Soil Basics: Soil Moisture

Summary

This educational video script delves into the concept of soil moisture, explaining four key classes: saturation, field capacity, wilting point, and available water. It introduces the term 'bar' to measure soil tension and describes how soil feels wet at field capacity (0.1 to 0.3 bars). The script outlines the process of determining soil moisture by collecting a moist soil sample, weighing it, drying it in an oven at 105 degrees Celsius, and calculating the percentage of moisture. The focus is on the available water between field capacity and wilting point, crucial for plant growth.

Takeaways

• 💧 Soil moisture can be categorized into four classes, each with specific characteristics and measurements.
• 🌊 Saturation occurs when both large and micropores in the soil are filled with water, typically at zero bars of tension.
• 🌱 Field capacity is the point at which large pores have drained and only micropores retain water, usually at a tension of 0.1 to 0.3 bars.
• 🥀 The wilting point is when plant roots can no longer extract water, which is held tightly at -15 bars of tension.
• 🔥 Oven dry weight is determined by drying soil in an oven at 105 degrees Celsius for 24 hours.
• 🌱 Available water refers to the amount of water between field capacity and the wilting point, which is crucial for plant growth.
• 🧪 To measure soil moisture, a sample is collected, weighed, and then oven-dried to determine the oven dry weight.
• 📊 Percent moisture in soil is calculated by subtracting the oven dry soil weight from the wet soil weight, then dividing by the oven dry soil weight.
• 🌳 Understanding soil moisture is vital for assessing plant available water and ensuring proper irrigation and plant health.
• 🌡️ The measurement of soil moisture tension is crucial for determining the water-holding capacity and availability for plant use.

Q & A

What are the four different classes or ways to look at soil moisture?

The four different classes or ways to look at soil moisture are saturation, field capacity, wilting point, and oven dry weight.

What is meant by the term 'bar' in the context of soil moisture?

In the context of soil moisture, 'bar' refers to a unit of pressure used to measure the tension or suction force that water experiences in the soil.

At what bar value does soil moisture reach saturation?

Soil moisture reaches saturation at zero bars, where both large and micropores are filled with water.

What is the soil condition referred to as 'field capacity' and at what bar range does it occur?

Field capacity refers to the condition where the soil is wet and retains water in the micropores after the large pores have drained. This occurs at a tension of 0.1 to 0.3 bars.

Why is the term 'wilting point' used in soil science?

The term 'wilting point' is used because it is the point at which plant roots can no longer extract water from the soil, as the water is held at a tension of -15 bars.

How is the oven dry weight of soil determined?

The oven dry weight of soil is determined by drying a soil sample in an oven at 105 degrees Celsius for 24 hours.

What is the significance of 'available water' in soil?

Available water refers to the amount of water between field capacity and wilting point that is accessible to plant roots for uptake, also known as plant available water.

How is soil moisture content determined in the field?

Soil moisture content is determined by collecting a moist soil sample, weighing it, drying it in an oven at 105 degrees Celsius, and then weighing the oven-dried soil to calculate the moisture content.

What is the formula used to calculate the percent moisture in soil?

The percent moisture in soil is calculated by subtracting the oven dry soil weight from the wet soil weight, and then dividing the weight of the water by the oven dry soil weight.

Why is it important to measure soil moisture?

Measuring soil moisture is important to understand the water availability for plants, which is crucial for irrigation management and assessing plant health and growth.

How does the soil moisture content affect plant growth?

Soil moisture content affects plant growth by influencing the availability of water for plant roots. Adequate moisture is necessary for nutrient uptake and overall plant health.