Effect Of Mineral Nutrient On The Vegetative Growth And Fruit Quality In Danshansu Pear

Dangshansu pear is a main cultivar and its cultivated area accounts for about 1/4 of the total pear area in China.In recent years the fruit quality of Dangshansu pear has degraded remarkably because of lower production inputs and careless management.There are many works reported about cutivation techniques for improvement of fruit quality and yield in Dangshansu pear,but there are a few researches on the Dangshansu pear balanced fertilization,and few effective techniques applied in the practical production.Now in Dangshan region the pear fertilization almost depend on the experience of grower entirely resulting in the imbalance of soil and tree nutrient.Based on the diagnosis of orchard soil and leaf nutrient the fertilization by foliage spray was applied to the tree with nutrient deficiency.The different concentration of potassium,boron and magnesium were used to study the effect of mineral nutrient on the vegetative growth and fruit quality in Danshansu pear.The main results gained are as follows.1.The dynamic changes of the three mineral elements content in Dangshansu pear leaf had been tested.The potassium content in young leaf was at the highest level,then decreased significantly,and went to the minimum in the period of fruit maturity.The boron content increased with shoot growth,reached the highest level at stage of shoot cease growth,and started to decline at last,showing a trend of low-high-low curve.The trend of dynamic change of magnesium content was almost the same as that of the boron's.2.After foliage spraying with different levels of potassium(0.2%,0.4%,and 0.6% KCl) the content of potassium in leaf increased in the treatment concentration of 0.2%to 0.4%.Proper potassium fertilizer would restrained the shoot growth,increased the single-leaf area,the weight per 100 leaves and the content of chlorophyll,and enhanced the content of soluble sugar,vitamine C and the pulp firmness of Dangshansu pear significantly.In consideration of tree vigour,fruit quality and production costs the fertilization by foliage spraying with 0.4%of KCl two or three times in the fruit swelling period(June to August) would gained the best result as the tree was in potassium deficiency.3.Boron fertilization by foliage spraying at 0.2%or 0.3%of Na₂B₄O₇ in Dangshansu pear could increased the boron content in leaf.Appropriate boron application would promote the shoot growth,enlarge the single-leaf area,the weight per 100 leaves and the content of chlorophyll,and increase the soluble sugar,the soluble solids content and pulp hardness,but the fruit acidity was decreased significantly.As the tree was deficient in boron,the foliage fertilization by spraying 0.3%boron two or three times in shoot growth period(April to July) was the best treatment refering to the tree vigour,fruit quality and production costs.4.Foliage spraying with 1%to 2%of MgSO₄ also could increase the content of boron in leaf.The single-leaf area,the weight per 100 leaves,the content of chlorophyll all increased in compare with the control.Magnesium application had significant influence on fruit quality.Considering tree vigour,fruit quality and production costs the fertilization by spraying 2%magnesium two or three times in the shoot growth period(April to July) could increase the content of soluble sugar and vitamin C and decrease the fruit acidity remarkablely as the tree was deficient in magnesium.