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Title: SOIL ORGANIC MATTER POOLS WITH CONVENTIONAL AND ZERO TILLAGE IN A COLD, SEMIARID CLIMATE

Author
item Franzluebbers, Alan
item ARSHAD, M - AGRI AND AGRI-FOOD CANADA

Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/14/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: In the past decade, zero and various reduced tillage management systems have received increased attention due to their potential for abating soil erosion, conserving soil moisture, enhancing water quality, and cutting monetary and energy inputs of crop production systems. Results from temperate climates indicate that reduced tillage systems can increase carbon sequestration in soils, which is important for improving soil physical, chemical, and biological properties, but also for reducing atmospheric carbon dioxide concentration that contributes to global warming. Soils varying in texture in northern Alberta and British Columbia were subjected to conventional and zero tillage for 4 to 16 years. In contrast to the results from more temperate climates, soil organic matter was relatively unaffected by zero tillage management. The cold, semiarid climate of the Canadian Prairies appears to have hindered any acceleration of decomposition of soil organic matter and crop residues due to soil disturbance with tillage. These soils appear to have little potential to sequester additional carbon with zero tillage compared with conventional shallow tillage, although nutrient dynamics and soil physical properties may be enhanced for improved soil quality.

Technical Abstract: Conservation of soil organic matter (SOM), especially in high-SOM surface soils of the Canadian Prairies, is essential for maintaining soil quality and regulating soil carbon dioxide emissions. We determined the depth distribution (0-50, 50-125, and 125-200 mm) of soil organic C, soil microbial biomass C, basal soil respiration, and net N mineralization in four Boralfs subjected to shallow conventional tillage (CT) and zero tillage (ZT). Tillage regimes were initiated 4, 4, 7, and 16 years prior to these measurements on a limed clay loam, unlimed clay loam, sandy loam, and silt loam, respectively. Soils under ZT were an average of 4% denser and 24% wetter than under CT. Soil organic C content to a depth of 200 mm was 65 Mg/ha under CT and 11% greater under ZT in the limed clay loam, but not different between tillage regimes in the unlimed clay loam (71 Mg/ha), silt loam (51 Mg/ha), and sandy loam (43 Mg/ha). Basal soil respiration averaged 40 kg C/ha/d under CT and 31 kg C/ha/d under ZT. However, net N mineralization averaged 34 kg/ha/24 d under CT and 41 kg/ha/24 d under ZT. The cold, semiarid climate of the Canadian Prairies apears to have hindered any acceleration of decomposition of SOM and crop residues due to soil disturbance.