Key points of fertilizer topdressing in three periods of skillful fertilization and high yield longan in Longan Bridge

Longan, flower bud differentiation, flowering and fruiting in the same year, its fertilizing period is related to the phenotypic period. In February, the spring bud of longan germinated, the inflorescence primordium formed, after inflorescence differentiation, flower organ formation, followed by flowering, fruit growth and development, longan fertilizer period combined with phenology, the whole year was divided into three stages: pre-flowering fertilizer, young fruit fertilizer and fruit-picking fertilizer.

Longan fertilization

1. Pre-anthesis fertilizer: pre-anthesis fertilization can promote flower bud differentiation, flower ear development, improve quality, reduce falling flowers, supplement the nutrition deficit of longan trees in the later stage of flowering, increase fruit, promote early summer shoot, strong fruit and promote shoot. Fertilization in this period is the most important. The amount of fertilizer application accounts for more than 50% of the whole year, mainly nitrogen fertilizer, phosphorus and potassium fertilizer, nitrogen, phosphorus and potassium fertilizer, the ratio of nitrogen, phosphorus and potassium is 1 ∶ 0.16 ∶ 0.54, organic fertilizer and chemical fertilizer are half. Compound fertilizer 1-2kg, urea 0.5kg, potassium chloride 0.25kg were applied per 50kg longan production. However, in this period, when the temperature is more than 18 ℃, it is necessary to prevent excessive application of nitrogen fertilizer, which will cause "shoot impact" and affect the yield. The experiment shows that the effect of applying heavy fertilizer before flowering is the best. Fertilization time is about mid-March to early April, early rather than late, longan spike inflorescence has been formed and applied when budding. If there is low temperature in the winter and early spring of the previous year, and it is difficult to spike, one ear-promoting fertilizer should be applied from late January to early February, and the amount of fertilizer should account for 1 / 3 of the pre-anthesis fertilizer, and 2 / 3 would be applied in the first ten days of April.

2. Young fruit fertilizer: young fruit fertilizer can supplement the nutrition consumed by longan tree flowering, promote longan expansion, prevent fruit drop, promote summer shoot growth, increase unit yield and reduce year size. The amount of fertilizer applied in this period accounts for about 20% of the whole year, mainly phosphorus and potash fertilizer, and nitrogen fertilizer. The fertilization time can be in the first and middle June after the first physiological fruit drop of Xiehua, when the size of young fruit and soybeans, according to the potential and fruit amount, the proper fertilization should be applied once in the middle of July when the aril is growing rapidly. According to the amount of fertilizer applied each time, the compound fertilizer 1.5-2kg, potassium chloride 1.5-2kg, urea 0.5kg, the ratio of nitrogen, phosphorus and potassium is 1 ∶ 0.16 ∶ 1.24 per 50kg longan.

3. Fruit-picking fertilizer: fruit-picking fertilizer, also known as fruit-bearing mother branch fertilizer, is divided into pre-harvest and post-harvest. The purpose of fertilization is to promote the late growth of longan and the recovery of postharvest tree potential, so that the last autumn shoots can be released on time around the middle of September and mature in the middle and late November. Fertilization in this period is very important, because autumn shoots are the mother skill of the following year, and autumn shoots are related to the yield of longan in the coming year. According to the growth characteristics of longan, it is mainly pre-harvest fertilizer, which is applied 10-15 days before fruit harvest, accounting for 30% of the whole year, mainly nitrogen fertilizer, combined with phosphorus and potassium fertilizer. Urea 1kg, potassium chloride 0.5kg and magnesium sulfate 0.25kg were applied according to each production of 50kg longan. For those trees with large amount of fruit, weak trees and old trees, it was difficult to shoot after harvest, available nitrogen should be applied again after harvest to promote autumn shoots. In autumn drought, fertilization in this period should pay attention to orchard irrigation in order to get good results.

In addition, extra-root topdressing is a fast and efficient measure to supplement fertilizer in longan cultivation and management, and it is essential for longan to have high and stable yield. Foliar fertilization does not need to be used alone, but can be combined with flower and fruit protection to control diseases and insect pests. 4-5 times a year, depending on the growth of longan trees. The type and concentration of fertilizer selected are 0.3% mi 0.5% urea and 0.1% mo 0.2% borax respectively, which are used before the leaves of new shoots are unfolded to turn green. The last foliar fertilization should be carried out 20 days before longan harvest.