If you’ve been building up your garden’s fertility with compost, manure, and green manures like legumes, congratulations: you’re doing it right. If you’ve been adding chemical fertilizers, this article suggests, not so much.

You’d think that adding lots of nitrogen fertilizer would increase the productiveness of the soil, but not so. In this case, less is more. Nitrogen is used more efficiently at low levels than at high, and the plants grow better. The excess runs off into nearby water bodies leading to anything from minor algal blooms right up to anoxic zones in coastal waters (there is an anoxic zone off Vancouver Island in the Saanich Inlet) — or is taken up into the atmosphere (producing smog and climate change chemicals). The article also says that mineral nitrogen actually promotes the loss of organic matter and soil nitrogen. So adding nitrogen in chemical fertilizer form can add fertility in the short term, but in the long run can lead to dependency on chemical fertilizer.

This is important stuff with implications for food security and environmental quality.

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