The history of orange cultivation in Van Chan began around 1990[1],[2]. The farm town of Tran Phu was the first place to grow oranges in the Van Chan district and was later developed throughout the neighboring communes. To meet the needs and tastes of consumers, from the Sanh orange variety first planted in Van Chan[3], Van Chan orange producer has diversified early ripening and late ripening orange varieties. Up to now, Sanh oranges, Duong oranges, CS1 oranges, and V2 oranges have been grown in the Van Chan district, Yen Bai province.

In terms of sensory, these oranges have a slightly sweet taste while CS1 and V2 oranges are much sweeter.

About quality: Oranges have Brix from 9.91 - 10.73oBx, and total sugar content from 7.83 - 8.72%. Sugar oranges have Brix from 7.70 - 10.90oBx, total sugar content from 6.31 - 7.12%, and water content from 87.15 - 91.12%. Orange CS1 has Brix from 12.80 - 13.35oBx, and total sugar content from 7.39 - 7.55%. Orange V2 has Brix from 10.05 - 11.52oBx, total sugar content from 8.90 - 9.20%, and Vitamin C content from 34.50 - 38.75 mg/100g.

Figure 1: Van Chan's oranges

Figure 2: Van Chan sugar oranges

Figure 3. CS1 Van Chan oranges

Figure 4. V2 Van Chan oranges

Van Chan orange cultivation area is located at an average altitude of 400m above sea level. Most of this land has a slope of 15-25o, many rivers and streams. The steep slope makes the soil easy to be washed away. To overcome this unfavorable natural condition, orange growers in Van Chan have designed orange plantations along contour lines. This garden structure allows the orange trees to get enough water during growth and development. The garden surface is easily drained, the plants are not waterlogged.

In addition to topographical conditions and characteristics, the specific quality of Van Chan oranges is also due to climatic conditions, soil conditions, and the caring hands of farmers in the geographical area. This area has an average annual temperature of 22 - 26oC, a large temperature range of day and night (average of about 8 - 9oC), relatively large rainfall (an average of 1,200 - 1,800 mm/year), The annual average humidity level is from 83% - 87%. The soil of the geographical area is red-yellow soil on clay and metamorphic rocks, the arable soil layer is over 1m thick, and the humus content in the soil is quite average (the average total humus content is over 1.8%). Using tree care techniques to help orange trees grow and develop well, and improve fruit quality such as: using most of the organic fertilizers, pruning branches, creating a canopy after each harvest, and arranging tree density reasonably (helps the orangery get suitable scattered light).

Geographical area: Cat Thinh Commune, Tan Thinh Commune, Dai Lich Commune, Chan Thinh Commune, Binh Thuan Commune, Thuong Bang La Commune, Nghia Tam Commune, Minh An Commune, Son Thinh Town, and Tran Phu's Nong Truong Town. Van Chan district, Yen Bai province.

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