Effects Of Organic Manure Combined With Fertilizers On NH₄-N+NO₃-N, DOM And Enzyme Activities Of Soil

Based on the field and indoor soil culture experiments,the effects of organic manurecombined with chemical fertilizers on cropping root soil carbon, nitrogen transformations,DOMand soil enzyme activity were studied.Results showed that:Under organic manure combined with chemical fertilizers,soil MBC,MBN,inorganic nitrogenand total soil respiration presented different change trends.Different organic manure combinedwith chemical fertilizers affected soil MBC content at different corn growth period in variousdegree.Soil MBC presented rising at the beginning and then declining.During the whole growthperiod,soil MBC content of pig manure plus chemical fertilizers,cow manure plus chemicalfertilizers were higher than chemical fertilizer alone.Soil MBN presented an increasing trendduring the whole growth period of corn.During the seedling stage,soil MBN had no significantdifferences between organic manure combined with chemical fertilizers and chemical fertilizeralone;during the maturation stage,there were significant differences of soil MBN between organicmanure combined with chemical fertilizers and chemical fertilizer alone;and chicken manure+chemical fertilizers,pig manure+chemical fertilizers had positive effect of soil MBN,whose soilMBN content were higher than chemical fertilizer alone.Different organic manure+chemicalfertilizers had significant effects on content of soil inorganic nitrogen.The soil inorganic nitrogencontent of all treatments gradually reduced.Soil inorganic content of pig manure+chemicalfertilizers,cow manure+chemical fertilizers treatments were higher than that of chemical fertilizeralone.There was no significant change of every treatment on soil NO3-N.There were significantdifferences between total soil respiration of organic manure+chemical fertilizers and that ofchemical fertilizer alone.Total soil respiration presented as follows:chicken manure+chemicalfertilizers> pig manure+chemical fertilizers> cow manure+chemical fertilizers> chemicalfertilizer alone.The respiration rate had the same change trends,and organic manure combined withchemical fertilizers was higher than chemical fertilizer alone.Organic manure combined with chemical fertilizers presented different effects on reducingsugar,phenolic compounds and DOC.Reducing sugar content of organic manure combined withchemical fertilizers was significantly higher than that of chemical fertilizer alone.Reducing sugarcontent of each treatment presented rising at the beginning and then declining.Phenolic compoundscontent in four different treatments soils gradually decreased during the whole growth period. Phenolic compounds content of organic manure combined with chemical fertilizers was lower thanthat of chemical fertilizer,especially of chicken manure+chemical fertilizers,pig manure+chemical fertilizers treatment.DOC contents of four different treatments presented rising at thebeginning and declining then rising again.After the whole growth period,DOC contents of organicmanure combined with chemical fertilizers was higher than that of chemical fertilizer.DOCcontents of chicken manure+chemical fertilizers,pig manure+chemical fertilizers were higherthan that of others.Soil urease,invertase,polyphenol oxidase and catalase of different organic manure combinedwith chemical fertilizers presented different change trends:Soil urease activity,invertaseactivity,polyphenol oxidase activity were significant improved by organic manure combined withchemical fertilizers,and only a little effects on catalase activity.Four enzymes activity of organicmanure combined with chemical fertilizers were all higher than that of chemical fertilizer.In thewhole growth period, the activities of soil urease,invertase and polyphenol oxidase of fourdifferent treatments presented a low trends at early stage,high at the mid,and lower at the late,butcatalase activity showed little change at early and mid stages,but he activity reduced at late stage.