Effects of five non‐agricultural organic wastes on soil composition, and on the yield and nitrogen recovery of Italian ryegrass

Abstract

Abstract. We studied the effects of five diverse non‐agricultural organic wastes on soil composition, grass yield and grass nitrogen use in a 3–year field experiment. The applied wastes were distillery pot ale, dairy salt whey, abattoir blood and gut contents, composted green waste (two annual applications each), and paper‐mill sludge (one annual application). With the exception of N immobilization in the paper‐mill sludge treatment, the wastes had no unfavourable effects on the soil. In the 2–year treatments, grass dry matter yields from the abattoir and distillery wastes (26.3 t ha−1) were larger than those from a NH4NO3 fertilizer treatment (24.3 t ha−1) and from the dairy waste (20.4 t ha−1) and composted waste (22.8 t ha−1). Yield and N recovery were impaired markedly after the single application of paper‐mill sludge, both in the year of application and in the following year. The results demonstrated clear differences in the ability of the applied wastes to provide crop‐available N. We conclude that in order to improve prediction of both the benefits and risks from waste recycling to land, more information should be gathered on soil/waste/crop interactions.