title: Effects of straw and biochar amendments on aggregate stability, soil organic carbon, and enzyme activities in the Loess Plateau, China.
abstract: Soil from the Loess Plateau of China is typically low in organic carbon and generally has poor aggregate stability. Application of organic amendments to these soils could help to increase and sustain soil organic matter levels and thus to enhance soil aggregate stability. A field experiment was carried out to evaluate the effect of the application of wheat straw and wheat straw-derived biochar (pyrolyzed at 350-550 °C) amendments on soil aggregate stability, soil organic carbon (SOC), and enzyme activities in a representative Chinese Loess soil during summer maize and winter wheat growing season from 2013 to 2015. Five treatments were set up as follows: no fertilization (CK), application of inorganic fertilizer (N), wheat straw applied at 8 t ha-1with inorganic fertilizer (S8), and wheat straw-derived biochar applied at 8 t ha-1(B8) and 16 t ha-1(B16) with inorganic fertilizer, respectively. Compared to the N treatment, straw and straw-derived biochar amendments significantly increased SOC (by 33.7-79.6%), microbial biomass carbon (by 18.9-46.5%), and microbial biomass nitrogen (by 8.3-38.2%), while total nitrogen (TN) only increased significantly in the B16 plot (by 24.1%). The 8 t ha-1straw and biochar applications had no significant effects on soil aggregation, but a significant increase in soil macro-aggregates (>2 mm) (by 105.8%) was observed in the B16 treatment. The concentrations of aggregate-associated SOC increased by 40.4-105.8% in macro-aggregates (>2 mm) under straw and biochar amendments relative to the N treatment. No significant differences in invertase and alkaline phosphatase activity were detected among different treatments. However, urease activity was greater in the biochar treatment than the straw treatment, indicating that biochar amendment improved the transformation of nitrogen in the soil. The carbon pool index and carbon management index were increased with straw and biochar amendments, especially in the B16 treatment. In conclusion, application of carbonized crop residue as biochar, especially at a rate of 16 t ha-1, could be a potential solution to recover the depleted SOC and enhance the formation of macro-aggregates in Loess Plateau soils of China.
authors.affiliation: Institute of Soil and Water Conservation, Northwest A&F University, Yangling, Shanxi, 712100, China.|Institute of Soil and Water Conservation, Chinese Academy of Sciences, and Ministry of Water Resources, Yangling, Shanxi, 712100, China.
authors.forename: Man
authors.initials: M
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Plant Nutrition and the Agri-environment in Northwest China, Ministry of Agriculture, College of Natural Resources and Environment, Northwest A&F University, 3 Taicheng, Yangling, 712100, China.
authors.forename: Gong
authors.initials: G
authors.lastname: Cheng
authors.affiliation: Institute of Soil and Water Conservation, Northwest A&F University, Yangling, Shanxi, 712100, China.
authors.forename: Hao
authors.initials: H
authors.lastname: Feng
authors.affiliation: Key Laboratory of Plant Nutrition and the Agri-environment in Northwest China, Ministry of Agriculture, College of Natural Resources and Environment, Northwest A&F University, 3 Taicheng, Yangling, 712100, China.
authors.forename: Benhua
authors.initials: B
authors.lastname: Sun
authors.affiliation: Key Laboratory of Plant Nutrition and the Agri-environment in Northwest China, Ministry of Agriculture, College of Natural Resources and Environment, Northwest A&F University, 3 Taicheng, Yangling, 712100, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: Institute of Soil and Water Conservation, Northwest A&F University, Yangling, Shanxi, 712100, China.
authors.forename: Haixin
authors.initials: H
authors.lastname: Chen
authors.affiliation: Key Laboratory of Plant Nutrition and the Agri-environment in Northwest China, Ministry of Agriculture, College of Natural Resources and Environment, Northwest A&F University, 3 Taicheng, Yangling, 712100, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Chen
authors.affiliation: Department of Renewable Resources, University of Alberta, 773 General Services Building, Edmonton, AB, T6G 2H1, Canada.
authors.forename: Miles
authors.initials: M
authors.lastname: Dyck
authors.affiliation: Key Laboratory of Plant Nutrition and the Agri-environment in Northwest China, Ministry of Agriculture, College of Natural Resources and Environment, Northwest A&F University, 3 Taicheng, Yangling, 712100, China.
authors.forename: Xudong
authors.initials: X
authors.lastname: Wang
authors.affiliation: Key Laboratory of Plant Nutrition and the Agri-environment in Northwest China, Ministry of Agriculture, College of Natural Resources and Environment, Northwest A&F University, 3 Taicheng, Yangling, 712100, China.
authors.forename: Jianguo
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Plant Nutrition and the Agri-environment in Northwest China, Ministry of Agriculture, College of Natural Resources and Environment, Northwest A&F University, 3 Taicheng, Yangling, 712100, China. zhangafeng@nwsuaf.edu.cn.
authors.forename: Afeng
authors.initials: A
authors.lastname: Zhang
mesh_terms: D002244:Carbon; D002606:Charcoal / Q000737:chemistry; D002681:China; D012987:Soil / Q000737:chemistry*
chemical_list: D012987:Soil; C540010:biochar; D002606:Charcoal; D002244:Carbon
keywords: Biochar; Enzyme activities; Loess Plateau; Soil aggregate stability; Soil organic carbon; Straw