| dc.description.abstract | Inherent low soil nitrogen (N) and phosphorus (P) is one of the major hindrances of increased
soybean productivity in Malawian soils. Although, inoculation of legumes with rhizobia, has been
advocated for decades as a way of boosting leguminous crops’ productivity through biological
nitrogen fixation (BNF), the effectiveness of this strategy, has been low. An experiment was carried
out to investigate the effect of the application of small doses of N and P to inoculated soybean. It
was laid out in a complete block design (CBD) replicated three times and the treatments included:
1. Soybean only, 2. Inoculated soybean, 3. Inoculated soybean + 30 kg N ha-1, 4. Inoculated
soybean + 30 kg N ha-1 + 25 kg P ha-1, 5. Inoculated soybean + 30 kg N ha-1 + 35 kg P ha-1. The
soybean in all treatment plots except for treatment 1 was inoculated with 30 kg N ha-1 applied as
urea to treatment plots 3, 4 and 5. Phosphorus as TSP was applied to treatment 4 and 5 at the rate
of 25 and 35 kg P ha-1. Data collected included; selected soil physical and chemical properties,biomass and pod yields. Data obtained were subjected to Analysis of Variance (ANOVA) using the
GenStat statistical package and treatment effects tested for significance using the F-test at 5%
level of significance. Means were separated using the least significant difference (P<0.05). Results
indicate that inoculating soybean with rhizobia and inoculating soybean with rhizobia plus applying
30 kg N ha-1 did not significantly increase biomass yields. However, inoculating soybean plus the
combined application of 30 kg N ha-1 and, 25 kg P ha-1 or / and 35 kg P ha-1 increased the soybean
biomass yields by 54% and 70% respectively above control. The lack of significant response when
N was applied without P points to the significant role played by phosphorus in root development
and energy transfer processes within the plant. Effective nodulation, however, was significantly
higher (p<0.05) above the control where inoculation was combined with the application of 30 kg N
ha-1 and 35 kg P ha-1, hence underlining the role played by phosphorus in nodule development and
the role of starter N in soils low in N. | en_US |
