synthetic fertiliser, it exhausts the mineral nutrients in the soil – especially phosphorus and potassium, but eventually also sulphur, calcium and manganese. It gets round this problem by adding crushed rock or squashed fish to the soil. These have to be mined or netted. Its main problem, though, is nitrogen deficiency, which it can reverse by growing legumes (clover, alfalfa or beans), which fix nitrogen from the air, and either ploughing them into the soil or feeding them to cattle whose manure is then ploughed into the soil. With such help a particular organic plot can match non-organic
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