Studies On Delayed Harvest Cultivation Technique Of Wase Satsuma Mandarin (Citrus Unshiu Marc.)

Citrus is one of the most important agriculture produce in the world, and China is the largest country of the mandarin (Citrus reticulata Blanco.), which occupied more than 40 percent of total yield in the world. Zhejiang province is one of main production area, which mainly cultivated with mandarin. But the unsuitable variety structure, the uneven quality of citrus fruit reduced the poor economic benefit considerably. Citrus delayed harvest is a high quality cultivation technique. So it was very urgent to study this technique for improving the quality of wase satsuma mandarin.The experiments were carried out by using wase satsuma mandarin as main material from 2001 to 2003. The development of fruit, seasonal changes of starch, soluble solid content and others were more systemically studied, and the supporting measures of cultivation with delayed harvest of wase satsuma mandarin were also suggested. The main results were as follows.(1) The growth curve of wase satsuma mandarin was a "S"-style, the growth rate of its fruit diameter was higher than Manju and Bendizao mandarin, which are both of the mid-ripe variety of mandarin.(2) The seasonal changes of Dry/Fresh ratio was about 30 percent at the time after blooming 45 days, the ratio was decrease along with fruit developing, and the ratio of wase satsuma mandarin was decrease very quickly.(3) The changes of starch content was a relative high level from blooming end up to the late July, and its content has a drop quickly. The near minimum occurred at mid-August for wase satsuma mandarin, and at Mid-October for Manju mandarin.(4) The sucrose content of wase satsuma mandarin kept very lower level before the late-August, and had a rapid increase at the mid or late stage of fruit development.(5) The changes of reducing sugar of wase satsuma mandarin wasincreased by fruit developing under water stress condition. But the reducing sugar in juice sac had some decrease even at the stage of common harvest and delayed harvest under the irrigation or open field culture.(6) During the fruit maturity of wase satsuma mandarin, TSS was increased gradually and slowly after mid-November. TA was on the contrary with TSS. Fruit specific gravity was decrease by degrees, and the changes of rind thickness became thinner at first turn to thicker at late. Puffing ratio was raised with ripping, and steep rise after first-November. The flavor, the degree of waste from strained fruit, rind peeling characters were obviously better than before at the stage of delayed harvest. This was the best period for eating. The best stage of delayed harvest was First or Mid-November in south-east Zhejiang citrus planting area.(7) The supporting measures of cultivation with delayed harvest of wase satsuma mandarin, including variety and orchard selection, management of soil, fertilizer and water, pruning and etc. were also suggested.