Canadian sludge

©  2009  Rose George

Farmers like free fertilizer. But people who are suspicious of the benefits of sewage sludge think it’s not only too variable and unknowable to be risk-free; it’s also not a very good fertilizer. Via sludgewatch, a former federal microbiologist in Canada calmly outlines his objections to sludge-spreading in his neighbourhood. Another concerned citizen makes the case that sludge may be fertilizer, but it’s not very good, because as nitrogen is diminished in the wastewater treatment digestion process, farmers over-apply it to get the right nitrogen levels, thus overloading the soil – or run-off, more commonly – with too much phosphorus. I wish I understand soil science better.