2021 was a good year...to dry farm??
More reasons to consider monitoring your soil moisture
Between stunted growth to unexpected nutrient deficiencies, this second consecutive year of drought threw us quite a few curve balls. One thing people aren’t expecting to hear though is that some places haven’t needed to irrigate all season. That’s right. Some vineyards we consult for have been just fine using no water for irrigation.
How is this the case? We take soil moisture very seriously. Let me break it down for you.
Here's a site we didn’t need to irrigate at all
It could be a combination of soil type, or balanced canopy size, but for whatever reason average soil moisture at this site has never dipped below 60% relative water content (we consider anything above 80% to be around field capacity). You can see slow and linear uptake of moisture. This means that the roots have had no trouble extracting water. As long as the curve looks like this, you can lay off irrigation, which in the case of this site meant no irrigation was needed since March.
Here's a site that looked dry but had deeper moisture
This site may have looked dry in the first few feet of soil but look at how much water was waiting down below. Now we could have started irrigating earlier, but then those roots would have never tapped into that water down below 40” soil depth. Why go searching for water when it’s being fed to you, right? Forcing the roots to dig deeper means the vine will develop a large healthy root system that takes advantage of the water already present in the soil. This will make the vine more drought tolerant and save you precious water, less dependent on irrigation. This is especially important in young vineyards. You do have to baby them a little, but ultimately you want them to build up their root system or build “down” their root system as it were. Otherwise, you may find yourself having to replant much sooner than expected.
Here's a site where water percolated too deeply
Knowing your soil moisture can also help you irrigate more effectively. This site for instance has a sandy soil that doesn’t hold onto water very well (i.e. low water-holding capacity). You can go ahead and irrigate this site all you want, but all that water is going to percolate way deeper than your roots go (most vine roots are found above 3 to 4 feet in depth). So instead of wasting that water, it’s better to give your vines small frequent drinks. At least small enough not to push water past the roots. That way you’re watering your vines more and your bedrock less.
Here's a site where water didn’t percolate
This site has the opposite problem. Water here hits the 24” mark and just stops. This could be due to abrupt change in soil texture or clay lens, compaction or hard pan. A four-hour-long irrigation only percolated down to 8” in this case, but a six-hour-long irrigation went down a bit deeper. In this case, a schedule of 6 hours every ten days percolates more deeply and stimulates deeper root activity. But soils such as this can’t take unlimited water – some simply don’t percolate deeply with drip irrigation. Visualizing soil moisture dynamics in this way allows us to irrigate to our soil. Again, if I didn’t know my soil moisture patterns, I’d just have to guess.
Here's a site that needed constant irrigation
The vineyard below needs to subsist on very little water all year. Thanks to soil moisture monitoring we were able to use every drop as efficiently as possible.
A lot goes into making irrigation decisions but knowing your soil moisture should be your first step. A capacitance probe will cost you under $1000, but will give you the knowledge that you’re using your water as efficiently as possible to produce the highest quality grapes.
Knowing how much water you have in your soil is as important as knowing how much water you have in your well or pond. If you want us to help with this next step, contact [email protected].
