How to Calculate Plant Available Water in Meters

Plant available water is the amount of water in the soil that is available for plants to use. Calculating the plant available water in meters is important for determining the amount of water that is needed to irrigate crops. The following steps can help you to calculate the plant available water in meters:

Step 1: Determine the Soil Texture

The first step in calculating plant available water is to determine the texture of the soil. Soil texture refers to the relative proportion of different-sized mineral particles in the soil. There are three main soil textures: sand, silt, and clay. Soil texture affects the water-holding capacity of the soil. Sandy soils have a low water-holding capacity, while clay soils have a high water-holding capacity.

Step 2: Determine Soil Moisture Content

The second step is to determine the soil moisture content. Soil moisture content refers to the amount of water in the soil as a percentage of the soil's total volume. To determine the soil moisture content, take a soil sample and dry it in an oven at 105 degrees Celsius until it reaches a constant weight. Weigh the dried soil sample and calculate the moisture content using the following equation:

Moisture content = (wet weight - dry weight) / dry weight x 100%

Step 3: Calculate Field Capacity

Field capacity is the amount of water that a soil can hold against the force of gravity. To determine field capacity, saturate a soil sample with water and let it drain until there is no more free water. Weigh the soil sample and calculate the field capacity using the following equation:

Field capacity = (wet weight - dry weight) / dry weight x 100%

Step 4: Calculate Permanent Wilting Point

Permanent wilting point is the point at which a plant can no longer extract water from the soil. To determine the permanent wilting point, take a soil sample that has been dried to a constant weight and place it in a desiccator for 24 hours. Weigh the soil sample and calculate the permanent wilting point using the following equation:

Permanent wilting point = (dry weight - desiccated weight) / desiccated weight x 100%

Step 5: Calculate Plant Available Water

The final step is to calculate plant available water. Plant available water is the amount of water in the soil between field capacity and permanent wilting point. To calculate plant available water, use the following equation:

Plant available water = field capacity - permanent wilting point

Once you have calculated the plant available water in meters, you can use this information to determine the amount of water that is needed to irrigate crops. Knowing the plant available water can help you to optimize irrigation practices and maximize crop yields.