Effects Of Magnesium Fertilizer On The Yield And Quality Of Citrus

Magnesium deficiency of different degrees exists in the main citrus-producing areas in China,and the area of magnesium deficiency in soil and leaves accounts for 65.1 %and 61.49 %.Magnesium is essential for citrus growth and development,magnesium deficiency will affect the growth and function structure of citrus.To study the appropriate amount of magnesium fertilizer and the effect of magnesium fertilizer on yield and quality of citrus,Ponkan,Newhall navel orange,Satsuma mandarin were selected as the test materials for field experiment with different magnesium application rates in Taoyuan county,Changed,Hunan province,Yizhang county,Chenzhou,Hunan province and Yichang,Hubei province.The results are as follows:The increasing application increased the SPAD value of leaves at each stage,making the SPAD of leaves reach the peak quickly at 81.0(Satsuma mandarin)and 82.8(Newhall navel orange)until November.Thus the leaves can can carry out higher intensity photosynthesis in a long time and produce more photosynthetic products,which provides the condition for the increasing of yield and quality of citrus.Meanwhile,the magnesium content of citrus leaves with the treatment of increased magnesium fertilizer higher than the treatment of without magnesium fertilizer.And also can decrease the extent of magnesium loss in spring leaves after July.Increasd application of magnesium fertilizer increased the yield of Citrus.In terms of high yield,the 2-year average yield of Newhall navel orange was 77.56 kg/plant without magnesium fertilizer treatment and 93.50 kg/plant with magnesium fertilizer treatment,with an average yield increase of 20.55 %.The 2-year average yield of Satsuma mandarin without magnesium treatment was 51.76 kg/plant,and the 2-year average yield with magnesium fertilizer treatment was 69.51 kg/plant,with an average yield increase of34.29 %.In terms of stable yield,the 2 years yield of Newhall navel orange without magnesium treatment was 94.41 kg/plant and 60.70 kg/plant with a range of 35.70 %.The yield of magnesium treatment ranged from 85.99 to 104.78 kg/plant,with a range of1.70 % to 14.48 %,the lowest of which was 1.70 % of that after T2 treatment(100 g/plant Mg O).The yield of Satsuma mandarin in 2 years without magnesium treatment was31.25 kg/plant and 72.27 kg/plant,and with a variation range of 56.76 %.The yield of magnesium fertilizer treatment ranged from 45.89 to 96.9 kg/plant,with a variation range of 17.06 % to 45.34 %.the lowest variation was 17.06 % of T2 treatment(100 g/ plant Mg O).Increased application of magnesium fertilizer also can improve the fruit quality.The appropriate amount of magnesium fertilizer can increase the diameter of the fruit and improve the shape of citrus fruit.In the aspect of coloring,the suitable magnesium can improve the color quality of the peel and make it more smooth,more red,more yellow and stronger color.In terms of pulp texture,the edible rate,juice yield and cohesion of citrus pulp were improved,and the pressure,hardness,maximum shear force and shear work were reduced,making the pulp juicy,compact and delicate,soft and easy to chew.In the nutrition and flavor of citrus juice,proper application of magnesium fertilizer can increase vitamin C,titratable acid,soluble solid content and solid acid ratio of citrus juice,increase the sweetness of citrus juice,intensify the sweet or sour flavor,increase the ability of making citrus juice concentrate,and enrich the nutrition.In the mineral nutrients in citrus fruits,increasing magnesium fertilizer can increase Mg content and decrease K,Ca,Fe and Mn content,but the change of these mineral nutrients mainly in the peel of citrus fruit,and will not affect the edible value.Combine the magnesium effect on the yield and quality of citrus,the suitable magnesium application for magnesium-deficient citrus orchards represented by Newhall navel orange is 130 ~ 200 g/plant Mg O,and the magnesium application for suitable magnesium citrus orchards represented by Satsuma mandarin is 100 ~ 150 g/plant MgO.