Soil water holding capacity – Definition & Detailed Explanation – Soil & Fertilizers Glossary

I. What is soil water holding capacity?

Soil water holding capacity refers to the ability of soil to retain water and make it available for plant roots. It is a crucial characteristic of soil that determines how well plants can access water for growth and development. Soil water holding capacity is influenced by various factors such as soil texture, structure, organic matter content, and compaction.

II. Factors affecting soil water holding capacity

1. Soil texture: Soil texture plays a significant role in determining the water holding capacity of soil. Sandy soils have larger particles and larger pore spaces, which allow water to drain quickly. On the other hand, clay soils have smaller particles and smaller pore spaces, which can hold onto water more effectively.

2. Soil structure: Soil structure refers to the arrangement of soil particles into aggregates or clumps. Well-structured soils have larger pore spaces that can hold onto water better than poorly structured soils. Compaction can disrupt soil structure and reduce water holding capacity.

3. Organic matter content: Organic matter acts as a sponge in the soil, holding onto water and making it available for plant roots. Soils with higher organic matter content generally have higher water holding capacity.

4. Compaction: Compacted soils have reduced pore spaces, which can limit the amount of water that can be held in the soil. Compaction can be caused by heavy machinery, foot traffic, or natural processes.

III. Importance of soil water holding capacity in agriculture

Soil water holding capacity is crucial for agriculture because it directly impacts crop growth and yield. Plants need water for various physiological processes, including photosynthesis, nutrient uptake, and transpiration. Adequate soil water holding capacity ensures that plants have a consistent supply of water, even during dry periods.

High soil water holding capacity can also reduce the need for irrigation, which can save water and energy costs for farmers. Additionally, soils with good water holding capacity are more resilient to droughts and extreme weather events, providing a buffer against climate variability.

IV. Methods to improve soil water holding capacity

1. Adding organic matter: Incorporating organic matter into the soil can improve its water holding capacity by increasing the soil’s ability to retain moisture. Compost, manure, cover crops, and crop residues are all sources of organic matter that can be added to the soil.

2. Mulching: Mulching the soil surface with materials such as straw, wood chips, or plastic can help reduce evaporation and maintain soil moisture. Mulches also help regulate soil temperature and suppress weed growth.

3. Avoiding compaction: Minimizing soil compaction through reduced tillage practices, controlled traffic, and avoiding heavy machinery on wet soils can help maintain soil structure and water holding capacity.

4. Improving drainage: Properly managing soil drainage through the installation of tile drains, contouring, or terracing can prevent waterlogging and improve soil water holding capacity.

V. Measuring soil water holding capacity

Soil water holding capacity can be measured using various methods, including:
1. Field capacity: Field capacity is the maximum amount of water that soil can hold against gravity. It is typically measured by saturating the soil with water and allowing excess water to drain.

2. Wilting point: The wilting point is the moisture level at which plants cannot extract water from the soil, leading to wilting. It is an indicator of the minimum amount of water required for plant growth.

3. Available water capacity: Available water capacity is the difference between field capacity and wilting point and represents the amount of water available to plants for growth.

VI. Examples of crops that benefit from high soil water holding capacity

1. Corn: Corn is a crop that benefits from high soil water holding capacity, as it requires consistent moisture throughout its growth cycle to produce high yields.

2. Soybeans: Soybeans also benefit from soils with good water holding capacity, as they have shallow root systems that rely on soil moisture for growth.

3. Wheat: Wheat crops thrive in soils with high water holding capacity, as they require adequate moisture for germination, tillering, and grain filling.

In conclusion, soil water holding capacity is a critical factor for crop production in agriculture. By understanding the factors that influence soil water holding capacity and implementing practices to improve it, farmers can optimize water use efficiency, increase crop yields, and build resilience to climate variability.