Effects Of Inoculating Bacterivorous Nematodes On Nitrogen Nitrification Of Red Soil

The soil nitrification is one of the nitrogen internal recycling important processes,which is both related with the soil nitrogen mineralizationbiology persisting, nitrogen fertility supply closly,and is relation to the nitrogen loss and the environment problems.The thorough research to the occur of the strong and weak nitrogen nitrification and where the nitration product goes is regarding to the correct appraisal nitrification to the nitrogen fertility maintenance,the nitrogen lose,the environmental pollution risk, effectively the forecast and the regulation nitrification,which has the important significance to the theory and the practice.In the past,the purseurs mainly research the net nitrification rate which raised in the room,pH,organic matter,water content of the soil and so on.But it lacks the research to the gross nitrification as well as to this foundation of biotic factor influence,especially for the soil animal.This article uses the intact soil core¹⁵N isotopic pool dilution approach to determine the gross nitrification rate of the different forest and soil fertility farmland.And after inoculating different density bacterial-feeding nematodes on the different way to observe the change of the gross nitrification rate,microorganism quantity,soil active and so on.At the same time,we use the acetylene suppression technical to research the autotrophic and the heteotrophic nitrification on the different use way.We also study the change of the autotrophic and heteotrophic nitrification rate after inoculating the bacterial-feeding nematodesThe main findings are as follows:(1) It is different for the the gross nitification rate between the different fertility farmland and forest obviously.The gross nitrification rate of the fertilizes farmland treatments is higher than other one(p＜0.05),which of the mixed forest treatment is the lowest.Along the different treatments of fertility farmland,the nitrification rate of the fertilizered treatment is higher than the one no fertilizer(p＜0.05),and the fertilized treatment increased 3.63μgN/g·d,but has not achieved the remarkable level.Along the forest treatments,the gross nitrification rate of the Pinus massoniama forest increased 24.8%, 66.9%to the Schima superba and the mixed forest.And the nitrification rate of the mixed forest is higher than the other forests.In the treatments of the farmland and the forest,the former NO₃^--N consumption is higher than the latter.Also during the six different treatments,the NO₃^--N consumption rate is higher than the gross nitrification rate.(2) After inoculating the bacterial-feeding nematodes to the farmland and the forest,the quantity of the ammonium oxidation bacterium increased to the CK.But under the high density nematodes,the increased range is not remarkable(p＞0.05).In the forest,the quantity of the ammonium oxidation bacterium increased remarkably under the low density nematodes.But under the high density nematodes,the quantity of the ammonium oxidation bacterium decreased.Both the quantity of the ammonium oxidation bacterium and the nitrous acid oxidation bacterium in the treatments under the low density bacterial-feeding nematodes increased remarkbly;but under the high density,the quantity of the nitryfing bacteria increased and decreased respectively.After inoculating bacterial-feeding nematodes in the farmland,the soil breath intensity strengthened obviously(p＜0.05),and the soil breath intensity under the high density bacterial-feeding nematodes,is higher than the low density.In the forest system,the soil breath intensity also strengthened,but not remarkably.The content of SMBN is more than the one under the low density nematodes in the farmland system.But in the forest system, the content of SMBN increasd obviously under the low density nematodes,and increased not remarkably under the high density nematodes.After inoculating the different density bacterial-feeding nematodes,the gross nitrification rate is higner than the CK in the different use way soil.In the farmland,with the nematodes density increasing the gross nitrification rate increased obviously(p＜0.05). In the forest,with the nematode density increasing the gross nitrification rate increased,but has not achieved the remarkable level(p＞0.05)And the gross nitrification rate reduced along the nematode density increase.Under the different use way the gross nitration rate is relation to the nitrifying bacteria quantity and the edaphon activeness concerns.(3) By using and without using acetylene,the gross nitrification rate is higher than CK after inoculating the different density acteria-feeding nematodes,and the gross nitrification increased with the increase of the number of the nematodes inoculated.But the gross nitrification rate under the high and low dengsity nematodes are different no obviously.In the forest,with the namatodes density increasing the gross nitrification rate increased,but has not achieved the remarkable level(p＞0.05).And the gross nitrification rate is higher than the CK after inoculating the different density acterial-feeding nematodes remarkably. And the gross nitrification rate under the low density nematodes is higher than the one under the high nematodes obviously.The conclusion is that the inhibitory effect of the acetylene to heterotrophic nitrification not change the trend of the gross nitrification rate.The nitrification is more important than the autothophic nitrification in the farmland and the forest.And the heterotrophic nitrification rate in the farmland is higher than the forest.After inoculating bacteria-feeding nematodes,the tendency of the heterotrophic nitrification rate has reduces under two useful ways.This has the possibility that the bacterial-feeding nematodes influence the ammonium oxidation bacterium and nitrous acid oxidation bacteriumin directly.Under the low density nematodes,the drop tendency of the percentage of the heterotrophic nitrification is not obviously(p＞0.05);But under the high density bacterial-feeding nematodes,the percentage of the heterotrophic nitrification reduces obviously(p＜0.05).The bacteria-feeding nematodes influence the gross nitrification rate by changing the heterotrophic nitrification rate.