Soybean plays roles in reducing soil erosion, in biological nitrogen fixation, in pests and disease management and is also an important source of plant proteins. However production remains low in Malawi because of several factors, including the limited use or non-use of rhizobial inoculants and phosphorus fertilizers. Studies were conducted in 2011/12 and 2012/13 growing seasons in central Malawi to test the response of soybean to inoculation with biofix and soil amendments with phosphorus (P) fertilizer. The research used two approaches of research designed-research managed (RDRM) and research designed-farmer managed (RDFM) on-farm trials. The RDRM trials were laid in split plots replicated three times whereas RDFM trials were laid out on randomly selected farmers’ plots and field book was used to capture data. Analysis of variance was performed using Genstat (16th Edition) and Micro Soft excel. Results showed that inoculation significantly increased biomass yield, grain yield and nodulation. P-fertilizer did not have significant impact on grain yield. The yield in RDFM trials were generally lower than RDRM. The implications of the findings in smallholder farming systems in Malawi are discussed.

1. Response soybean to inoculation with rhizobia and
application of phosphorus fertilizers in Malawi
Chataika, B. Y. E.1*, Phiphira L.2
1International Centre for Tropical Agriculture (CIAT), Chitedze Research Station, P. O.
Box 158, Lilongwe, Malawi
2International Institute for Tropical Agriculture (IITA), N2Africa Project, Chitedze
Research Station, P. O. Box 30258, Lilongwe 3, Malawi
*Corresponding author. E-mail: B.Chataika@cgiar.org. Tel: +265 1 707 022/+265 8
88 894 595.

2. Outline of presentation
• Legumes and BNF
• Overview of the research Process
• Major Findings
• Conclusion and Recommendations

3. Legumes and biological nitrogen fixation
• Nitrogen is the nutrient element most limiting to plant growth.
• Replacement of soil nitrogen is generally accomplished by the
– 1. addition of N-fertilizers
– 2. BNF.
• BNF= atmospheric nitrogen
biologically useful form.
• Root Nodules = factory for N-fixation
to ammonia
• The symbiotic relationship (LxR)
contribute largest amounts of fixed
nitrogen to agriculture.
• Grain legumes contribute more
than 20 million tons of fixed N to
agriculture each year (Herridge et
al. 2008).

4. Overview of the Research Process
RDRM and RDFM
Agronomy trials (RDRM Trials): Dedza, Lilongwe and Salima
• Split plots
Delivery and Dissemination(RDFM Trials): Dedza, Lilongwe and
Salima.
• Identification and training of participants
• Distribution of seed, biofix innoculant and fertilizer
• Administration of field book

5. Field layout and Seed Inoculation

6. Grain yield response of soybeans to inoculation with biofix rhizobia
across sites in 2011/12 growing season (kgha-1)
Inoculation Dedza Mitundu Msundwe Salima Mean
RH- 1442c 1444c 933a 1460c 1411
RH+ 2140d 2269d 1194b 2445e 2220
Site mean 1791 1857 1063 1952 1762
LSD<0.001(Site x Inoculation) = 147.8
CV = 18%

7. Grain yield response of soybeans to inoculation with biofix rhizobia
across sites in 2012/13 growing season (kgha-1)
Inoculation Dedza Msundwe Salima Mean
RH- 1887cd 867a 889a 1327
RH+ 2098d 1634c 1180b 1689
Site mean 1993 1251 1034 1508
LSD0.018 (Site x Inoculation) = 278
CV = 49.6%

8. of soybean averaged over the two seasons across
• Biofix significantly
increased grain yield
in all the sites
• Inoculation with
biofix increased
grain yield by an
average of 42%
(57% in 2011/12 and
27% in 2012/13
seasons)
2106
1194
2267
2509
1428
933
1443 1465
3000
2500
2000
1500
1000
500
0
Dedza LL-Msundwe LL-Mitundu SALIMA
Grain yield(kg/ha)
Site/Environment
RH+ RH-Yield
sites in RDRM

9. Soybean varietal response to inoculant in RDRM
Soybean varieties

10. Effect of biofix rhizobia on biomass (RDRM)
Putting Nitrogen to work for smallholder farmers in Africa

11. Effect of inoculants on nodulation (RDRM)
6
5
4
3
2
1
0
Dedza Mitundu Msundwe Salima
Nodule score
Site
RH+ RH-

12. Effect of Inoculants and P-fertilizer on soybean grain yield (RDFM)
• The treatment with biofix
inoculant produced the
highest yield (1237kgha-1)
which was significantly
different from the control
(661kgha-1) and
phosphorus fertilizer
treatment (672kgha-1).
• Seed treatment with
biofix, led to an increase
in grain yield by 87% as
compared to the control.
661 672
1237 1132
1600
1400
1200
1000
800
600
400
200
0
No biofix,
No P
No boifix, +P With Biofix,
No P
With Biofix
& P
Yield in Kg ha-1
Inoculant and P fertilizer

13. An overview of financial impact of biofix on
smallholder farmers
Factor
Farmer Category
Grain Producer Seed Producer
Biofix requirement (g/ha) 400 400
Cost of Biofix/ha 6.4 6.4
Grain Yield without Biofix 661 661
Grain Yield with Biofix 1237 1237
Market price of produce* 0.5 1.75
Total Revenue($) without Biofix 331 1157
Total Revenue($) with Biofix 619 2165
*1$=400MK
Note: The table is very simplified for the purposes of highlighting the general picture

14. Conclusion and Recommendations
• Our results demonstrated the consistent positive impact of using biofix
inoculants on grain yield of soybeans across the test sites.
• Un-inoculated treatment modulated in Dedza suggesting the presence of
native rhizobia (though in low populations)
• Nodulation in Mitundu was heavily dependent of inoculant.
• We have also demonstrated that farmers’ productivity is far below
potential even with the use of inoculants. Management could thus be
another element that need to be enforced.
• We recommend further investigation on the presence of native rhizobia
and survival rate of rhizobia in inoculated fields in soybean growing areas.

15. Acknowledgement
• We acknowledge Bill and Melinda Gates Foundation
for funding this research.
• We also acknowledge staff from the Department of
Agricultural Research Services for the support.

16. THANKS FOR YOUR TIME