Reasons for clayey soil having little air:

Clayey soil is known for its high clay content, which significantly affects its air-holding capacity. Here are the reasons why clayey soil has little air:

1. Particle Size: Clay particles are the smallest among the different soil types (sand, silt, clay). Due to their small size, the spaces between clay particles are very compact, limiting the movement of air within the soil.

2. High Water Retention: Clayey soil has a high water-holding capacity. When the soil is saturated with water, the air spaces within the soil are filled with water, leaving little room for air. As a result, the soil becomes poorly aerated.

3. Poor Drainage: Clayey soil has poor drainage due to its fine particle size and compact structure. The fine clay particles pack tightly together, creating small pore spaces that restrict the movement of water and air. This limited drainage further reduces the amount of air in the soil.

Reason for mixing horse dung in the soil used for making surahis and matkas:

Horse dung, or horse manure, is often mixed with soil used for making surahis and matkas due to its numerous benefits. Here is why horse dung is used in this context:

1. Organic Matter: Horse dung is rich in organic matter, which provides essential nutrients and improves the soil structure. When mixed with the soil, it enhances its fertility and promotes healthy plant growth.

2. Nutrient Source: Horse dung contains a variety of nutrients, including nitrogen (N), phosphorus (P), and potassium (K), which are vital for plant growth. These nutrients are slowly released into the soil as the dung decomposes, providing a sustainable source of nutrition for the plants.

3. Soil Conditioning: Horse dung helps improve soil structure by enhancing its ability to hold water and nutrients. It increases the soil's water-holding capacity and reduces erosion by improving its ability to retain moisture.

4. Microbial Activity: Horse dung is a rich source of beneficial microorganisms that contribute to the overall health of the soil. These microorganisms aid in breaking down organic matter, releasing nutrients, and improving soil fertility.

5. pH Regulation: Horse dung has a slightly alkaline pH, which can help neutralize acidic soils. By mixing horse dung into the soil, it can help regulate the pH levels, creating a more favorable environment for plant growth.

In conclusion, clayey soil has little air due to its small particle size, high water retention, and poor drainage. On the other hand, horse dung is mixed with the soil used for making surahis and matkas because it provides organic matter, essential nutrients, improves soil structure, enhances microbial activity, and regulates pH levels.