Supply of moisture, nutrients and air affect physical properties of soil cause significant influence on tree growth. Such properties of soil relate chiefly to its texture, structure and porosity.

1. Soil Texture

The relative proportion of the various size groups of individual soil particles. The individual size groups are referred to as soil separates. Soil groups are recognized as clay (<0.002mm), silt (between 0.002 &0.02mm), fine sand (between 0.02 &0.2mm), coarse sand (between 0.2 & 2mm) and gravel (>2mm). Coarse textured soil is called light soil and fine textured soil is called heavy soil.

Importance

Soil texture plays crucial role for nutrient supplies, aeration, root development, moisture relations, etc

• Nutrient supplies: The fine-textured soils are high in nutrient status; but sandy soils are low in fertility.
• Aeration: Coarse-textured soils are better aerated than clayey soils.
• Root development: percentage of soil particles affect root development.
• Moisture relations: Coarse-textured soils are easily drained; fine-textured soils are poorly drained and hold much water on the large surface area

2. Soil Structure

The arrangement of individual soil particles into aggregates of definite size and shape. Clod (>25mm), prism, crumb (3mm), granules (upto6mm), etc are soil aggregates and their sizes differ.

Importance

• It affects soil moisture and soil air relations
• It is an indication of nutrient status and activity of micro-organisms in the soil
• It affects soil erosion. Crumb is least liable to erosion while single-grained structure is most liable to erosion

3. Soil Porosity

The extent to which gross volume of the soil is unoccupied by solid particles. Pore space is the space unoccupied by soil particles. Clayey soil has very small pore spaces and retain too little air, on the other hand sandy soils are well-aerated. Capillary porosity is the portion of soil not fulfilled by water when the soil is wet, whereas Non-capillary Porosity is the air space in a soil at field moisture capacity.

Importance

• It determines moitureand air relations of the soil
• It affects internal drainage and diffusion of soil air.