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MMWD Blog: Think Blue Marin

Welcome to our blog! Written by staff at MMWD, “Think Blue Marin” explores all things water in south and central Marin—water supplies, conservation, new projects, watershed management, and more.

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Apr 17

Getting the Biggest Bang for Your Buck

Posted on April 17, 2015 at 11:07 AM by Ann Vallee

by Charlene Burgi

We have all heard of stretching a dollar, but how about stretching your water? With new conservation regulations now in effect, let's look at ways we can use less water while still keeping plants happy and healthy. Creativity and knowledge is all it takes. Plants are made up of over 85% water, so it goes without saying that the medium they grow in (soil) and our irrigation methods must be the focus for maximizing effectiveness and efficiency.

First, let's focus on the condition of our soil. It is important to know what type of soil you have in your garden since this impacts how water behaves. Most Marinites have clay-based soil that holds water for extended periods of time. If you could see the pattern formed as water is applied in clay, you would note it takes on a pancake form as it slowly moves down toward the roots. Though this type of soil will retain water for a long period of time, water will run off quickly if the precipitation rate from either rain or the overhead sprinklers is greater than the soil can absorb. While we don't have control over the precipitation rate of rain, we can control our irrigation precipitation rate by either:
  • Changing our nozzles to apply water very slowly;
  • Using multiple start times on the controller and allowing the water to perk into the soil before it runs off; or
  • Converting overhead spray systems to drip irrigation (more on this subject next week).
We can also control the condition of the soil by adding amendments such as organic compost, ground bark, peat moss, manure, and gypsum (for a temporary fix). Soil conditioners help break up the clay, allowing for greater movement of water through the soil.

In rare cases, some Marinites live along or near old riverbeds where drainage is excellent but water may move through the soil too quickly, leaving the root system without enough water. Surprisingly, the recipe to slow down the water is exactly the same as it is with clay soils: add soil amendments. You can also add soil-moisture retention polymers to this type of soil. The polymers will absorb water and slowly release the captured moisture over a longer period of time.

Let's not forget the motto of "Slow it, spread it, sink it." If you are on a slope or hilly site, soil can be graded to form bioswales. You can capture runoff from the rain by trenching across the slope and back filling with bark or other loose organic material. The berm in front of the trench is native soil that will slowly release the water to the plants below.

 sheet mulching
 Sheet mulching
Holding the moisture in the soil for longer periods of time can also be accomplished by adding mulch, mulch, mulch. Three to four inches of mulch will not only abate the growth of weeds that can steal water from your prize peonies but reduce evaporation from the soil caused by sun and wind. Plants thrive with mulch! Sheet mulch is even better as the cardboard provides an added layer that holds the moisture in the ground. And don't forget MMWD is offering rebates up to $50 on organic mulch!

Do you have some interesting methods for stretching the water in your garden? Others want to hear about it. Share your wealth of knowledge. Stay tuned next week as we explore other creative ideas for irrigating during drought conditions.

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