Abstract: To characterize soil nitrogen mineralization in protected vegetable fields of Beijing suburbs,110 soil samples were studied by both shortterm and longterm aerobic incubation with intermittent leaching.Results showed that the average quantity of mineralized nitrogen of all the samples was 17.50 mg/kg,ranging from 2.50 to 112.00 mg/kg,but 81 percent of the samples were between 2.50 and 23.99 mg/kg in two weeks,indicating a relatively consistent mineralization capacity of the soils in protected vegetable fields in Beijing suburbs.The soil mineralized nitrogen has significantly positive correlation with organic matter and total nitrogen,but no correlation with alkali nitrogen.In addition,45 soil samples were chosen for longterm incubation in 21 weeks.The cumulative quantity of the mineralized nitrogen ranged from 19.00 to 337.00 mg/kg(avg.102.00 mg/kg).There were three phases for the change of mineralized nitrogen rate:a fast phase in the first three weeks;a slower one between the third and the seventeenth week;and a steady mineralization phase later.Nitrogen supplied by soil of protected vegetable fields in Beijing suburbs was 214.00 mg/kg in 21 weeks at average,which was higher than the nitrogen requirements of crops for normal growth in one growth season.

Key words: Protected vegetable fields, Quantity of the mineralized nitrogen, Nitrogen mineralization rate

CLC Number: 

• S18.2