A LONO-TERM FIELD TRIAL ON RESIDUAL EFFECT OF PHOSPHORUS AND ON THE USE OF RECYCLED NUTRIENTS IN A FARMING SYSTEM

Results from a twelve years field experiment on a calsic cinnamon soil in west Liaoning China indicated that the crop yields from the treatments with low rate (14. 4 kg.hm-2) of phosphorus every year and with high rate (86. 4 kg hm-2) of phosphorus every six years were very similar but the former gave a little higher yields. The average recoveries of phosphorus of both treatments in twelve years were 0. 38 and 0. 36 respectively impling the significant residual effect of phosphorus on this soil. Based on the use of nitrogen and phosphorus fertilizer, the recycled pig manure, made by 80% of the grain from the treatrient to feed a pig and 2/3 of the stalk used as bedding material. could increase crop yields by 1 t.hm-2 or 17% increase rate on average. After twelve years of appling recycled pig manure annually, the nitrogen suppling ability of the soil reached as high as 180-200 kg(N) per hectare per year, the yield of maize reached about 9 thm-2without using nitrogen fertilizer.