Abstract: With enclosed and static chambers and ion exchange resin bags, this paper studied the effects of water addition (W), nitrogen addition (N), and water and nitrogen addition (WN) on the ammonia volatilization and nitrate leaching of a sandy grassland in southeastern Keerqin Sandy Land, taking no water and nitrogen addition as the control (CK). Treatments N and WN promoted the ammonia volatilization significantly, and the maximum ammonia volatilization rate was significantly higher than that of the control (P<0.05). The cumulative amount of ammonia volatilization in treatments N and WN was 111.80 mg·m^-2 and 148.64 mg·m^-2, accounting for 1.1% and 1.5% of the nitrogen added, respectively. The cumulative amount of the ammonia volatilization was significantly higher in treatment WN than in treatment N (P<0.05), but had no significant difference between treatments W and CK. Treatments N and WN increased the leaching amount of nitrate-N at 20 cm soil depth significantly (P<0.05), being 1.96 and 4.22 times of the CK, respectively. No significant difference was observed in the leaching amount of nitrate-N at 40 cm soil depth among the treatments W, N, WN, and CK (P>0.05). The results suggested that both nitrogen addition and water and nitrogen addition promoted the ammonia volatilization, but had little effects on the nitrate leaching of the sandy grassland.

Key words: Eco agriculture, Integrated evaluation, Benefit index, Deqing County