Soil Science Mastery: The key to soil degradation restoration.

Soil Biology

Soil biology, is an understanding of the biological complexity and functions attributed to the different soil citizens in consideration to their abundance, related types of functions they perform, and how their living interact with each other. ?These organisms range in size from being visible with plain eyes to the very tiny ones that can only be seen from the advanced microscopes. They exist mainly at the top layer of the soil containing organic matter are significantly important in relation to the availability of soil micronutrients which naturally exist in complex forms. Organic matter in the soil is classified in terms of solubility in form with the water-soluble form being the fulvic acids (low molecular weight microbial products) and the water insoluble humin (humic acid acids). ?

Micro-nutrients occur in form of metal complexation with humic substances with different ionic bonding with low molecular weight organic acids. Fulvic acid which has a low molecular mass is associated with availability of pools of soil solutions forming dissolved mineral complexes. Therefore soil minerals such as copper considered as higher complexation stability has been attributed to its lower availability to plants affecting its mobility and availability. ?The overall availability of plant nutrients is associated with direct organic matter complexation, indirect organic matter complexation and microbial reduction or incorporation into amino acids and natural organic matter. The relation of the bonds between a particular mineral element and the organic matter solution is attributed to the availability or unavailability of the particular mineral element. Some elements may show signs of deficiency or toxicity depending on the buffering that stimulate bioavailability influenced by soil PH and organic bounds in the soil.

The great genetic diversity of the populations and mixtures of the soil biota (living components comprising earthworms, fungi, bacteria and viruses), play a significant role in soil health and affects the performance of the crops grown. The soil health attributes affects soil structure, water availability and the complexation of the mineral elements critical for crop growth. Soil decomposition, nutrient cycling and nutrient availability to plants is associated with the below ground interactions of this soil community.

Soil Biology relationships

The complex relationship of the lives below the soil contributes a great value to air and water quality and form the greatest contribution to agricultural productivity. A great diversity of the live below the soil comprising of several genera of classified according to size from visible to invisible ranging from spiders, insects, earthworms, mites, springtails, arthropods, nematodes, protozoa, algae, fungi (mushrooms, yeasts, mildews, molds and rusts), bacteria and viruses. The soil food web is therefore a complex of relationships that influence the crop health, productivity, sensitivity to drought and diseases. There are a complex of many chemical transformations and reactions occurring in the soil at all times where these living organisms derive their livelihoods on.

ORGANISM TYPE AND SOIL FUNCTIONS

The components of a healthy soil contain a complex and very large number of different kinds of species representing different kingdoms classification in biological terms. These species range from the small animals, plant roots, fungi and bacteria. The range of the functions of the biological diversity in the soil ranges from decomposition of organic matter, mixing up of the soil aggregates, population dynamics control, induce diseases or opportunistic pest infestation (nematodes) induction, nitrogen cycling and carbon sequestration. Since plant roots comprise almost 25% of their plant mass, the role of these microorganisms is important in their breakdown and release into the soil for the next crop. Importance of the fungi in soil ecosystems related to breaking down of dead plants and animal tissues into humus, cellulose, starch and lignin which forms the food for the next level of organisms being the bacteria contributing massively to the nutrient cycling process. Mycorrhizal fungi also greatly contribute to nutrient cycling through their associations with bacteria and plants roots including biological nitrogen fixation. Some bacteria are also associated with conversion of soil nitrate into gaseous forms contributing to denitrification. Bacteria is also attributed to degradation of different organic compounds added into the soils such as herbicides, insecticides and other chemicals rendering them less harmful to the environment.

The main importance of understanding these relationship is for the health of the soil ecosystem, its stability and resilience to different cropping regimes without breaking down. The resilience of a healthy soil ecosystem is its ability to perform these functions under diverse conditions and its ability to bounce back or resume normal functioning after a disturbing incidence such as fire or a severe drought.

Different relationships between soil organisms exists such as commensalism involving two organisms living side by side without negatively affecting each other, parasitism?involves one organism benefiting from another with zero benefits to the other, and symbiosis where organisms relationship is beneficial to them. These relationships are affected by different soil operations with intense tillage decreasing microbial activity through destruction of unique microhabitats in the soil resulting in reduction of the microorganism diversity. Tillage activities increase oxygen loving microorganisms, while reducing the ability of the anaerobic microorganism.?Chemicals in Pesticides (fungicides, herbicides and insecticides), affect these soil relationships differently through creating imbalances where one species or more species may result in unstable relationships which may later be exhibited by excessive diseases or pests otherwise controlled in a healthy functioning ecosystem.

A healthy soil has features of predator-prey conflicts, mutual partnership, exploitation partnerships and different food pyramids all deriving their livelihoods from the energy of the sun and micronutrients found in the soil from decomposition of plant roots and leaves.

soil NUTRIENT AVAILABILITY. ?????

The availability of plant nutrients in the soil are greatly influenced by soil microbial activity, where soil fungi through mycorrhizal form mutualistic relationships enabling the plant to obtain nutrients while the fungi get carbon from plant roots. Legumes are known to have root nodules housing rhizobium bacteria which it provides with carbon, while this relationship helps in nitrogen fixation from the atmosphere for the plant to use including excess used later by subsequent plants once the legume plant dies. Soil water dynamics are influenced earthworms through burrowing in the soil creating small tunnels for water and plant roots to travel. Water influences the nutrient absorption by plant roots and thus the great value of earthworms greatly affected by pesticides and extensive tillage.?

Soil chemistry

This involves the analysis of the available nutrients that a soil can provide to support some planned activities and the relationship towards the specified activities ranging from deficiencies, excess, toxicity, and the equations of availability affecting the their relationship concerning their exchange. The analysis also helps in determining toxicity or presence of heavy metals which may not be effective in supporting some planned activities. Soil chemical composition somehow determines the presence and abundance of living organisms. Generally chemical composition is evaluated in the organic matter (40 – 45%), organic matter (5%), water (25%) and air (25%).

The chemical composition of the soil determines the soil reactions and the buffering ability in acidic or basic soils. Soil PH is the scale between being in an acidic state (1-6.5), neutral (6.6- 8.0) and alkaline (basic) 8.1- 14.0.?PH values below 5.5 have some of the nutrients strongly binding to the solution especially calcium, magnesium and phosphorous making them unavailable to plants for their optimal growth. Often soil remediation is done using calcium lime to make the crops obtain these nutrients from the soil.

?Soil PH in humid areas range between 3.5 – 6.5 considered acidic and in drier areas ranges between 6.6 – 9.0 considered alkaline. The description of the soil based on the PH value gives either the name of acidic soil, neutral (6.5-7.5) or alkaline.?The neutral PH range of 6.5- 7.5 has been indicated to be the best range for majority of crops where soil reactions are optimum. Most dry areas experience saline soil due to accumulation of soluble salts on the top layers of the soil. Globally, soils have been classified within their 6 categories of clay, sandy, silty, peaty, chalky and loamy giving 12 orders based on the parent material namely Alfisols, Andisols, Aridsols, Entisols, Gelisols, Histosols, Inceptisols, Mollisols, Oxisols, Spodosols, Ultisols and Vertisols. The addition of lime especially based on gypsum, increases the ability of the soil to absorb water reducing erosion and increases phosphorous availability for better crop performance.

?The soils electrical conductivity (EC) is a function that aims at determining the amount of salts in the soil (soil salinity), and is normally used as an indicator of nutrient availability relying on soil texture and available soil moisture.?Soil chemistry has been considered as the natural soil chemical composition of the soil in focus based on the natural chemical parent material. The type of rock could be classified as igneous, sedimentary, and metamorphic all giving distinct characteristics of the soil formed from them and their mineral component.

?Soil Physics

Physical soil properties studied in soil physics have a profound value in relation to soil ecosystem services in crop production and have been summarized in terms of soil consistency, density, porosity, structure, temperature and texture. These properties influence water content (water retention and transport), heat flow and gases exchange (oxygen and carbon dioxide) in the root zone, which are important in plant growth. ?The value and importance of these soil physical properties is their role and influence in the water movement, infiltration, soil evaporation and solute transport processes. Soil physics involves the understanding of the soil in its solid, liquid and gaseous phases, and their interactions to crop growth and related processes.

The universal term of soil structure relate to the composition of the different soil components in the particular soil type and how they influence the texture and bulk density of the said soil. The main soil aggregates of clay, loam and sand and their constituent percentages define the available pores in the soil responsible for the water holding ability of the soil used frequently in irrigation systems to determine irrigation frequency. The soil water dynamics influence soil water movement in infiltration and drainage, runoff and intensity of soil erosion.?Often soil is depicted as consisting of solids 50%, 25% and 25% gas, all with important aspects to the soils performance.

The liquid phase of the soil is comprised of soil water with its dissolved nutrients (chemicals) forming a solution influenced by the water quality. This liquid phase varies from 1% (extremely dry soil) to approximately 50 % (saturated/ flooded soil), which defines the state of the soil pores and relationship with water. Soil gaseous phase includes a mixture of gases such as nitrogen, oxygen and carbon dioxide which is normally estimated at 25% though highly influenced by moisture content.

The solid phase of the soil additionally contains minerals and organic matter with the coarse fragments and fine earth fractions in different percentages whereby the soil matrix has been indicated to comprise of sand, silt and clay. Sand is classified as having a size varying from 0.05 mm to 2 mm (terms used are very fine, fine, medium, coarse and very coarse) and are significantly associated with the water drainage properties of the given soil. Silt has size range of 0.02 mm to 0.05 mm with a larger specific surface area per unit mass and clay with less than 0.02 mm particle sizes having the largest specific surface area per unit mass.?Clay particles carry a negative charge, with their sticky and plastic behavior absorbing water, with observed swelling or shrinking depending on moisture content. Soil texture is influenced by the relative proportion of the soil aggregates of sand, silt and clay. Textural class is given by the different proportions of these aggregates contained in a particular soil. These textual classification, are used as an indicator of the suitability of the given land to support the different land use options and design appropriate soil management systems. Soil holding capacity in terms of moisture and nutrients, heat transfer, aeration and movement are all associated with the particular soil texture character.

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The percentage of the clay component influence the soil characteristics greatly and the importance of the inorganic soil component comprise more than 95% by weight of the total solid fraction for most mineral soils (top soil). These characteristics are influenced by the weathering of the parent material and secondary minerals and define the inorganic soil component. The important inorganic components can be summarized as size, shape, surface area, clay minerals and charge properties, swelling and shrinkage, water absorption and heat of wetting and finally the packing arrangement. The soils clay fraction, influence most soil properties and behavior related to.

a)?????Swelling and shrinkage capacity due to the expanding nature of the clay lattice.

b)?????High plasticity due to its ability to retain shape when moist clay is molded

c)?????Ease of hydration because of its high water affinity

d)????Dynamism of stickiness when moist and shrinkage causing caking and cracking when dry because of cohesive forces.

e)?????Presence of high density of negative charge leading to formation of electrostatic double layer when fully hydrated resulting from deficit created through ionic substitution or broken bonds.?