华北典型区域土壤耕作方式对土壤特性和作物产量的影响

华北平原是我国重要的小麦玉米种植区,长期土壤旋耕免耕和秸秆全量还田带来耕层变浅、犁底层变厚和上移、土壤养分表聚等现象,通过耕作方式改变,解决上述问题对维持区域粮食生产有重要意义。试验以冬小麦-夏玉米轮作系统为研究对象,分别在代表华北平原高产区的栾城试验区和代表中低产区的南皮试验区进行,设置冬小麦播种前进行土壤深耕、深松、窄深松3种处理,以生产上常用的旋耕为对照。所有处理夏玉米季均采用土壤免耕播种,测定项目包括土壤容重、作物根系、作物产量和水分利用效率。结果表明,不同耕作方式对土壤特性和作物产量的影响具有区域差异。南皮试验区土壤深耕(松)显著地(P0.05)提高了作物产量,深耕、深松和窄深松处理的冬小麦产量比旋耕分别增加16.5%、19.3%和13.1%,夏玉米产量分别增加17.3%、16.2%和21.9%,周年产量分别增加16.9%、17.6%和17.8%;深耕、深松和窄深松处理间作物产量差异不显著。栾城试验区冬小麦、夏玉米产量和周年产量各处理之间差异不显著。土壤深耕、深松、窄深松和旋耕均能降低0～20 cm土层土壤紧实度和土壤容重。冬小麦播种后,与土壤耕作前比较,土壤深耕、深松和旋耕处理土壤紧实度南皮试验区分别平均降低71.6%和68.2%,栾城试验区分别降低88.8%和?7.7%,常用的旋耕模式在栾城试区没有降低土壤紧实度。小麦收获时不同耕作方式0～40cm土层的土壤容重均低于土壤耕作前的土壤容重,至夏玉米收获时不同耕作处理的土壤容重与耕作前基本一致,不同耕作处理对土壤容重的影响差异不显著。在南皮试验区, 3种耕作方式与旋耕相比,均显著提高了冬小麦和夏玉米水分利用效率;在栾城试验区,各处理冬小麦和夏玉米水分利用效率差异不显著。本研究结果显示在华北平原高产区连续实施土壤旋耕模式没有影响作物产量,而在中低产区实施土壤深耕或者深松模式更利于作物产量提高。

Soil tillage practices affecting the soil characteristics and yield of winter wheat and summer maize in North China

The North China Plain (NCP) is one of the most intensively farmed agricultural regions in China, with approximately 70% of the total cultivated land being used for an annual double-cropping system of winter wheat and summer maize. Owing to the long-term rotary and no tillage practices accompanying with the whole straw of winter wheat and summer maize return to field for several years, soil physical characteristics are gradually changing in terms of the increased soil pan depth, bulk density and content of soil nutrients in the surface soil layer. Improving soil quality by changing the tillage practices might help to maintain crop productivity in this region. An experiment was conducted for the winter wheat-summer maize rotation system in Luancheng County, which represented a high yield region, and in Nanpi County, which represented a medium and low yield region, in the NCP. Four treatments-soil deep tillage (DT), subsoiling (SS), narrow subsoiling (NSS), and rotary tillage (control, CK)-before winter wheat sowing and no tillage before summer maize sowing to all treatments were simultaneously conducted at the two areas. Soil bulk density, crop root growth, soil water use, yield and water use efficiency (WUE) were monitored throughout. Results showed that the effects of different tillage practices on soil and crop were different in the two regions. At Nanpi, deep tillage and subsoiling significantly increased crop yield. Compared with traditional rotary tillage, winter wheat yield was improved by 16.5% under DT, 19.3% under SS, and 13.1% under NSS. Yield of summer maize was increased by 17.3%, 16.2%, and 21.9%, respectively, with annual yield increases of 16.9%, 17.6% and 17.8%, respectively. Yield differences were not observed among the DT, SS, and NSS treatments. However, no significant difference in crop yield among the four treatments was found at Luancheng. Furthermore, four tillage practices reduced soil penetration resistance and bulk density for the 0-20-cm soil layer in both Luancheng and Nanpi. At Nanpi, after sowing winter wheat, the soil penetration resistance of the 0-20-cm soil layer under DT, SS, NSS and CK decreased by 69.7%, 72.7%, 72.5% and 68.2%, respectively. At Luancheng, soil penetration resistance of the 0-20-cm soil layer was reduced by 88.8% averagely under treatments of deep tillage and subsoiling, and slightly increased by 7.7% under CK. Soil bulk density of the 0-40-cm soil layer under the four tillage treatments were all lower at wheat harvest compared with that before tillage. Until the summer maize harvest, soil bulk density under different tillage treatments was essentially similar to that before tillage, and there was no significant difference among the four tillage treatments. At Nanpi, WUE of winter wheat and summer maize was significantly increased under DT, SS, and NSS compared with that under CK. At Luancheng, the WUE of winter wheat and summer maize was similar among the four treatments. These results indicated that different tillage practices in the low yield regions benefited crop production and water productivity. However, in the high yield regions, the three tillage practices did not enhance crop performance compared with traditional tillage practice. Therefore, it is suggested that the model of soil rotary tillage can be continuously implemented in the high yield regions of the NCP, whereas DT can be beneficially implemented in the medium and low yield regions.