Soil is the upper layer of the earth's crust, which was formed as a result of the destruction of the planet's rocks and the vital activity of microorganisms. Soil can be considered the living matter of the earth's crust, which gives life to plants.
Microorganisms settle on mountain rocks. They feed on carbon, nitrogen from the atmosphere and rock minerals, and release substances that gradually destroy the stone. Further, mosses and lichens are taken up, which also change the composition of the rock.
Lichen residues are decomposed by microorganisms that synthesize humus (humus) and enrich the still infertile soil. On this soil, trees and shrubs grow, which herbivores feed on. The remains of living organisms further change the structure of the soil and enrich it with nutrients. As a result of this constant process, a layer of soil is developed from several centimeters to 2-3 meters.
First of all, the soil serves as a support for the plant. Fixing roots in the soil, the plant receives the necessary minerals, fertilizers, water, air. Most land plants will not survive unless their roots "breathe". While in the soil, the plant roots are protected from sudden temperature changes.
The soil consists of minerals (about 55-60%), organic matter (5-10%), water (20-30%) and air (10-20%). Microorganisms and other animals live in the soil, which loosen and process it. The soil contains clay and sandy particles. Clay soils do not absorb water well, because clay particles are very small and tightly pressed against each other, sandy, on the contrary, absorb well and pass water through themselves.
Heavy soils contain a lot of clay particles, which contain a lot of nutrients, but they are damp and sticky and poorly breathable. Light soil contains a lot of sand, which makes it more crumbly, but it does not retain water and nutrients well. The loose (or granular) structure of the soil consists of lumps of different sizes, absorbs moisture well and allows air to pass through. When humus is introduced into it, such soil is best suited for plant roots.
There are also loamy and sandy loam soils, in which the ratio of sandy clay particles is approximately the same. Such soils are also suitable for farming.
Soils without a dust structure are the least suitable for growing plants. It does not hold water well, and air does not penetrate to the roots.
Soils are acidic, neutral and alkaline. The higher the concentration of hydrogen ions (H +) in the soil, the more acidic it is. If there are few such ions in the soil, then it is alkaline.
The indicator of soil acidity is pH, the lower its value, the more acidic the soil:
To determine the acidity of the soil, litmus indicator papers are used. Papers are placed in a solution with soil and its pH is determined by color in accordance with the scale attached to the instructions.
Different plants need different soil. For example, azalea will not grow in alkaline soil, and lemon will not grow in acidic soil. When watering, fertilizing, the pH of the soil changes, therefore for plants accustomed to acidic soil, a few drops of lemon juice are periodically added to the water for irrigation.
Acidity, like alkalinity, affects the availability of various elements for a plant: nitrogen, phosphorus, potassium, etc. For example, a plant will not receive nitrogen in strongly acidic or highly alkaline soil, in neutral soil there will be a low availability of manganese.
Basically, plants are suitable for soils from slightly acidic to alkaline, from pH 5 to pH 8
Peat, coniferous and heather land are acidic soils, and soddy (taken from chernozem) - neutral or alkaline soils.
The universal soil for plants has a pH of 5.5-7.5, the soil for flowering plants is pH 5.5-6.8, and the soil for violets is pH 5.5-6.0.
To increase acidity, you can add to the soil mixture:
To lower the acidity of the soil, use: