PPT CHEM SOIL

• Nature and Composition of the Soil

  • It is known that soil has its importance in different aspects. For example, in production of food; maintaining the balance of carbon, nitrogen, and phosphorus; and for the construction of building materials.
• Nature and Composition of the Soil

  • Soil also consists of water and air.
  • A typical productive soil has a solid fraction of almost five (5) percent organic matter and ninety-five (95) percent inorganic matter.
  • Other soils have at least one (1) percent organic matter, but some, such as peat soils, may contain as much as ninety-five (95) percent organic matter
• Horizon – the layer of a typical soil and is the product of complex interactions between processes that develop during weathering.

  The rainwater that percolates through the soil bring dissolved and colloidal solids to lower horizons where they are deposited.
• • Bacterial decay of residual plant biomass (biological process) produces slightly acidic carbon dioxide (CO2), organic acids, and complexing compounds that are carried by rainwater to lower horizons where they combine with clays and other minerals resulting in the change in the properties of minerals.
• • O Horizon/Organic Layer – The very top layer, made up of freshly fallen leaves, twigs, and other organic matter.
• • A Horizon/Topsoil
  • also contains most of the soil organic matter and is important in the productivity of plants.
• E Horizon/Eluviation Layer

  • It's the layer where dissolved minerals, organic matter, and fine clay particles have been leached (washed out) by percolating rainwater and moved to lower horizons.
• • B Horizon/Subsoil Layer
  • The B horizon is where materials that have been leached from the A and E horizons gather.
• • C Horizon/Parent Rock Layer
  • It's the partially weathered bedrock or other material from which the soil was formed.
• • R Horizon/Bedrock Layer
  • The solid, unweathered bedrock beneath the soil.
• • Not all soils have all horizons: The number and development of horizons can vary greatly depending on climate, vegetation, and other factors.
• • Horizon development is a slow process: It can take hundreds or even thousands of years for a fully developed soil profile to form.
• • Human activities can impact horizons:

   Practices like agriculture, urbanization, and pollution can alter soil horizons and their functions.
• • Water is essential for plant growth. It's part of the soil, acting like a highway to carry nutrients from the soil to the plant's roots and leaves. The water in a plant evaporates into the atmosphere from the plant’s leaves, a process called transpiration.
• • Soil transports nutrients to plants as they remove carbon dioxide and release oxygen during photosynthesis. The opposite happens during plant respiration.
• • Water in soil is influenced by capillaries and pores, with larger spaces being more available to plants. Soils with high organic matter can hold more water, but it's less accessible to plants due to sorption.
• Clay particles in soil have a strong interaction with water, absorbing it on their surface due to their high surface/volume ratio. However, when soil becomes saturated, it can lead to changes in physical, chemical, and biological properties.
• • This saturation can lead to oxygen depletion, causing degradation of organic matter and disrupting soil structure, which is harmful to plant growth. Most crops, except rice, struggle to grow in waterlogged soil lacking essential air for root growth.
• Soil Colloid

  • The term colloid is coined from the Greek word “kolla” meaning glue
  • Soil colloids are finer size fractions (clay and organic matter) of the soil. Because of their large surface area and the chemical structure of the materials involved, soil colloids are also considered as the most chemically active portion of the soil.
• Soil Colloid

  The clay fraction of the soil contains particles less than 0.002 mm in size. Particles less than 0.001 mm diameter in size possess colloidal properties known as soil colloids.
• Properties of Soil Colloid

  
• • Inorganic colloids are produced from the weathering of parent rocks and minerals. 
  • They are mostly fine clay particles that display thin plate-like bodies under a microscope. When these particles are homogenized in water, they stay afloat in absolutely, changing the water dark.
• hese colloids:

  • are repositories of water and plant nutrients which can be made available to plants as needed.
  • plays a role in the detoxification of substances that could harm plants that often absorb toxic substances in soils
• In determining soil productivity, the abundance and nature of inorganic colloidal material in soil are certainly an important aspect.
• The most common elements on the earth's crust are:

  Oxygen

  Sulfur

  Aluminum

  Iron

  Sodium

  Magnesium

  Potassium

  Titanium

  
• Organic Matter In Soil

  • Organic colloids also called humus which is the dark-colored, stable colloidal organic decomposed plant and animal remains
  • An organic colloid is normally amorphous or shapeless
• • Organic matter mostly determines soil productivity even though it typically constitutes only less than five percent of a productive soil.
• Importance of organic matter in soil:

  • source of food for microorganisms
  • undergoes ion exchange chemical reaction
  • influences the physical properties of a soil

  contribute to the weathering of mineral matter (a process by which soil is formed).
• Organic Matter in Soil

  Factors that Influencing the Build-up of Organic Matter in Soil:

  • temperature 
  • the availability of oxygen
• • Since the rate of biodegradation decreases with decreasing temperature, organic matter does not degrade rapidly in colder climates and tends to build up in soil.
• In water and in waterlogged soils, decaying vegetation does not have easy access to oxygen, and organic matter accumulates. The organic content may reach 90% in areas where plants grow and decay in soil saturated with water.
• Major Classes of Organic Compounds in Soil

  
• Major classes of Organic Compounds in Soil

  
• Major classes of Organic Compounds in Soil

  
• Soil Humus

  Humus is composed of:

  Humic and Fulvic Acids

  • a base-soluble fraction and an organic material that remains in the acidified solution
• Humin

  • an insoluble fraction and is the residue left when bacteria and fungi biodegrade plant material
• Humification

  • the process by which humus is formed
• Soil Humus

  • Humus is the Latin word for "earth" or "ground".
  • Humus is the dark organic matter in soil that is formed by the decomposition of plant and animal matter. 
  • It is rich in nutrients and retains moisture in the soil. 
  • Part of each molecule of humic substance is nonpolar and hydrophobic, and part is polar and hydrophilic. Such molecules are called amphiphiles
• • Humic substances, despite their small percentage in soil composition, significantly influence soil properties by acting as acid-base buffers, increasing water-holding capacity, binding metals, stabilizing soil particle aggregates, and increasing organic compound sorption.
• The soil solution is the aqueous portion of soil that contains dissolved matter from the chemical and biochemical processes in soil and from the exchange with the hydrosphere and biosphere.