Effects of Urea Fertilizer Application on Soil Microbial Activity of Chuzhou Chrysanthemum morifolium Ramat

Urea is the most popular N fertilizer used in China.Field experiments were conducted to investigate the effects of nitrogen application on the quantity of microorganisms,activity of enzymes and yield of Chuzhou Chrysanthemum morifolium Ramat.Results showed that urea application had significant effects on the quantity of microorganisms and activity of enzymes.Change of soil bacterium,fungus,actinomycete and soil enzyme activity of protease,catalase,urease showed a single-peaked curve,respectively with the increase of urea application rate.Enzymes activity were higher in treatment N1(225 kg N/hm2) and N2(450 kg N/hm2),while in treatment N3(675 kg N/hm2) the activity decreased appreciably.Larger amounts of urea decreased their activities.Phosphatase activity increased with increasing urea rate and maximum activity of urease activity was observed with treatment N3(675 kg N/hm2).Change of soil microorganism C and N population showed a single-peaked curve with the increase of urea application rate,obvious change occurring with soil microorganism N especially.The results suggested optimal urea application rate would lead to increase the quantity of microbes and enzymes activity in Chuzhou Chrysanthemum morifolium Ramat rhizosphere.