Promote blossom and protect fruit and improve quality of Ponkan

First, promote flowers and protect fruits

Under the condition of better nutrition accumulation and proper water control, the flower bud differentiation is good. Therefore, the mandarin blossoms more, but there are also a lot of fallen flowers and fruits. Adult trees usually bear fruit with 10, 000 to 50, 000 flowers, but the fruit-setting rate is only 2%-8%, and the fruit-setting rate of low-yield citrus orchards is less than 1%. The fruit drop of Ponkan is mainly in the first physiological fruit drop period, with pedicel falling off, which is mainly caused by hypoplasia of floral organs, abnormal flowers and poor pollination and fertilization, and less fruit drop in the second physiological fruit drop period. the reasons for fruit drop are lack of nutrition, contradiction of fruit tips, imbalance of endogenous hormones and so on. In addition, the fruit drop of Ponkan was caused by weak tree, slender fruiting mother branch and fruiting branch, low temperature and low temperature in flowering period, less sunshine, weak photosynthesis, abnormal high temperature and drought in young fruit stage, wind damage, insect pests and so on.

The following measures should be taken to promote flowers and protect fruits:

1. Fertilization and water control promote flower bud differentiation.

Before flower bud formation, in the early and middle of November, rotten organic fertilizer was applied, and flower bud differentiation began to properly control water in order to increase the concentration of somatic sap, which was beneficial to flower bud differentiation. Fertilizers are applied with retting-ripened bran (cake) or pig and cattle manure soil, or 0.3% potassium dihydrogen phosphate or 1% compound fertilizer is sprayed on the leaves for 2 times.

2. Increase the number of leaves to keep them through the winter.

Ponkan usually has more leaves and fruits, so it can cultivate strong tree potential, increase leaves, prevent falling leaves, help flower bud differentiation and increase yield. Drought in summer and autumn will lead to abnormal defoliation, which should be irrigated or covered in time. In winter, the producing areas with frost injury should guard against cold and protect leaves, and organic fertilizer should be applied before and after fruit harvest to restore tree potential and control diseases and insect pests.

3. Regulate the quantity of flowers and improve the quality of flowers.

For the trees with too many flowers, nitrogen fertilizer should be applied before flower bud differentiation to reduce the number of flowers and improve the quality of flowers. In addition, reasonable pruning, thinning too weak and some too many flower branches can also reduce the number of flowers.

4. Skillfully applying topdressing to promote flowers and protect fruits

Spring shoot growth and flowering consume a lot of nutrients, while the new leaves that do not turn green produce only enough carbohydrates for their own growth. by the time of flowering, the leaves contain very little nitrogen and phosphorus. Therefore, about 15 days before budding, flower-promoting fertilizer based on nitrogen fertilizer can be applied, and phosphorus and potassium fertilizer can be applied properly after flowering, so as to reduce fruit drop and normal fruit development. However, fertilization can not be more, in order not to cause summer shoots. Fertilization for trees is often adopted, that is, trees with less fruit are applied less or not, while trees with more fruit are applied properly.

Spraying 0.3% 0.5% urea during the spring shoot turning green period can promote the spring shoot to turn green; re-apply organic fertilizer in the early and middle of July to promote autumn shoot with strong fruit; from flowering to young fruit shedding period, foliar fertilization can not be applied in the rhizosphere due to continuous overcast and rain.

5. Control the summer shoot and adjust the contradiction between the top and fruit.

The emergence of summer shoots will lead to a large number of fruit drop, so fertilizer control is used to restrain early summer shoots in cultivation at this time. In addition to fertilizing the trees after Xiehua, the germinated summer shoots should be wiped out in time.

6. Use growth regulator and micro-fertilizer to regulate and control

According to the experiment of Xu Jiankai et al of South China Agricultural University in 1987, when the autumn shoot of Ponkan turned green and mature in the middle of October, all the autumn shoots in the middle and upper part of the crown were sprayed with 500 mg / kg P333 (paclobutrazol) until dripping, and the flower quantity of these autumn shoots in the following year was 211% of that of the control. It should be noted that P333 can inhibit the growth of citrus and can not be used in weak trees. Spray 50 mg / kg GA3 plus 0.3% 0.5% urea or 0.2% potassium dihydrogen phosphate or 0.15% borax when Xiehua 3 / 4, and spray once every 15 days (0.15% borax can be changed to 0.15% 0.25% magnesium sulfate) to improve the fruit setting rate of mandarin obviously.

Second, improve the quality

In order to improve the fruit quality of Ponkan, in addition to selecting excellent new varieties and selecting the most suitable ecological area, measures can be taken in terms of fertilizer, water and fruit thinning.

First, increase the application of organic fertilizer and attach importance to the coordination of nitrogen, phosphorus and potassium. The production shows that proper application of phosphate fertilizer can reduce the acid content of the fruit; spraying 0.2% potassium dihydrogen phosphate or 2% calcium superphosphate leaching solution in autumn can significantly increase the sugar content of the fruit and make the color good. Second, irrigation in autumn and winter, that is, proper irrigation before fruit coloring, can promote fruit expansion and improve fruit quality. The third is fruit thinning. After the second physiological fruit drop, the ratio of leaf to fruit (40: 50): 1 can increase the fruit and improve the quality. Fruit thinning is also beneficial to promote autumn shoots and reduce small year fruit.