why organic growth is not as dependent on soil pH as conventional growing.
The rocks that cover the earth’s surface are the source of soil.
Different types of minerals may be found in these rocks. As a result, the mineral content of soils made from these rocks varies.
Physical, chemical, and biological weathering reduces the rocks to ever-tinier fragments. Based on size, an arbitrary categorization scheme for these particles was developed. This category includes anything from clay particles to enormous rocks (very small). Sand, silt, and clay, which are the smallest of them, are the mineral components of soil.
Where they have worn from the rocks, soil particles could stay in situ (parent material). These soils vary over the surface as the underlying rock types differ, and they reflect the mineral composition of the parent material.
Soil particles are carried by streams and deposited in certain places, such as flood plains and river deltas. The streams collect soil particles from a variety of different rock types and across a wide region. Alluvial soils are what they are.
The movement of enormous icebergs, or glaciers, is another important factor in the formation of soil. As glaciers travel, the surface rocks are ground into soil particles. When glaciers melt, they leave behind soils that are rich in minerals and comprised of a variety of various rock types.
Organic matter, which includes both live and dead organisms, is present in soils.
These organisms enhance the quantity of air and water in soils by opening up pore spaces in the soil. The soil organisms, as well as the plants, depend on this air and water. In addition to other advantages, a healthy soil environment makes nutrients accessible for plant uptake.
In the soil, two gas cycles are ongoing continually. The carbon cycle entails the uptake of carbon dioxide by plants, the release of oxygen, and the production of glucose. The nitrogen cycle relies on soil microbes to transform free nitrogen from the atmosphere into nitrogen compounds a plant can consume.
Sand, silt, and clay are the three smallest rock fragments that make up soil minerals. These account for at least 95% of the soil solids. Sand and silt, the first two, are often made of silicon dioxide (quartz).
(There are a few exceptions to this, such the Caribbean’s calcium-containing sands and Hawaii’s black mineral sands.) Because silicon is the most prevalent mineral on earth after oxygen, most sands and silts are quartz.
The most stable of the typical minerals found in rocks, it is also. In terms of chemical weathering, quartz is more resilient. Conditions that are both acidic and basic have relatively little impact on it.
We utilize glass, a substance produced from quartz, to store caustic chemicals because of this. It is insoluble as well. Additionally, biochemical and biological weathering have little impact on quartz.
Additionally, quartz is more resilient to physical deterioration. Abrasion has less of an impact on it since it is one of the hardest minerals. This indicates that other minerals are broken down into very small particles and moved away by these forces when water and air move these particles around.
The comparatively stable quartz particles are left behind. Sand has a size range of 2 to.05 mm. Silt has a size range of.05 to.002 mm.
Clay is the third mineral that makes up soil. Since clay particles are so tiny, they cannot be seen individually without a magnifying glass. Sand and silt vary from clay in terms of their mineral composition and structure.
Clays were created largely via chemical and biological processes. Chemical recombination produces increasingly intricate chemical and physical structures from the minerals that wear away from the parent material.
The clays that are more stable among these are. Consequently, the unstable minerals in rocks recombine to form clays. Depending on the kinds of minerals present and the degree of weathering, clays differ in composition and structure. The size of clay particles is smaller than.002 mm.
The majority of clay particles are arranged into thin, plate-like formations. This structure enables clays to trap ions between these “plates” and stop water circulating through the soil from leaching them. Adsorption is the name of this holding mechanism. Water may also be absorbed between the plates by clay particles. Clay soils swell as a result of this.
The soil’s microbial community and the remnants of dead plants and animals in different states of decomposition make up the organic component of the soil. The organic matter in soils is made up of all of these things.
The average percentage of organic matter in total soil solids is 5 percent or less.
Typically, organic matter is split into three categories:
thoroughly broken-down scraps or humus
The alive, the recently deceased, and the “been dead a long time” are these groupings, to put it simply.
Numerous species of various sizes make up the live component of the soil’s organic matter. These include fungus, algae, bacteria, and protozoa. Additionally, there are mobile organisms like flagellates, nematodes, and microarthropods. Arthropods, mites, and earthworms are the biggest of them.
Even the living plant roots are included. About 15% of the soil’s organic matter is made up of this living component. These creatures continuously consume other organisms while exuding wastes, or they consume both recently deceased species and these wastes while exuding wastes. In the living portion of the soil, a continuous cycle of life, death, and feeding takes place.
Dead organisms, plant matter, crop leftovers, deceased roots, and organism wastes are all examples of fresh residues, often known as “the recently dead,” found in or on the soil. These serve as the live soil creatures’ nourishment. Numerous plant-needed nutrients are released when the fresh waste is digested, and humus is also created.
The term “humus” or “been dead for a long time” is sometimes used to refer to the whole soil organic matter. It is more accurately used to describe the stable, dark-colored part of soil organic matter.
Humus is generally stable because it contains complex molecules that are difficult for soil organisms to break down and new residue molecules that are too complicated for any creature to break down quickly.
Even though humus only constitutes about 5% or less of the organic matter in most soils, it has a variety of properties that make it an essential component of the soil solids. One of them is humus’ capacity to retain certain plant nutrients and stop them from leaching. Heavy metals and other potentially dangerous substances in the soil may be absorbed by plants but be buffered by humus.
All of the soil’s solids—water, minerals, and organic material—are composed of these three components. However, when we examine a loam soil that is in excellent condition, we discover that the solids make up just half (50%) of the soil’s overall volume.
Pore space makes up the remaining half of the volume. Both macropores—the gaps between soil aggregates—and micropores—the spaces inside soil aggregates—make up this area. The soil water is stored in both of these kinds of pores.
In ideal conditions, water occupies 20–30% of the pore space, or around 14% of the total soil volume. Water may fill all of the pore spaces during and immediately after a severe downpour or irrigation.
The soil’s porosity is essential for plant life. The majority of nonporous soils lack the ability to hold on to and absorb water for plant usage.
A nonporous soil also hinders the ability of most plant roots to develop.
The remaining 50% of the pore space, or all of the pore space devoid of water, is occupied by soil air. Depending on the water content, the soil’s air content changes. Rain or irrigation-generated water seeps into the soil, filling the pores and expelling the air. Air is sucked back into the soil as a result of water evaporating at the surface and draining out of the pores.
PHYSICAL PROPERTIES OF SOIL
Air, water, and soil are all interconnected. In other words, the quantity of pore space for soil air depends on how much water is going into or out of the soil.
Two phrases are used to describe the physical characteristics of soil: texture and structure. Despite the fact that they are often used interchangeably to refer to the same physical characteristics of soil, they are quite distinct.
The relative proportions of sand, silt, and clay that make up the soil’s mineral content are referred to as the soil texture. One characteristic of the soil that cannot be changed economically over a significant region is this one.
For specialty crops, texture in tiny sections may be altered by adding sand to a bed of clay soil, but soil management has little impact on texture.
In-place soil formation from parent rock material often reflects the makeup of the underlying rocks. Floods may add new material to the alluvial soils that blanket flood plains, although the material is typically deposited with the same texture. Because of prior stresses, glacial soils are now texturally stable.
The sizes of the mineral particles that make up soil are indicated by the four main labels used to categorize soils:
• Loamy; Sandy; Silty; Clayey;
Three of them—sandy, silty, and clayey—contain significant quantities of or just those elements. A group of soils known as loamy include a certain proportion of each particle size.
Sandy refers to soils with up to 15% of clay particles and at least 70% sand-sized particles. The texture of these soils ranges from medium to quite coarse. Sand is visible as individual grains, and when pressed, sandy soil crumbles.
Sand and/or clay make up the remainder of soils that include less than 100% silt, whereas soils that contain between 40% and 100% silt are described as being silty. The texture of these soils is medium.
Of the individual grains, only the largest can be seen.
Silt behaves and feels like clay when wet but like sand when dry. Dry silt has a sand-like texture and is readily crumbled. Wet silt tends to spread and adhere to one another and feels smooth and slick like clay.
A soil is referred to as being clayey if it includes at least 35 percent clay particles and the remaining material is made up of various sand and silt mixtures. The texture of these soils is good. Without magnification, one cannot see the individual clay granules.
Any amount of moisture in clay makes it seem slippery, and clayey soils are difficult to crumble.
Different quantities of the three soil size particles are present in loamy soils. These soils are the most complex in terms of soil texture class and have several subdivisions.
All of the several varieties of loam soils, including Clay Loam, Silt Loam, and Loamy Sand, include between 10 and 55 percent clay, between 60 and 88 percent silt, and between 0 and 85 percent sand.
However, the Loam Soil classification itself has a very low amount of clay, with the remaining ingredients being sand and silt: 7–27% clay, 28–50% silt, and 22–52% sand.