Full TGIF Record # 219004
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Web URL(s):https://listings.lib.msu.edu/nttfd/1951.pdf#page=7
    Last checked: 01/16/2017
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Publication Type:
Content Type:Abstract or Summary only
Author(s):Hagan, Robert M.; Stockton, John R.
Author Affiliation:Division of Irrigation, University of California, Davis, California
Title:[Porous mineral materials as amendments or conditions to improve the physical properties of soils]
Meeting Info.:October 7-9, 1951
Source:Proceedings of National Turf Field Days. 1951, p. 7-10.
# of Pages:4
Publishing Information:West Point, Pennsylvania: West Point Lawn Products
Keywords:TIC Keywords: Inorganic amendments; Perlite; Physical soil analysis; Problem-solving; Pumice; Soil amendments; Soil conditioners; Soil properties; Soil water retention; Vermiculite
Abstract/Contents:"For the past several years porous mineral materials such as vermiculite, pumice and expanded perlite have been used to a large extent as a plant rooting media and in packaging plants for shipment. Within the last year or two, they have been offered for sale as amendments or conditioners to improve the physical properties of soils. A few are extensively advertised and some extravagant claims are made for them. Among the advantages claimed for the use of these inorganic materials as general soil conditioners are that they "lighten" the soil, making tillage easier, improve soil aeration, retain nutrient elements, and hold water. They have been shown to be helpful where used in very large proportions as in rooting cuttings. However, it is questionable whether appreciable benefits are obtained when they are introduced in smaller proportions as would generally be necessary under field conditions. This study deals only with the effect of general soil amendments on the water relations of soil. Considerable interest has developed in the possibility of using inorganic soil amendments under turf, especially golf course putting greens. Were it possible to extend appreciably the interval between irrigations on putting greens, the cost of incorporating these materials might easily be justified. Too, the fact that these inorganic materials are relatively inert should afford the advantage of being effective over a long period of time as compared with organic substances. Inorganic soil amendments have no chemical effect on the soil, and probably little influence on the aggregation of soil particles; they merely dilute the soil without altering its inherent structure. Any improvement in the water relations of soils arising from their influence on root growth and water infiltration rates. The effectiveness of a given material will depend upon its specific physical properties, particularly its porosity. Pumice is a natural glass foam of volcanic origin. Its porous structure was developed by the rapid expansion of entrapped gases when the material was erupted. The pores are often tubular and many are of small diameter; its porosity is about 65% of its apparent volume. Approximately one-half of these pores can be filled with water, while the remaining pores are sealed or have dead ends which entrap air preventing the entrance of water. As yet it is not known whether plant roots could enter the finer pores of this material, or whether the rate of de-watering would be sufficiently fast to be of importance to plants. Scorea is a basic, vesicular lava in which relatively large pores have formed by the expansion of gases before the material hardened. Most of the pores are separated by thick walls and are interconnected. Expanded perlite is often called synthetic pumice. It is made by a process which expands natural perlite (a variety of obsidian) to produce many enlarged bubbles. The physical properties of perlites depend both on the raw obsidian used and on the processing. Two expanded perlites on the market today are "Soil Air" and "Sponge Rok". Most of the expanded perlite now produced is used for light-weight concrete aggregate where it is prized because of its very low moisture and gas absorption. However, it is possible that by suitable processing expanded perlites of quite different characteristics can be produced. Expanded perlites are very fragile and unless great care is exercised in mixing, much of the material is crushed to a fine dust. Vermiculite has a very unique accordion-like structure with spaces between plates which are easily penetrated by water. It retains more water than the other materials studied; its mechanical strength is low, and if kept wet, it may soon slake down to a pasty mass. Other products, including slate pellets and haydite have not as yet been examined. The usefulness of these numerous materials for water retention in soils is largely dependent upon the nature of their porosity. Total porosity is meaningless. What is needed is a measure of the open and interconnected pores. Also information on the size distribution of pores inasmuch as water will not completely fill very small pores unless air is removed under a high vacuum prior to wetting. A newly developed mercury injection apparatus is being used to determine pore size distribution. To evaluate the influence of amendments on the water relations of soils, consideration must be given to their effect on field capacity, wilting point, and total available soil moisture. Measurements were undertaken of the field capacities and wilting points for two soils mixed with several amendments. Data are now available for only two expanded perlites ("soil Air" and "Sponge Rok") and for vermiculite, as each reacted with Yolo loamy sand and Yolo clay. The water retention data suggest tentatively that the coarser particles of "Soil Air" and "Sponge Rok" have blind pores. When mixed with a sandy loam soil even in amounts up to 50% by volume, they do little to alter the field capacity, wilting portfolio or available mositure capacity. Most sandy soils are quite permeable to water and permit deep root growth. Therefore, it would seem that the use expanded perlites would not extend appreciably the irrigation interval on sandy soils. When added to clay soils, these materials may have little effect on the total available water per unit depth of soil but they may cause deeper rooting and improve infiltration rates. When added in the amounts now recommended, that is up to 20% volume, it appears that perlites would have little influence on the water relations of plants on many soils. Possible indirect amendments should be examined. In contrast, the use of vermiculite in sandy soils appears to offer a means for enlarging the available water capacity and lengthening the periods between irrigations. Its use in clay soils for this purpose would be less effective. In such soils, its value would probably depend upon its influence on rooting depth and infiltration rates. Unfortunately, when kept moist, vermiculite may slake down into a pasty material, causing poor drainage in high vermiculite soil mixtures. This property would seem to restrict its usefulness for improving the water relations of turf soils. It is hoped that these findings may be helpful in interpreting results of plot work. Some plots have been established in Los Angeles by Dr. Stoutemeyer and John Gallagher using pumice, scorea, expanded perlite and vermiculite. Additional plots are planned. Anderson in Missoula, Montana, has plots with vermiculite. The plots are essential for investigating such things as the resistance of these amendments to crushing under service conditions, their effect on rooting depth and their influence on the growth and general appearance of the grass. The other materials now available, especially pumice, will be studied. A better understanding of the pore structure of these products should aid in the selection of the most promising materials for field tests. In the lasts analysis the usefulness of these materials will have to be verified under typical field conditions before their value can be ascertained."
Note:This item is an abstract only!
ASA/CSSA/SSSA Citation (Crop Science-Like - may be incomplete):
Hagan, R. M., and J. R. Stockton. 1951. [Porous mineral materials as amendments or conditions to improve the physical properties of soils]. Proc. Natl. Turf Field Days. p. 7-10.
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    Last checked: 01/16/2017
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