Agriculture Reference
In-Depth Information
There are some kind of interactions between genistein and some plant regula-
tors such as the plant hormone, auxin. Falvonoids can adversely or positively affect
the activity and transport of auxin (Brown et al.
2001
). Geneistin may inhibit the
transport of auxin in the plant. It has been indicated that the use of auxin transport
inhibitors in soybean may result in the formation of nodule like organs, and expres-
sion of genes, which induce morphogenesis alteration in the roots resulting in the
formation of root nodules (Fang and Hirsch
1998
).
Soybean and N Fertilization
During the past 30 years, soybean yield has increased continuously, due to the im-
provement in the use of genetic techniques and agricultural practices with the yearly
increase of 28 kg ha
−1
, globally (Specht et al.
1999
; Wilcox
2004
). Biological N
fixation and mineral N fertilization are the main sources of providing necessary
N for soybean growth. However, biological N fixation by the residing bacteria in
the root nodules and mineral N fertilization can behave antagonistically, especially
when the other soil stresses are not present (Streeter
1988
; Soares Novo et al.
1999
;
Purcell et al.
2004
).
If there is not adequate amounts of N for plant use, plant will re-translocate N
from the leaf to the grains, reducing plant photosynthetic potential and hence crop
production. Van Kessel and Hartley (
2000
) indicated that rate of yield production
can adjust nitrogenase activity, as higher amounts of yield results in higher nitro-
genase activity. This is especially the case for when soybean plants yield at rates
higher than 4.5 t. ha
−1
(Mengel
1994
).
In situations where the process of N-fixation is not able to supply the necessary
N for plant growth and yield production, plant response to N-fertilization can be sig-
nificant (Thies et al.
1995
). However, usually there are antagonistic effects between
N-fixation and N-fertilization. Nitrate present in the soil can decrease the process
of N-fixation (Herridge and Rose
1994
). Even little amounts of N-fertilization can
suppress N-fixation during the first stages of plant growth; however at the same
time N deficiency may delay the onset of nodule formation and hence, N-fixation
by adversely affecting crop growth (Zhang and Smith
2002
; Ikeda et al.
2011
).
Salvagiotti et al. (
2008
) analysed a complete set of data regarding N-fixation and
N-fertilization related to different parts of the world. They found that N-fixation
is negatively and exponentially related to N-fertilization when it was applied to
the soil surface at 20 cm. Their economical analyses, with respect to soybean and
N-fertilization pricing, indicated that N-fertilization is advantageous when plant re-
quirements are not met by the process of N-fixation. They accordingly suggested
that to enhance the efficiency of N uptake by plant, future research must indicate
the contribution of each N component including, N-fixation, N-fertilization and
soil N. It is because, if N-fertilization is supplied adequately, while not affecting
N-fixation, it can enhance the efficiency of plant N uptake (Ikeda et al.
2011
).
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