Author: Mr. Homegrown

Too Much Phosphate

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Gardening, Soil
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Symptoms of chlorosis. Image from the Washington State University

Our possible backyard lead situation is a good reason to get a soil test, but if that didn’t convince you the Garden Professors at Washington State University just blogged about another important motivation: the bad effects of too much phosphate.

An overabundance of phosphate can interfere with a plant’s ability to uptake iron resulting in interveinal chlorosis, a yellowing of the leaves between the veins. So adding fertilizer that contains phosphate to soil that doesn’t need it is a waste of money, damages the environment and can kill your plants. Of all the soils I’ve tested in Los Angeles, all are already high in phosphate, meaning that most fertilizers, both organic and chemical are both unnecessary and potentially toxic to plants.

As the Garden Professors also note in another post, it can be very difficult to diagnose problems just with visual cues. Chlorosis, for instance, can also be caused by other factors.  As Garden Professor Linda Chalker-Scott puts it, “You can’t fly by the seat of your pants on this one, folks.” While I’m probably a bigger proponent of intuition and “woo-woo” than Chalker-Scott, I think it’s a good idea to balance our left and right brains. No reason you can’t get a soil test and talk to those plant Devas.

Weekend Movie Recommendation: Buck

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Reviews
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Even if you’re not owned by a horse, there’s a lot to learn from an extraordinary movie called Buck. The subject of this documentary, “horse whisperer” Buck Brannaman, crisscrosses the country teaching a method of horse training (or is it people training?) that can be applied to any animal. The results are amazing–a dance between man and horse.

Brannaman’s techniques embody a stoic calm and sensitivity born out of a miserable childhood. As a survivor of abuse, he’s very in tune with the nature and effects of fear. He teaches that the relationship we have with our animals is much more about our own baggage than what’s going on with the animal. As he puts it, “Your horse is a mirror to your soul, and sometimes you may not like what you see. Sometimes, you will.”

This is a beautifully shot and edited documentary, thought provoking and very much worth watching. Good news: if you have Netflix, it’s a available for instant viewing.

What We’re Going To Do About That Lead

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Gardening, Lead
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White sage, yarrow, rosemary and aloe vera–the kind of plants we’ll be planting more of.

Let’s assume that we have a lead problem in our backyard. That’s a big assumption at this point because we now have two very conflicting test results. But, for the sake of an argument, let’s say the first alarming test is true, what are we going to do about it?

These are the options:
  • Radical remediation: Remove all the soil in the yard and replace with new soil.
  • Cover the contaminated soil so that it doesn’t give off dust, and so people can’t come in direct contact with it, e.g. lay sod, cover the yard with concrete or decking, or lay down a thick layer of mulch.
  • Grow ornamental plants only
  • Grow all food in raised beds
  • Attempt phytoremediation (grow plants that uptake lead, pull them and send them to the dump)
  • Move

It turns out we were already doing some of these things, so we’re just going to keep on going as we were with a few changes. Our yard has always been covered in a thick layer of mulch and we do most of our growing in raised beds. We will stop growing edibles directly in the ground. We’d already planned to redesign the yard to include lots more native and Mediterranean flowering plants. These we can’t eat, but will secure the soil and provide food and shelter for lots of beneficial insects who will aid our food crops. We’re really happy that we’ve always mulched, because it has helped keep the (potentially) contaminated soil in place and has increased bio-activity as the mulch decomposes.

This raised be would have to be raised higher.
Most plants don’t take up much lead, it turns out. Our soil phosphate levels are high and the pH is moderate, two factors that further decrease the ability of plants to access lead. The main health concern comes from directly ingesting dirt, and that can be avoided by washing and peeling vegetables and fruits. The recommended wash for lead is a splash of vinegar in water (1 tsp per 1 1/2 qts water).
I’d be more concerned if we had kids and they played in the backyard. Little kids, of course, are most at risk because they tend to ingest dirt during play. If it turns out there is a lead problem at our house, I plan on knocking on the doors of my neighbors with kids, warning them about what I’ve found and offer to help them do a lead test. In our public speaking and teaching we emphasize the importance of getting a soil test and we’ll keep doing this.
Phytoremediation, the process of growing plants that concentrate lead, pulling them up every year and disposing of them holds a lot of promise. Unfortunately I don’t see how it would be practical in a residential situation. If the contamination is widespread I’d have to remove every plant and tree and grow nothing but, let’s say, sunflowers, for perhaps several decades. (Sunflowers pull up lots of lead.) In short, phytoremdiation is an intense, long term process.
I think the most important thing we can do is spread the message that soil is a sacred resource–something that we should not foul up in the first place. More and more we’re coming to realize that soil is everything–our future and our well being is inextricably tied to its health. We know how to treat it right. We’re just not doing it. We know what toxins are, and we’ve know it for a long time. For instance, lead has been known to be a problem for thousand of years. Benjamin Franklin, in a letter dated July 31, 1786, comments on lead poisonings caused by contaminated rum, and the lack of concern about this problem: “You will observe with concern how long a useful truth may be known and exist, before it is generally received and practiced on.”  
You said it, Ben.

Get a Soil Test!

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Gardening, Lead
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Regular readers have probably already got this message, but right now we can’t repeat it enough. If there’s a lesson with our backyard lead scare , it’s to practice due diligence when beginning a garden –or better yet, when you buy property–and that means getting a soil test from a soil lab. They’re not that expensive, especially when you consider the high cost of remediation, and the well being of your self and your family.

Test soil for both nutrients and heavy metals when:

  • Buying a house or land
  • Starting to grow food in your yard  
  • Are growing food and have never tested
  • Starting a plot in a community garden or a school garden
  • Buying soil in bulk

Property does not have to be on the former site of gas station to be suspect. Lead contamination comes not only from lead paint on older houses, but was also deposited all over urban centers and near busy roads via a constant rain of fine particulates from auto emissions.

    It really is a shame that lead testing is not a standard part of the inspection phase of home-buying, especially as this is a pervasive problem in urban areas.

    Do companies that sell bulk soil test that soil for lead? A few phone calls Darren Butler made to local companies indicate that they don’t. So let the buyer beware here too. Wondering about bagged soils? Susan Carpenter, at the LA Times, tested a bunch and found no problems.  She did find a possible lead link to fish fertilizer, however.

    We’ve used all three of these services. UMass is the cheapest by far, but gives the least analysis. However, if you just want your lead level numbers, that’s not a problem.

    Wallace Laboratories
    UMass Soil Testing Service
    Timberleaf Soil Testing

    In our next lead post we’ll let you know what our plan is. And we know there’s interest in all this, so over the week we’ll talk about remediation, raised beds, what’s dangerous, what’s edible, and more. Fun for all, guaranteed!