Soil Temperature Regimes as Influenced by Rotation,Tillage and Row Spacing for Winter Wheat

Conservation tillage management modifies soil temperature by its influence on surface residues. This study investigated the effects of rotation, tillage and row spacing on soil temperature under winter wheat (Triticum aestivum L.) in southern Alberta in 1993～1994 and 1994～1995. The main treatments were three crop rotations (continuous winter wheat, WW; winter wheat canola (Brassica campestris L), WC; winter wheat fallow, WF) with two tillage sub treatments (conventional tillage CT vs. zero tillage ZT) and two row spacing sub sub treatments (uniform vs. paired row spacing). The results showed that crop residues under ZT reduced frost penetration depth, e.g. on the WW rotation in 1993～1994, the maximum -5℃ isotherm depth was 22 cm shallower under ZT than under CT. Lower soil temperatures under ZT, due to higher levels of surface residue, were more pronounced on the WC and WW rotations than on the WF rotation. On four dates at monthly intervals in spring 1994, ZT was significantly cooler than CT at the 2.5 cm depth on the WC and WW rotations. The largest difference between the tillage treatments occurred on the WW rotation on April 8 when the ZT treatment was 4.1℃ cooler than the CT treatment. Crop residue level due to rotation dominated the magnitude of the tillage effect with the WF rotation showing the least differences due lower levels of crop residue. Soil temperatures were significantly higher under paired row spacing than under uniform row spacing in spring 1994. While soil temperatures may be manipulated by management practices such as rotation, tillage or row spacing, the effects are not likely to negatively impact crop performance.