据1989年的调查,丰都县共有果园9.4万亩,但平均亩产较低,绝大多数果园亩产都在1000公斤以下。为此,我们在1990、1991两年,对选定的5000亩低产果园进行了改造,其中3500亩为柑桔低产园,占70％。现就该县柑桔低产园成因及改造作一介绍。一、丰都县柑桔低产园形成的原因 1、建园质量差。近年来,丰都县果园面积增长迅猛,每年均以数千亩速度递增。由于片面追求速度,忽视质量,果园选址不合理,土质差,土层薄而板结,有的土层仅10厘米左右。建园时未爆破,挖深耕壕,施足底肥,土壤有机质含量低。栽植后未能及时深翻,扩穴,压埋基肥。由于苗木繁育上出圃苗不合规格,品种不纯.苗木质量差,栽植不科学等,也造成严 According to the 1989 survey, Fengdu County has a total of 94,000 mu of orchards, but the average yield per mu is relatively low. Most of the orchards have a production of less than 1,000 kilos per mu. For this reason, in the two years of 1990 and 1991, we renovated the selected 5000 mu low yield orchards, of which 3500 mu are low-yield citrus orchards accounting for 70%. Now on the cause of the county’s low-yield citrus garden and make an introduction. First, the reasons for the formation of low-yielding citrus fruit garden in Fengdu County 1, the construction of poor quality. In recent years, the abundance of orchard area in Fengdu County has witnessed rapid growth with an annual increase of several thousand mu. As one-sided pursuit of speed, neglect of quality, orchards site selection is unreasonable, poor soil, thin layer and knot, and some soil is only about 10 cm. No bursting during construction of the park, digging deep trenches, Shi enough base fertilizer, soil organic matter content is low. Not timely deep plowing after planting, expansion of hole, buried base fertilizer. Due to seedling nursery out of nursery irregularities, species impure. Poor quality nursery stock, planting unscientific, but also caused by strict