Effect Of Tree Age On Fruit Quality,Soil-Tree Nutrient And Its Relationship

Ponkan mandarin(Citrus reticulata Blanco) as an important citrus cultivar is widely planted in central China, but in recent years its fruit quality has deteriorated with tree age.However, research about relationships between the deterioration of Ponkan mandarin fruit quality with tree age and changes in tissues nutrient concentrations and soil properties with tree age increasing. Five, 8, 13, 18 and 38 year old Ponkan mandarin(Citrus reticulata Blanco) orchards were selected in Yuxiakou town, a region with a humid subtropical monsoon climate in Yichang, Hubei province in 2013. The trees were sampled in 2013 and then again in 2014. Fruit quality(various physicochemical characteristics), nutrient(e.g N, P, K, Ca, Mg, Fe, Mn, Cu, Zn and B) concentrations in fruits, leaves and roots and soil properties(e.g available N, P, K, Ca, Mg, Fe, Mn, Cu, Zn and B concentrations, p H and organic matters concentrations) were measured to uncover relationships between Ponkan mandarin tree-age-related deterioration of fruit quality. The overall objective was to determine whether tree-age-related deterioration of fruit quality is associated with nutrient concentration changes in Ponkan mandarin trees and to determine recommended fertilization regimes for citrus trees of different tree age. The main results are as follows:1. Ponkan fruit quality changed with tree age changing, and was affected by fruit production. In 5 to 9 year old trees and trees more than 18 year old trees with high fruit production, the fruits had lower concentrations of soluble solids and ratios of soluble solid to titratable acid than other aged trees in the same survey year. In about 13 year old trees with high fruit production, fruits were large and round, and fruit internal quality was at a high level in the both survey years. In 38 and 39 year old trees, fruit vitamin C concentrations were lower than for other aged trees in the same survey year.2. The effects of tree age on tree vigor and leaf chlorophyll concentrations, soil properties and nutrient concentrations in roots, leaves and fruits in Ponkan orchards were studied.The main results are as follows: crown area and trunk perimeter increased, and leaf chlorophyll concentrations initially increased and then decreased with an increase of tree age. Soil p H, organic matter concentrations and available Ca concentrations decreased with increasing tree age. K concentrations in fine root and medium root decreased firstly and then increased, Mg concentration in fine root decreased, and Mg concentrations in medium root and coarse root with initially decreased and subsequently with year old increasing. K concentrations in leaf increased, Mg concentration in initially increased and then subsequently kept the constant. The effect of tree age on leaf nutrient concentrations differed between survey year: in 2013, leaf N concentrations decreased firstly and subsequently increased, and Ca concentrations decreased. In 2014, leaf N concentrations slowly decreased, and Ca initially decreased and subsequently increased with tree age increasing. K concentrations in fruit increased, and Mg concentrations in fruit initially increased and then subsequently kept the constant with increasing tree age. In the same survey year, short tree age(5 to 9 years) Ponkan trees had higher leaf Ca concentrations;6 and 9 year old trees had lower fruit Mg concentrations and higher leaf K concentrations;18 and 38 year old trees had lower leaf Ca concentrations and higher fruit K concentrations; 38 and 39 year old trees had lowest Cu concentrations.3. Different tree age Ponkan orchards had different nutrient distributions: in 6 and 9tree age Ponkan orchards, leaf K concentration was lower than that in fruit and fine root,fruit Mg concentration was lower than that in leaf and fine root, and fruit Zn concentration was lower than that in leaf and root; In 19 and 39 tree age Ponkan orchards,fine root K concentrations and Mg concentrations respectively were significantly lower than those in fruit.4. There were significant correlations between Ponkan fruit quality and nutrient fruit,leaf nutrient, fine root nutrient, middle root nutrient, coarse root nutrient and soil properties, but the correlations varied from different research years. In 2013, there were significantly negatively correlations between fruit soluble solids concentrations and fruit K concentrations, between ratios of soluble solid to titratable acid and fruit Kconcentrations, however positive correlations between soluble solids concentrations and leaf Ca concentrations, and between Vc concentrations and Cu concentrations in leaf and fruit. In 2014, positive correlations between soluble solids concentrations between fruit soluble solids concentrations and leaf K and fruit Mg concentrations, between ratios of soluble solid to titratable acid and leaf K and fruit Mg concentrations, and between Vc concentrations and leaf Cu concentrations.5. In short tree age(5 to 9 year) and long tree age(18 to 38 years) Ponkan trees,large and elliptic fruits could be to higher N concentration in leaf and lower Zn concentration in fruit; Fruits with lower soluble solid concentration and ratio of soluble solid and solid acid, may be related to lower fruit Mg concentration and leaf K concentration in short tree age(6 and 9 year) Ponkan trees, and may be due to lower leaf Ca concentration and higher fruit K concentration in long tree age(18 and 38 years)Ponkan trees; In 38 and 39 year old trees, fruit vitamin C concentrations, lower than other year old trees in the same survey year, were related to Cu concentrations in leaf and fruit.