ACTIVITIES OF SOIL ENZYMES IN CORN FIELDS ENRICHED WITH MANURE

Elevated enzyme activities in soils have been reported to be associated with enhanced contents of organic matter and total nitrogen (N). This research sought to evaluate the changes in enzymatic activities in cornfield soil enriched with organic matter. Corn field plots had been treated for 8 seasons with increasing amounts of green manure or barnyard manure (0 – 100% of 20 ton ha-1) and decreasing amount of chemical fertilizers (100 – 0% of 300 kg Urea + 200 kg SP-36 + 100 kg KCl ha-1). Soil samples were taken at the maximum vegetative stage and at harvest time, and analyzed for enzymatic and chemical properties. The results clearly showed that enrichment with barnyard manure significantly increased alkaline phosphatase activity. Both manures did not affect the activities of acid phosphatase, arylsulfatase and β-glucosidase. The greater effect of barnyard manure on alkaline phosphatase was closely related with increases in soil pH, available P, and microbial activities. Barnyard manure also significantly increased organic C and total N content. The activities of acid and alkaline phosphatase, arylsulfatase, and β-glucosidase showed high and significant correlations with soil pH, organic C, total N, and available P. Acid phosphatase showed a significant correlation with corn yield.