|Zhang, Mingchu - UNIVERSITY OF ALASKA|
|Sparrow, Stephen - UNIVERSITY OF ALASKA|
Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 1, 2006
Publication Date: March 1, 2006
Citation: Sharratt, B., Zhang, M., Sparrow, S. 2006. Twenty years of tillage research in subarctic Alaska: II. Impact on soil hydraulic properties. Soil & Tillage Research (in press, available online doi:10.1016/j.still.2006.01.010) Interpretive Summary: Wind erosion and precipitation are a concern in sustaining spring crop production in the semi-arid region of interior Alaska. Lack of precipitation in spring can cause soil blowing and water stress during early crop development. Although the soil in spring was wetter in no tillage, infiltration of surface water was retarded by the thick organic layer that has formed at the soil surface over the past 20 years of continuous no tillage. This organic layer will not only suppress water recharge of the soil, but also suppress soil warming and therefore 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 and maximize infiltration by using more sustainable minimum tillage practices such as chisel plow in autumn or disk in spring.
Technical Abstract: Soil management practices are needed in the subarctic that stabilize the soil against the forces of wind and water as well as conserve soil water for crop production. There is a paucity of information, however, regarding the long-term effects of conservation tillage on soil hydraulic properties in subarctic Alaska. The objective of this study was therefore to characterize infiltration, water retention, and saturated hydraulic conductivity of a soil 20 years after establishing tillage and straw management treatments in interior Alaska. The split plot experimental design, established on a silt loam and maintained in continuous barley (Hordeum vulgare L.), included tillage as the main treatment and straw management as the secondary treatment. Tillage treatments included no tillage, autumn chisel plow, spring disk, and conventional tillage (autumn and spring disk) while straw treatments either retained or removed stubble and loose straw from the soil surface after harvest. Soil properties were measured after sowing in spring 2004; saturated hydraulic conductivity was measured by the falling-head method, infiltration was measured using a double-ring infiltrometer, and water retention was assessed by measuring the temporal variation in in-situ soil water content. No tillage resulted in greater saturated hydraulic conductivity and generally retained more water against gravitational and matric forces than other tillage treatments. Infiltration was greater in autumn chisel plow than other tillage treatments and was presumably suppressed in no tillage by a thick organic layer overlying mineral soil. Infiltration was also enhanced by retaining straw on rather than removing straw from the soil surface after harvest. No tillage is not yet a sustainable management practice in this region due to lack of weed control strategies and well as development of an organic layer that has important ramifications for the soil hydrological and thermal environment. Therefore, minimum tillage (i.e. autumn chisel plow or spring disk) appears to be a viable management option for maximizing infiltration and water retention in interior Alaska.