74 / 92
t
his article is the 20th in a series of articles highlighting a spe-
cific pasture crop species that can play an imperative role in
conservation agriculture (CA) based crop-pasture rotations.
Besides improving the physical, chemical, hydrological and
biological properties of the soil, such species, including an-
nual or perennial cover crops, can successfully be used as
animal feed.
Livestock production systems are in many ways dependant on the
utilisation of pasture species, in this case as an annual legume cover
crop, and can therefore become an integral component of CA-based
crop-pasture rotations.
It is imperative to identify a pasture species fulfilling the require-
ments of a dual purpose crop, i.e. for livestock fodder and/or soil
restoration. This article focuses on a cover crop with enormous pas-
ture crop potential used to improve soil conditions and to provide
good grazing for ruminants.
Lablab purpureus L., Dolichos lablab L.
or lablab
Dolichos lablab
is an annual legume, biennial or short-lived peren-
nial (depending on the ecological zone where planted) with flowers
ranging in colour from white to purple, cultivated for human food,
livestock fodder or as a green manure cover crop.
If not overgrazed, it can become a biennial. Lablab is an extremely
valuable protein source for human and animal feed. This legume
improves soil fertility through a process of nitrogen (N) fixation as
a result of the symbiotic relationship between the plant and soil
Rhizobium bacteria.
Lablab is also well-known as a cover crop to be rotated with other
crops. This crop is rich in minerals, especially phosphorus and cal-
cium and vitamins A and D.
Agro-ecological distribution
Lablab is adapted to warm, humid climates with a rainfall of 450 mm
- 1 200 mm. What makes this crop attractive is that it can be drought-
tolerant when established and can grow in less than 500 mm pre-
cipitation per annum. However, during such times of drought, it can
be expected that the plant will lose many leaves.
This crop has a deep root system and can extract water as deep as
2 m in heavy textured soils. This legume is also known to tolerate
short periods of flooding unless the soil is not well-drained and root
systems are flooded for prolonged periods.
Lablab can survive high temperatures and grows best when tem-
peratures range between 15°C - 30°C. It has the ability to sustain
growth at very low temperatures, but not for too long, and can be
damaged by frost. This species provides its value in autumn offer-
ing valuable feed between summer and winter seasons.
Regarding the soil requirements most suitable for the growth of
lablab, it is interesting to note that this crop grows in a wide range
of soils, from deep sands to heavy clay soils. The most important
factor to consider with any soil, is that it needs to be well-drained
and even though lablab grows well on acidic soils, the soil pH should
preferably not be lower than 4,5 and higher than 7,5.
When considering the soil microbiology required for effective
nodulation for nitrogen fixation, it has been shown that lablab does
not nodulate well with native strains of rhizobia and remains impor-
tant to use the most appropriate rhizobia strain for lablab.
Management and utilisation
Generally it is most important to have a fine seedbed for smaller
seed species, however, lablab has a large seed and a fine seedbed
is not a major requirement. It is advised that this crop be planted in
rows and preferably with a spacing of 30 cm apart in the row and
45 cm between rows.
Seeds can be planted as deep as 5 cm and covered properly.
An acceptable seeding rate is 25 kg/ha. For fodder and grazing
15 kg/ha - 20 kg/ha seed can be planted in rows during October/
November.
It is extremely important to inoculate the seed properly before plant-
ing. As a legume species no nitrogen fertiliser is required; however,
a small amount at planting can support the initial root system until
the nodulation process is fully functional to ensure nitrogen fixa-
tion. Lablab is known to have a good disease resistance and is not
easily attacked by insects. This legume crop can be conserved into
hay or silage, and can be fed as green feed in moderate amounts
to cattle as a legume supplement with high protein content.
WAYNE TRUTER,
University of Pretoria,
CHRIS DANNHAUSER,
Grass SA,
HENDRIK SMITH,
Grain SA and
GERRIE TRYTSMAN,
ARC-Animal Production Institute
Integrated crop and pasture-based
livestock production systems
– Part 20
AGRICULTURE
Conservat ion
Series
ON FARM LEVEL
Conservation agriculture
November 2015
72