Soil Science Commons^™

How Do Bacteria Move Through Soil?, Mark S. Coyne, J. M. Howell, R. E. Phillips

Soil Science News and Views

The contamination of water supplies by fecal bacteria is an important water quality issue in Kentucky. Contamination may come from point sources, such as straight pipes depositing raw sewage into streams, or nonpoint sources, such as manure runoff from cropland. A direct cost of contaminating water supplies is the expense that homesteads or water companies incur to chlorinate, filter, and otherwise treat water to make it potable. Indirect costs are the time lost to illness from drinking inadequately treated water, slower weight gain in livestock drinking contaminated water, and the degradation of aquatic habitats.

Profitability Of Variable Rate Fertilization On A Kentucky Soil (A Theoretical Analysis), Lloyd W. Murdock, Paula L. Howe

Soil Science News and Views

Grid soil sampling and variable rate fertilizer applications are a part of the precision agriculture movement that has captured the interest of many farmers. Variable rate fertilization requires extra expense and effort plus the use of often unfamiliar technology. Global Positioning Systems (GPS) equipment and computer software are used to outline and grid the field into small manageable units or “cells” (usually 2.5 acres). Each grid cell is soil sampled and tested for pH and available nutrients. Fertilizer recommendations are made on each grid cell and the fertilizer is spread by each grid cell using a truck equipped with GPS …

Tillage Slows Fecal Bacteria Infiltration Through Soil, Mark S. Coyne, S. W. Mcmurry, E. Perfect

Soil Science News and Views

Bacterial pathogens can degrade ground water quality by infiltrating and eroding from land treated with poultry wastes. The potential for ground water contamination (as well as associated health risks and cost of water treatment) greatly depends on the depth of soil to the water table or bedrock and soil structure. Pathogens must move through the soil profile to contaminate ground water (although sinkholes can provide a direct channel from the soil surface to the water table in karst areas). Deep soils have less potential for contamination than shallow soils. Structureless soils retain fecal bacteria better than well structured soils. Research …

Infiltration Of Fecal Bacteria Through Soils: Timing And Tillage Effects, Mark S. Coyne, C. S. Stoddard, John H. Grove, William O. Thom

Soil Science News and Views

Land-applying animal wastes potentially exposes humans and animals to fecal pathogens, either by direct contact with soil and produce, or via ground water contamination. Some of these organisms are Salmonella, certain pathogenic Escherichia coli strains, protozoa such as Cryptosporidium and Giardia, and enteric viruses. Whether soil adequately filters these pathogens before they reach ground water depends on the interaction of porosity, texture, depth, water content, rainfall intensity and duration, and soil management.

The Effect Of Organic Matter On Maximum Compactability Of Soil, Grant W. Thomas, Gerald R. Haszler, Robert L. Blevins

Soil Science News and Views

Bulk density is the weight of a given volume of soil expressed by soil scientists as grams per cubic centimeter (g/cm3). The higher the bulk density, the lower the volume of soil occupied by pore space, that volume of soil in which air and water reside. Because of this, there is much interest on the degree to which soil can be compacted.

The Proctor test is a means of determining the maximum bulk density that can be attained in a soil sample. This "maximum compactibility" is widely used on highways and building foundations but has had little use in agricultural …

Factors Affecting Crop Response To Liming, Kenneth L. Wells, J. L. Sims

Soil Science News and Views

Soil acidity levels directly affect the rate, kinds, and degree of chemical reactions which take place in soil. Crops respond to varying degrees to these chemical reactions. For the most part, these reactions affect the solubility of mineral elements in soil and the activity of the soil's biological processes. As a result, the availability of many plant nutrient elements is regulated by soil acidity. The level of availability of plant required nutrients can be adequate, deficient, or toxic to the plant, depending on the nutrient, soil acidity, and the crop. That is why measurement of soil acidity is regarded by …

Developing Efficient Crop Production Systems, Kenneth L. Wells

Soil Science News and Views

Land is initially the most limiting resource to consider in setting up a farm system aimed at maximizing returns. This is because soil, its topographical features, and its physical and chemical properties are largely fixed. There is little which can be done about them except to manage soil fertility and control erosion. Over the long run, crop production from any land tract will be directly influenced by the nature and character of the soils in that land tract. For this reason, the most basic step in initiating or redesigning a farming operation is to get an evaluation of the soil …

Managing Soil Content Of Nitrate Nitrogen, Kenneth L. Wells

Soil Science News and Views

The concerns about leaching of fertilizer nitrogen (N} into groundwater which were raised in the late 1960's were largely silenced during the 1970's as our agricultural economy was massively expanded. But since the early 80's they have been raised again to the point that national legislation (the Clean Water Act) was put into place to bring purity of the nation's water supplies into compliance with EPA-established standards. Beyond the apprehension largely about nitrate (NO₃) levels in groundwater, the groundwater issue today also includes concerns about pesticides. At the current time, the public is apprehensive about drinking water and …

Effectiveness Of Surface Application Of Phosphorus And Potassium On Yield Of No-Till Corn Grown On Soils Testing Low Or Medium Below A Depth Of 3 Inches, Grant W. Thomas

Soil Science News and Views

When crops are grown continuously under no-tillage or very minimum tillage, there is a tendency for phosphorus (P) and potassium (K) to become concentrated at or near the soil surface. This occurs when P and K fertilizers are broadcast on the surface and not mixed with the soil as would occur with plowing. The result is a stratification of P and K such that the surface few inches become very high in those nutrients, but soil test levels remain largely unaffected below that. The question is whether high yields of no-till crops can be obtained under these conditions.

Tests With A Product Having Alleged Value For Increasing Plant Available Water In Soil, Gale Dunn

Soil Science News and Views

Currently, there are a number of products being marketed for agricultural and horticultural use that have tremendous water absorbing properties. Some of these products are polyacrylamides which are synthetic compounds with chemical and physical properties which allow them to absorb large amounts of water relative to their dry weights. The implied advantage for use of such materials is that they can absorb more water than the soil itself, and acting like a sponge, hold more plant available water in the root zone.

Managing Soils For Optimum Crop Production, Kenneth L. Wells

Soil Science News and Views

The major resources which must be manipulated to develop a farm operation are LAND, LABOR, CAPITAL, and MANAGEMENT. Of these four broad categories of resources, LAND is the one which imposes constraints which ultimately determine the productive capacity of the individual farming system developed. This is because land is a fixed resource from the standpoint of the nature and amount of it available for developing a specific farming system. In this regard, the allocation of LABOR, CAPITAL, and MANAGEMENT should be directly linked to LAND productive capability in order to economically optimize the farming system developed. In other words, the …

Potassium Mineralogy Of Kentucky Soils, Anastasios D. Karathanasis

Soil Science News and Views

Feldspars and mica minerals are the two primary natural sources of potassium for most agricultural soils in Kentucky. Potassium feldspars are common mineral constituents of loess deposits in western Kentucky. Mica minerals, although dominant in shales, are also found in variable quantities in siltstone, sandstone and limestone parent materials of soils in the other regions of Kentucky. Because most of the soils in the western Coalfields and western Pennyroyal, and to a lesser extent in eastern Pennyroyal and Bluegrass, are covered by a loess cap of variable thickness, their surface mineralogy has been influenced by the feldspar-rich mineralogy of the …

Using Residual Soil Fertility Effectively, Grant W. Thomas

Soil Science News and Views

During the past 30 years, the use of commercial fertilizer in Kentucky has resulted in increases in the levels of phosphorus and potassium in soils. As might be expected, the soil test levels are higher with tobacco than with any other crop. but all soils for all crops show increases in fertility levels. Comparisons between 1975 and 1985 (the latest year available) show the proportion of samples sent to the University of Kentucky that are medium or high in soil test phosphorus has increased considerably. Even more striking is the decrease in very low values of phosphorus.

Soil Microbes And Biotechnology, M. Scott Smith

Soil Science News and Views

There is nothing new about attempts to develop and market microbial products for crop or soil improvement. Several types of microbes have been sold for a variety of agronomic purposes for many years. With the important exception of rhizobial inoculants. these have been generally unsuccessful. Recently however. the scientific revolution in genetics and molecular biology, the need for low cost agronomic inputs. and widespread concern for environmental safety have tremendously stimulated research and commercial activity on microbial products. Claims that cheap, effective microbial inoculants can be developed for pest control, detoxifying pollutants, providing plant nutrients and improving soils have been …

Cutting Production Costs In 1986, Kenneth L. Wells, John H. Grove

Soil Science News and Views

With the stressful economic situation that continues to face Kentucky farmers in 1986, the College of Agriculture is continually asked, "What are some of the things which can be done to ease the cost-price squeeze?" In response to this question, the following suggestions for improved, more cost efficient soil and crop production management are offered: These management techniques to get the highest possible yields without added costs are sometimes overlooked although they can offer increased yield potential at no added cost.

Effect Of Soil Additives On Water Infiltration On Kentucky Soils, Lloyd W. Murdock

Soil Science News and Views

Many products are advertised and sold in Kentucky as soil additives to aid the movement of water into and through the soil. Most of these additives contain compounds that reduce the surface tension of water. That means that they change the way water is absorbed onto surfaces that have a tendency to repel water. However, their effectiveness in this regard has been questioned due to the huge volume of soil to be effected and the fact that our Kentucky soils are not hydrophobic. In order to determine the effectiveness of these types of products, an experiment was designed to test …

Mineralogy Of Kentucky Soils, Anastasios D. Karathanasis

Soil Science News and Views

Very few mineralogical data have been published for soils in Kentucky. As an initial attempt to classify mineralogy of the subsoil, a general mineralogy map of the state was constructed based on currently available information (Fig. 1). The map suggests that quartz, mica, and feldspars are the dominant minerals of the sqnd and silt size fractions and that illite, smectite, kaolinite and hydroxyinterlayered vermiculite or smectite dominate the clay size soil fraction. Soils of the Western Coalfields, Eastern Coalfields, and Eastern Pennyrile regions generally contain more quartz in the sand and silt fraction than soils of the Purchase, Western Pennyrile, …

Soil Testing: Improving Reliability, John H. Grove

Soil Science News and Views

Late summer is a good time to check forage and row crop fields for possible nutritional problems and to make plans for fall soil sampling. "Problem" areas can be identified for selective sampling and the test results can be used to plan fertilizer and lime expenses for the next crop production season. Fields scheduled for tobacco, small grain and/or double cropping need to be sampled first in order to determine lime, phosphorus (P) and potassium (K) needs before fall application.

Does Use Of Gypsum Improve Soil Structure In Kentucky?, V. P. Evangelou, Kenneth L. Wells

Soil Science News and Views

Gypsum is sometimes recommended as a soil amendment in order to improve structure. Although this practice is often used for reclamation of sodic soils (Na⁺ saturated) in the western USA, it's value in improving soil structure in Kentucky is questionable. The following discussion explains way.

Causes Of Soil Compaction And Ways To Minimize Them, Lloyd W. Murdock

Soil Science News and Views

In order for a soil to become compacted, two conditions must be present, pressure and a soil that will compact . Different soils have different compaction characteristics. Sandy loam soils compact most readily; however, most soils with a high percentage of sand compact easily. Silt loam soils are more resistant to compaction, but they too are easily compacted when wet. When silt loam soils are not wet, it requires high pressure to compact them. When the soil is wet, each particle is lubricated and less pressure is required to compact the soil. Clayey soils can be compacted; but, as they …

Effect Of Lime Quality On Soil Ph Changes, Monroe Rasnake

Soil Science News and Views

Quality of a liming material depends primarily on two factors - purity and size of the individual particles. Purity is an indication of how much active material is present. Particle size determines how fa st the lime can dissolve and react with soil acidity.

Current Research On Band Application Of Fertilizer To Burley Tobacco, J. L. Sims

Soil Science News and Views

Present Status: Generally, past research conducted in the United States has shown that only one-half to two-thirds as much fertilizer is required to produce maximum crop yields when the fertilizer is properly banded as when it is broadcast. However, the magnitude of plant response to banding compared to broadcast applications varies widely with soil nutrient levels, soil temperature, soil pH, and the mobility of the nutrient being applied. Greatest benefits from banding result from (a) applications to soils having low or very-low soil test levels of the nutrient in question, (b) applications to crops grown in cool climates, (3) applications …

Does No-Till Change Soil Management Practices?, Robert L. Blevins

Soil Science News and Views

Successful no-tilling requires a different approach to soil management practices. Since continuous no-tillage systems leave residues on the soil surface without mechanically mixing them into the plow layer and since lime and fertilizer are surface-applied, no-tilled soils have biological, chemical and physical properties contrasting with those of a plowed soil. For any crop production system to be widely accepted and used it must provide and maintain desirable physical properties of the soil, control erosion and replace nutrients removed by crops and other losses. This can be accomplished in a no-till system if proper management is used.

Soil Ph: What It Is, How It Is Measured, Why It Is Important, John H. Grove

Soil Science News and Views

Soil pH is related to the hydrogen ion (H⁺) activity of the soil-water system. The chemical definition of pH is as follows: pH=-log (H⁺). In other words, for a pH drop of 1 unit (e. g. from pH 6 to pH 5) there will be a ten~fold increase in H⁺ activity in the soil solution. If pH 1 rises by 1 unit, only one-tenth as much acidity will be present in solution. As such, pH is only a measure of the active acidity in the soil water solution bathing plant roots. This fraction of total …

Liming Tobacco Soils, J. L. Sims

Soil Science News and Views

Control of soil acidity by liming is very important in successful tobacco culture. Adding lime to an acid soil increases the availability of nearly all plant nutrient elements, increases the efficiency of added fertilizers, and prevents the toxic effects of high concentrations of soluble aluminum, manganese, and iron. It is a natural tendency for most Kentucky soils to become acid with time due to losses of bases (calcium, magnesium, potassium, and sodium) from soil by rainfall, However, tobacco soils possess certain unique problems that warrant careful monitoring of soil pH every two to three years.

Fertilization Of Double-Crop Soybeans, Grant W. Thomas

Soil Science News and Views

The improvement of minimum-and no-tillage methods has helped increase the double-cropped acreage of soybeans in Kentucky to about 700,000 acres. Similar increases have been observed in our neighboring states. Most double-cropped soybeans in Kentucky follow winter wheat harvested for grain. Thus, they are at a disadvantage if the wheat leaves the soybean crop with a nutrient-deficient soil.

Band Vs. Broadcast Application Of Fertilizer, Kenneth L. Wells

Soil Science News and Views

Current fertilizer prices coupled with other increased production costs have renewed interest in band applications of fertilizer as a means of lowering fertilizer costs while maintaining crop yields. Fortunately, much basic soil fertilizer research has been conducted over the years which provides an understanding of the relative merits of band and broadcast placement. The following discussion outlines the basic considerations involved in deciding which of these two placement methods may be more economically useful for specific crop production systems. To better understand these considerations, certain principles related to adding fertilizer to the soil should be kept in mind. These are …

Liming Needs Of Kentucky Soils, William O. Thom

Soil Science News and Views

A sound liming program is the first step in building and maintaining soil fertility. Lime lowers the acidity (raises pH) of soil and prevents the adverse effects of high concentrations of soluble aluminum, iron, and manganese on crop growth--effects often associated with acid soils. Maintaining a suitable pH assures adequate levels of calcium and magnesium. Liming an acid soil increases the availability of most essential plant nutrients, increases the efficiency of fertilizers, improves the effectiveness of some herbicides, and makes beneficial soil organisms more active.

Nitrification Inhibitors, Wilbur Frye

Soil Science News and Views

Nitrogen often limits the production of nonlegume crops because of inefficiency of N fertilizers. In some cases, more than half the fertilizer N may be lost from the soil. Therefore, it is important to use it as efficiently as possible. One way in which N fertilizer efficiency may be improved is by slowing the nitrification process in the soil.

Soil Surveys In Kentucky, Harry Hudson Bailey

Soil Science News and Views

Fifty-four Kentucky counties have modern soil surveys (published 1959, or later) using the mapping and soil classification procedures of the National Cooperative Soil Survey. The cooperators in the program include the USDA-SCS, USDA-FS, Kentucky Department for Natural Resources and Environmental Protection and the Kentucky Agricultural Experiment Station.