Responses of biomass to the addition of water, nitrogen and phosphorus in Keerqin sandy grassland, I

The effects of water, nitrogen and phosphorus on productivity of sandy grassland were investigated with a fully factorial experiment to find out the main factors limiting natural restoration of grassland productivity in the southeastern Keerqin sandy land. In total, eight treatments were designed as water addition (W), nitrogen fertilizer addition (N), phosphorus fertilizer addition (P), water + nitrogen fertilizer addition (WN), water + phosphorus fertilizer addition (WP), nitrogen fertilizer + phosphorus fertilizer addition (NP), water + nitrogen fertilizer + phosphorus fertilizer addition (WNP) and control (CK). Each treatment was replicated six times and randomly assigned to 48 plots (4 m × 4 m) that were separated by a 2-m buffer. Results show that restoration of productivity is only limited by nitrogen factor for sandy grassland of Keerqin sandy land and not limited by water and phosphorus. Relative to CK plots, the biomass and the aboveground net primary productivity (ANPP) of all the plots added with nitrogen fertilizer were significantly enhanced (P < 0.05)="" in="" 2005="" growing="" season.="" grass="" root="" mass="" is="" dominant="" in="" underground="" biomass.="" the="" present="" study="" possibly="" underestimates="" net="" primary="" productivity="" of="" grassland="" in="" northern="" china,="" due="" to="" limitation="" of="" underground="" biomass="" measurements.="">