Agriculture Reference
In-Depth Information
Industrial manipulation of the nitrogen cycle is reported to have already
exceeded safe boundaries for global environmental change (Rockstrøm
et al
.
2009). Thus, there is a strong need to reduce our reliance on chemical nitrogen
fertilisers and instead optimize alternative nitrogen inputs. Biological nitrogen-
fixation is one such alternative input and is seen as an integral aspect for
improving nitrogen use efficiency (Hirel
et al
. 2007). The legume-rhizobia
symbiosis represents the world's most important biological nitrogen-fixation
association, producing roughly 200 million tons of nitrogen annually (
e.g.
,
Peoples
et al
. 2009). Thus, optimising legume nodulation can increase crop
yields and enhance soil fertility, whilst also reducing monetary costs and
environmental impacts associated with nitrogen fertiliser usage (Giller and
Cadisch 1995; Vance 2001). These are all extremely significant issues that
agriculture is facing in the world today.
S
OYBEAN
-
T
HE
W
ORLD
'
S
M
OST
E
CONOMICALLY
S
IGNIFICANT
L
EGUME
S
PECIES
Soybean (
Glycine max
(L.) Merr.) is one of the world's most
agriculturally important crop species with a global production value of roughly
$45 billion per annum (Food and Agriculture Organization of the United
Nations 2010). It is the world's most cultivated legume and the third most
cultivated crop species overall. It is thought to have originated from China and
Southeast Asia and to have been domesticated for over 5000 years. Currently,
the USA is the world's largest soybean producer, with Brazil, Argentina,
China and India also being major soybean growing countries. The majority of
soybean varieties grow best in subtropical environments, but there are also a
number of varieties that have been isolated for their ability to thrive across a
range of temperatures and climates. Indeed, there are currently thousands of
varieties available in what is both a very large and very well established
soybean germplasm.
Soybean seeds are typically creamy-yellow in colour, but varieties also
exist that produce red, green, brown and black seed. The seeds contain 35-
40% protein and 18-20% oil. As a result, they can be used to make a multitude
of processed products, including both consumable and industrial products.
Indeed, soy products are estimated to be found in nearly two-thirds of all
manufactured food products. Due to its high seed protein content, soybean is
an extremely important source of protein for human consumption and for
