美国柑桔园过去多用酸橙作砧木,近年来采用粗柠檬或枳橙,加之多数柑桔园都建在比较深厚的沙土或沙壤土上,因此植株高大,虽然亩植18—20株,也会发生柑桔园的郁蔽,亦不利于机械操作。由于美国劳动力价格昂贵,无法采用人工修剪,故现在普遍推行机器篱剪。采用篱剪的柑桔树大多在20年生以上,行间已开始交接或交叉。其大致作法是:第1年剪单数行间两边的树冠,使呈75—60°篱壁状,剪出2米左右的空间;第2年则剪双数行间;第3年剪顶,使顶部呈平面。第4—6年为第2轮修剪,重复头3年的作法。他们认为第1轮修剪每年会减产10％,第2轮 In the past, citrus orchards in the United States used limes as rootstocks. In recent years, they used coarse lemons or citrange trees. In addition, most citrus orchards are built on relatively deep sand or sandy loam. Therefore, the plants are tall and there are 18-20 acres of mu Occurrence of citrus garden Yu, is not conducive to mechanical operation. Due to the high cost of labor in the United States and the inability to use manual trimming, it is now common practice to implement hedge shears. Most citrus trees with hedgerows are over 20 years of age and the transition has taken place between the lines. The general approach is: the first year cut the canopy on both sides of the tree between the rows, so that was 75-60 ° fence wall shape, cut out about 2 meters of space; Make the top flat. The first 4-6 years of the second round of pruning, repeat the first three years of practice. They think the first round of pruning will cut 10% each year, the second round