Introduction

One of the essential requirements for plant growth and development is water. However, plants cannot use all the water in the soil, and the amount of water available to plants varies according to soil type, climate, and other factors. Understanding how to calculate plant available water is crucial for determining proper irrigation schedules and predicting crop yields.

Definition of Plant Available Water

Plant available water refers to the amount of water in the soil that plants can use for growth and development. It comprises water held in the soil pores, which plants can extract through their roots, and excludes water held too tightly in soil particles where the roots cannot access it. The plant available water is also affected by the forces holding the water in the soil, namely gravitational, capillary, and osmotic forces.

Factors Affecting Plant Available Water

Several factors affect the amount of plant available water in the soil. The first is soil texture; sandy soils have lower water holding capacity and, therefore, less plant available water than clay soils. Other factors include soil structure, organic matter content, temperature, and rainfall. The amount of plant available water also varies with the depth of soil, as some plants have longer roots and can access water deeper in the ground.

Methods to Calculate Plant Available Water

Various methods can be used to calculate plant available water. One of the most common is the soil water retention curve, also called the soil moisture characteristic curve. This curve plots the soil moisture content against the soil water potential, and it shows how much water is held in the soil at various tensions. The difference between the moisture content at field capacity and at the wilting point is also used to calculate plant available water.

Another method is the neutron probe, which measures soil moisture content by emitting neutrons into the soil and calculating the number returned. The probe can determine water content at different depths, providing information about the amount of plant available water for different crops.

Importance of Plant Available Water

Understanding how to calculate plant available water is crucial for irrigation scheduling and predicting crop yields. Irrigating crops at the right time with the appropriate amount of water can improve crop yield, quality, and water use efficiency. Additionally, predicting the amount of plant available water in the soil can help farmers make informed decisions about crop selection and planting dates.

Conclusion

In conclusion, plant available water refers to the amount of water in the soil that plants can use for growth and development. Soil texture, structure, organic matter content, temperature, rainfall, and root depth are all factors affecting the amount of plant available water. Various methods, such as the soil water retention curve and neutron probe, can be used to calculate plant available water. Understanding the importance of plant available water is crucial for proper irrigation scheduling and predicting crop yields.