Abstract: By using ultra-centrifugal technique and KCl extraction, the contents of soil soluble organic nitrogen (SON), dissolved organic nitrogen (DON), and f ree amino acid (FAA) in three horticultural production systems, i.e., organic (O S), transitional (TS), and conventional (CS), were determined, and their correla tions with some other soil properties were investigated. The results showed that SON content in the three production systems was in the order of OS>CS>TS, and t he ratios of SON to soil total soluble N (TSN) and total N (TN) in OS, CS, and T S were 429%, 245%, and 184%, and 111%, 119%, and 74%, respectively. T he DON content in OS, TS and CS was 438, 168 and 326 mg·kg-1, occup ying 479%, 221% and 261% of TSN, and 29%, 23% and 36% of TN, respect ively. FAA content occupied 1%〖KG-*2〗-〖KG-*7〗3% of TSN and 2%〖KG-*2〗-〖KG- *7〗10% of SON, and decreased in the order of CS>TS>OS. Correlation analysis sho wed that TSN, SON and FAA were significantly correlated with soil total N, total carbon, NO3--N and NH4+-N. Different management measures of horticult ural production system changed the SON content and its characters.

Key words: soil springtails, low temperature adaptation, behavior strategy, drought dehydration.