重庆三峡库区柑橘镁营养水平及其影响因子研究

Citrus magnesium nutrient level and its impact factors in the Three Gorges Area of Chongqing

【目的】为了解重庆三峡库区柑橘叶片镁含量状况，以及果园土壤交换性镁、土壤酸碱度、砧木、品种、树龄和成熟期对叶片镁含量的影响，【方法】于2010--2012年在该区域10个主产区县的代表性果园采集土壤样品260份和柑橘叶片样品584份进行了测定分析。【结果】除涪陵区外，其余9个主产区县的土壤交换性镁含量均处于适量水平及以上，但柑橘叶片镁含量普遍偏低，51．71％的叶片样品为低镁水平，适宜比例仅36．99％；相关性分析显示，各区县的果园土壤交换性镁含量与柑橘叶片镁含量均未达显著水平（P〉0．05）。不同pH土壤上的柑橘叶片镁含量存在差异，碱性土上的柑橘叶片镁含量最高（0．30％），酸性土上的柑橘叶片镁含量最低（0．23％），且有80．00％叶片样品镁含量低于适宜范围。砧木方面，酸柚砧柑橘叶片镁元素含量最低（0．21％），枳橙砧柑橘叶片镁含量最高（O_31％）。品种方面，杂柑的叶片镁含量最高（0．31％）；柚类缺镁最为严重，缺镁比例高达50．00％。树龄方面，8a生以上树的叶片镁含量较3～8a生树低，且镁含量低于适宜范围的比例升高20．17％。成熟期方面，早熟品种叶片镁缺乏最为严重，高达50．00％的叶片缺镁，夏橙次之。【结论】重庆三峡库区柑橘树体普遍镁不足，果园土壤测定难以反映树体镁状况，树体镁状况受到土壤酸碱度、砧木、品种、树龄和成熟期等因子影响，该区域应重视镁肥施用。

[Objective]This study aimed to understand the content of citrus leaf magnesium level and its impact factors, including soil exchangeable magnesium content, soil pH value, rootstock, citrus cultivar, tree age and mature period in the Three Gorges area of Chongqing. [Method]260 soil samples and 584 leaf samples collected from 10 main citrus producing counties during 2010--2012 were analyzed. [Result]The results showed that the average soil exchangeable magnesium contents of the 10 counties except Fuling county were in optimum range, but citrus leaf magnesium-deficiency was also dominant and severe in cit- rus orchards, 51.71% leaf samples showed magnesium deficiency, and only 36.99% leaf samples were in optimum range . Correlation analysis showed that there was no significant correlation between soil avail- able magnesium contents and leaf magnesium contents（P〉0.05）. Further study showed that soil pH value significantly affected leaf magnesium content. Leaf magnesium contents were the highest in citrus trees grown in soils with pH values between 7.5 and 8.5, while leaf magnesium contents were the lowest in citrus trees grown in soils with pH values between 4.5 and 5.5, and 80% leaf samples showed magnesium deficiency. Furthermore, among different rootstocks, citrus on sour pommelo rootstock had the lowest leaf magnesium content （0.21%）, and citrus on citrange rootstock had the highest leaf magnesium con-tents（0.31%）. For different citrus cultivars, tangor had the highest leaf magnesium contents and pommelo showed the most severe magnesium deficiency（50.0% ）. Compared with 3 to 8 years old citrus trees, the adult citrus trees（8 years old or above）had the lower leaf magnesium contents, and 25.29% leaf samples showed magnesium deficiency. Moreover, significant differences were found among different mature peri- ods, early mature cultivars showed severe magnesium deficiency（50.0%）, followed by Valencia orange. [Conclusion]Citrus leaf magnesium-deficiency is widespread in the Three Gorges Area of Chongqing, and it is difficult to reflect the citrus tree magnesium level by soil test. Besides soil exchangeable magnesium content, soil pH value, rootstock, citrus cultivar, tree age and mature period have significantly effects on citrus leaf magnesium content.