Effects Of Long-term Application Of Organic Manure On Soil Fertility And Nitrogen Mineralization For Greenhouse Vegetable Planting Soils

Organic manure is one of the effective agricultural technology to improve soil fertility.Effect of long-term application of organic fertilizer on soil fertility was examined in the greenhouse vegetable field in Xiaofengying village,Yanqing County,Beijing.Treatments inclued unfertilized control（CK）,low level of organic manure（CM1,30 t/hm²）,medium level of organic manure（CM2,60 t/hm²）,and high level of organic manure（CM3,90 t/hm²）.Soil samples from 0 to 20 cm were taken for analysis soil physical,chemical,and biological properties to investigate the effect of organic fertilizer on soil fertility.Meanwhile,the ¹⁵N isotope dilution technique was used to investigate the effect of organic fertilizer on soil mineralization.The main results of as follows:（1）Soil fertility had been improved after application of organic manure.The maximum water holding capacity,organic matter,total nitrogen,Olsen-P,avalible K,cation exchange capacity,total exchangeable base capacity,and exchangeable cation(Ca²⁺、Mg²⁺、K⁺、Na⁺)increased significantly with ferilized treatments.However,soil pH,alkaline proteinase and urease activity decreased,while,soil EC increased in CM3treatment with 90 t/hm² organic manure.（2）Organic matter was an important factor for soil fertility index.There was significant correlation between organic matter and total nitrogen,avalible K,soil EC,exchangeable base capacity,total exchangeable base capacity,exchangeable calcium,exchangeable potassium,exchangeable magnesium,Olsen-P,exchangeable sodium,soil pH,alkaline proteinase and urease activity.（3）After the ¹⁵NH₄¹⁴NO₃ solution was added,the%¹⁵N excess and nitrogen mineralization rates gradually decreased across four treatmets with the incubation time.The average mineralization rates from 0 to 4 days were CK:29.2 mg/(kg·d^-1);CM1:27.1 mg/(kg·d^-1);CM2:28.4 mg/(kg·d^-1);CM3:24.6 mg/(kg·d^-1).Mineralization rate reduced significantly with high organic manure with 90 t/hm².（4）There was a significant positive correlation between the 0-4 d mineralization rate and soil pH.A significant negative correlation was found between 0-4 d mineralization rate and soil EC,total soil nitrogen,available K,total exchangeable base capacity,exchangeable magnesium,exchangeable potassium,and exchangeable sodium.Stepwise regression analysis showed that exchangeable potassium was an important factor for soil mineralization rate in manured sois.