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

Life Sciences Commons

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

156949 Full-Text Articles 181052 Authors 18103694 Downloads 355 Institutions

All Articles in Life Sciences

Faceted Search

156949 full-text articles. Page 2 of 3701.

The Regulatory Reform Recommendations Of The National Performance Review, Jeffrey S. Lubbers 2017 Selected Works

The Regulatory Reform Recommendations Of The National Performance Review, Jeffrey S. Lubbers

Jeffrey Lubbers

Of ten recommendations Mr. Lubbers discusses, several were of particular interest. These include encouraging consensus-based rule making and ADR in enforcement, as well as ranking risks and improving regulatory science.


The Specific Surface Area Values For Iowa Tills, Keith E. Schilling, Brian L. Gedlinske 2017 Selected Works

The Specific Surface Area Values For Iowa Tills, Keith E. Schilling, Brian L. Gedlinske

Brian Gedlinske

Specific surface area is a property used by earth scientists to estimate the proportion of expandable clay minerals in soils. In this study, specific surface area method is shown to compare favorably with standard clay mineralogical techniques in determining gross differences in expandable clay mineral content in tills. The results of over 100 measurements on till samples from Iowa indicate undifferentiated pre-Illinoian tills from southern and southwestern Iowa have the highest specific surface area values of Iowa tills (ranging from nearly 100 to greater than 150 m2/g) and Wisconsinan Dows Formation tills have the lowest average specific surface ...


Location And Efficiency Of The Iowa Feed-Manufacturing Industry, Allan A. Warrack, Lehman B. Fletcher 2017 University of Alberta, Edmonton

Location And Efficiency Of The Iowa Feed-Manufacturing Industry, Allan A. Warrack, Lehman B. Fletcher

Research Bulletin (Iowa Agriculture and Home Economics Experiment Station)

The American commercial mixed-feeds industry has experienced rapid growth, especially since World War II. Changes have occurred in the product produced, in the number, size, location, and technology of plants, and in the number, size, and organization of the purchasers of the industry’s products. The purpose of this study was to develop and use an analytical procedure to solve for the efficient number, size, and location of plants in the Iowa feed-manufacturing industry. Such information should assist the industry in adjusting to rapidly changing demand and technology.

The problematical situation out of which the specific objectives emerge is to ...


Plant Availability Of Added Phosphorus In Different Iowa Soils, Oetit Koswara, John J. Hanway 2017 Iowa State University of Science & Technology

Plant Availability Of Added Phosphorus In Different Iowa Soils, Oetit Koswara, John J. Hanway

Research Bulletin (Iowa Agriculture and Home Economics Experiment Station)

Laboratory and greenhouse experiments were conducted to study the availability of fertilizer P in 20 samples of different soils representing 10 of the principal soil associations in Iowa.

Ryegrass plants recovered an average of approximately 50 percent of the added fertilizer P during a 385-day cropping period in the greenhouse. It appeared that continued cropping would have resulted in very little additional recovery of the added P. Differences in recovery of the added P from the different soils were relatively small, despite differences in rate of fertilizer addition or differences in soil pH, CaCO3 content, level of available soil ...


Potential Agricultural Production And Resource Use In Iowa, Jerry A. Sharples, Earl O. Heady, Mahmoud M. Sherif 2017 U.S.D.A.

Potential Agricultural Production And Resource Use In Iowa, Jerry A. Sharples, Earl O. Heady, Mahmoud M. Sherif

Research Bulletin (Iowa Agriculture and Home Economics Experiment Station)

The purpose of this study is to estimate the production or supply potential of Iowa agriculture and is part of a regional study designed for this purpose. Two levels of efficiency are examined in the Iowa study, average technical efficiency and advanced technical efficiency. The pattern of output, resources used, and levels of farm income are analyzed under both conditions. This summary, however, refers only to the conditions of advanced technical efficiency.

A representative farm-aggregation model was used in a linear-programming analysis of resource allocation and potential production. Thirty-one Iowa farms (representative of all the commercial crop and livestock farms ...


Projected State And Regional Resource Requirements For Agriculture In The United States In 1980, Leo V. Mayer 2017 Iowa State University of Science & Technology

Projected State And Regional Resource Requirements For Agriculture In The United States In 1980, Leo V. Mayer

Research Bulletin (Iowa Agriculture and Home Economics Experiment Station)

This study projects resource requirements for United States agriculture under alternative farm programs and various levels of export demand in 1980. Cropland, man-hours of labor, and capital required to produce each level of output are projected for a farm economy ranging from a free market with no controls on crop production to strict controls on all major crops through acreage quotas. Resource requirements are estimated by first allocating crop production among the various regions o f the United States in a manner to minimize total costs of producing and transporting grain and oilseed crops to the final point of consumption ...


Allocation Of Milk Among Products To Maximize Gross Income Of The Nation's Dairy Farmers Under 1964 Demand Functions, George W. Ladd, Gail E. Updegraff 2017 Iowa State University of Science & Technology

Allocation Of Milk Among Products To Maximize Gross Income Of The Nation's Dairy Farmers Under 1964 Demand Functions, George W. Ladd, Gail E. Updegraff

Research Bulletin (Iowa Agriculture and Home Economics Experiment Station)

Linear equations of farm level demand were obtained for milk used in six different products. These demand equations were used in several quadratic-programming analyses to determine levels of farm marketings of milk and cream or allocation among products that would have maximized farmers’ cash receipts from marketings of milk and cream in 1964. Each analysis computed farm and retail prices for milk used in various products, quantity used in each product and total cash receipts. In one quadratic program, the solution was unconstrained; i.e., no upper limit was imposed on prices, and no lower limit was imposed on quantities ...


Factors Affecting Farmland Values In The United States, John E. Reynolds, John F. Timmons 2017 University of Florida

Factors Affecting Farmland Values In The United States, John E. Reynolds, John F. Timmons

Research Bulletin (Iowa Agriculture and Home Economics Experiment Station)

Farmland value has more than quadrupled since 1940. Before the early 1950's, however, changes in farmland value had been closely related to changes in farm product prices and net farm income. But since that time, farmland value has increased substantially without a corresponding rise in net farm income. This widening spread between farmland values and net farm income created the interest for this study.

Our major objective was to identify the principal factors affecting farmland value and to estimate the effect of these variables. To accomplish this objective, we developed hypotheses to explain the changes in farmland value that ...


Advance Of Irrigation Water On The Soil Surface In Relation To Soil Infiltration Rate: A Mathematical And Laboratory Model Study, Mohamed Asseed, Don Kirkham 2017 Purdue University

Advance Of Irrigation Water On The Soil Surface In Relation To Soil Infiltration Rate: A Mathematical And Laboratory Model Study, Mohamed Asseed, Don Kirkham

Research Bulletin (Iowa Agriculture and Home Economics Experiment Station)

Mathematical equations describing the horizontal advance of an irrigation stream on a soil surface are derived and discussed for different types of infiltration equations corresponding to different known field conditions. Complex variable theory is applied to transform certain complicated forms of infiltration equation solutions to algebraic forms. An irrigation model having a visible Plexiglas photographic front was constructed and operated to test the theory and obtain data not covered by the theory. Glass beads or soil aggregates constitute the porous medium; water is used as the seepage fluid. Potassium dichromate dye is injected into the porous medium to trace the ...


Econometric Analysis Of The Cattle Cycle In The United States, Josef Gruber, Earl O. Heady 2017 Iowa State University of Science & Technology

Econometric Analysis Of The Cattle Cycle In The United States, Josef Gruber, Earl O. Heady

Research Bulletin (Iowa Agriculture and Home Economics Experiment Station)

This study has been made to further explain the cattle cycle in the United States and in three selected regions. Structural models of the cattle cycle are specified and estimated, and hypotheses about their parameters are tested. For this study, the cattle cycle is divided into three cycles that include the inventory cycle, the price and income cycle and the slaughter and import cycle. Further analysis is then made to determine the important explanatory variables within each cycle. Several simultaneous equation models are constructed of the form:

y' (t)C + x' (t)B + u' (t) = o'

where y' (t), x ...


Estimation And Imputation Of Crop Yield Advances By States And Regions, Ludwig Auer, Earl O. Heady 2017 Economic Council of Canada

Estimation And Imputation Of Crop Yield Advances By States And Regions, Ludwig Auer, Earl O. Heady

Research Bulletin (Iowa Agriculture and Home Economics Experiment Station)

The objectives of this study were: (a) to estimate the proportions of crop yield change attributable to crop variety improvement, higher rates of fertilization, regional specialization and other crop yield variables and (b) to determine how the relative economic yield level per acre changed over a 20-year period.

The analysis covers major crops on a state, regional and national basis. Based on time-series data, over 80 state crop-production functions were estimated for corn, wheat, oats, barley, grain sorghum, soybeans, flax, cotton and tame hay. Annual state crop yields were considered a function of inherent soil fertility, weather, crop variety improvement ...


Cost Economies In Cattle Feeding And Combinations For Maximization Of Profit And Stability, Earl O. Heady, James R. Gibbons 2017 Iowa State University of Science & Technology

Cost Economies In Cattle Feeding And Combinations For Maximization Of Profit And Stability, Earl O. Heady, James R. Gibbons

Research Bulletin (Iowa Agriculture and Home Economics Experiment Station)

Economic growth is having many important impacts on the structure of farming. One of the greatest effects of national economic growth on farm structure comes through changes in the relative prices of resources.

At low stages of growth, as in the United States a century back or in underdeveloped countries now, the supply of capital is small relative to the supply of labor. Consequently, the price of capital is relatively high, and the price of labor is relatively low. This situation of resource price favors farming methods or technology resting mainly on labor. The advantages of large-scale production methods, as ...


Rural Value-Orientations And Farm-Policy Positions And Actions, George M. Beal, Joe M. Bohlen, Rex H. Warland 2017 Iowa State University of Science & Technology

Rural Value-Orientations And Farm-Policy Positions And Actions, George M. Beal, Joe M. Bohlen, Rex H. Warland

Research Bulletin (Iowa Agriculture and Home Economics Experiment Station)

There is limited consensus within the agricultural sector of the United States concerning government farm policy. American farmers differ widely in their perceptions of the proper role of government in agriculture.

It is generally believed that value and belief differences among farmers are meaningfully associated with the variety of positions and actions taken by farmers with respect to government farm policy. Several observers have suggested that, if these value and belief diversities can be clearly articulated and resolved, more rapid progress can be made toward solving many present farm problems. However, there is little information on the relationship between values ...


Efficient Organization Of The Farm Industry In The North Central Region Of The United States In 1959 And 1980, William E. Saupe, Donald R. Kaldor 2017 University of Wisconsin

Efficient Organization Of The Farm Industry In The North Central Region Of The United States In 1959 And 1980, William E. Saupe, Donald R. Kaldor

Research Bulletin (Iowa Agriculture and Home Economics Experiment Station)

For the organization of the farm industry to be efficient in terms of income maximization would require that farm output be produced at minimum factor cost, that aggregate farm output clear the market at prices covering the factor opportunity costs and that the product mix be geared to the consumers’ wants. Meeting these requirements would mean that the income of individual farm operators would be maximized and that the farm industry would make its maximum contribution to national income.

Implicit in conducting the research reported here was the hypothesis that existing resource and production characteristics of the farm industry were ...


Some Factors Influencing Populations Of The European Corn Borer, Ostrinia Nubilalis (Hubner) In The North Central States: Resistance Of Corn, Time Of Planting And Weather Conditions Part Ii, 1958-1962, A. N. Sparks, H. C. Chiang, C. A. Triplehorn, W. D. Guthrie, T. A. Brindley 2017 U.S.D.A.

Some Factors Influencing Populations Of The European Corn Borer, Ostrinia Nubilalis (Hubner) In The North Central States: Resistance Of Corn, Time Of Planting And Weather Conditions Part Ii, 1958-1962, A. N. Sparks, H. C. Chiang, C. A. Triplehorn, W. D. Guthrie, T. A. Brindley

Research Bulletin (Iowa Agriculture and Home Economics Experiment Station)

A cooperative project was conducted by the agricultural experiment stations of Iowa, Minnesota and Ohio and the U. S. Department of Agriculture to study the effects of weather, planting date and resistant hybrids as factors influencing populations of the European com borer, Ostrinia nubilalis (Hübner). Identical studies were carried out at Ankeny, Iowa; Waseca, Minnesota; and Wooster, Ohio, during a 10-year period, 1953-1962.

The first 4 years of the study (1953-56) were reported by Everett et al. (1958). The work reported herein is a companion bulletin to the Everett et al. (1958) publication and deals with the results of experiments ...


Evaluation Of A Firm Model In Estimating Aggregate Supply Response, Jerry A. Sharples, Thomas A. Miller, Lee M. Day 2017 U.S.D.A.

Evaluation Of A Firm Model In Estimating Aggregate Supply Response, Jerry A. Sharples, Thomas A. Miller, Lee M. Day

Research Bulletin (Iowa Agriculture and Home Economics Experiment Station)

The North Central Regional Research Project NC- 54, “Supply Response and Adjustments for Hog and Beef Cattle Production,” was started in 1961. The project statement lists these objectives:

(1) To estimate farm resource use and supply response of hogs and beef cattle in representative farm situations.

(2) To estimate total production of hogs and beef cattle and patterns of resource use for states in the North Central Region and for the nation.

(3) To determine the production situations and the areas in which a specified output of hogs and beef cattle would or could be produced most efficiently under various ...


Using The Storm Water Management Model To Predict Urban Headwater Stream Hydrological Response To Climate And Land Cover Change, J. Y. Wu, Janette R. Thompson, R. K. Kolka, Kristie J. Franz, Timothy W. Stewart 2017 Iowa State University

Using The Storm Water Management Model To Predict Urban Headwater Stream Hydrological Response To Climate And Land Cover Change, J. Y. Wu, Janette R. Thompson, R. K. Kolka, Kristie J. Franz, Timothy W. Stewart

Timothy W. Stewart

Streams are natural features in urban landscapes that can provide ecosystem services for urban residents. However, urban streams are under increasing pressure caused by multiple anthropogenic impacts, including increases in human population and associated impervious surface area, and accelerated climate change. The ability to anticipate these changes and better understand their effects on streams is important for developing and implementing strategies to mitigate potentially negative effects. In this study, stream flow was monitored during April-November (2011 and 2012), and the data were used to apply the Storm Water Management Model (SWMM) for five urban watersheds in central Iowa, USA, representing ...


Riparian Buffer Systems -- The Basics, Thomas M. Isenhart, Michael J. Tidman 2017 Iowa State University

Riparian Buffer Systems -- The Basics, Thomas M. Isenhart, Michael J. Tidman

Thomas M. Isenhart

If you have a stream running through your farm, you may be interested in learning about a conservation technique that has gained the respect of many Iowa landowners and conservation professionals. It is called a riparian buffer system and involves planting trees, shrubs, and native grasses along streams to prevent sediment and chemicals from entering creeks and rivers.


Quantifying The Role Of Riparian Management To Control Non-Point Source Pollution Of Pasture And Cropland Streams, James R. Russell, Daniel G. Morrical, John Kovar, Daryl R. Strohbehn, John D. Lawrence, Mathew M. Haan, Shelly Lee Nellesen, Thomas M. Isenhart, Richard Schultz 2017 Iowa State University

Quantifying The Role Of Riparian Management To Control Non-Point Source Pollution Of Pasture And Cropland Streams, James R. Russell, Daniel G. Morrical, John Kovar, Daryl R. Strohbehn, John D. Lawrence, Mathew M. Haan, Shelly Lee Nellesen, Thomas M. Isenhart, Richard Schultz

Thomas M. Isenhart

Grazing management practices have the potential to mitigate some problems with sediment and phosphorus loading in pasture streams. The project demonstrated possible strategies to lessen grazing impacts on streams.


Relation Of Riparian Buffer Strips To In-Stream Habitat, Macroinvertebrates And Fish In A Small Iowa Stream, Jeremy P. Duehr, Michael J. Siepker, Clay L. Pierce, Thomas M. Isenhart 2017 Iowa State University

Relation Of Riparian Buffer Strips To In-Stream Habitat, Macroinvertebrates And Fish In A Small Iowa Stream, Jeremy P. Duehr, Michael J. Siepker, Clay L. Pierce, Thomas M. Isenhart

Thomas M. Isenhart

Macroinvertebrate and fish habitat is often degraded as a result of agriculture. Riparian buffer strips are commonly used to counteract the negative effects of agriculture in headwater streams. We assessed the relation of multi-aged riparian buffer strips to in-stream habitat, macroinvertebrate and fish assemblages in an Iowa stream. In-stream habitat, macroinvertebrates, and fish were sampled from two buffered sites and two unbuffered sites, with the greatest substrate, water depth, and velocity heterogeneity occurring in buffered sites. The highest macroinvertebrate richness (11) as well as fish species richness (14), diversity (1.99) and IBI score (3 7) were found in the ...


Digital Commons powered by bepress