| Soil urease is a kind of extracellular induced enzymes,and in given conditions,urease activity in agricultural soil can reflect the quality of soil biotic environment and the conversion rate of soil matter,besides reflect the fertility difference among different soils clearly,so soil urease is often used to be as an important index,which can measure soil fertility level.Soil urease mainly roots in edaphon.In the same condition of induce factors,the constitution and activity level of soil microflora will affect consumingly the soil urease activity certainly.In the same time,even the soil microflora constitution is same,the level of induce factors and the change of zymolyte quantity will also cause great difference of urease activity.But,the constitution and activity level of soil microflora depends on the characteristic physicochemical property of soil developed in different pedogenic condition,and the effect of different agricultural use mode on soil biotic environment.So the study on distribution rule of urease activity in soil with certain soil formation and agricultural utilization patterns,could fartherly make the principal factors effected soil urease activity and their interrelation clearer,and mastering the development trend of urease activity with different soil formation condition and soil utilization patterns,can make better use of soil urease activity index, the important factor of soil fertility,for offerring guide to agricultural industry act with adjusting measures to soil.Purple soil is a kind of lithomorphic soil that developed from purple parent rocks,has especial pedogenic characteristics which manifestate in general:physical weathering is stronger than chemical weathering,soil-forming time is short,the differences between horizons is not obvious,the material composition and physical-chemical characters strongly influenced soil characters. Meanwhile,because of the affect of agricultural land use,differences were produced on purple soil at many aspects such as development,profile-forming and physical-chemical characters.However, questions just like how the existing differences of those characters influence soil urease activity,the distributional characters of urease activity under different land use model and its impact factors are lack of systemic research.Hence,soil urease activity of part typical purple soil profiles in Chongqing area was systemic researched,in the hope of finding the distributional differences and characters of urease activity and their impact factors,complementaring the lack of urease activity reaserch in purple soils.The main results are as follows:(1) Under 5 land use models,the collective order of urease activity in purple soil profiles is: dryland use＞paddy use,the concrete order is:orchard soil＞dryland soil＞paddy soil＞vegetable soil＞flood-drought soil.The highest value(81.7 mg·kg-1·24h) is in vegetable soil, While the lowest value(1.94 mg·kg-1·24h) is in the orchard soil.Meanwhile,the change range of urease activity in dryland soil is bigger than in the paddy soil;In profiles developed from different parent materials,The urease activity in soil profile which developed from Suining parent material ((?) =17.9 mg·kg-1·24h) is stronger than that developed from Shaximiao parent material((?) =10.6 mg·kg-1·24h).However,is this character pervasive,still need further study.(2) Under 5 land use models,at the vertical direction,the distributional character of urease activity is:in profiles which developed from Jurassic Shaximiao materials,the urease activity shows to be consistent in each horizons in paddy soil and flood-drought soil;in dry land soil,the order of urease activity is A layer≈B layer＞C layer;in the vegetable soil,the urease activity is A layer＜B layer≈C layer;in orchard soil,the urease activity decrease with the depth of the profile;in profiles which developed from Jurassic Suining materials,the urease activity basically decrease with the depth of the profile.(3) Under 5 land use models,the similarity of the urease activity in the same layer of different profiles is the change range is biggest in the topsoil.The differentia is as follows:in the soil of paddy-winter waterlogged fields and paddy-wheat fields,the urease activity in P layer and C layer tends to be decrease but not very strongly;In dryland soil,the change range is approximately similar; In vegetable soil and orchard soil,the change range strongly decreases with the depth of the profile, and in the C layer,the urease activity tends to be approximate.(4) In purple paddy soils,the urease activity showes significantly positive correlation with the contents of organic,total N,available N,available P at 0.01 confidence level(r0.01=0.418),showes significantly positive correlation with total P content at 0.05 confidence level(r0.05=0.325 ),the order of its path coefficient's absolute value is:T.N＞A.P＞0.M＞pH＞T.P＞A.K＞P.KIn purple soil,the urease activity showes significantly positive correlation with the total P content at 0.01 confidence level(r0.01=0.393),the order of its path coefficient's absolute value is T.P＞A.N＞pH＞A.P＞O.M＞T.K＞T.N＞A.K.(5) Under different land use model,the impact factors of soil urease activity act in different way.The order of its path coefficient's absolute value is as follow:Paddy soil:T.N＞A.N＞A.P＞0.M＞T.P＞pH＞T.K＞A.KFlood-drought Soil:T.P＞0.M＞T.N＞pH＞T.K＞A.N＞A.K＞A.PDryland Soil:A.N＞pH＞0.M＞T.N＞A.P＞T.P＞T.K＞A.KVegetable Soil:T.P＞A.P＞pH＞A.N＞A.K＞T.K＞0.M＞T.NOrchard Soil:A.N＞A.K＞0.M＞pH＞A.P＞T.P＞T.K＞T.N...
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