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<big>''[[Vigna angularis]]'' (Willd.) Ohwi & Ohashi</big>

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{{DISPLAYTITLE:''Vigna angularis'' (PROTA)}}

:Protologue: Journ. Jap. Bot. 44(1): 29 (1969).

== Synonyms ==

== Vernacular names ==

== Origin and geographic distribution ==

== Description ==

''Vigna'' comprises about 80 species and occurs throughout the tropics. ''Vigna angularis'' belongs to subgenus ''Ceratotropis'', which also includes ''Vigna radiata'' (L.) R.Wilczek (mung bean), ''Vigna umbellata'' (Thunb.) Ohwi & H.Ohashi (rice bean), ''Vigna mungo'' (L.) Hepper (black gram) and ''Vigna aconitifolia'' (Jacq.) Maréchal (moth bean). Cultivated plants of ''Vigna angularis'' have been classified as var. ''angularis'', wild plants as var. ''nipponensis'' (Ohwi) Ohwi & H.Ohashi. Wild adzuki bean has an indeterminate growth habit with thin twining stems, small leaves, short and strongly dehiscent black to grey pods and black-mottled seeds. Numerous cultivars have been recorded within ''Vigna angularis'', differing in time to maturity, seed colour and plant habit. Intermediate types between wild and cultivated plants, called weedy types, have been found in Japan.

The seeds of adzuki bean retain their viability for at least 5 years when stored with about 13% moisture content, at 15% relative humidity. Germination requires a soil temperature above 6–10°C, with 30–34°C being optimal. Emergence takes 7–20 days. Growth is slow compared to other pulses. Flowering lasts 30–40 days and can occur up to 3 times when planted early in the growing season. Self-pollination is predominant, but cross-pollination also occurs. The growth duration is (60–)80–120(–190) days. Nitrogen fixation levels up to 100 kg N/ha have been observed, the amount depending on soil moisture content and pH. Adzuki bean effectively nodulates with ''Bradyrhizobium'' bacteria.

== Ecology ==

Adzuki bean performs best in subtropical and warm temperate climates. It requires average temperatures of 15–30°C for optimal growth. It tolerates high temperatures but is sensitive to frost. In the tropics it is more suitable for higher altitudes. Adzuki bean grows in areas with average annual rainfall of 500–1750 mm. It is a quantitative short-day plant but day-neutral cultivars exist. Adzuki bean can be grown on a wide range of soils (pH 5–7.5), provided they are well drained.

== Management ==

Propagation of adzuki bean is by seed. The 1000-seed weight is 50–200 g. Sowing practices differ greatly but usually seed is sown 2–3 cm deep, in rows 30–90 cm apart and 10–45 cm within the row; sometimes it is broadcast. Seed rates vary widely (8–70 kg/ha). Because of the relatively slow growth of adzuki bean, weed control is very important, particularly between germination and flowering. Fertilizer application differs widely. An adzuki bean crop yielding 2160 kg/ha was recorded to have an uptake per ha of 74 kg N, 18 kg P and 50 kg K. Irrigation of adzuki bean is not normally done. In China adzuki bean is often intercropped with maize, sorghum and millet. In Japan adzuki bean is grown in rotation with many crops (e.g. rice, wheat, sweet potato, yam). The seed may be sown directly in rice stubble at a high rate to reduce weed problems. Numerous fungi and bacteria are known to cause diseases in adzuki bean, including powdery mildew (''Erysiphe polygoni'', synonym: ''Erysiphe betae''), brown stem rot (''Cephalosporium gregatum'', synonym: ''Phialophora gregata'') and bacterial blight (''Xanthomonas campestris''). Several insect pests, such as the adzuki pod worm (''Matsumuraeses phaseoli''), the Japanese butterbur borer (''Ostrinia scapulalis pacifica'') and cutworm (''Spodoptera litura'') attack the crop. Bean weevil (''Callosobruchus chinensis'') attacks the stored seed. In general the pods of adzuki bean do not shatter readily and the crop can be harvested with a mower or bean harvester. Traditionally, plants are cut by hand and allowed to cure on the ground for several days before being stacked into drying piles. Drying occurs until moisture content of the seed is about 16% and threshing can start. Some pods are very thin and in wet conditions seed may germinate in the pods. For hay, adzuki bean should be cut when the pods are about half mature. For seed, cutting is done when all pods are mature. Seed yields up to 3500 kg/ha are obtained. In an experimental planting in Kenya seed yields were 500–600 kg/ha.

== Genetic resources ==

== Author(s) ==

== Correct citation of this article ==