Agriculture Reference
In-Depth Information
TABLE 7.9 (continued)
Straw Yield (kg ha
−
1
) of 15 Dry Bean Genotypes as Influenced by N
+
Rhizobium
and Genotype Treatments
Genotype
0 kg N ha
−
1
0 kg N ha
+
Inoculant
Inoculant
+
50 kg N ha
−
1
120 kg N ha
−
1
BRS Ametista
1931.11bc
2591.48abc
2556.66bc
3072.59bc
Diamante Negro
2265.55abc
2628.15abc
2782.96abc
2961.07bc
Corrente
2732.59ab
2763.33abc
2678.51bc
3765.05abc
BRS Valente
2165.92bc
1924.44c
2408.51c
3027.96bc
BRS Grafite
3065.55a
2872.59abc
2911.11abc
4538.89a
BRS Marfim
2415.55ab
1991.85bc
2644.05bc
3086.67bc
BRS Agreste
3063.70a
3755.93a
3132.05abc
4089.62ab
Average
2392.86c
2644.49c
2932.31b
3211.50a
F-test
Year (Y)
**
N + inoculant (N)
**
Y × N
**
Genotype (G)
**
**
Y × G
**
N × G
**
Y × N × G
CVY (%)
18.58
CVN (%)
22.49
CVG (%)
19.52
Source:
Adapted from Fageria, N. K. et al. 2012. Response of dry bean genotypes to nitrogen and rhizobia under field con-
ditions. Paper presented at the Soil Fertility Meeting, 17-21 September 2012, Maceio, Brazil, Brazilian Soil
Science Society/Federal University of Alagoas, Brazil.
**Significant at the 1% probability level. Means followed by the same letter in the same column do not differ significantly at
the 5% probability level by Tukey's test. Average values are compared in the same line.
Overall, the straw yield varied from 2938 to 4281 kg ha
−1
under different N + inoculation treat-
ments in the first year. In the second year, the variation in straw yield was 1848-2142 kg ha
−1
. When
the straw yield values were averaged across 2 years, it varied from 2393 to 3212 kg ha
−1
. Both the
N and inoculation treatments improved the straw yield significantly compared to control treatment.
The improvement in straw yield with the addition of N was related to the increase in leaf area as well
as shoot dry weight (Fageria and Santos, 2008). Straw yield is genetically controlled as well as influ-
enced by environmental factors, including mineral nutrition (Nelson and Larson, 1984; Rasmusson
and Gengenbach, 1994; Fageria and Santos, 2008). Figures 7.2 through 7.8 show the growth of dry
bean genotypes at different N levels. It is very clear from these figures that the growth of all the
genotypes was better at inoculate + 50 kg N ha
−1
and 120 kg N ha
−1
compared to control and con-
trol + inoculate treatments.
7.7 STRATEGIES TO ENHANCE BIOLOGICAL NITROGEN FIXATION
The greatest success in terms of modified agricultural practices arising from scientific research
on biological N fixation has undoubtly been the development of rhizobial inoculants (Giller and
Cadisch, 1995; Seneviratne et al. 2000). Soybean has been the only example where there has been
widespread adoption, primarily due to the relative specificity of soybean for rhizobia (Seneviratne
et al., 2000). Inoculation of soybean is a significant agency for the manipulation of rhizobia for
