Soil Texture and Water Holding Capacity---Part 1

We have had three days of temperatures exceeding 90^o F in our area. My husband asked me about the water holding capacity of an acre of land. This requires knowledge of the soil texture, which is something that can be provided by having the soil tested. We know from our soil test that we have sandy loam soil. You can also perform your own analysis of your soil texture by following the steps outlined at the Natural Resources and Conservation Services (NRCS) site. The Soil Textural Triangle can also be found on the NRCS site.

Once you know what type of soil you have, you can get a rough estimate of the water holding capacity of your site from the following guidelines provided by Terry Prichard. Following a normal winter with rainfall and snowfall, the soil is at field capacity and the dormant grapevine is provided with enough water for spring growth. The field capacity is provided in the chart shown at the left. Another way to look at the same data is provided at the
Cornell Vineyard Site Evaluation website.

It's important to know this information because if you need to irrigate your vineyard, you will need to calculate the waterholding capacity of your soil and have some indication of your vine water status. That being said, I learned in the Viticulture for Winemakers course that midseason water deficit, from fruit set to veraison can be beneficial leading to reduced vegetative canopy growth, allowing increased fruit exposure to light assuming photosynthesis is not a limiting factor.