the effect of nitrogen source and level on the trend of enzymatic activity in a calcareous soil cultivated with forage maize

abstract the addition of manures and chemical fertilizers as soil amendments for the improvement of soil fertility and quality could affect the seasonal changes in the activity of soil microbes and enzymes. this study aimed at investigating the effect of different levels of nitrogen from broiler litter and urea sources on the trend of urease, alkaline phosphatase and saccharase activities in a clay loam calcareous soil cultivated with maize (zea mays l.) under field conditions. the treatments were a control (no fertilizer and broiler litter), 100, 200, 300 kg n ha-1 from broiler litter and 100, 200, 300 kg n ha-1 from urea, using a split-plot experiment arranged in a completely randomized block design with four replications. the activity of soil enzymes was monitored at five different stages after treatments imposition with 20-day intervals during the growth period. results of this research show that the activity of urease, alkaline phosphatase and saccharase in broiler litter- and urea- treated soils were significantly greater than that in the control soil (no broiler litter and urea added). the level of broiler litter and urea fertilizers and time had a significant effect (p<0.05) on soil enzyme activities. the result of the current study also indicated a positive, significant correlation (r=0.58***) between urease activity and maize yield, whereas maize yield had no correlation with alkaline phosphatase and saccharase activities. in summary, results illustrate that broiler litter is more effective in increasing the activity of soil enzymes than urea, due in large part to the stimulation of microbial activities resulted from labile carbon in broiler litter.