Orange trees were introduced to Luc Ngan district in the 1990s with three main varieties, including: CS1 orange, sweet orange, and V2 orange. Currently, oranges are the second key fruit crop in Luc Ngan district in terms of cultivation area (after lychee). Thanks to unique geographical conditions (climate, soil, and production techniques), Luc Ngan oranges stand out for their superior sweetness, which is well-received by the market (particularly in the southern provinces due to their alignment with the preference for sweet-tasting fruits).

Yellow-fleshed oranges are produced from the CS1 orange variety, with a rich sweet taste, and a total sugar content greater than or equal to 9.7%. Sweet oranges are produced from the Duong Canh orange variety, with a sweet taste, and a total sugar content greater than or equal to 9.01%. V2 oranges are produced from the V2 orange variety, with a rich sweet taste, and a total sugar content greater than or equal to 9.1%.

Figure 1. Luc Ngan yellow-fleshed orange

Figure 2. Luc Ngan sweet orange

Figure 3. Luc Ngan V2 orange

The characteristics of these products are related to geographical conditions.

The climatic and soil characteristics of the geographical area are highly suitable for the ecological requirements of orange trees, enabling the oranges grown in Luc Ngan to thrive and develop well. In addition to favorable natural conditions, the unique quality of "Luc Ngan oranges" is also linked to the production techniques in the geographical region.

Unlike other orange-growing regions where phosphorus is primarily applied once per crop (as a basal dose after harvest), Luc Ngan orange region applies phosphorus fertilizer twice per crop (as a basal dose after harvest and as a top dressing during the fruit development stage). As a result, oranges grown in Luc Ngan district have a higher total sugar content (sweetness level) compared to similar products grown elsewhere.

Additionally, for sweet orange trees in Luc Ngan, growers also perform the technique of girdling the trunk and branches annually in April-May (2-3 times per crop, with the second session 6-8 days after the first, and the third session 15-18 days after the second). The girdling method not only allows the canopy to accumulate more nutrients but also restricts the nutrient flow to the lower parts (including the roots), limiting water absorption from the base and concentrating nutrients for the fruit, thereby improving yield and enhancing fruit quality.

Figure 4. Root and branch girdling technique for sweet orange varieties in Luc Ngan district

Geographical area includes Chu town and communes: Thanh Hai, Kien Lao, Bien Son, Kien Thanh, Tan Hoa, Giap Son, Bien Dong, Quy Son, Tru Huu, Phuong Son, Phi Dien, Tan Quang, Dong Coc, My An, Nam Duong, Tan Son, Ho Dap, Kim Son, Phu Nhuan, Deo Gia, Tan Moc, Tan Lap, Hong Giang, Son Hai, Phong Van, Phong Minh, Sa Ly, and Cam Son belonging to Luc Ngan district, Bac Giang province.

Source: Bảo hộ chỉ dẫn địa lý “Lục Ngạn” cho sản phẩm cam

Translator: Nguyễn Hải Phong