Abstract: Determination of N preservation and supply performances of 15 pairs of fertile and infertile brown earth type vegetable garden soils sampled from northern, central and southern Liaoning province show that in most soil samples tested, fertile soils and their various particle sizes of microaggregates had a larger amount of total N and adsorbed and desorbed NH₄⁺, but a smaller desorption rate than infertile soils and their corresponding particle sizes of microaggregates. There are significant different between total N, adsorbed and desorbed NH₄⁺ of fertile and infertile soils and their microaggragate of <10μm. The amount of adsorbed and desorbed N decreased with the increment of microaggregates particle sizes in both fertile and infertile soils, but the desorption rate was reversed. NH₄⁺ adsorption had no significant linear relationship with soil nutrients and enzyme activities,but NH₄⁺ desorption of fertile soils and their various particle sizes of microaggregates had significant linear positive relationships with soil organic matter and its binding status, total Ncontent, urease and phosphatase activities, NH₄⁺ desorption of infertile soils and their corresponding particle sizes of microaggregates had no significant linear positive relationships with all nutrients contents and enzyme activities.

Key words: N-preservation and supply, Brown earth type vegetable garden soil, Soil microaggregates, Soil fertility