Base cations and micronutrients in soil aggregates as affected by enhanced nitrogen and water inputs in a semi-arid steppe grassland.
The intensification of grassland management by nitrogen (N) fertilization and irrigation may threaten the future integrity of fragile semi-arid steppe ecosystems by affecting the concentrations of base cation and micronutrient in soils. We extracted base cations of exchangeable calcium (Ca), magnesium (Mg), potassium (K), and sodium (Na) and extractable micronutrients of iron (Fe), manganese (Mn), copper (Cu), and zinc (Zn) from three soil aggregate sizes classes (microaggregates, <0.25mm; small macroaggregates, 0.25-2mm; large macroaggregates, >2mm) from a 9-yearN and water field manipulation study. There were significantly more base cations (but not micronutrients) in microaggregates compared to macroaggregates which was related to greater soil organic matter and clay contents. Nitrogen addition significantly decreased exchangeable Ca by up to 33% in large and small macroaggregates and exchangeable Mg by up to 27% in three aggregates but significantly increased extractable Fe, Mn and Cu concentrations (by up to 262%, 150%, and 55%, respectively) in all aggregate size classes. However, water addition only increased exchangeable Na, while available Fe and Mn were decreased by water addition when averaging across all N treatments and aggregate classes. The loss of exchangeable Ca and Mg under N addition and extractable Fe and Mn in soil aggregates under water addition might potentially constrain the productivity of this semi-arid grassland ecosystem.
State Engineering Laboratory of Soil Nutrient Management, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China.
Ruzhen
R
Wang
Sustainable Soils and Grassland Systems Department, Rothamsted Research, North Wyke, Okehampton, Devon EX20 2SB, UK.
Jennifer A J
JAJ
Dungait
School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Clifton BS8 1RJ, UK.
Heather L
HL
Buss
State Engineering Laboratory of Soil Nutrient Management, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China; Key Laboratory of Regional Environment and Eco-Remediation, College of Environment, Shenyang University, Shenyang 110044, China.
Shan
S
Yang
Key Laboratory of Regional Environment and Eco-Remediation, College of Environment, Shenyang University, Shenyang 110044, China.
Yuge
Y
Zhang
State Engineering Laboratory of Soil Nutrient Management, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China.
Zhuwen
Z
Xu
State Engineering Laboratory of Soil Nutrient Management, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China. Electronic address: jiangyong@iae.ac.cn.
Yong
Y
Jiang
Calcium; Copper; Irrigation; Magnesium; Manganese; Nitrogen deposition