EFFECT OF LONG-TERM SEWAGE SLUDGE APPLICATION ON THE DISTRIBUTION OF NUTRIENTS IN MAIZE (ZEA MAYS L.)

The distribution of the nutrients nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and iron (Fe) in maize (Zea mays L.) was studied in a long-term sewage sludge field application in an acid coarse sandy soil at Bordeaux, France. Sewage sludge had been applied since 1974 at 100 t (dry weight) ha^?1 per 2 years (SS 100) in plots cultivated annually with maize. Treatment with farmyard manure (FYM) at 10 t (dry weight) ha^?1 per year and mineral fertilization served as control. Five plants per treatment were investigated at six different growth stages. The plants were separated into their different organs and the distribution of nutrients was determined in up to 12 different plant parts. Sludge application did not significantly influence the nutrient partitioning in maize, but improved slightly the plants' nutrient status compared with the FYM treatment. Grain yield was similar for both treatments. The values for N, P, K, Ca, Mg and Fe content in sludge-treated plants were in the recommended range for optimal growth. Thus, sewage sludge would be a valuable source for maize nutrition even after long-term application, if the critically high copper (Cu) and zinc (Zn) concentrations, previously reported in these sludge-amended plants, could be avoided by the use of sludge low in these elements.