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一、起因苹果是我区引黄灌区主要果树之一,近年来有较大的发展。我区地处北纬37°34′～39°15′,日照较长,全年总日照时数为2678～3012小时,温差大,20年平均最大温差达26度,因此,同一苹果品种在我区表现色泽好,糖份大,品质较好。但是,我区从1951年开始引进苹果以来,相继发生了幼树(1～10年生)的抽干和冻害死亡现象,这是多年来我区苹果生产发展较慢的主要原因之一。据调查,宁夏灌区1957年、1964年、1968年及1971年的抽干、冻害和腐烂病严重蔓延以及1977年的花芽严重冻害等特殊年份而造成大量的苹果因抽干、冻害死亡和冻花减产,其损失是极其严重的(见表1、2)。从表1中可看出,树龄4～10年生的,调查总株数21024株,全抽、半抽干的达11322株,占58.6％。从表2中见,不仅幼龄
First, the cause Apple is one of the main fruit trees in the Yellow River Diversion Region in our region, in recent years have a greater development. My area is located at latitude 37 ° 34 ’~ 39 ° 15’ and has a long sunshine duration. The annual total sunshine duration is 2678-3012 hours. The temperature difference is large, and the average maximum temperature difference in 20 years reaches 26 degrees. Therefore, District performance color, sugar, good quality. However, since the introduction of apples in 1951 in our district, stemming and freeze-death of young trees (aged from 1 to 10 years) have occurred one after another, which is one of the major reasons for the slow development of apple production in our region for many years. According to the survey, a large number of apples died from freeze-drying, freeze-thaw death and frozen flower in Ningxia irrigated area in 1957, 1964, 1968 and 1971 due to the serious spread of frostbite and rot disease and the special year of 1977, Production loss, the loss is extremely serious (see Table 1, 2). As can be seen from Table 1, the total number of trees with 4 to 10 years of age is 21,024, with a total of 11,322 strains, accounting for 58.6%. See from Table 2, not only young