Baoqing Red Beans

Baoqing Red Beans

　　Adzuki beans belong to the legume family (Fabaceae), genus Vigna, and are annual herbaceous plants. They have underdeveloped taproots but long, slender lateral roots. The plants grow to a height of 80–100 cm and come in upright clumping, semi-trailing, or trailing vine types. The leaves are compound, each made up of three leaflets that are either round-tipped or sword-shaped. Flower stems emerge from the leaf axils, with several flowers blooming at the tip. They are self-pollinating crops with small yellow or light gray flowers. The keel petals are spiraled, and each flower stem produces 1–5 pods, which are 7–16 cm long and contain 4–18 oval or oblong seeds. The seeds are mostly reddish-brown, but can also be black, gray, white, mottled, or light yellow. The thousand-seed weight ranges from 50–210 grams, most commonly around 130 grams.

Adzuki beans have strong adaptability. They are not demanding on soil and can thrive in poor, infertile conditions, growing well in both clay and sandy soils, as well as in valleys and mountainous areas. They tolerate both waterlogging and drought, are late-planted but early-maturing, have a short growth period, and require simple cultivation techniques, making them suitable as catch-crop plants. They are typically sown in holes with row spacing of 25–35 cm, plant spacing of 16 cm, and 4–5 seeds per hole. The seeding rate is 1.5–2.5 kg per mu, with a growth period of about 100 days. They can be planted in spring or summer, either as a pure crop or intercropped. The average yield is 150–250 kg per mu. Northern Shaanxi has a semi-arid climate with a frost-free period of about 165 days. The soil is loessial, loose, and deep, which is conducive to seed germination, seedling emergence, and root development. The annual average temperature is 9.7°C, with an effective accumulated temperature above 10°C of 3499.2°C and about 176 days with temperatures consistently above 10°C. The area receives about 2615 hours of sunshine annually and around 480 mm of precipitation, most of which concentrates in midsummer—352 mm falls between June and September, accounting for 73% of the annual total, coinciding with the warmest season. June to September is also the peak growth period for adzuki beans. These natural conditions are highly favorable for the beans to accumulate starch and protein while maintaining their bright red color, creating optimal conditions for their growth and development.