SOIL ORGANIC MATTER POOLS DURING EARLY ADOPTION OF CONSERVATION TILLAGE IN NORTHWESTERN CANADA

Authors: Franzluebbers, Alan; ARSHAD, M - AGRI & AGRI-FOOD CANADA

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/21/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: In the past decade, zero and reduced tillage systems have received increased attention due to the potential of these conservation tillage systems 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 convervation tillage can increase carbon sequestration in soils, which is important for improving soil physical, chemical, and biological properties, but also for reducing atmospheric carbon dioxide that contributes to global warming. A lowland clay soil in northern Alberta was subjected to conventional, reduced, and zero tillage for six years. Tillage had relatively small effects on soil organic matter pools. Tilled fallow with conventional tillage led to both higher inorganic soil nitrogen and mineralizable nitrogen, such that less nitrogen fertilizer would be required to achieve optimum yields following fallow than with reduced or zero tillage. More active pools of soil organic matter indicated that reduced and zero tillage were contributing to conservation of carbon, but at a slower rate than in more temperate climates.

Technical Abstract: Changes in soil organic matter pools during adoption of reduced (RT) or zero tillage (ZT) affects soil physical properties, nutrient cycling, and carbon dioxide flux between soil and atmosphere. We determined soil organic C (SOC), soil microbial biomass C (SMBC), basal soil respiration (BSR), and mineralizable N to a depth of 200 mm at the end of 3, 5, and 6 yr of tillage management on a fine, montmorillonitic, frigid Typic Natriboralf in a canola (Brassica campestris L.)-wheat (Triticum aestivum L.)-barley (Hordeum vulgare L.)-fallow cropping system. At the end of 6 yr, SOC was not different among tillage regimes and averaged 86 Mg/ha. At the end of 3 and 5 yr, SMBC was not different among tillage regimes, but at the end of 6 yr SMBC was 7% greater in RT and 9% greater in ZT than in conventional tillage (CT). BSR following fallow was 22, 25, and 26 kg C/ha/d in CT, RT, and ZT, respectively. At 0 to 50 mm depth, there was no increase in SOC at the end of 6 yr, a 17 to 36% increase in SMBC, and a 12 to 69% increase in BSR with ZT compared with CT. Relatively small changes in C pools with adoption of conservation tillage may be attributable to the large amount of SOC initially present and the cold, semiarid climate that limits SOC turnover.