Abstract: This paper reports a preliminary study on the patterns of litter formation in Leymus chine-sis grassland in Songnen plain.The mortality process of Leymus chinesis is observed,itsmortality rates in different seasons are calculated,and the mathematical models of litterproduction are constructed.The gross quantity of litter is determined as 145.5g穖^-2,whichequals to the sum of annual production of litter and its weight losses during the period.

Key words: Rice, Nitrogen fertilizer, Nitrogen utilization efficiency