Chin J Plant Ecol ›› 2016, Vol. 40 ›› Issue (5): 480-492.DOI: 10.17521/cjpe.2015.0374

• Research Articles • Previous Articles     Next Articles

Effects of N and P additions on net nitrogen mineralization in temperate typical grasslands in Nei Mongol, China

Qin-Pu LUO1, Ji-Rui GONG1,*, Sha XU1, Taogetao BAOYIN2, Yi-Hui WANG1, Zhan-Wei ZHAI1, Yan PAN1, Min LIU1, Li-Li YANG1   

  1. 1State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, College of Resources Science & Technology, Beijing Normal University, Beijing 100875, China

    2College of Life Sciences, Inner Mongolia University, Hohhot 010021, China
  • Online:2016-05-10 Published:2016-05-25
  • Contact: Ji-Rui GONG

Abstract: <i>Aims</i>

Nitrogen (N) mineralization is an important ecological process which determines soil N supplying ability, and it is a key research domain of soil N cycling worldwide at present. Nutrient addition can play a key role in regulating soil N transformations. The objective of the study was to evaluate the effects of different levels of N and P additions on in situ N mineralization during growing seasons in the temperate grasslands.


We conducted an field N and P fertilization addition experiment in the temperate grassland in Nei Mongol in June 2014. Five levels of N (0-25 g N·m?2·a?1), five levels of P (0-12.5 g P2O5·m-2·a-1) addition treatments, and a control were set up. We measured the in situ net mineralization rate, ammonification rate, and nitrification rate using the resin core incubation technique once a month from July to October 2014. Aboveground biomass and some selected soil chemical and microbial properties were also measured in the study.

Important findings

High nitrogen addition did significantly affect the contents of inorganic N. High N addition levels (25 g N·m?2·a?1 + 1 g P2O5·m-2·a-1 and 10 g N·m?2·a?1 + 1 g P2O5·m-2·a-1) significantly increased soil inorganic N content, and the 25 g N·m?2·a?1 + 1 g P2O5·m-2·a-1 treatment markedly increased soil nitrate- (NO3- -N) and ammonium-N (NH4+ -N). Compared to N addition, P addition had limited effects on soil inorganic N, NO3- -N and NH4+ -N. Only the 12.5 g P2O5·m-2·a-1 + 2 g N·m?2·a?1 treatment significantly increased soil ammonium-N and inorganic N. N addition did significantly affect microbial N transformation rates. The 25 g N·m?2·a?1 + 1 g P2O5·m-2·a-1 treatment significantly stimulated soil net N nitrification rate, mineralization rate and ammonification rate, suggesting that high N addition can effectively improve soil available N supply. N was a limiting factor to soil organic N mineralization in the study area. P addition had negligible effects on soil net N mineralization and nitrification rates, and only the 12.5 g P2O5·m-2·a-1 + 2 g N·m?2·a?1 treatment significantly enhanced ammonification rate in the middle of growing season. The results also indicated that impacts of P addition on soil N mineralization were weaker than impacts of N. Moreover, N and P addition significantly increased aboveground biomass. Under the N and P addition, soil moisture was significantly correlated with net mineralization and nitrification rate, which suggested that it was one of the dominant factors affecting N. Net N mineralization and nitrification rate under N fertilization was significantly correlated with environmental factors (soil organic C, soil C/N and soil total N). Soil N mineralization was not positively correlated with the soil microbial biomass N or C.

Key words: temperate grassland, N and P additions, nitrogen mineralization, soil inorganic N, affecting factor