Agriculture Reference
In-Depth Information
Perola
120 kg N ha
-1
0
0 + rhizobium
50 + rhizobium
FIGURE 7.2
Dry bean genotype Perola growth at different N treatments in the second year of experi-
mentation. Left to right 0 kg N ha
−1
, 0 kg N ha
−1
+
inoculation with rhizobium, inoculation with rhizo-
bium + 50 kg N ha
−1
, and 120 kg N ha
−1
.
BRSMG Talisma
0
0 + rhizobium
50 + rhizobium
120 kg N ha
-1
FIGURE 7.3
Growth of dry bean genotype BRSMG Talisma at different N treatments in the second year of
experimentation. Left to right 0 kg N ha
−1
, 0 kg N ha
−1
+
inoculation with rhizobium, inoculation with rhizo-
bium + 50 kg N ha
−1
, and 120 kg N ha
−1
.
improving crop productivity and fertility (Keyser and Li, 1992). It can lead to the establishment of
a large rhizobial population in the plant rhizosphere and to improvement in nodulation and N
2
fixa-
tion, even under adverse soil N conditions (Peoples et al., 1995a,b).
Biological N fixation by legumes is an important biological process that deserves special atten-
tion due to its economic and environmental impacts. Attempts to increase N
2
fixation will require
optimization of this process under the diverse environmental conditions to which crop plants are
exposed. Some of the strategies that can be adopted to optimize the N
2
fixation process are selection
of an appropriate strain for inoculate, appropriate rhizosphere conditions surrounding the plants,
and also planting efficient crop species or genotypes within species.
7.7.1 s
eleCtIon
of
a
pproprIate
s
traIns
for
I
noCulatIon
Thies et al. (1991) quantified the indigenous soil rhizobia population, finding greater responses to
rhizobia inoculation when populations were <10 cells g
−1
of soil, and little to no responses existed
