柑桔营养若干问题的研究

作者对柑桔营养若干问题进行了探讨,初步表明:1.不同产量级芦柑园土壤化学性质的差异,主要表现在土壤表层的速效磷、钾含量上。2.九月,芦柑叶片氮、磷、钾含量与当年果实产量呈较显著至显著负相关,而叶片钙、镁含量与当年产量呈较显著正相关;桶柑叶片氮、镁含量与产量的相关性和芦柑有所不同;两品种叶片含钾量与产量的相关性较为一致,表明了施钾的重要性。3.上述品种叶片钾与镁、钙、氮的相互关系甚为一致,特别是钾与镁、钾与钙间呈较明显的拮抗。4.不同砧穗组合对叶片元素组成有显著影响,尤其不同属砧木对同一接穗的影响更大。5.柑桔缺镁,可通过喷布镁盐予以矫治,试验证明,喷布1%硝酸镁效果最佳。

STUDIES ON PROBLEMS RELATED TO THE NUTRITION OF CITRUS

1.Our preliminary studies from soil analysis of over eight orchard sites representing orchards of different yield grades showed that the most signifi- cant soil chemical characteristic relative to citrus nutrition seems to be the amount of readily available phosphorus and potassium present in the soil especially in the top-soil. 2.Our work with Lukan and Tongkan citrus varieties(Citrus reticulata Blanco)show a significant negative correlation between the content of nitro- gen,phosphorus and potassium in leaf(during September),with fruit yield (r=-0.4884~+,-0.5907~* and -0.5920~*,respectively).There is a significant positive correlation,however,between the foliar content of calcium,mag- nesium and fruit yield(r being 0.5558~+ and 0.5562~+,respectively). Furthermore,we found varietal difference,for instance with the Tong- kan var.the correlation between the mineral content of the leaf and fruit yield is different from that of Lukan.The chief difference lies in the foliar content of nitrogen and magnesium.Incidentally,both varieties studies showed pronouncedly a close relationship between the foliar content of potassium and annual fruit yield.We are thus led to believe in the importance of pota ssium as a fertilizer in citrus fruit production. 3.In the present work,the interaction of K and Mg,Ca,N are similar among the two citrus varieties Lukan and Tongkan studied.However,it should be pointed out that there exists between K and Mg,K and Ca,an antagonistic action.This phenomenon is particularly evident between K and Mg(with a significant negative correlation value,r=-0.9143~(**) and -0.5778~+). On the other hand,a positive correlation seems to exist between K and N ions.This situation warrants further investigation. 4.The fact that citrus trees representing different stockscion combinations have a definite effect on their mineral nutrition,is also supported by the results of our studies.This effect is particularly evident when the stocks belong to different botanical genera.It is therefore necessary,for a proper fertilization program to include the determination of stock-scion combina- tions and their effect on mineral nutrition in the orchards. 5.Magnesium deficiency in our citrus orchard soils has been found to be serious especially in certain districts where improper soil managements are practiced.Our preliminary study showed that after the month of May by foliar-spraying of 1% magnesium nitrate once every month successively for three months will correct the malady effectively.The results of spraying with 1% magnesium chloride ranks second in effectiveness,while spraying with 1% magnesium sulfate is least effective.Further investigation involving soil treatment and spraying at different concentrations with magnesium sulfate should he made.