轮作、耕作及行距对麦田土壤温度动态的影响

研究了加拿大南部冬小麦田在轮作、耕作和行距共同作用下的土壤温度动态。田间裂区试验主区为3个轮作(冬小麦连作、冬小麦/油菜轮作和冬小麦/夏休闲),副区包括两种耕作技术(免耕和常规耕作),小裂区包括两种种植行距(等行距和大小行)。结果表明,免耕处理下秸秆覆盖有效地降低了冬季土壤的冻结深度。在1993～1994年度,连作小麦免耕土壤的-5℃等温线要比常规耕作浅22cm。免耕秸秆覆盖的温度效应在冬小麦连作和冬小麦/油菜两种轮作上比在冬小麦/夏休闲上更为明显。在冬小麦连作和冬小麦/油菜轮作下,免耕土壤2.5cm的春季温度连续4个月显著低于常规耕作土壤。1994年4月8日,免耕和常规耕作农田2.5cm处的温差在冬小麦连作处理上达到4.1℃。对于冬小麦/夏休闲处理,由于秸秆覆盖量较少,耕作措施对土壤温度的影响不太明显。在1994年春季,大小行种植的土壤温度显著高于等行距种植的土壤温度。因此,免耕主要通过秸秆覆盖来改变土壤的温度状况。通过轮作、耕作和行距等措施,可以在一定程度上实现土壤温度的人为调节

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.