The available water capacity of soil is the amount of water that is held in the soil which is available for plants. This video contains a short illustration of available water from orchard soils. Authors Tianna DuPont, Andy McGuire, David Granatstein, WSU Extension. Recording from WSU virtual workshop Soil Health in Orchards with project support from the Washington State Tree Fruit Research Commission.
Text Transcript and Description of Visuals
| Audio | Visual |
|---|---|
| Title card reading “Available Water Capacity”, shown over an image of a hand holding a clump of soil | |
| Soils are a lot like sponges in the way they hold and release water. | Two hands hold soil samples. The top hand is labeled “High OM” and the bottom hand is labeled “Low OM”. The top hand squeezes the moist soil, releasing water. |
| If a soil contains mostly large pores, like coarse sand, it loses water quickly through drainage. | A close up image of a hand holding a clump of sandy soil. The soil appears |
| If a soil contains mostly small pores like fine clay, it holds on to water better, but water infiltration, aeration, and root growth can be limited. | A close up image of a hand holding a clump of fine clay soil. |
| The available water capacity of soil is the amount of water held in the soil available for plants. | Two soil samples are shown side by side in white filter papers, set in funnels over beakers. Water is poured onto both soils. Text labels identify one sample as 84 percent sand with low available water capacity and low organic matte, and the other as 58 percent sand with higher available water capacity and higher organic matter. |
| For example, in these two orchard soils, the soil at left has 84% sand and only 0.1 g/g available water capacity. In comparison, the orchard soil at right has less sand and 0.4 g/g of available water capacity. | Water is shown infiltrating the soil samples and collecting in the beakers below. |
| The amount of organic matter as well as the sand effects the available water capacity. | Water continues to collect in the beakers below, rising quicker for the beaker with the higher sand content. |
| In this demonstration, the soil with higher sand content had 72 of 100 ml drain through, which means 28 ml or 28% of the water was held in the soils. The higher organic matter soil had 57 ml of 100 ml drain through, which leaves 43 ml which were held in the soil. | Two graduated cylinders are shown side by side containing collected water from each soil sample for comparison. |
| Based on the actual available water capacity measured from these soils, which is done with a pressure plate, the sandy soil held less than an acre inch of water (0.89) compared to 3.5 acre inches in the high organic matter soil. | |
| End card displays “Soil Health in Orchards Workshop” with an illustration of a tree and links to additional workshop resources. |
