Effect Of Film Mulching On The Contents Of Mineral Elements In Citrus And Its Relationship With The Sugar And Acid Quality

Effect of film mulching (FM) on the contents of fruit total soluble solution (TSS), titratable acid (TA), and6mineral elements (K, P, Mg, Ca, Fe and Mn) in fruit juice sacs and/or leaf was investigated in this study by using6-year old of Ponkan(Citrus reticulata) and/or20-year old Sasuma mandarin (C. unshiu cv. Guoqing no.l) as materials. The main results were showed in the following.Under FM treatment, TSS and sugar were significantly increased while TA were decreased in the fruit juice sacs.Under FM treatment in the leaf of Ponkan, contents of K and Mn were decreased significantly; contents of P, Ca and Mg were obviously increased while Fe content did not change significantly. As for in the juice sacs, FM decreased K and Ca contents significantly, increased significantly Fe and Mn contents at20days after FM; at40days after FM, contents of P, Mg, Ca, Fe and Mn were obviously higher than those in the control except for K which was still obviously lower than that in the control.In Sasuma mandarin, P and Mg contents of the juice sac were lower than they in the control, but not change significantly at20and40days after FM; Contents of Fe and Mn at20d after FM did not change significantly as compared with the control; Ca element in both periods was significantly higher than that in the control, and K content was lower than that in the control.Comparision between Ponkan and Satsuma mandarin showed that changes of mineral elements between the two cultivars were not exactly the same. For example, Ca at20days after FM and the changes of Fe and Mn at4days after FM changed reversely against the control between the two cultivars. However, in spite of the differences of varieties, climate, soil and environmental conditions, there were still some changes of mineral elements changed similarly. For instance, K contents in the both FM leaves and fruitjuice sacs were significantly lower than those in the control while P and Mg showed no significant differences in both cultivars. Taken together, the results suggested that the influence of mineral accumulation in juice sacs by FM might contribute to the improvement of fruit quality, i.e., the increase of TSS and the decrease of TA. K injection experiment showed that the injection of K increased the K content in the fruit juice as well as TSS while decreased TA, implying that increase of K have the direct function to increase the sugar accumulation. However, in the FM experiment, K content was decreased and sugar accumulation was increased, suggesting that the increase of sugar accumulation under FM might be related with the canges of other mineral elements aside from the osmotic regulation theory. The connection between other mineral elements with the sugar accumulation under FM needs to further investigate in the future.