Changes Of Nutrient Element Contents And Accumulation In Fruit Of Navel Orange During Fruit Growth And Development

Fertilization is important for citrus production. Fertilizer type, application rate and date have strong effects on citrus yield and quality. Fruit is the important organ that accumulates and consumes nutrition elements, especially for adult citrus tree. Therefore, to study the changes of nutrient element contents and accumulation in citrus fruit during its growth and development is useful both for determining the appropriate rate and suitable date of fertilizer application in citrus production.In this experiment, changes of nutrient element contents and accumulation of N, P, K, Ca, Mg, S, Fe, Mn, Zn, Cu and B in fruits of the28-year-old Seike navel orange (Citrus sinensis Osbeck cv Seike) and Newhall navel orange(Citrus sinensis Osbeck cv Newhall) on trifoliate orange(Poncirus trifoliata (L.)Raf.) Root stocks, which were grown in orchard of the Citrus Research Institute of Southwest University, were studied. The main results are as follows.(1) During the Seike navel orange fruit development, N, P, Mg, S, Mn and Zn contents in fruit were at the highest levels in April. Fruit K and Fe contents reached its highest contents in July, and Ca content reached the highest level in October, but B and Cu contents changed very little. Fruit N, P, K, Mg, S, Zn and B contents were at or close to the minimum levels at fruit maturation stage in November, but Ca and Fe contents showed their minimum levels at young fruit stage in April to June. N, P, K and Cu contents in fruit pulp were significantly higher than in fruit peel, but Ca, Mn and B were significantly lower in fruit peel. Mg and S contents in fruit pulp and peel were almost the same. The contents of Zn and Fe in pulp were significantly higher than in peel before September, and after then they were opposite. The accumulation of nutrient elements in fruit was undergoing a period of rapid increase from May on. The main accumulation period of fruit N, P, K and Mg was in June and July, which accounted for45.6%,44.6%,53.7%and57.2%of their total accumulation amount per fruit, respectively. N and K, each was about560mg per fruit, were the highest accumulated nutrient elements in Seike navel orange fruit, and next was Ca (274.9mg per fruit), then P, Mg and S in turn(57.3-42.3mg per fruit).Each microelement accumulated in per fruit was0.17-3.3mg.(2) During the Newhall navel orange fruit development, N, P, Mg, Mn, Zn and B contents in fruit were at the highest levels in April. Fruit K and S contents reached the highest level in September, and Ca content reached the maximum value in October, and the peak value of Fe content showed in August. However, fruit B content changed very little during the fruit development period. The main accumulation period of macroelements in fruit was from June to September, and which of microelement in fruit was from May to September. As the Seike navel orange, Newhall navel orange also accumulated most N and K in fruit, and then Ca, P, Mg and S in turn. For microelements accumulated in fruit, the maximum amount was Fe and B, then Mn, Zn and Cu in turn. However, as compared with Seike navel orange fruit, all nutrient elements accumulated in Newhall navel orange per fruit were lower, which was mainly due to its small fruit size and weight.In general, the main accumulation period of nutrient elements in fruit was also the peak period for citrus tree requiring fertilizer. In order to meet the demand of nutrition for fruit growth and development, fertilizer should be applied before the main accumulation period of nutrient elements in fruit. According to this results, Seike navel orange fruit began rapid accumulation of nutrient elements in May, the fertilizer application date for fruit rapid growth should be May. However, for Newhall navel orange, due to its rapid accumulation of nutrient elements began in June, the fertilizer application date for fruit rapid growth should be June.