![]() Arsenic can be absorbed by plants to some extent and can be toxic at high levels, but again, none of the bagged soils had much. Likewise, chromium is not a risk in food because plants can’t draw it out of the soil. He said cadmium uptake in plants is inhibited by zinc, so it can’t be transferred to edible crop tissues in dangerous amounts when zinc levels are high. Had they been at significantly higher concentrations, zinc and copper would be more likely to injure or kill a plant before it could bear edibles, according to Chaney. Heavy metals were present in every bagged soil I had tested but only at very low levels. What are heavy metals, and why should we care about them? Although some heavy metals such as iron, copper and zinc are essential to human life in small quantities, others, such as cadmium, arsenic and lead, are usually a result of pollution and are toxic at certain concentrations. ![]() “Every soil in the world has heavy metals,” said Chaney, “so don’t be automatically afraid.” I just couldn’t remember which ones I’d put in that planter box, and which ones I’d used elsewhere. I had blended about eight products made by different manufacturers to create a soil mix that would result in luscious leafy greens, and it did. I received dozens of letters from readers who wanted to know which product was the culprit. The experience also got me thinking: What, exactly, is in all these bagged soils? The results were enough to make me rip out all the leafy greens I’d been growing in my custom-built planter and throw them into the black trash bin, not even the green waste bin or my compost pile, because I didn’t want this stuff recycled. ![]() According to the head of the lab that did the testing, I shouldn’t have eaten more than one-quarter pound of the leaves a day or I’d risk lead poisoning. In September I wrote about an unsettling incident in which I’d found high levels of lead in the chard I’d grown in a backyard planter box filled with store-bought soil.
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