Key Points of Fertilizer and Water Management Techniques for Longan Cultivation

Scientific fertilization based on the growth characteristics of longan and the requirements of its annual growth cycle is the foundation for early fruiting, high yield, and premium quality in longan trees. Experiments have proven that a longan orchard producing 1 ton of fruit per mu should apply 20-25 kg of pure nitrogen annually (of which organic fertilizer nitrogen accounts for about 40% of the annual nitrogen application). The reasonable ratio of nitrogen, phosphorus pentoxide, potassium oxide, calcium oxide, and magnesium oxide is 10:(5-6):(10-11):8:4, from which it can be seen that longan has a significantly higher demand for potassium, calcium, and magnesium fertilizers than other fruit trees. Annual cycle fertilization for longan is mainly divided into 3 periods.

1. Pre-flowering stage.

Apply during the flower bud differentiation stage and before flowering to promote flower bud differentiation, flower spike development, and reduce flower and fruit drop. Nitrogen and potassium account for 20%-25% of the annual application, and phosphorus accounts for 25%-30% of the annual total.

2. Young fruit stage.

To promote fruit growth, reduce physiological fruit drop, and promote summer shoot emergence, fertilization at this stage should appropriately increase the proportion of nitrogen, with nitrogen accounting for about 25%-30% of the annual total, phosphorus accounting for 40% of the annual total, and potassium accounting for 40%-50% of the annual total.

3. Fertilizer before and after fruit harvest.

To rapidly restore tree vigor and promote the emergence of sufficient healthy autumn shoots, fertilization at this stage should appropriately increase the proportion of nitrogen, with nitrogen accounting for 45%-55% of the annual total, phosphorus accounting for 30%-35% of the annual total, and potassium accounting for 25%-40% of the annual total.

In addition, from May to June, apply a foliar fertilizer once every 15-20 days or so in combination with pesticide spraying; the fertilizers are generally monopotassium phosphate, magnesium sulfate, potassium sulfate, etc., to supplement the tree's fertilizer requirements.

Irrigation.

Water in combination with fertilization. In July, longan fruit enters the rapid pulp growth period, but in some years a July drought often occurs; if water is not supplied in time, it will affect normal fruit enlargement. When a summer drought occurs, irrigate once every 7-10 days, applying 40-50 liters of water per square meter of tree canopy projection area (equivalent to 40-50 mm of rainfall), keeping the soil moist. This also helps prevent severe pre-harvest fruit cracking; heavy rain around “Beginning of Autumn” often causes the fruit skin to burst because the pulp suddenly absorbs a large amount of water. When there is excessive rain, drain promptly to prevent waterlogging.

Reasonable intercropping.

In longan orchards planted for 1-4 years, the idle space between rows can be used for reasonable intercropping to increase short-term returns. Intercrops include short-stature crops such as soybeans, mung beans, and peanuts; tall-stature crops such as corn and sorghum, as well as vegetable crops with relatively high water requirements, must not be intercropped. In addition, green manure crops and the like can also be intercropped to improve the soil environment.