This year I’m dedicating Earth Day to mulch. Mulch often takes second place to its organic rival compost in most garden and landscape discussions, but in this edition of The Scoop, mulch moves to #1, and for good reason.

When asked what’s the most cost-effective strategy for improving soil quality, I typically respond with the dual mantras: Compost, compost, compost, and mulch, mulch, mulch. The truth is, mulch should get more of the glory.

Mulch does the heavy “covering” that enables its soil amendment cousin – compost – to feed the soil food web. Though defined simply as a “ground cover,” there’s a lot more to that role than often thought.

In these drought-centric times, I recall a 2005 UC Cooperative Extension study on Water Retention and Evaporative Properties of Landscape Mulches by Shaw, Pittenger & McMaster, which found that a 5-inch application of yard waste (green waste) mulch had a mean water holding capacity of 1.13 inches followed by a 3- inch green waste application at 0.63 inches of water. Add to this a documented 35 percent reduction is lost soil moisture, and mulch deserves an Earth Day round of applause.

As noted by the California Center for Landscape and Urban Horticulture, selecting permeable mulch that retains water and prevents soil evaporation can significantly reduce the need for irrigation, or eliminate it altogether. Appropriate water-wise mulches include green waste, recycled clean wood from pallets and construction debris, straw, cardboard, burlap, and thick layers of newsprint. Bulk application of recycled wood mulch like that produced by WM EarthCare™ not only improves moisture conditions in your garden or landscape, but also adheres to the Bay-Friendly Landscaping & Gardening Coalition principle of Landscaping for Less to the Landfill (www.bayfriendlycoalition.org). To obtain a free downloadable English or Spanish copy of A Bay-Friendly Landscaper’s Guide to Mulch go to: https://www.bayfriendlycoalition.org/publications.shtml

In addition to improving soil moisture, mulches also play an important role in reducing soil erosion, alleviating soil compaction, and moderating soil temperature. Mulch prevents erosion by reducing the force delivered by rainfall and sprinklers. Alleviating compaction is achieved by creating a mulch cushion between foot or vehicle traffic and the soil surface. This cushion also protects the soil surface from the harsh effects of solar radiation. You can think of mulch as the Dr. Scholl’s for soil. Your soil will be “gellin” with mulch.

Garnering more Earth Day accolades, organic mulches bind heavy metals, reduce weed germination, combat disease, and improve plant establishment.

Hey, could you want one landscape product to do more for the price? I think not.

So celebrate this Earth Day by spreading some mulch, and sharing the wealth about its benefits.

Happy Earth Day!

Mulch! Mulch! Mulch!

The Soil Sommelier

 

Hooray, we’ve just experienced the first significant rainfall of the winter in the San Francisco Bay Area. But was it enough to break us from our recent cycle of drought. Unfortunately NO.

In fact, we may be in for an extended period of much drier years to come in the future. According to UC Berkeley paleoclimatologist Lynn Ingram, California hasn’t been this dry since 1580. If that doesn’t alarm you, it should. Our water management infrastructure was created primarily in the last century when the climate in California was milder and wetter than previous periods in geologic history. Maintaining water supplies during decades of severe to extreme drought will require a decentralized parcel-by-parcel approach aimed at saving every drop from every yard and business.

So what does this mean for landscape professionals and gardeners? In short it means a 180 degree shift from the 20^th century view of moving water from yard to curb and then storm drain, to the current view of capturing, filtering, and reusing as much water as possible on site with little or none escaping as runoff. It also means that we seriously reconsider the merit of every home and business having a lush green lawn and other thirsty plant materials not suited for our semi-arid climate.

To jumpstart the move to measures that will help all of us sustain our landscapes during a period of prolonged drought, I offer the following eight tips.

1. Lose Your Lawn (LYL)

It’s no secret that 70% of residential water use is for landscaping, and the biggest gulp of that swallowed up by turf. It should stand to reason then, that the easiest way to reduce home water use is to lose your lawn.

The days of the lush green escrow lawn are over! Future water use regulations are likely to prohibit conventional turf in landscapes, except in very special cases (and at extremely high cost). You’d be wise to make the switch from conventional turf to drought tolerant and native species now rather than be mandated to do so in the future. It won’t be long before a new breed of enforcement officers emerges to lay down the law on lawns and water waste.

If that doesn’t convince you, then maybe the impact on the value of your property will. I predict that within a decade homes and businesses that continue to maintain a lawn will be have a market value significantly less than similar properties where the lawn has been replaced with native plants.

If you need additional incentive, consider the number of lawn conversion rebate programs available to residential and commercial property owners offered by water districts and municipalities throughout the Bay Area. With rebate amounts ranging from $500 to as much as $20,000 it’s worth taking the few minutes needed to learn about the program in your area and whether you qualify. It’s important too that you do your homework before you run out and start killing the grass. Most programs require an on-site before and after visit and have limits on the total square footage of converted lawn eligible for a rebate.

2. Upgrade Your Irrigation System

Many residential and commercial properties were constructed with irrigation system controllers that apply water based upon time of day and day of week without regard to actual weather and soil moisture conditions. These 10-minute a day, 7 day a week controllers are no match for today’s modern generation of “smart” controllers. If you need a comparison just think back to the days when a rotary phone was hanging in your kitchen and then reach into your pocket for that mobile masterpiece of communications technology. You get the idea.

Smart controllers use real-time weather conditions, and in some cases soil moisture, to determine when irrigation is needed. Installation typically includes a programmable controller and weather sensor array (sunlight, temperature, rainfall, relative humidity, wind speed). The task of installing one of these water wise sentinels is best left to a irrigation pro like a Bay-Friendly Qualified Professional (BFQP) who has the training and experience needed to get the job done right. For a complete list of BFQPs in your area go to: http://www.bayfriendlycoalition.org.

Similar to the LYL rebates, many water districts now offer smart controller upgrade rebates. Some districts will even supply the smart controller coupled with a rebate for professional installation. In most cases, the cost to upgrade is fully recovered (or nearly so) by the rebate. Once again, it’s important to consult with your water district before initiating an upgrade. Not all smart controllers are created equal, and not all smart controllers qualify for a rebate. Remember to do your homework first.

3. Water Deeply

I’m sure that you’re familiar with sprinklers that put more water into the air and on the street than into the landscape. This is a common problem that results in a huge waste of water. Devices that deliver water to the landscape as a spray including the most efficient sprinklers, put moisture into the air instead of the soil.

You can correct this by converting the sprinklers in your landscape to deep drip irrigation.  Unlike standard drip emitters that apply water at or near the soil surface within a limited area, deep drip spikes deliver water from a few inches to several feet into the ground.

Getting water deeper into the soil profile will stimulate your landscape plants to develop a deep root system. Plants with deeper more developed root systems respond much better when water becomes less plentiful. Deep drip stakes have the added benefit of not needing to be moved as often as plant materials grow.

4. Capture Every Drop

Arguably the most significant change in landscape water management is the emphasis on capturing, filtering, and reusing water where it falls. As drought conditions persist, rain gardens, rainwater catchment, and gray water systems will become the norm in landscape design.

You can get a jump on the trend by becoming an “early adopter” and incorporating one or more landscape water saving features into your yard now. These include “sculpting” your garden to include a network of small depressions for collecting rainwater and disbursing it throughout the site without the need for mechanical assistance. In other words, letting gravity have all the fun moving the water that you’ve collected.

 

 

If you’re thirsty for more, consider installing a rainwater catchment system with a cistern. Doing so could have you harvesting 14,000 gallons or more of rainwater off your roof that otherwise would have gone down a storm drain.

This is water that can be used to irrigate your landscape, protect your property against wildfire, and sustain your life during a disaster. Watch for insurance companies to start offering policy discounts for homes and businesses having rainwater harvest systems

If you want to take water harvesting to the next level, consider installing a gray water system. The focus here is making the most of the water resources that you already have available including the water in your household plumbing.

Remember that all water is recycled and that you need to make the most of each drop as it passes through the recycling process. There are no “new” sources of water to be found. All that we have is already here, and we need to make the most it.

One last point on capture, filter, and reuse. Be sure to check your local building code before you become a water harvest crusader. Codes have a tendency to lag behind allowing what ecosystems do naturally.

5. Plant Water-Wise

When it comes to planting with water use in mind think drought tolerant and native species. Selecting the right plants can be a bit tricky, but thanks to a new labeling partnership between the Bay-Friendly Landscaping and Gardening Coalition and Devil Mountain Nursery the job of identifying drought tolerant plants got a lot easier. Plants bearing the “Drought Devils” label will take the guesswork out determining which plants will survive under drought conditions.

Beyond looking for label identification of drought tolerance, plan to purchase your plant materials in the smallest container size possible. Ideally you want to buy plugs, but any size up to 1 gallon is acceptable. Why small plants? They need less water, experience less transplant stress, and consequently will send roots looking deeper and farther out for moisture. Also be sure to space your plants far enough apart to accommodate growth over time. Plants that are spaced too closely tend to have limited root development and are prone to pests and disease.

To be plant water-wise in an established landscape, divide or thin plant material to remove those that are stressed or diseased.

 

6. Stop Fertilizing

Drought is not the time to apply fertilizer (either synthetic or organic). Fertilizers promote new plant growth that requires additional water. In the absence of the additional moisture needed to sustain the new growth, the plant will become stressed, creating an opportunity for invasion by pests. This isn’t a pretty picture!

To make the situation worse, fertilizers can “burn” plant roots and create a buildup of salts, particularly sodium salts, that cause soil aggregates (soil structure) to breakdown. Loss of soil structure leads to erosion, compaction, loss or porosity, higher bulk density, and other soil ills. There is a better way to provide your landscape plants with needed nutrients without the use of fertilizers, and I bet you know what it is (if you’re a faithful reader, you certainly do).

7. Apply Compost

The single best action that landscape professionals and homeowners can take to improve moisture retention in soil is the addition of 1-2 inches of compost (organic matter) every other month. A 1% increase in soil organic matter quadruples the water holding capacity of the soil (textural differences aside) while also feeding soil microbes responsible for moving water and nutrients to plant roots. And, in case you’re wondering, compost retains soil moisture as well as, or better than, all of those polymer-based products that are now being marketed as magic water magnets. Don’t be tricked by slick marketing schemes. My advice is to stick with a stable and mature, high quality compost like WM EarthCare™ Homegrown Compost, to improve moisture retention.

Remember, however, that to protect the moisture retention of compost it must be covered with at least three inches of organic mulch – recycled wood, straw, pine needles, or shredded newspaper. Failure to apply an adequate layer of mulch on top of compost will greatly diminish its water holding capacity.

Everyone together with me now: Compost! Compost! Compost!

8. Apply Mulch

With compost being tip #7, is follows that my final tip is to apply mulch. Lots of mulch! The easiest way to achieve immediate water savings in your landscape is to apply at least three inches of recycled wood mulch. Mulch not only aids in soil moisture retention, it also inhibits weed growth, moderates soil surface temperatures, guards against soil from erosion, and a long list of other benefits.

The point is: Mulch! Mulch! Mulch! And do it now!

If you have a landscape or gardening question that you’d like me to answer, send it my way via email at: sandrews@berkeley.edu.

Keep thinking rain, and make the most of every drop!

 

 

With the new year now underway and CompostCon, the celebration of compost, occurring on January 25, I thought I would spice up this installment of Everyday Soil Science with a tasty controversy.

There’s a great debate among self-proclaimed “foodies” about the significance of microclimates, geography, water, and, of course, soil on the flavors we associate with wines, cheeses, breads, meats, poultry, garden vegetables, and just about everything we eat that hasn’t been processed.

I’m talking of course about terroir. Terroir (tair-WAHR) is the French term for soil often used in conjunction with the phrase gout de terroir or, taste of the soil. The term is particularly beloved among wine lovers. If you’ve seen Dirt! The Movie, you’ll undoubtedly recall the scene in which a well-regarded wine expert compares the flavor of the Sangiovese he just chugged to a pinch of the vineyard sandy loam swirling in his mouth. That’s commitment. And, yes, I’ve done it! (Though I don’t recommend making a habit of tasting soil.)

I happen to be among those who believe that “living” soil, filled with microbes, does impart unique flavor characteristics (among other benefits) to the unadulterated food that we grow and eat. The body of scientific knowledge on the mechanisms of terroir is less than copious, and some of it quite frankly borders on non-sense, but recent research conducted at the University of California, Davis (Go Aggies!) and published in the Proceedings of the National Academy of Sciences has unearthed a correlation between microbes and terroir.

Without getting into the nitty gritty details of the study, the Davis scientists found that California white wine grapes of the same cultivar, or grown in the same region were inoculated with a related suite of bacteria and fungi in spite of the diversity of microbial communities found throughout the state. Where terroir was once thought to be associated with purely environmental factors like weather, elevation, and soil mineralogy – microbial biology now enters the picture as a factor that integrates all of the previous elements of terroir.

As you’ll undoubtedly remember from previous installments of Everyday Soil Science – microbes are the key to living soil. That microbes, or the byproducts that they produce, can actually influence the flavor or what we eat and drink makes perfect sense to me. What makes a loaf of sourdough bread made in San Francisco different from a loaf made in Boston? It’s the microbes in the starter. San Francisco sourdough tastes the way it does due to the microbes that are native to the Bay Area. The same line of thinking can be applied to cheese produced in Point Reyes or Monterey. What ultimately gives flavor to much of what we eat is associated with the microbes that have inoculated it.

So what’s the bottom line? Keep your soil alive and thriving with organic matter (compost, compost, compost), and your neighborhood microbes will kick up the gout de terroir in everything you grow and eat. You can try this simply enough by growing your own organic carrots and comparing them to organic carrots sold at your favorite grocery. I informally had a group of my Berkeley students do this one summer for fun and the results, though anecdotal, were quite compelling. In repeated blind tasting the students consistently selected the homegrown organic carrots as having both better taste (as defined by richness and uniqueness of flavor), and more taste (as defined by intensity and duration of flavor on the palate) than the grocery counterparts. True, it wasn’t a scientific study, nevertheless the consistency of the results begs the question about the role of microbes and terroir.

Eat, drink, and celebrate gout de terroir!

 

 

For more information about terroir, visit the following sites:

Livermore Valley Winegrowers Association – Terroir & Appellation

Wineanorak.com – Mechanisms of terroir: How soils affect the taste of wine

Organic Trade Association – Nutritional Considerations

 

Photos courtesy of Block122.com

Will it ever rain? That’s recently been the number one question on the mind of most Bay Area gardeners. Here we are in November and barely a drop has fallen from the clouds. Are we experiencing a drought? Climate change?

What’s a gardener to do?

The lack of precipitation is a major concern, especially when we consider that 55-75 percent of the 174,000 gallons/year of water used by the average household is for landscaping. Getting moisture into the ground, and keeping there should be a major priority for all California gardeners.

In this installment of Everyday Soil Science, I will address the use of mulch to improve the moisture holding capacity of your soil. Mulch, for the purpose of this discussion, is any material spread over the soil surface to protect soil quality and preserve soil function. Using this definition, mulch is confined to organic materials like chipped or shredded wood waste, wood shavings, saw dust, pine needles, bark chips, straw, grass clipping, leaves, mixed plant debris (aka chipper trash), cardboard, newsprint, and compost. Notably not included are geotextiles, plastic sheeting, and rock.

Maintaining three or more inches of mulch around plantings and over open areas can increase the moisture holding capacity of some soil types by as much as 500 percenet. As we start looking for ways to conserve every drop of moisture, mulch stands alone as the easiest, quickest, and most cost-effective landscape technique to conserve water.

Everyone, say it with me now: “Mulch, mulch, mulch!”

Using mulch in the landscape is by no means rocket science, but it requires sticking to a few basics and a little common sense. Below are the mulch basics recommended by the Bay-Friendly Landscaping & Gardening Coalition.

Mulch Basics

1. Prepare the site before applying mulch, by removing weeds and moistening thoroughly. Yes, you need to get some moisture into the soil initially to hold there.

2. Replace grass with mulch under trees and around poles. If you don’t already know this, you should: Grass and trees don’t mix! Eliminate grass around trees by six feet to mimic the way trees grow in nature. Utilize the leaves that accumulate under trees as a mulch source.

3. Keep mulch six (6) to 12 inches away from the base of shrubs and larger plantings. Retaining moisture too close to the base of any plant can be a recipe for disease and rot. Place mulch so that you see that the root flare keeps the base dry.

4. Choose the application rate that will give you the best results.

• Apply a layer that settles to two (2) to four (4) inches deep. This is considered the best general application rate, especially for use in planting beds. Bay-Friendly Rated Landscapes require a minimum of three (3) inches of coarse mulch.
• Fine Mulch: Apply no more than two (2) inches. Thin layers of mulch (those having a particle size of less than half an inch) are less likely to impede air and water. Fine mulches decompose more quickly and need to be replenished more often than coarse-textured mulches.
• Coarse Mulch: Use four (4) to six (6) inches or more to control weeds in open spaces. Coarse mulch is best for weed control; it prevents annual weeds from germinating while also preserving soil moisture. To maintain weed control and moisture retention, replenish once per year.
• Reduce the thickness of mulch on poorly drained soils to avoid the development of anaerobic conditions.
• Keep mulch on the soil surface to prevent nitrogen withdrawal. Avoid incorporating any woody material into the soil profile.

For complete information about utilizing mulch to conserve water order a copy of “A Bay-Friendly Guide to Mulch” available on the Bay-Friendly Landscaping & Gardening Coalition website: www.BayFriendlyCoalition.org.

Rain or shine… it’s time to mulch, mulch, mulch!

~The Soil Sommelier

After reading the title of this month’s Everyday Soil Science installment you might be scratching your head. Sweet and salty soil? Are you nuts, Soil Sommelier? Of course not!

Sweet and salty soil actually refers to two common chemical indicators of soil health and quality: pH and EC (electrical conductivity).

You’ve probably heard pH used in the description of everyday household items such as soaps, shampoos, medicines, and foods, but may not think much about it in relation to soils. pH generally refers to the acidity or alkalinity of a soil. For those that want to nerd it up, pH is defined as the log10 hydrogen ions [H+] in the soil solution. pH values are represented on a scale that ranges from 0 (most acidic) to 14 (most alkaline); with pH 7 being neutral. pH values that are less than 7 are termed acidic, while values greater than 7 are termed alkaline or basic.

The availability of plant nutrients like Ca+2, Mg+2 as well as the health of important microbes (bacteria, actinomycetes, and fungi) is linked to the pH of a soil. Optimum uptake for most plant nutrients and activity for microbes is attained when the soil pH is in the range 6.5 to 7. Soils in the pH 6.5 to 7 range are considered sweet. In soils where the pH is less than 7, lime in the form of calcium carbonate or magnesium carbonate, or gypsum, is added to raise the pH value to the desired “sweet” range. Soils with a pH greater 7 are often amended with sulfur, iron sulfate, urea, pine needles, or sawdust to lower the pH to the desired value.

Soil pH and plant nutrient availability

Testing the pH of your soil every fall is a good way to monitor soil acidic/alkalinity and to make adjustments, if needed. Methods for measuring soil pH include test strips, colorimetric test kits, and various types of meters used in the field and laboratory. Routine measurements used for annual monitoring can easily and economically be achieved with high quality test strips or a colorimetric test kit.

pH test strips are a fast and economical way to monitor the pH of your soil. A roll, like the one shown, has a retail cost of about $15.

For more detailed information about soil pH, download this factsheet from the NRCS: pH Factsheet

The second chemical measure of soil quality for discussion this month is electrical conductivity (EC). EC is a measure of the electric current carried by soil water. Yes, there is electricity in soil! The electrical current is associated with ions (Ca2+, Mg2+, K+, Na+, NH4+, SO42-, Cl-, NO3-, and HCO3-) held in water-filled pores of the soil.

EC is often used as a measure of soil salinity. The greater the concentration of ions in solution, the greater the soil salinity will be. Soil texture also influences EC. In general, EC increases with the clay content of a soil. High electrical conductivity can dramatically affect the growth of plants, soil structure, and diversity of microbes in a soil.

This image shows how changes in EC affect the growth of a tomato plant. The plant on the right was treated with non-saline water having a low EC. The plant on the left was treated with very slightly saline water having an EC of 2.6 dS/m.

Image courtesy of the USDA, NRCS.

Adding to the concern associated with EC is the new dimension of recycled water (purple pipe) used for irrigation. Recycled water is often slightly to moderately saline, which, when added to naturally high soil salinity can pose a significant management challenge. A similar problem occurs where saltwater has intruded into groundwater and the water table is sufficiently high to make root contact.

Another factor influencing EC is organic matter added as a soil amendment. Manure and compost often add ions to the soil solution that can negatively affect soil quality if the levels are excessively high. The most common methods for decreasing EC are improved drainage and leaching.

Like pH, EC can be easily and economically with a small pocket meter. Taking EC measurements of irrigation water, and soil amendments (like compost and manure) should be performed regularly and monitored.

Classes of salinity and EC (1 dS/m = 1 mmhos/cm) adapted from the NRCS Soil Survey Handbook

EC (dS/m)	Salinity Class
0<2	Non-saline
2<4	V. slightly saline
4<8	Slightly saline
8<16	Moderately saline
≥16	Strongly saline

 

For more information about EC and soil, download this factsheet from the NRCS: EC Factsheet

You’ve now been introduced to the sweet and salty that influences the quality and health of your soil. Get your test strips and meters and start measuring so that you can monitor and manage your soil resources for sustainability.

Remember, soil sustains life!

~The Soil Sommelier