原平县同川,是山西省最大产梨区,已有1500多年的栽培历史。全区有梨园4万多亩,栽培各种梨树25万余株,其中树龄百年以上的居多,平均70年左右,树龄老化,品种低劣,病虫猖獗,产量下降。1985～1990年,对4万多亩低产老龄梨树进行了一系列技术改良研究,以去头换优效果最好。截至1990年底去头换成酥梨、鸭梨、雪花梨等优良品种已挂果的有6.2万株,年产量750万公斤,增加收入1125万多元。一、去头换优的技术与管理 (一) 嫁接时间春季树液流动至开花后(3月中旬至5月上旬)都可进行,嫁接成活率均在80％以上,尤其在梨树开花前5～10天(4月上中旬)嫁接成活率高达94～97％。 Yuanping County Tongchuan, Shanxi Province is the largest pear district, has 1500 years of cultivation history. There are more than 40,000 mu of pear orchards in the district and more than 250,000 pear trees are cultivated. Among them, the trees are more than 100 years old with an average age of about 70 years. The trees are aging with poor varieties, with rampant pests and diseases and declining production. From 1985 to 1990, a series of technical improvement studies were conducted on the low-yielding aged pear population of more than 40,000 mu, with the best results being attained. As of the end of 1990 to replace the pear, pear, snow pear and other fine varieties have fruiting 62,000, annual output of 7.5 million kilograms, an increase of more than 11.25 million yuan. First, head to head for the optimization of technology and management (A) grafting time Flow of spring sap flowering until after flowering (mid March to early May) can be carried out, grafting survival rates were above 80%, especially in pear before flowering 5 to 10 days (mid-April) graft survival rate as high as 94 to 97%.