[Objective] Thinning is one of effective management practices in mature canopy overcrowd apple orchards with standard rootstocks. The aim of the study is to study a better thinning system. [Method] A 18-year-old 'Fuji' apple orchard (3×4 m) with standard rootstocks thinned in 2004 was used in 2008 when it became canopy overcrowd again to evaluate the light penetration into trees canopies, leaf characteristics and quantity and quality of fruits with different treatments. [Result] Conditions of apple trees were improved significantly with thinning (Method Ⅰ). The relative light intensity outer and inner of tree canopies of apple trees with thinning (Method Ⅰ) was bigger than non-thinned apple trees (Method Ⅱ and Ⅲ). The relative light intensity inner trees with thinning (Method Ⅰ), pruning large branches(Method Ⅱ) and not pruning large branches (Method Ⅲ) were 26.4%, 20.8% and 14.3%, respectively. Compared to trees with thinning, the average quantity of shoots was 4.56% and 15.91% more than those of trees with Method Ⅱ and Method Ⅲ, respectively. Moreover, the average leaf area of trees with thinning was 0.46% and 7.28% bigger than those of trees with Method Ⅱ and Method Ⅲ. The soluble solids and coloring of fruits of trees were increased in a similar trend,while fruit firmness of trees with Method Ⅱ was better than those of trees with thinning and Method Ⅲ. [Conclusion] The results showed that thinning treatment for apple trees with overcrowd canopies significantly increased light penetration into tree canopies as well as yield of apples. The quality of leaves and fruits were significantly improved, especially the leaf area index were increased up to 3.26. Based on this study, thinning is proved to be convenient and efficient means to improve the light penetration into tree canopies of apple orchards with standard rootstocks in Weibei region of China.%[目的]成龄乔砧苹果郁闭园改造是生产中的主要问题,通过对改形后再次郁闭园进行不同改造,比较几种处理方法的改造效果,找出最佳的改造方法,为其推广应用提供理论依据.[方法]以改形后再次郁闭的18年生乔化‘红富士’苹果(3 mx4 m)为材料,研究不同处理对冠层光照、各类枝(梢)叶片数量、质量及产量品质的影响.[结果]间伐(处理Ⅰ)冠层光照条件好,各类枝(梢)平均叶片数量多、质量高、果实硬度大,可溶性固形物含量高,着色最好,叶面积指数合理,产量较高.疏大枝(处理Ⅱ)树冠光照和叶片状况及果实品质均比间伐处理差,但优于不疏大枝树(处理Ⅲ).冠层内相对光照强度处理Ⅰ、Ⅱ、Ⅲ分别为26.4％、20.8％和14.3％,冠层内不同方位相对光照强度和日变化为处理Ⅰ＞处理Ⅱ＞处理Ⅲ.处理Ⅰ各类型新梢的平均叶片数量分别比处理Ⅱ和处理Ⅲ高4.56％、15.91％,单叶面积分别比处理Ⅱ和Ⅲ高0.46％和7.28％.而产量是处理Ⅱ＞处理Ⅰ＞处理Ⅲ.果实品质是处理Ⅰ＞处理Ⅱ＞处理Ⅲ.[结论]对密度3 m×4 m改形后再次郁闭果园实行间伐,可改善树冠光照条件,使叶面积指数达3.26,提高叶片质量和果实品质,产量也较高,且这种方法改造的果园管理方便,能根本性解决乔化苹果园光照恶化问题,适宜渭北苹果产区推广应用.
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