Ecology for best yields

Dolichos Lablab (Lablab purpureus (L.) commonly known as lablab bean or turtle beans, (locally referred to asย njahi) is a legume small species native to Asia.

It is a bushy, semi-erect, perennial herb, a multipurpose crop grown for pulse, vegetable and forage.

Njahi is a versatile crop that grows in altitudes from 500-1,800m above sea level, tolerates droughts, heat as high as 28-350C, and wide range of soils, including acidic and black cotton.

You can njahi in Kenya in Central, Eastern, Coast and Rift Valley. Soils should be free draining, sandy-loam of pH 5-7. For best yields, apply a tonne of manure per acre and 30-50kg of DAP at planting.

The crop can grow in areas with rainfall as low as 400mm with dry spell incidence and where deep soils are available, but best in excess of 750mm but not above 2,500mm.

The crop is extremely tolerant to soil texture, growing in deep sands to heavy clays, provided drainage is good. Salinity reduces the plant population and produces chlorotic leaves.

Lablab does not easily nodulate with native strains of rhizobia, and although it is often not inoculated, it is preferable to treat the seed with the cowpea strain CB756 found in Mea Ltd.

Check colour of nodules on lablab to be dark pink at six weeks, and black at 12 weeks as indication of nitrogen fixation, as diagnostic check on successful strain inoculation.

The most common varieties are KAT/DL-1, KAT/DL-2 and KAT/DL-3 sold by Kenya Seed Company, Dryland Seeds and Kalro Seed Unit and they yield between 2.5-4 tonnes/acre.

The fodder dolichos bushy-legume types can be conserved into hay or silage or fed green to dairy cattle or as a legume supplement and varieties for fodder purposes include DL1002, DL1009 and Rongai.

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It can produce up to 5-10 tonnes/ha of green matter, which can be used as fodder or green manure. To increase N-fixation, inoculate with Biofixย inoculants.

Agronomy and yield
Seedbed for planting of dolichos should be well-prepared, by 1 plough and 1-2 harrows. Seed rate is 25kg per acre, space at 45cm between rows and 30cm from plant to plant (placing two seeds per hole), or 40×10-15cm and one seed per hole in pure stand.

It has excellent ability to compete with weeds when once established, but its early growth is slow and so it should not be subject to weed competition at this stage.

Weeding should be done two to three weeks after germination and should be weed-free until harvest. Dolichos is a hardy legume, has no enemies (pests and diseases) of economic importance.

It is commonly attacked by stem rot caused by Sclerotinia sclerotiorum under wet conditions. Insects attack roots mainly the nematodes like Helicotylenchus dihystera, Meloidogyne hapla and M. incognita and also attacked by leaf-eating insects.

Spray with any contact or systemic insecticides like Dududrin to control insects. Of all the bean varieties in the market for sale, Dolichos fetches the highest price ranking from Sh5,000-Sh7,000 for a 90kg bag.

The pods of Dolichos in Kenya are cooked and eaten like green beans. Young leaves are eaten raw in salads while older leaves are cooked like spinach.

Dry beans make stew and are mostly served with chapati or rice in restaurants.

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