Tillage depth and timing effects on soil water profiles in two semiarid soils

Authors: Wuest, Stewart

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/25/2010
Publication Date: 8/2/2010
Citation: Wuest, S.B. 2010. Tillage depth and timing effects on soil water profiles in two semiarid soils. Soil Science Society of America Journal. 74:1701-1711. doi:10.2136/sssaj2010.0046

Interpretive Summary: The two-year winter wheat--fallow rotation continues to be the most profitable and productive cropping system in much of the Pacific Northwest, USA. Sustainability of soils in the region depends on our ability to halt or greatly reduce wind and water erosion. An incomplete understanding of how tilled summer fallow preserves seed-zone moisture for timely fall crop establishment has slowed efforts to optimize tillage techniques for creating profitable and erosion resistant systems. This two-year study created a series of soil mulches at two sites representing major soils in the region. It was found that timing and depth of mulch creation had consistent effects on all four site-years. Tillage performed in mid-June at depths of 10- and 15-cm preserved significantly greater water content compared to no-till or 5-cm tillage. To optimize timing and depth of summer fallow tillage it will be necessary to characterize spring water storage plus the potential for end-of-summer water storage for each soil type. Temperature profiles demonstrated different shapes under different mulch treatments, which may prove useful in making quick comparisons between mulch types in the field. The data also demonstrated the importance of using mass-depth instead measuring depth from the soil surface to make unbiased comparisons where treatments differ in surface compaction.

Technical Abstract: The two-year winter wheat--fallow rotation continues to be the most profitable and productive cropping system in much of the Pacific Northwest, USA. Sustainability of soils in the region depends on our ability to halt or greatly reduce wind and water erosion. An incomplete understanding of how tilled summer fallow preserves seed-zone moisture for timely fall crop establishment has slowed efforts to optimize tillage techniques for creating profitable and erosion resistant systems. This two-year study created a series of soil mulches at two sites representing major soils in the region. It was found that timing and depth of mulch creation had consistent effects on all four site-years. Tillage performed in mid-June at depths of 10- and 15-cm preserved up to 0.01 g g-1 greater water content compared to no-till or 5-cm tillage, an amount that can make substantial differences in germination. The later or shallower tillage treatments produced water contents similar to no-till at 30 cm depth. To optimize timing and depth of summer fallow tillage it will be necessary to characterize spring water storage plus the potential for end-of-summer water storage for each soil type. Temperature profiles at 1-cm resolution demonstrated different shapes under different mulch treatments, which may prove useful in making quick comparisons between mulch types in the field. The data also demonstrated the importance of using mass-depth instead of linear depth from the soil surface to make comparisons not confounded with soil bulk density differences.