What is soil

Soil is a thin layer of material of about one meter thick on the Earth’s surface. It is a natural resource consisting of weathered mineral and organic materials, air and water. There are three main types of mineral particles that can be found in soils: sand, silt, and clay. The mineral composition of the soil affects its properties, such as the capacity to adsorb water and nutrients.

 How is soil formed?

Soil formation occurs with matter originated from erosion, weathering of the bedrock, and deposition of materials through wind and water. Here in the Netherlands, sedimentation of soil particles by wind, water and ice has played a large role in the first step of soil formation. The second step in soil formation is the weathering by physical, chemical and biological processes on this matter

✅Soil profile the vertical section of the soil that indicate different layers (horizons) in soil.

✅Origin means different layers in soil profile which are similar in composition and other properties

✅O- horizon -also called organic horizon. An uppermost horizen in forest soils

✅A horizon elluviation process (washing out) of maximum leaching takes place.

✅B horizon illuvial process (washing in ) takes place

✅C horizon parent horizon, unconsolidated mineral matter

✅Master horizons - O ,A,E,B,C

Soil orders and there features 

Soils can be grouped into categories based on their present properties. The most general soil category is called order. 

All world soils are place into 12 orders.

1. Inceptisols :

 Young, embryonic soils with few diagnostic features.

These soils have better profile development than entisols but are less developed. The horizons are formed mostly from alteration of the parent materials with accumulation of clay. The productivity is limited due to poor drainage. Found in humid regions.

2. Entisols

Recently formed (Alluvial soils), little profile development.

Those soils that have natal, if any, profile development are known as entisols. Soils in desert belong to this classification. The productivity of these soils varies with their location and properties. With controlled water supply and proper fertilization, these soils have good productivity and good for vegetables, groundnut, citrus, wheat, paddy, etc.

3. Vertisols :

Dark or black swelling clays, deep cracks develop when dry.

 These have a high content of clays that swell when wetted (more than 30%). During the dry season, these soils on tract and give rise to deep cracks which disappear in the wet season or after irrigation. Found in sub humid or semi arid (Temperate to tropical) climates where temp. are moderate to high. Good for crop production with fine texture which are plastic and sticky when wet and hard when dry. Difficult to manage due to very little time for their proper preparation by tilling good for the production of cotton, millet, sorghum, wheat, paddy, etc.

 4. Oxisols : 

Oxide, sesquioxide rich soil, highly weathered soils of tropical regions.

These are most developing in tropical and subtropical climates. The subsurface horizons are high in clay and acid. The soils are productive with supplements of ‘P’ micro-nutrients.

5. Alfisols :

Relatively young soils, acid soils, larger in forest soils.

Develop in humid and sub humid climates (500 mm to 1300 mm rainfall) with gray to brown surface horizons. Soils are slightly too moderately acid and quite productive with good texture. Soils are frequently under forest vegetation.

6. Histosols :

 

Called organie soil, have more than 20% O.M.

These are organic soils (pleats and mucks) consisting of variable depths of accumulated plant remains in bogs, marshes and swamps that have developed under water saturated environment. Highly rich in organic matter i.e. Org. Carbon ranges from 12 to 18% in soils with low to more than 50% clay content.

7. Aridisols : 

Desert soils of arid regions.

Soils found in arid or dry areas with light in colour, poor inorganic matter and are not subjected to leaching, used for cultivation with irrigation. 

Process a horizon of CaCO3 (lime), Calcium sulphate (Gypsum) or more soluble salts. These are desert soils.

8. Spodosols:

Such soils are with sub soil accumulation of sesquioxide and humus.

Soils belong to forests with low content of bases, having coarse texture (sandy). Found in humid climates where temperatures are low. The subsurface horizons have accumulation of org. matter and sesquioxide.

9. Ultisols : 

Low nutrient, low base status, forest soils. Oldest soil.

These are strongly acid, normally forest soils with low content of bases extensively weathered soils of tropical and subtropical climates, respond to good mgt. practices, have clay of 1:1 type and give good crop production with adequate fertilization.

10. Mollisols :

Soft, grass land dark soils of steppes and prairies, high base status

Mostly these are grasslands having thick surface horizon of dark colour, dominated by divalent cations. Process normal granular or crub structure, do not harden on drying and with moderate to have fertilization soil are productive.

11. Endisols :

Devoloped due to volcanic eruption.

12 Gelisols

 Why are soils important?

Soils are the basis of life for a large amount of plants and animals. Next to their importance for biodiversity, soils are the essential substrate on which most agricultural plants grow. It means that this is where the food we eat comes from. In addition to that, soils play an important role in the structuration of the ground, which is essential for any sort of construction.

Why do plants grow in soils?

Plants thrive in soils because it brings them everything they need. They offer stability for their roots to support the stem, and nutrients such as nitrogen, phosphorus and potassium. They also contain a vast amount of interconnecting cavities - or “holes” in which the roots can find air and water, two essential elements for their growth.

 What is soil quality?

The definition of soil quality depends on the use of the soil. A good quality soil for agricultural production differs from a good quality soil used for building houses. In the case of agricultural production, physical, chemical and biological factors determining soil quality may be distinguished. Examples of physical factors are soil structure and water holding capacity. Regarding chemical factors, examples are pH or total amounts and available fractions of plant nutrients. Biological factors determine the capacity of the soil organisms to recycle nutrients and to resist to plant diseases.

What is a healthy soil?

A healthy soil is a stable living environment which enables all essential biological processes, and which is resistant against pests and diseases. It contains enough diversity of organisms coexisting so that germs do not affect it dramatically. Moreover, a healthy soil is able to recycle nutrients from the decomposition of organic matter into plant available forms, without high losses of nutrients in the environment.

Nutrients & Thier Sources

Nitrogen (N):-

Organic matter

Phosphorus (P):-

Apetite and Al & Fe phosphate

Potash (K):-

Micas, Feldspar, Biotite

Calcium:-

Dolomite,Calcite

Magnesium(Mg):

Dolomite,Muscovite

Sulphur (S):-

Gypsum ,Pyrite, Organic matter

Iron (Fe):-Pyrite, Magnetite

Molybdenum (Mo):-Olivine

Boron (B):-Tournialine

Manganese:-Magnetite

Zinc ('Zn):-Sphalerite

Chlorine (Ci):-Apetite