摘要:
缺镁是闽南山地柑桔普遍发生的缺素症之一。缺镁使叶片寿命短,叶绿素减少,光合作用率下降,根系发育差,植株早衰,导致大小年或隔年结果。出现缺镁症的柑桔园土壤交换性镁含量大都在50ppm以下,交换性钾多在150～200ppm以上,钾、镁(毫克当量/100克土)比值大于0.5。土壤属强或极强酸性。叶片钾、镁含量与土壤交换性钾、镁呈正相关。缺镁植株叶片含镁量低于0.25%,最低的仅0.03%,老叶比新叶含量低且出现症状,钾大都超过1.2～1.6%的适量范围。闽南山地缺镁是由于土壤中可供吸收利用的交换性镁含量低与土壤交换性钾、镁的比例失调所引起。植株出现的症状以A、B型为多。喷布1%硝酸镁可迅速提高叶片含镁量,使叶片钾含量降低到适量范围,叶片钙的含量相应提高,还有增加叶绿素的效应,与对照区比较差异都达显著和极显著。在矫治缺镁症时应以施用石灰或含镁的白云石灰,把土壤pH值调整至6～6.5为基本措施,并应根据土壤有效钾的含量酌施钾肥。
Abstract:
Magnesium deficiency is one of the common phenomena occuring in the mountainous citrus orchards in South Fujian.It causes the short-life of foliage and lower chlorophyll content; it also retards the process of photosynthesis, arrests the growth of the roots and makes the plant to deteriorate and thus leads to alternate bearing of fruits.The amount of exchangeable magnesium in the soil of magnesium deficient orchard is usually below 50 ppm, and that of exchangeable potassium is usually above 150-200 ppm.The exchangeable potassium-magenesium ratio value is higher than 0.5.The soil shows highly or very highly acid.The potassium-magnesium content in the foliage correlated with the exchangeable potassium-magnesium content in the soil positivelly.The magnesium content of the magnesium deficient plant’s foliage is below 0.25% with the lowest is 0.03% only.The magnesium content in the old leaves is lower than that in the young leaves and visual symptom, could be observed.As far as potassium is concerned, it usually exceeds the intermediate range of 1.2-1.6%.The conditions that cause the magnesium deficiency in the mountainous land of South Fujian are two fold, l.the content of assimulab-Je exchangeable magnesium in the soil is low; 2.the ratio value between the exchangeable poatssium and the exchangeable magnesium is out appropriate proportion.The visual symptoms appear in the plant are mostly of A and B types.A spray of 1% magnesium nitrate may quickly increase the magnesium content of the plant foilage and cause its potassium content to drop to a reasonable range,while the calcium content of the foilage would correspondently be heightened and effect an increase of its chlorophyll. This, in comparison with the control plot shows a significant or highly significant differences.A basic measure for the remedy of magnesium deficiency is to apple magnesium fertilizer and use lime or dolomitic lime to adjust the pH value to 6-6.5, and also to apply potassium fertilizer,according to the existing potassium content of the soil.
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