Why do floating plants have air spaces in their roots, stem and leaves? Large air cavities provide buoyancy for the leaf. These air spaces occur within stems, leaves and roots, and frequently link up to form a continuous passage for the circulation of oxygen to all parts of the plant.

Air is not essential for a plant’s growth; they can live without it. Plants absorb carbon dioxide from the air to use during photosynthesis. Air is absorbed into the roots of the plants to provide the necessary oxygen.

Important Uses of Air

• Sustain life and growth.
• Combustion.
• Maintaining Temperature.
• Supplier of Energy.
• Photosynthesis.

Air is important for living things. Breathing is part of a process called respiration. During respiration, a living thing takes in oxygen from the air and gives out carbon dioxide. This process gives animals and plants the energy to eat, grow, and live life!

Explanation: Take a beaker, and put some soil into it. Not enough to fill the beaker, about quarters of the way through would be okay. If air bubbles form on the surface, there is air in soil.

Air in water: Air is also present in water. Aquatic animals breathe the air which remains dissolved in water. When water is boiled, air bubbles can be seen coming up from the bottom of the pan. This simple activity shows that air is present in water.

Silt soils have less air space and clay soils offer the least. These soils have the ability to hold water, but often it can be too much, eliminating air that is required by roots for nutrient and gas exchange. Ideally, equal amounts of sand, silt and clay particles are desired.

Clay soil

All soils contain mineral particles, organic matter, water and air. The combinations of these determine the soil’s properties – its texture, structure, porosity, chemistry and colour.

Sand soil

The physical properties of the soil are very important for agricultural production and the sustainable use of soil. The amount and rate of water, oxygen, and nutrient absorption by plants depend on the ability of the roots to absorb the soil solution as well as the ability of the soil to supply it to the roots.

The mineral components of soil are sand, silt and clay, and their relative proportions determine a soil’s texture. Properties that are influenced by soil texture include porosity, permeability, infiltration, shrink-swell rate, water-holding capacity, and susceptibility to erosion.

Answer. The major soil physical properties are: Soil Texture. Soil Structure.

4. PHYSICAL PROPERTIES OF THE SOIL

• 4.1 Texture: Texture refers to the relative proportions of particles of various sizes such as sand, silt and clay in the soil.
• 4.2 Structure:
• 4.3 Consistence:
• 4.4 Partiole density.
• 4.5 Bulk density.
• 4.6 Pore space:
• 4.7 Atterberg limits:
• 4.8 Soil colour:

Two of the most important properties of soils are their texture and structure . By texture, we mean what soils are composed of and how this affects the way they feel and their cultivation. The main components of soil texture are: sand, silt and clay particles and organic matter.

The main physical soil properties are depth, temperature, texture, structure, bulk density and water-holding capacity. The main processes involved are infiltration, tillage, compaction, percolation, leaching, runoff and erosion (Fig. 6.1).

A soil’s physical and chemical properties affect plant growth and soil management. Some important physical and chemical properties of soil are mineral content, texture, cation exchange capacity, bulk density, structure, porosity, organic matter content, carbon-to-ni- trogen ratio, color, depth, fertility, and pH.