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切断防护林伸向毗邻农田的侧向根系,通过减少根系竞争增加作物产量。在内布拉斯加的波斯县的Boelus—Loretto复合壤质细沙土和Thurman壤质细沙土的农田里分别进行两项试验,旨在评价多行农田防护林带切根后对玉米和大豆的产量效应。于1986和1987年两年,每年进行两个切根深度和两个距林带南缘不同距离的试验。在与林带相垂直的田间选三个样点取农作物资料。既使在这两个超过常年降雨的年份,也改进了作物产量和农学性状。在距林带20m处,结一个以上豆荚的大豆枝数,平均每株增加0.5枝,生物量增加26％;在距林带7.5m的所有断根处理同对照比较,产量增加31％。断根使距林带18m处的玉米穗数和杆棵重量都有所增加,同时在33.3m处各处理的玉米产量比对照增加18％。增产稳定的处理(深度深,距离近)在18m和26m的位点上分别增产35％和23％。
Cut off shelterbelts to the lateral roots of adjoining farmland and increase crop yields by reducing root competition. Two trials were conducted in the Boelus-Loretto composite loamy and Thurman loamy sand fields in Persia County, Nebraska, to evaluate the effects of cutting corn and soybeans on multiple shelterbelts effect. In 1986 and 1987, two cut depths and two different distances from the southern margin of the forest belt were performed each year. In the vertical field with the forest selected three samples of crop information. Crop production and agronomic traits have been improved even in these two years that exceeded annual rainfall. At the distance of 20m from the forest belt, the number of soybean branches with more than one pods increased by an average of 0.5 per plant and the biomass increased by 26%. Compared with the control, all the treatments of 7.5m away from the forest belt increased by 31%. Broken roots increased the number of maize spikes and barn trees at 18 m from the forest belt, and the yield of maize processed at 33.3 m increased by 18% compared with the control. The treatment of increasing yield (deep depth and distance) increased yields by 35% and 23% respectively at 18m and 26m sites.