|Zhang, Mingchu - UNIVERSITY OF ALASKA|
|Sparrow, Stephen - UNIVERSITY OF ALASKA|
Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 1, 2006
Publication Date: May 5, 2006
Citation: Sharratt, B., Zhang, M., Sparrow, S. 2006. Twenty years of tillage research in subarctic Alaska: I. Impact on soil strength, aggregation, roughness and residue cover. Soil & Tillage Research (in press, available online doi:10.1016/j.still.2005.11.006) Interpretive Summary: Wind erosion is a concern in the subarctic region of interior Alaska where high winds, lack of precipitation, and conventional tillage practices cause soil blowing in spring. Soil blowing can be reduced by using soil management practices that either strengthen or cover the soil surface. Although no tillage provides adequate protection against wind erosion by strengthening and covering the soil surface during spring, a thick organic layer has formed on the soil surface over the past 20 years of continuous no tillage. This organic layer insulates the soil and will likely suppress soil warming and crop production in the future. Therefore, no tillage is not yet a sustainable conservation tillage practice in the subarctic. Farmers in interior Alaska can minimize wind erosion by using more sustainable minimum tillage practices such as chisel plow in autumn or disk in spring.
Technical Abstract: Soil properties affecting wind erosion can be manipulated through tillage and crop residue management. Little information exists, however, that describe the impact of long term tillage and residue management on soil properties in the subarctic region of the United States. This study examines the impact of 20 years of tillage and residue management on a broad range of physical properties of a silt loam that govern wind erosion processes in interior Alaska. The spilt plot experimental design was established in 1983 and included conventional tillage (autumn and spring disk), minimum tillage (spring disk or autumn chisel plow), and no tillage with straw either retained on or removed from the soil surface superimposed upon the tillage treatments. Soil and residue properties measured after sowing barley (Hordeum vulgare L.) in May 2004 included penetration resistance, soil water content, shear stress, bulk density, random roughness, aggregate size distribution, and residue cover and biomass. No tillage was characterized by larger aggregates, greater soil strength (penetration resistance and shear stress), wetter soil, and greater residue cover compared to all other tillage treatments. Retaining straw on the soil surface promoted greater residue biomass and cover despite crop failures both years preceding this study. Although no tillage appeared to be the most effective management strategy for controlling erosion, no tillage is not yet a sustainable practice due to a lack of strategies to control weeds and also to an accumulation of organic material on the soil surface. The accumulation of organic material on the soil surface (50 mm thick) over the past 20 years has important ramifications for long term crop production in the subarctic where mean annual temperatures are <0°C. Autumn chisel and spring disk appear to be viable minimum tillage options to conventional and no tillage in controlling erosion. Autumn chisel and spring disk promote greater roughness, aggregation, and residue cover as compared with conventional tillage.