Soil organic matter dynamics in long-term temperate agroecosystems: rotation and nutrient addition effects

• Published in: Canadian Journal of Soil Science Vol. 98; no. 2; pp. 232 - 245
• Main Authors: Li, Jichen, Ramirez, Guillermo Hernandez, Kiani, Mina, Quideau, Sylvie, Smith, Elwin, Janzen, Henry, Larney, Francis, Puurveen, Dick
• Format: Journal Article
• Language: English
• Published: Ottawa Canadian Science Publishing 01-06-2018; Canadian Science Publishing NRC Research Press
• Subjects: aggregation; Agricultural ecosystems; agroecosystem; agrégation; biomasse microbienne; Communities; Crop rotation; Crops; Forest soils; Forests; Land management; Land use; Legumes; matière organique du sol; microbial biomass; Microorganisms; Nitrogen; Nutrient dynamics; Nutrients; Organic carbon; Organic matter; Organic soils; qualité du sol; Soil dynamics; Soil organic matter; Soil properties; Soil quality; Total organic carbon; écosystème agricole
• ISSN: 0008-4271; 1918-1841; 1918-1833
• DOI: 10.1139/cjss-2017-0127

Soil organic matter (SOM) is a major driver of key agroecosystem functions. Our objective was to examine the dynamics of organic matter in whole soil, particulate (POM; >53 µm size), and mineral-associated (MAOM) fractions under varying crop rotations and nutrient managements at two long-term experimental sites (Breton and Lethbridge). Soil samples were collected from simple (2 yr) and complex (5 or 6 yr) crop rotations at the 5–10 cm depth. We found associations between SOM pools versus microbial community and soil aggregation. Compared to cropped soils, an adjacent forest exhibited a significantly higher soil total organic carbon (TOC) and a shift in SOM fractions with substantially higher POM. However, the forest soil had the lowest microbial biomass C among all the assessed land use systems (P < 0.05), suggesting that other factors than the amount of labile SOM (i.e., POM-C) were controlling the microbial community. When contrasted to simple 2 yr rotations, the complex rotations including perennials and legumes significantly raised TOC and soil total nitrogen as well as the stable SOM fraction (i.e., MAOM-C and -N) consistently for both Breton and Lethbridge sites. Our findings highlight that varying land managements have profound feedbacks on soil quality as mediated by alterations in long-term SOM dynamics.