IN previous communications1 it was reported that the value of farmyard manure (cow dung) is due not only to its nitrogen content but also to its power to fix nitrogen of the air. Our field experiments show that when wet, fresh collected cow dung is added to soil at the rate of 25 tons per acre, 33 lb. of nitrogen present in the cow dung is added and 135 lb. of nitrogen per acre is actually fixed from air, while in the dark the fixation is 65 lb. per acre.