WATER-LOK: Soil Definitions
HYGROSCOPIC WATER: is water that dry soil will absorb from an atmosphere of water vapor.
CAPILLARY WATER: is water that is held with the aid of surface tension.
soil water tension is same as suction.
PETER VON FRAGSTEIN
University of Kassel, Department of Agriculture, Division of Alternative Agricultural Methods. Norbahohofst. 1a, D-3430 Witzenhausen, F.R.. Germany
Silicate Rock Dusts as Natural Fertilizers- Extracts from IFOAM - Bulletin for Organic Agriculture.
The use of silicate rock dust is very common in organic farming, especially in Central Europe. Reasons for that are: 1. rock powders combine nearly all nutrients that are liberated during pedogenic processes and which are essential components for all soil fertility and plant growth. Only nitrogen and phosphorous occur in minute quantities in the primary minerals. All elements valuable and those of no value are slowly released into the adjacent medium, thus the risk of over dosage can be neglected, Biological activity of the soil or compost heap plays the greatest role in solublizing nutrients out of the minerals, which suits that philosophy of fertilizing in organic farming. Nutrient losses by leaching, often a problem in modern fertilizing regimes, only take place in low rates. Thus a higher efficiency can be given by the application of these slow release fertilizers, especially on light soils.
Conclusion: Silicate rock dust act as slow release fertilizers with a wide nutrient supply except for N. The best profit will be made by their use on soils which tend to high nutrient losses due to natural conditions (tropical soils) or due to conditions of intensive production.
Various rock dust samples form other countries show varying degrees of heavy metals such as Mercury, Lead, and Cadmium which could lead to a possible build-up in the soil at the suggested high application rates needed for growth response.
According to Chuck Dixon of Turf Diagnostics Water-Lok increases reservoir capacity of the soil by increasing pore space. This is also documented by Agri-Systems in their report and percolation rate with sand and Water-Lok mix.
Corry Casci says it works well with Blue grass, which is the hardest grass to start. It works well with Fescue, Bermuda, Blue Grass
Soil water. Prime agricultural soils can store as much as 12 inches (30 centimeters) of available water, which is a great advantage in times of drought. Water is held in the soil by cohesion to other water molecules and by adhesion to colloid surfaces. Soils with smaller pores are more effective at holding water against the forces of gravity. Large pores are best at conducting water through the soil when water content is high.
When the ground is saturated, all the pores in a soil are filled with water. After about two days, water drains from the large pores, and the soil is in a condition known as Field Capacity. This is the maximum amount of water a soil can hold against the forces of gravity. Some water is held so tightly by adhesion that plants cannot pull it away. When plants cannot remove any more water from the soil, the field has reached what is called the wilting point. The amount of water between field capacity and the wilting point indicates the amount that is available to plants.
Soil particles. Sand, silt, and clay, which comprise the soil particles that are less than 8/100 inch (2 millimeters) in diameter, are often referred to as soil separates. Stone, gravel, cobbles, and boulders may be part of a field soil, but, because they are larger than 2 millimeters, they are not included in the analysis of soil texture. Sand particles range from 2/1,000 to 8/100 inch (0.05 to 2 millimeters) and are gritty to the touch. Silt is as smooth as flour when dry and holds water well; these particles are smaller than sand but larger than clay. Clay particles are less than 8/100,000 inch (0.002 millimeter) in diameter and are the soil separates most involved in chemical reactions in the soil. Clay particles have 10,000 or more times the surface area of the same weight of sand. Since water, nutrients, and organic matter are all held on surfaces, soils low in clay cannot support much plant growth. Too much clay, however, can make the soil sticky, plastic, and slow to take in water or air. Water-Lok does break down to clay size particles. However, Water-Lok does not become sticky and swell. Since nutrients, water and organic matter are held on surfaces, Water-Lok can improve plant growth when used in conjunction organic material that the desert is low on.
How to Improve Soil
Sandy soils can be improved only by adding humus and Water-Lok. Landscape gardeners sometimes add clay, but that is too difficult and expensive for the home gardener. Clay soils are lightened by the addition of humus and ground limestone. A layer of so-called agricultural limestone one inch thick can be spread over clay soil and dug in. This should be used in addition to the humus. Coal ashes, if they have been allowed to lie outside in the rain and snow over winter, can also be used to lighten clay soil. The ashes should be screened and only the finer particles used. A four-inch thick layer over the surface should be dug in to a depth of about eight inches.
No matter how rich the soil may be, as plants grow they take foods out of it. Unless food materials are returned, the soil grows poorer and poorer. For this reason, gardeners use fertilizer on the soil. Some plants, however, prefer poorer soils. Fertilizer should be applied in the spring when the soil is being turned over. Sandy soils require five or six pounds of fertilizer to every hundred square feet of surface. On loam and clay soils, three pounds are enough.
How Soil Is Formed
Soils are developed from mineral and organic matter and generally contain an active population of organisms. Unlike solid rock, soils are full of pores and channels that serve to conduct air and water. Each type of soil expresses characteristics of the parent material from which it developed and reflects changes imposed by its surrounding environment.
Five major influences on soil formation include the nature of the original parent material, weathering, climate, land surface features, and the action of plants and animals. These factors determine the physical and chemical properties of various kinds of soil.
Parent material is the basic mineral and organic material from which the soil is formed. There are three kinds of parent material: transported, residual, and organic. Transported material is by far the largest category; it is carried by wind, water, or glaciers from one site to another. Among the wind-transported materials are loessial deposits (composed of packed layers of fine, powdery soil), which give rise to many of the productive prairie soils and to dune soils formed by blowing sands in desert and coastal regions. Alluvial materials are deposited by rivers and provide rich productive deltas, floodplains, and terraces. Lacustrine deposits, formed in lakes, were later exposed by receding glaciers. Marine deposits occur along the margins of most oceans and gulfs. During the last Ice Age, huge continental ice sheets moved across much of Northern Europe, Asia, and North America. Their enormous weight crushed and transported material that later served as parent material for soil.
The residual parent material from which soil is formed is loose, slightly weathered rock called regolith. Residual formations settle in layers that range from fully weathered material at the top to unchanged parent material at the bottom. Organic parent material occurs when organic deposits accumulate in wet or cool regions. This material eventually develops into peat, or bog soil.
Temperature and precipitation are the main weathering and climatic factors that affect soil development. In arid regions where water is generally unavailable as a weathering force, temperature changes from day to night cause rocks to expand and contract, eventually cracking them into smaller and smaller particles. With little or no water to leach out minerals, the soils in arid regions are neutral or alkaline and have an accumulation of soluble salts. In areas of high precipitation, minerals are leached out of the soil at a rapid rate, rendering most tropical and semitropical soils highly acidic.
The greater the weathering processes at work, the finer the particles of soil that result. These particles range from gravel to sand, silty material, and, finally, clay. Clay formation is more rapid under conditions that favor weathering and leaching of minerals. Under extreme conditions, soluble elements such as potassium, nitrogen, calcium, and magnesium are removed, and the clay changes to koalinite and other highly oxidized clays.
Land surface features affect soil development by controlling the amount of erosion of topsoil and by influencing how water drains into the soil. The greater the slope in surface features, the longer soil takes to develop because steep slopes are more exposed to erosion that removes soil as it forms. On the other hand, depressions in the land that result in poor drainage and lack of adequate oxygen retard plant growth.
Plants and animals also help develop soil. When plants die, water leaches plant food from them and carries it down into the pore spaces. This organic matter, or humus, helps the soil to stay porous and crumbly. Plant roots help water to drain or percolate into the soil. In dry times capillary action draws water up the channels made by the roots, bringing with it material that has leached down. Plant root lets can split rocks by exerting pressure after working into cracks and crevasses.
Soil is enriched by the wastes and decayed bodies of animals. Some animals--ants and earthworms, for example--help by mixing the soil. Many insects directly enrich the soil by fertilizing flowers, thus aiding the spread of plant life.
How Soil Conservation Works
The United States had no national program of soil conservation until the economic depression and drought of the early 1930's. In 1933 the Soil Erosion Service (soon renamed the Soil Conservation Service) was created as a major division of the United States Department of Agriculture. It joined other federal and state agencies in providing technical advice in conservation programs.
The Soil Conservation Service has devised a land classification system that offers guidance in the proper use of land. Such factors as slope, type of soil, amount of rainfall, and humidity and vegetation are considered when determining land use for maximum productivity. Of the eight government-designated land classifications, classes I, II, III, and IV may be used for cultivated crops; however, classes III and IV require skillful management to avoid serious erosion. Classes V through VII can be used for forests and for grazing. Class VIII land, which includes sandy shores and extremely rocky places, is considered suitable only for wildlife or for scenic and recreational purposes.
Covering the ground with plants is one of the key elements in soil conservation. To confirm this, the Department of Agriculture experimented with two steep plots of adjacent land--one planted with crops and the other thickly covered with grass. The cultivated plot lost seven inches of topsoil in 11 years. By contrast, it was estimated that it would take 34,000 years to lose the same amount of topsoil from the grass-covered plot.
Plant cover tends to hold rainwater where it falls and thus prevents the soil from blowing or washing away. Gullies can be healed in many cases by new plants--for example, grasses, legumes, shrubs, and trees. They provide a tangle of leaves and stems that trap and hold in place part of the soil carried by runoff. Another way to heal gullies is to build brush dams across them at regular intervals. Then soil and water running down the gully are caught behind the dams and held in place.
To help prevent the start of erosion, farmers may use a variety of conservation measures:
Contouring. This practice involves plowing, planting, and cultivating sloping fields around hillsides, with curving furrows horizontal to the hill, instead of furrows running straight uphill and downhill. The curved furrows catch rainfall and allow much of it to soak into the ground. They also catch soil washing from higher levels.
Strip-cropping. Strips of close-growing plants, such as grasses or clover, are alternated between strips of clean-tilled row crops, such as corn and soybeans. The strips of close-growing plants hold water and keep it from eroding the cultivated strip below. These strips are planted on the contour.
Terracing. On long slopes a low ridge thrown along the outer side of the slope catches soil and rainwater and retards runoff.
Listing. In dry regions a lister plow can be used to throw a ridge of dirt to each side, creating a trough about 18 inches wide and 7 inches deep. Crops are planted in the bottom of the trough.
Shelterbelts. On treeless plains, belts of trees planted at the edges of fields break the force of winds across the fields and reduce wind erosion.
Deep tillage, stubble mulching. Instead of turning over the earth with a moldboard plow, a deep-tillage plow breaks the earth below the surface. It leaves the surface vegetation, or trash from the previous crop, to act as a cover.
Crop rotation. Planting different crops each year on a piece of land keeps the soil productive. One crop helps the next. For example, nitrogen needed for plant growth is added to the soil by legumes, such as clover, alfalfa, soybeans, and cowpeas. These combine nitrogen from the air with other elements and store it in the soil through their roots. In a year or two the plants can be plowed under. This is called green manuring. After the roots have rotted, other plants that need nitrogen but cannot use nitrogen in the air--for example, corn and potatoes--can use the stored nitrogen for growth. Rotations are programmed with strip-cropping by shifting the close-growing strips and the tilled strips at fixed intervals.
Cover crops. Land is kept covered in winter and summer with either a growing crop or the residue, such as corn stalks, from the crop previously grown. When cover crops are plowed under for green manuring, the plant foods added to the soil improve its water-holding capacity and increase its fertility.
Fertilization. Chemical or natural fertilizers replace the soil substances used up by crops.
Composition of Soil
Soils are composed of mineral matter and organic matter and contain pore spaces filled with water or air and soluble nutrients. Organic matter serves as a binder for mineral particles, contributing to good soil structure and tilth, which refers to the behavior of soil under cultivation.
The organic matter content of mineral surface soils ranges from less than 0.5 percent in highly weathered, sandy soils to more than 6 percent in poorly drained prairie soils. Soil organic matter undergoes continual breakdown from fresh plant residue to relatively stable humus. Initially plant residues are attacked by soil animals such as insects or worms. As breakdown proceeds, soil microorganisms begin their work. Carbon is changed to carbon dioxide, and complex nitrogen compounds are transformed to soluble forms that plants can use. Humus is also an important storehouse of phosphorus and sulfur.
Soil water and gases fill the spaces between mineral and organic matter. A total pore space that is 50 percent air and 50 percent water offers an ideal growth medium for most plants. The amount of space that is filled with water and the extent to which the water is held within the soil depend on the degree of saturation. As the soil dries, water is held more tightly in thin films that coat the particles of soil, and this water is not available for use by plants.
Minerals and nutrients that have been dissolved in the soil water contribute to the soil solution that is the nutrient lifeline for plants. Plants get food not from solid particles but from water in which food elements are dissolved. As plants take these nutrients out of the soil solution, many are replaced by the continual release of minerals from the breakdown of parent material. The type and amount of minerals in the soil and the rate at which they dissolve into water help determine the fertility of the soil.
Soil air occupies all the pore spaces in soil that are not filled with water. This air contains several hundred times as much carbon dioxide as the atmosphere and has nearly 100 percent relative humidity. The exchange of atmospheric and soil air is reduced in soils that have a high water content (as in poorly drained soil) or that have a reduced pore space (as in finely textured clays).
The color, texture, and structure of different soils can reveal clues about soil development and the presence of soil water. Color, the most easily observed property, can be used to identify chemical characteristics of soil that are otherwise difficult to determine. The most common colors are combinations of red, yellow, black, brown, and gray; each color indicates different soil characteristics.
The basic chemistry of soil includes colloidal structures, minerals, and macro nutrients and micro nutrients essential to plant life. Clay and organic matter are finely divided soil particles called colloids, which provide the site for most of the chemical reactions in soils. Colloids, though small, possess large surface areas and electrical charges that attract nutrients and water. Soil colloids bind nutrients and prevent them from being leached out of the soil.
Clay minerals are silicates arranged in microscopic sheets of aluminum and silica. The specific arrangement of these sheets and the type of elements within them determine the clay type. Many of these clays possess negative electrical charges that help retain elements such as potassium, calcium, and magnesium for plant use. These nutrients can move into the soil solution and be absorbed by plant roots.
Essential plant elements are those required for plant survival and growth. Three of these elements--carbon, oxygen, and hydrogen--are supplied by water and air, while 14 others, categorized as either macro- or micro nutrients, must be supplied by the soil. Macro nutrients include nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. Nitrogen, phosphorus, and potassium, known as primary elements, are commonly supplied in fertilizers. The other three are secondary elements and are added to the soil in the form of lime or, in the case of sulfur, as by-products of phosphorus fertilizers.
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