沙质农田作物不同间作采收模式休耕期的防风效应
Windbreak effect of different intercropping and harvesting modes in fallow period of sandy farmland crops
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摘要: 油沙豆(Cyperus esculentus)是集粮、油、牧、饲于一体的高利用价值新兴经济作物,在我国沙区调整种植结构及沙化土地治理中有重要作用,但其茎块采收方式容易破坏表层土壤,引发风蚀。因此,为探究沙质农田油沙豆休耕期防风阻沙的最优保护性耕作模式,该研究基于风洞模拟试验,以研究区主要作物玉米、向日葵为间作作物与油沙豆进行带状间作,探究不同风速下6种间作模式(2种间作作物×3种带间距)及单作油沙豆全采收模式的防风蚀效果。研究结果表明:(1)不同带间距模式在各风速下的风速廓线均呈对数形式,粗糙度随带间距的增加而减小,间作玉米中带间距8 m模式的粗糙度最大,间作向日葵中带间距24 m模式粗糙度最小。(2)各模式在不同风速下的流场结构分布特征基本一致,间作玉米各带间距模式近地表风速均低于6 m/s,低于起沙风速;间作向日葵各模式近地表风速约为9 m/s,高于起沙风速。(3)风速对玉米、向日葵间作模式的防风效能具有显著影响,各间作模式的防风效能随风速的增大呈减小趋势。(4)间作玉米模式的防风效能大于间作向日葵模式,防风效能随带间距的增加而减小,表现为:带间距8 m>带间距16 m>带间距24 m。其中,玉米带间距16 m模式近地表防风效能大于50%,是油沙豆休耕期兼顾生态效益和经济效益的最优间作模式。Abstract: Cyperus esculentus is an emerging economic crop with a high utilization value that integrates grain, oil, animal husbandry and forage. It plays an important role in adjusting structural planting in sandy areas in China and desertification combating. However, the traditional harvesting easily damages the surface soil and causes wind erosion. Therefore, the optimal protective tillage mode for wind and sand resistance during the fallow period of C. esculentus in sandy farmlands should be explored. In this study, the wind erosion prevention effect of six intercropping modes (two types of intercropping crops × three types of spacing between intercropping strips) and no-harvest modes under four axial wind speeds of 6, 8, 12 and 16 m/s were explored based on wind tunnel tests. The results showed that (1) the wind velocity profiles of the intercropping modes under different wind speeds conformed to logarithmic functions. The roughness decreased with increasing belt spacing, where the roughness of the mode was the smallest with a 24-m intercropping strips spacing. (2) The wind velocity flow distribution characteristics of the intercropping modes under different wind speeds were similar. The near-surface wind speeds of the Zea mays L. intercropping models were lower than 6 m/s. The wind speeds of the sunflowers intercropping modes were approximately 9 m/s, which was higher than that the threshold wind velocity of sand movement. (3) The wind speed significantly affected the windbreak efficiency of the intercropping modes. The windbreak efficiency of each intercropping model decreased with wind speed increasing. (4) The windbreak efficiency of the intercropping Zea mays L. model was higher than that of the intercropping Helianthus annuusL. model. The windbreak efficiency decreased with intercropping strips spacing in the increasing order of 8 m, 16 m, 24 m. Among all the intercropping modes, the near-surface windbreak effect of Zea mays L. strip with a 16 m intercropping strips spacing was greater than 50%, therefore it is an optimal intercropping mode considering ecological and economic benefits during the fallow period of C. esculentus.
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