Question

4 inches of sand surface soil, the rest of the sail makes a ball with a 3/4 ribbon. What’s is the available water holding capacity?

Answer 1

To determine the available water holding capacity (AWHC) of a soil, we often consider several factors, including the texture and structure of the soil layers, as well as the depth of the soil. Based on the information you’ve provided, it seems like we have a sandy surface layer.

1. **Identifying Soil Type:** You mentioned "4 inches of sand surface soil." Sandy soils typically have a low water holding capacity due to their larger particle size. They tend to drain quickly.

2. **Soil Structure:** The "3/4 ribbon" could suggest that the underlying soil has more clay content, as clay soils can be molded into ribbons.

3. **Water Holding Capacity Values:**
- Sandy soil has approximately 1 to 3 inches of water holding capacity per foot.
- Clayey soils can hold approximately 6 to 8 inches of water per foot.

Assuming the underlying soil is a clay loam or similar and you only provided information about the sandy surface layer, we can approximate the AWHC:

### Calculation Steps:
1. **Determine the depth of soil:** You have 4 inches of sandy topsoil. For the sake of calculation, let's assume a deeper layer of clay below (let's just say 12 inches for reference).
2. **Estimate water capacity:**
- For the sandy top layer (4 inches):
- A conservative estimate is about 1.5 inches of water holding capacity per foot of sandy soil. Since this layer is only 4 inches (1/3 of a foot), we multiply this by 1.5 and convert:
- \(AWHC_{sand} = 1.5 \, \text{inches per foot} \times \frac{1}{3} \text{foot} = 0.5 \, \text{inches}\)

- For the clay layer (assuming 12 inches):
- Clay can hold about 6-8 inches of water per foot. For calculation, let's take an average of 7 inches.
- \(AWHC_{clay} = 7 \, \text{inches per foot} \times 1 \text{foot} = 7 \, \text{inches}\)

3. **Total AWHC:**
- Combine both capacities:
- \(AWHC_{total} = AWHC_{sand} + AWHC_{clay} = 0.5 \, \text{inches} + 7 \, \text{inches} = 7.5 \, \text{inches}\)

### Conclusion:
The available water holding capacity of your soil setup (4 inches of sand over a 12-inch clay layer) would be approximately **7.5 inches of water**. However, this is a generalized estimate and can vary based on exact soil textures, structures, and conditions present.