Vigna umbellata, previously Phaseolus calcaratus, is a warm-season annual vine legume with yellow flowers and small edible beans.

The cultivated Asiatic Vigna species belong to the sub-genus Ceratotropis, a fairly distinct and homogeneous group, largely restricted to Asia, which has a chromosome number of 2n = 22 (except V. glabrescens, 2n = 44).

It is thought to be derived from the wild form V. umbellata var gracilis, with which it is cross-fertile, and which is distributed from Southern China through the north of Vietnam, Laos and Thailand into Myanmar and India (Tomooka et al., 1991).

It can be grown in diverse conditions and is well known among farmers for its wide adaptation and production even in marginal lands, drought-prone sloping areas, and flat rainfed tars (unirrigated, ancient alluvial river fans).

Wild forms are typically fine-stemmed, freely-branching and small-leaved, with a twining habit, photoperiod sensitivity and indeterminate growth (Lawn, 1995).

In many areas, landraces which retain many of these characteristics persist, in particular with regard to daylight sensitivity, growth habit and hard seeds.

Apart from various recipes for dal soups and sauces, pulses are also used in a number of other ways, either whole, cooked or roasted, as flour, or ground to make various deep fried dishes or snacks.

However, the amino acid composition is reported by several authors to be well balanced for human consumption (e.g. Chandel et al., 1978; Mohan & Janardhan, 1994; de Carvalho & Vieira, 1996).

As in other pulses, an important problem is that ricebean contains various antinutrients,[3] notably phytic acid or phytate, polyphenols and fibres that reduce micronutrient uptake, in particular iron and zinc.

While most legumes contain one or several enzyme inhibitors and similar antinutritive or toxic factors (Smil, 1997), the content of such substances appears to be low in ricebean.

This has an important bearing on dietary choices, as this perception not only promotes a balance between hot and cold food stuffs in daily nutrition, but also encourages or discourages the consumption of various items according to season, and during sickness.

In Nepal, ricebean tends to be categorised as a cold food (e.g. in Gulmi, Kailali, Syangja, Dang, Gorkha districts) and it is said to cool people in the summer.

Another account from Ilam stated that ricebean, although creating some stomach unrest, was milder and more digestible than other pulses, and therefore often served to people who suffer from indigestion.

Whether hot or cold, the major share of ricebean is consumed soon after harvest, so the crop will only indirectly impact on food security during the lean season in the pre- and early monsoon period.

This is in contrast to black gram which is used for ceremonial purposes among high caste Hindus, and also for instance among Rai people in the Arun Valley.

In addition, black gram is considered tastier and fetches a higher market price, so will tend to replace ricebean if the farmer has to make a choice.

Quantee (or kwati in Newari) is a mixed bean sprout soup served at the Janai Purnima or Raksha Bhandan festival.

One source mentioned that since ricebean is supposed to make you strong, people will often serve it to labourers, while also occasionally consuming it themselves in connection with tasks requiring hard work.

Most varieties are highly photoperiod sensitive, and so when grown in the subtropics are late flowering and show strong vegetative growth.

However, the use of ricebean as a green manure crop was studied in a series of field experiments in Nepal, and this revealed that it is one of the best legumes for the purpose due to high biomass production over a short period of time, is easy to incorporate into the soil, and decomposes rapidly.