Agriculture Reference
In-Depth Information
like Irish potatoes'. Plate 6.5 shows tubers of
Pueraria tuberosa
, together with nodulated
roots. These tubers may grow to 35 kg and have a high protein content (Anon, 1979),
but in parts of India are mainly used as a source of drugs against malaria and as
contraceptives (H.S. Gehlot, personal communication).
Erythrina
is a genus usually known for its fine tree species, which have multiple uses.
In a monograph edited by Westley and Powell (1993), many of these are listed, but no
mention is made of the one species known to have edible (most are poisonous) seeds,
E. edulis
(Plate 6.6). These seeds have been used since the time of the Incas in Peru,
Venezuela and neighbouring areas. They can be harvested at a time when no other such
foods are available and thus fill an essential gap. As well as providing food, the small
trees are also used for construction, poles for fencing, animal fodder, mulching and as
shade for other crops. Its potential for developing regions is outlined in 'Lost Crops
of the Incas' (Anon, 1989). Other crops described in this publication include a type of
Phaseolus vulgaris
, known as the 'popping bean' because the seed is roasted rather than
boiled at altitude when the air pressure is too low to cook them in a reasonable time
and without using too much fuel. When roasted they 'pop' rather like popcorn.
6.2 Forage legumes
In temperate regions forage legumes have been developed for many years. Current
work is looking at developing new species for use in tropical and warm temperate
areas, especially those with low rainfall. Of these, some of the more interesting are
those adapted to acidic infertile soils, such as found in parts of South Africa and
southwest Western Australia (see also Chapter 2). Howieson et al. (2008) discuss the
rationale for developing these species, some of which nodulate with non-classic rhizo-
bia (see Section 4.2). At the Centre for Rhizobium Studies (CRS) inMurdoch University,
Perth Western Australia, a range of perennial forage legumes is being developed for
use in animal production. The ideal plant for this must be able to grow well in annual
rainfall of 150 to 250 mm, be highly fecund, with easily harvested seed, acid as well
as drought tolerant, palatable to livestock and, perhaps most important, to nodulate
effectively with acid-tolerant rhizobia. One of several species that is showing great
promise is
Lebeckia ambigua
, which has an extensive woody root system (evolved for
regeneration after fire) that generates succulent shoots, palatable to livestock (Plate 6.7).
Although producing plenty of seed, it is thought to be a low risk for weediness (Sec-
tion 2.6) (J.G. Howieson, personal communication). It nodulates freely with an as-
yet-unnamed species of
Burkholderia
. Other South African species of genera
Lotononis
(Yates et al., 2007) and
Lessertia
(Howieson et al., 2008) also have potential for acidic
soils. Further details of this and other related work can be found on the CRS website.
An Australian native species,
Cullen australasicum
, also shows potential as a low rainfall
perennial pasture species. In this case its low palatability to sheep was considered an
advantage, to prevent over-grazing (Dear et al., 2007).
In order to develop new legumes for agriculture, Howieson et al. (2008) identify
five key steps. First, why they are needed and why current species are failing; second,
what are the relevant social and economic issues that may affect its adoption; third,
