To Fertilize The Overton Arm And Gregg Basin Areas Of Lake Mead, Larry J. Paulson Nov 1984

A Proposal To Fertilize The Overton Arm And Gregg Basin Areas Of Lake Mead, Larry J. Paulson

Publications (WR)

Several limnological studies have been conducted in Lake Mead during the past decade. The recent studies clearly show that most of Lake Mead is deficient in nutrients, especially phosphorus, and very low in productivity. The reservoir-wide average total phosphorus concentration for 1981 - 1982 was only 9 mg/m3. This is below levels found In most oligotrophic lakes and reservoirs. Algal biomass, as measured by chlorophyll-a, averaged only 1.5 mg/m3. That also places Lake Mead in the oligotrophic range. Transparency, as measured by a Secchi disc, averaged 9-5 m in Lake Mead during 1981-1982. That far exceeds …


Wetlands Forest Communities As Indicators Of Flooding Potential In Backwater Areas Of River Bottomlands, Edward E. Dale Jr. Sep 1984

Wetlands Forest Communities As Indicators Of Flooding Potential In Backwater Areas Of River Bottomlands, Edward E. Dale Jr.

Arkansas Water Resources Center Technical Reports

A phytosociological study was made of forest types that occur in backwater and river bottomlands of the Gulf Coastal Plain, Arkansas Valley, and Mississippi Delta Regions of Arkansas. Twenty different forest types dominated principally by a single species were identified and described. Their occurrence was then correlated with flooding conditions in their habitats and the types were arranged along decreasing moisture gradients. Those forest types tolerant of flooding or saturated soils between three months to a year or more are Taxodium distichum, Nyssa aquatica, Cephalanthus occidentalis, Salix nigra, and Planera aquatica types. Those tolerant from one to three months are …


Use Of Microcomputers To Aid Wastewater Treatment Plant Operations, David G. Parker, Sandra C. Parker Sep 1984

Use Of Microcomputers To Aid Wastewater Treatment Plant Operations, David G. Parker, Sandra C. Parker

Arkansas Water Resources Center Technical Reports

This report presents the development of a microcomputer based data management system for wastewater treatment plants. The relational database model was shown to be well suited for data management applications in wastewater treatment plants. A general data management system was developed for use with a microcomputer using a commercially available relational database management system. Use of the developed system requires no special computer training. The system was tailored for use at the wastewater treatment plant at Springdale, Arkansas. The capabilities of the system were demonstrated with actual data from the Springdale plant.


Water Management Simulator Presentations, Leslie E. Mack Sep 1984

Water Management Simulator Presentations, Leslie E. Mack

Arkansas Water Resources Center Technical Reports

One of the larger stumbling blocks to comprehensive water management is the lack of public understanding of the multitude of variables that operate at the same time within the hydrologic cycle. With more public understanding, there is greater public support for various water projects. Dr. John R. Amend from Montana State University developed a water management simulator which could handle a large number of variables simultaneously of natural surface and groundwater flow plus a number of water use variables on an accelerated time sequence. By using several remote control devices, participants can "control" their water use but have no control …


Evaluation Of Nitrogen And Phosphorus Enrichment Using In Situ Enclosure Bags With Temporal Indigenous Phytoplankton Populations, Richard L. Meyer, W. Reed Green Sep 1984

Evaluation Of Nitrogen And Phosphorus Enrichment Using In Situ Enclosure Bags With Temporal Indigenous Phytoplankton Populations, Richard L. Meyer, W. Reed Green

Arkansas Water Resources Center Technical Reports

An in situ experimental procedure and protocol was developed to evaluate nitrate and phosphate enrichment using isolated indigenous phytoplankton assemblages during different seasons. Results of the comparison of the parameters-temperature, pH, alkalinity, conductivity, and dissolved oxygen between the open water and enclosed systems indicated that there was no significant influence of the physicochemical factors on the isolated biological processes. Growth responses were measured by turbidity, biomass and chlorophyll-a, the most sensitive being chlorophyll-a. Additions of nitrate and phosphate were added in known concentrations and in different magnitudes of concentration based upon ambient conditions and ratio. During the fall, phosphorus influenced …


Groundwater Quality And Mineral Deposits Relationships In The Ozark Mountains, Kenneth F. Steele Sep 1984

Groundwater Quality And Mineral Deposits Relationships In The Ozark Mountains, Kenneth F. Steele

Arkansas Water Resources Center Technical Reports

Ninety-nine groundwater sites were sampled in northern Arkansas in order to determine the effect of local manganese, phosphate, pyrite, lead-zinc and uranium mineralization on the groundwater chemistry. Most of this study (75 springs) was concentrated in the Batesville manganese district. Hydrogeochemical exploration for these types of manganese deposits appears possible with 44 percent of the springs within 2000 feet of mineralization having anomalous metal concentrations (especially manganese). Because only a few springs were sampled in the remaining areas, the results are not conclusive; however, only the pyrite and small lead-zinc deposit would appear worthy of additional investigation. None of the …


Studies Of Effectiveness Of Commercial Home Treatment Systems, William W. Trigg, Raymond D. Couser Sep 1984

Studies Of Effectiveness Of Commercial Home Treatment Systems, William W. Trigg, Raymond D. Couser

Arkansas Water Resources Center Technical Reports

Eleven home water systems were tested representing six different types of filtering systems. Tests were made for Sulfates, Nitrates, Phosphate, Iron and Escherichia coli and Enterobacter aerogenes before and after passing through a home treatment system. All of the systems removed iron adequately but had little effect on the removal of nitrates, phosphates, sulfates or control of pH. Since none of the ground waters was contaminated by coli- forms, nothing was established regarding the effectiveness of bacterial removal by these systems.


Factors Affecting The Removal Of Suspended And Dissolved Solids In High Strength Wastewater From Vegetable Processing, William A. Sistrunk Sep 1984

Factors Affecting The Removal Of Suspended And Dissolved Solids In High Strength Wastewater From Vegetable Processing, William A. Sistrunk

Arkansas Water Resources Center Technical Reports

Fifty or more individual factorial experiments were designed to study the effectiveness of physical-chemical and micro-biological treatments in removal of suspended and dissolved solids in effluent from potatoes, hominy, dry beans and other vegetables. The wastewaters were obtained from local processing plants and treated with 3 to 5 inorganic salts, 13 polymers, and 3 or more pH levels during 12 months. Also, selected strains of yeast and fungi were used to assimilate the effluent. Individual inorganic salts were more effective on a certain vegetable effluent than others. Polymers (anionic and cationic) were more effective in coagulating suspended solids in combination …


Evalution Of Drainage Tile To Alleviate Salt Building In Heavy Soils Irrigated With Brackish Water And Cropped With Rice And Soybeans, T. C. Keisling, J. T. Gilmour, H. D. Scott, A. M. Sadeghi, R. E. Baser Aug 1984

Evalution Of Drainage Tile To Alleviate Salt Building In Heavy Soils Irrigated With Brackish Water And Cropped With Rice And Soybeans, T. C. Keisling, J. T. Gilmour, H. D. Scott, A. M. Sadeghi, R. E. Baser

Arkansas Water Resources Center Technical Reports

The use of tile drains for alleviating soluble salt accumulation on silt loam soil was investigated during 1984. Although the chemical analyses of the floodwater and tile drainage water were very similar suggesting that the floodwater was moving to the tile drain, the overall results so far indicate that this is not a feasible solution owing to lack of significant drainage. Application of DRAINMOD utilizing soil and weather data from Arkansas showed no significant effluent from the tile drains for our experimental site during rice production. This was attributed to the extremely slow saturated hydraulic conductivity values for this particular …


Precedings Of Arkansas Lakes Symposium Limnological Studies Of Lake Chicot, Arkansas, Joe F. Nix, Frank R. Schiebe Aug 1984

Precedings Of Arkansas Lakes Symposium Limnological Studies Of Lake Chicot, Arkansas, Joe F. Nix, Frank R. Schiebe

Arkansas Water Resources Center Technical Reports

Lake Chicot is an oxbow lake that was created more than 600 years ago by the meandering of the Mississippi River. It is located in Chicot county in southeastern Arkansas adjacent to the present Mississippi River. As the largest natural lake in Arkansas it earned an early reputation for its good fishing and recreational value. Development of a levee system forced the enlargement of the lakes watershed to its present 350 square miles. Initially this alteration affected only the volume flow through the lake, drastically reducing the water residence time. Because the watershed was located in one of the most …


Identification Of Critical Water Levels In Flooded Rice Fields, Carl L. Griffis Aug 1984

Identification Of Critical Water Levels In Flooded Rice Fields, Carl L. Griffis

Arkansas Water Resources Center Technical Reports

A mathematical model was developed to simulate the transient hydrology of a flooded rice field. With the model, users can determine the critical interlevee areas in which to monitor the water levels so that the irrigation well can be turned on at the critical low water level, and turned off at the critical high water level, in order to maximize water application efficiency. Sensitivity analysis performed with the model showed that it will be necessary to calibrate the model for each specific field. A calibration procedure has been developed.


Seasonal And Spatial Heterogeneity In The Limnetic Zooplankton Community Of Lake Mead, Gene Robert Wilde May 1984

Seasonal And Spatial Heterogeneity In The Limnetic Zooplankton Community Of Lake Mead, Gene Robert Wilde

Publications (WR)

Zooplankton samples collected from throughout Lake Mead, in 1981-1982, demonstrate the presence of a statistically significant seasonal and spatial heterogeneity in zooplankton densities. Seasonally, the major zooplankton groups were most abundant in the spring and fall, coincident with maxima in chlorophyll-a concentrations. Successions among the various rotifers, cladocerans and copepods present in the reservoir were influenced by food availability, diapause, predation by planktivorous fish and, possibly, water temperatures. Spatial heterogeneity in zooplankton densities was unrelated to water temperature, pH, conductivity and dissolved oxygen concentrations, but was related to the abundance of phytoplankton (chlorophyll-a concentrations) and fish. Statistical analyses indicate that …


Phytoplankton Ecology And Dynamics In The James River Estuary Virginia, U. S. A., Margaret J. Filardo Apr 1984

Phytoplankton Ecology And Dynamics In The James River Estuary Virginia, U. S. A., Margaret J. Filardo

OES Theses and Dissertations

Autotrophic biomass and productivity as well as nutrient distributions and phytoplankton cell populations in the James River estuary, Virginia, from Newport News Shipyard to the 0 o/oo isohaline, were sampled on a monthly basis from August of 1981 to December of 1982. Particular emphasis was placed on the very low salinity region (defined as the location where surface salinity measured between 0.0 and 0.75 o/oo based on conductivity) in order to determine the fate of fresh water phytoplankters upon being advected into the estuary because of their suspected role in the biogeochemical cycling that occurs there.

Both chlorophyll a and …


Laser-Photoacoustic Detection Of Water Pollutants, Gregory J. Salamo, Richard J. Anderson Mar 1984

Laser-Photoacoustic Detection Of Water Pollutants, Gregory J. Salamo, Richard J. Anderson

Arkansas Water Resources Center Technical Reports

We have investigated the potential of amplitude-modulation laser-photoacoustic scheme for the detection of trace pollutants in water. The technique has been found to be non-disturbing and easy-to-apply. In particular, the technique could be used to detect pollutants with a concentration corresponding to an absorption coefficient of 10-6cm-1. The sensitivity was found to be limited by a background signal resulting from light absorption by water. In addition to the amplitude-modulation scheme we also investigated the potential of a wavelength modulation scheme. Although this approach did reduce the background signal due to water absorption, we found the technique to be much more …


Las Vegas Wash Multispectral Scanner Survey, T. H. Mace, M. V. Olsen, Environmental Protection Agency Feb 1984

Las Vegas Wash Multispectral Scanner Survey, T. H. Mace, M. V. Olsen, Environmental Protection Agency

Publications (WR)

At the request of the U.S. Bureau of Reclamation, Boulder City, Nevada, the U.S. Environmental Protection Agency's Environmental Monitoring Systems Laboratory at Las Vegas collected multispectral scanner imagery of Las Vegas Wash on October 1, 1982. A combined maximum likelihood classification and editing procedure was used to classify the multispectral scanner imagery into 12 categories of land cover. The classification identified four categories of marsh vegetation, one category of riparian, two categories of mixed scrub, and two desert categories. Turbid water and cultivated land formed an "other" category. Area tabulations were formed by georeferencing the classification to the Universal Transverse …


Pasture Research Programme For The Medium Rainfall Zone Of Wa, C K. Revell, C W. Thorn Jan 1984

Pasture Research Programme For The Medium Rainfall Zone Of Wa, C K. Revell, C W. Thorn

Experimental Summaries - Plant Research

Field Assistants: I.R. Rose S.P. Davis Soil Analysis: I.A. Pritchard. A. Screening trials M. polymorpha var brevispina. M. truncatula. T. cherleri - 84KA41, 84KA42, 84KA43, 84KA47. B. Large scale M. polymorpha evaluation - 84KA38, 84KA39, 84KA40, C. Long term Medic species evaluation - 82KA44, 82KA45. D. Species characterization trials - 83KA66, 83KA67. E. M. murex evaluation - 83KA45. F. Dwalganup replacement subclovers - 83KA69. Since 1981, the major emphasis of the Katanning pasture programme has been to select pasture species suitable for replacing ryegrass on soils where Annual Ryegrass Toxicity (ARGT) has been a major problem. These soils have traditionally …


Algal Problems Of The Estuary, E. P. Hodgkin, P. B. Birch Jan 1984

Algal Problems Of The Estuary, E. P. Hodgkin, P. B. Birch

Journal of the Department of Agriculture, Western Australia, Series 4

The Peel-Harvey esturine system study began in 1976 because people living near Peel Inlet complained about the accumulation of water weeds and algae on the shores and the smell of hydrogen sulphide (rotton egg gas) that resulted from their decomposition. From 1974 efforts had been made to control this 'algal problem' by raking up the weed with tractors and carting it away. This 'cosmetic activity had little impact on the problem.

The immediate cause was obvious: a carpet of green algae covering about 20square kilometres of the bottom of Peel Inlet. From time to time this 'goat weed' floated to …


Sulphur Nutrition Of Pastures. Potassium Nutrition Of High Rainfall Pastures On Deep Sands, J. S. Yeates, M. F. Clarke Jan 1984

Sulphur Nutrition Of Pastures. Potassium Nutrition Of High Rainfall Pastures On Deep Sands, J. S. Yeates, M. F. Clarke

Experimental Summaries - Plant Research

A. Sulphur - High Rainfall. 1. Sources, rates, time of application of sulphur to pastures - 80AL1, 80AL4, 80AL48. 2. Sulphur nutrition of pastures - 83PE36. 3. S sources and rates on sandy soils of the high rainfall areas - 84HA20, 84HA27. 4. Maintenance of S on pastures on sandy soils - 84AL35, 84HA19, B4HA26. B. Sulphur - Low Rainfall. 1. Sulphur on pastures - 82AL9, 82KA4. C. Potassium. 1. Sources, rates, time of application of potassium on high rainfall deep sand pastures - 80AL6.


Lupin Growth And Water Use; Wheat, Barley, Pea, Rob Delane, J. Hamblin, A Bishop Ms Jan 1984

Lupin Growth And Water Use; Wheat, Barley, Pea, Rob Delane, J. Hamblin, A Bishop Ms

Experimental Summaries - Plant Research

84C16/84C17 Lupin Growth and Water Use. 84C19 Effect of Density and Nitrogen on Growth and Yield of Uniculm and Tillering Wheat. 84C20 Maturity, Nitrogen and Density Effects of Barley. 84C21 Wheat Variety Trial. 84C18/23/28/33 Pea Research in the Geraldton Region. 84C32 Effect of Terra Sorb on Wheat Yield.


Phosphorus Nutrition Of High Rainfall Pastures - Peel Harvey Estuarine System Study, J S. Yeates, D M. Deeley, M. F. Clarke, R A. Deyl, G. Cockerton Jan 1984

Phosphorus Nutrition Of High Rainfall Pastures - Peel Harvey Estuarine System Study, J S. Yeates, D M. Deeley, M. F. Clarke, R A. Deyl, G. Cockerton

Experimental Summaries - Plant Research

1. Field experiments. A. Sources, rates, time of application of phosphorous on high rainfall Pastures - 80AL2, 80ALS, 81AL5, 81AL6, 81KE2, 81MA4, 82AL10, 82HA31, 82HA32, 83HA26, 83HA27. B. Soil test calibration curve trials. 82HA20, 82HA26, 82HA29, 83HA20, 83HA21, 83HA22, 83HA23, 83HA24, 83HA25. C. P sources and rates on sandy soils of the high rainfall areas - 84AL33, 84AL34, 84HA18, 84HA25. D.Maintenance P trials - 84AL32, 84HA17, 84HA24, 84HA28. 2.Glasshouse Experiments. 84GL5 - 1. Phosphorus sources on subterranean clover on sandy soils. 2. Soil test calibration experiment.


Lupins Wheat Rotation Long Term Rotation Trials, I Rowland, W Hawkins Jan 1984

Lupins Wheat Rotation Long Term Rotation Trials, I Rowland, W Hawkins

Experimental Summaries - Plant Research

Long term rotation trials - 66M29, 67Cl3, 67N4, 68E5, 68SG5, 73SG16.

Lupins Wheat Rotation - 80TS3, 82TS2, 82M26.


Ecology Of Skeleton Weed (Chondrilla Juncea) In Western Australia, F D. Panetta Jan 1984

Ecology Of Skeleton Weed (Chondrilla Juncea) In Western Australia, F D. Panetta

Experimental Summaries - Plant Research

For the first time a laboratory for conducting this type of research has been established in South Perth, and it has been possible to type plants from mature leaf material. This obviates the necessity of waiting for plants to seed to be able to identify them. A total of six new collections were identified as belonging to either the broad-leaf or narrow-leaf forms, the locations for which are given in Table l.l..

Seed viability. To determine the amounts, viability and dormancy status of seeds produced by field-grown plants during summer and autumn months. Time course of seed production by field-grown …


Foliar Disease Of Wheat, A. G. P. Brown Jan 1984

Foliar Disease Of Wheat, A. G. P. Brown

Experimental Summaries - Plant Research

Wheat leaf diseases were at much reduced levels in 1984. This may have been caused by prolonged summer rain prematurely setting off dispersal of spores and also initiating microbiological breakdown of stubble residues. No survey was carried out in 1984 but a good indication of the seasonal effect can be gained by noting that in the spray-timing experiment at Badgingarra disease levels were extremely low until the end of August some 90 days after sowing. Timing of fungicide for Septoria and Yellow Spot control. 84BA32, 84GE59. Effect of Yellow-spot at Merredin (with S. Trevenen) 84ME57. Yellow-spot is common though not …


Water Use Of Alternative Wheatbelt Crop Species, A P. Hamblin, M W. Perry, D Tennant, Neil C. Turner Dr Jan 1984

Water Use Of Alternative Wheatbelt Crop Species, A P. Hamblin, M W. Perry, D Tennant, Neil C. Turner Dr

Experimental Summaries - Plant Research

84M5, 84M6, 84M7. Location: Merredin Research Station Merredin, Western Australia. Three experiments were conducted to measure the productivity and water use of alternative wheatbelt crop species on contrasting soil types in a dry mediterranean environment. Crop species investigated were wheat, barley, cereal rye, narrow leafed lupin and field pea. These were grown on three contrasting soil types, a red-brown earth, a sandy loam over clay and a deep loamy sand; all soils occurring within close proximity to each other. Detailed measurements were made of meteorological conditions, dry matter production, leaf area, root growth, soil water profiles, light interception and plant …


Molybdenum Nutrition, M M. Riley Jan 1984

Molybdenum Nutrition, M M. Riley

Experimental Summaries - Plant Research

Field trials. 1. Residual value of Molybdenum on an acid soil - 81NO40. 2. Residual value of Molybdenum on an acid soil - 81M2. 3. Residual value of Molybdenum on an acid soil - 81LG12. 4. Residual value of Molybdenum on an acid soil - 83ME82. 5. Residual value of Molybdenum on and acid soil - 82NO7. 6. Residual values of different Molybdenum sources - 84ME10. 7. Residual values of different Molybdenum sources - 84GE49. 8. Molybdenum requirements of wheat and lupins - 83ME10. 9. Molybdenum requirements of wheat, triticale and lupins - 84ME8. 10. Forms and rates of soil …


Grain Legume Agronomy Program, G H. Walton Jan 1984

Grain Legume Agronomy Program, G H. Walton

Experimental Summaries - Plant Research

Lupin Agronomy - varieties x environment - Wongan Hills R.S., Badgingarra R.S., Newdegate R.S., Mt Barker R.S. Lupin Agronomy - morphology x split seed – Mr J. wood, “Karakin”, Lancelin. Lupin Agronomy - Erregulla regeneration and rotation – Lancelin, Moora, Watheroo. Grain legume species comparison – 84ES1, 84LG38, 84MO10, 84ES1. Field pea evaluation – varieties. Aim: To compare the biological and seed yield adaptation to environment between morphological types of field pea. Field pea agronomy – 84KA18, 84LG25, 84ME42, 84MO33, 84MO34, 84N16, 84SG20, 84SG28. Sowing time x seed rate. Pea and wheat response to applied P – 84LG24, 84ME43, 84NO46, …


The Ecology Of Skeleton Weed .(Chondrilla Juncea L.) In Western Australia , Afghan Thistle (Solanum Hoplopetalum) Ecology, J. Dodd Jan 1984

The Ecology Of Skeleton Weed .(Chondrilla Juncea L.) In Western Australia , Afghan Thistle (Solanum Hoplopetalum) Ecology, J. Dodd

Experimental Summaries - Plant Research

1. The ecology of skeleton weed .(Chondrilla juncea L.) in Western Australia - 84PE18 Seed production and water use in the glasshouse. 1.2 Seed production and water use of field-grown skeleton weed (84BA17, 84BA18). Water use. 1.3 Germination in relation to soil water content. 2. Afghan thistle (Solanum hoplopetalum) ecology. 2.1 Water relations (84N048). 2.2 Growth in Afghan thistle (84N050). 2.3 Afghan thistle reproductive biology (84N049, 84N063, 84PE19).


Comparison Of Conventional Boomspray And C.D.A. Equipment For Weed Control In Cereals, J R. Peirce, B. J. Rayner Jan 1984

Comparison Of Conventional Boomspray And C.D.A. Equipment For Weed Control In Cereals, J R. Peirce, B. J. Rayner

Experimental Summaries - Plant Research

l. 84N067 - Ryegrass

2. 84N068 - Capeweed

3. 84ME69 - Capeweed

4. 84 (40-41) - Ryegrass & Radish

5. C.D.A. - Capeweed

6. Boomspray Capeweed

Comparison of conventional boomspray and C.D.A. equipment for weed control in cereals – 84C40, 84C41, 84ME69, 84NO67, 84NO68.

Effectiveness of Roundup C.T. with and without crop oils applied through Controlled Droplet Applicators (C.D.A.) – Wongan Hills Research Station.

Effectiveness of Roundup C.T. with and without crop oils applied through a conventional boomspray – Wongan Hills Research Station.


Pasture Species Evaluation In The Medium Rainfall Zone, C W. Thorn, C K. Revell, S Davies, I Rose Jan 1984

Pasture Species Evaluation In The Medium Rainfall Zone, C W. Thorn, C K. Revell, S Davies, I Rose

Experimental Summaries - Plant Research

The effect of mechanical defoliation on the production of legume species in the Katanning region - 84KA26. The effect of grazing on the seed production of legume species - 84KA27. The effect of gypsum and establishment techniques on Circle Valley medic - 84KA29. The effect of gypsum, tillage and nitrogen on cereal yields in a continous crop system - 84KA28. The effect of gypsum on cereal crop yield - Katanning, E. Garlick Kwobrup, D. Webse. Pasture probe evaluation. Aim: To determine the suitability of the Vickery single probe earth plate capacitance meter for determining pasture production.