Introduction

Plant available water holding capacity (PAWHC) refers to the amount of water that soil can hold for plants to absorb. It is a crucial soil property that determines the success or failure of agricultural and horticultural activities. In this article, we will explore the various methods of finding PAWHC and how this information can be used to make informed decisions about crop selection and irrigation.

Method 1: Field Capacity and Permanent Wilting Point

The field capacity is the maximum water holding capacity of soil after continuous saturation with water. In contrast, permanent wilting point is the minimum moisture level in soil after prolonged exposure to drought. The difference between field capacity and permanent wilting point is an indicator of PAWHC. This method involves taking soil samples and using laboratory techniques to determine the field capacity and permanent wilting point. Once these values are obtained, the PAWHC can be calculated as the difference between field capacity and permanent wilting point.

Method 2: Field Estimation

Field estimation is a practical method of determining PAWHC without laboratory analyses. This method involves digging a hole in the soil and gradually adding water while observing the soil’s behavior. The soil is considered to have reached field capacity when water starts to seep out of the hole. Similarly, the soil is considered to have reached the permanent wilting point when the added water fails to increase the soil moisture level. By subtracting the weight of the soil at permanent wilting point from the field capacity, the PAWHC can be calculated. Field estimation is simple and accessible, but it may not give precise and accurate results.

Method 3: Soil Texture Analysis

Soil texture analysis involves measuring the proportions of sand, silt, and clay in the soil. The water-retention capacity of soil is closely related to soil texture. For example, sandy soil has low water retention capacity, while clayey soils have high water retention capacity. Soil texture analysis can be performed by a laboratory, or it can be done through the use of simple field tests such as the ribbon test. Once the texture of the soil has been determined, the PAWHC can be estimated based on the texture classification.

Method 4: Soil Moisture Sensors

Advancement in technology has led to the development of soil moisture sensors. These sensors can be inserted into the soil to measure the soil’s moisture level in real-time. This method provides accurate and precise PAWHC data as soil moisture levels can be monitored throughout the crop growth cycle. Soil moisture sensors have the added benefit of reducing over-irrigation, which can lead to waterlogged soils and nutrient leaching. However, this method can be expensive and may require technical expertise.

Conclusion

In conclusion, the determination of PAWHC is essential in agriculture and horticulture to optimize plant growth, minimize water usage, and prevent soil degradation. The methods of determining the PAWHC discussed in this article include field capacity and permanent wilting point, field estimation, soil texture analysis, and soil moisture sensors. Each method has its advantages and limitations, so it is necessary to choose the most appropriate method based on the resources available and the accuracy required. By employing these methods, farmers and gardeners can make informed decisions about crop selection and irrigation practices to achieve optimal results.