Grain Legumes and Green Manures for Soil Fertility in ... - cimmyt

Table 2. Maize yields from the cereal· grain legume rotations,
2000-2001.
Maize/ Maize/soya Maize Maize Maize/
maize (t/ha) /groundnut /bambara Cowpea
(t/ha) (t/ha) (t/ha) (t/ha)
Site 1 3.3 5_8 5.4
Site 3 2.6 4.2 4.1
Site 3 4.0 4.5 4.3
Site 4 4.3 4.6 4.5
Site 5 2.0 4.0 3.8
Site 6 1.5 3.0 2.7
Site 7 2.0 3.5 2.5
Site 8 1.6 3.0
Average 3.2 4.7 4.2
L-.­
Table 3. Maize yields from the green manure demonstration plots,
2000-2001.
Maize/maize Maize/velvet Maize/
(t/ha) bean sunnhemp
(t/ha)
(t/ha)
Site 1 2.1 3.7
Site 2 1.6 3.5
Site 3 1.5 3.5
Site 4 2.0 2.0
Site 5 2.5 3.0
Site 6 1.1 1.4
Site 7 0.9 1.0
Site 8 1.1 1.3
Site 9 2.0 2.0
Site 10 2.5 3.0
Average 1.5 1.6 1.4
Maize after a legume outperformed maize after
maize at all sites (Table 2). With the green manure
technology, farmers preferred sole cropping to in­
ter-cropping, mainly because of the constraints en­
countered during harvesting. The demonstrations
were held for two years only and no arrangements
were made for the third year because project fund­
ing had terminated. The data collected was from the
sole cropping.
The average grain yield of maize after maize was
out-yielded by maize after a green manure (Table
3). Results from Table 3 indicate that the yield in­
crease over the two years did not compensate for
the yield lost during the first year.
Farmer feedback sessions
Attendance at field days was overwhelming. Atten­
dance ranged from 50 to 160 people at some sites.
At least 14% and up to 60% of the targeted farmers
used annual legumes (such as velvet bean and soya­
bean) as soil fertility interventions. However, farm­
ers cited the following setbacks (AGRlTEX, 2000;
2001):
Table 4. Participation of Chiota farmers in legume production, 2000­
2001.
LEGUME TOTAL NO. OF AOOPTERS WITHIN AOOPTERS
PARTICIPATING THE GROUP OUTSIDE
FARMERS
THE GROUP
No. % No.
ROTATION 1433 818 57 381
GREEN MANURES 631 185 29.3 94
- Lack of planting material.
- Lack of knowledge on the utilization of legumes
for human consumption and stock-feed.
- Lack of knowledge on either uses of velvet bean
and sunnhemp.
- Lack of knowledge on the residual nutrient levels
because of the rotation and green manure.
- The concept of input reduction costs was not properly
demonstrated.
.
- Generally, management of the green manure was
poor.
"Adopters" were considered to be those farmers
who used the technology. The table above shows
the total number of adopters over two years. The
number is expected to rise through farmer-to­
farmer contacts.
There was need to repeat the demonstration in the
second year, but this could not be carried out due to
unfavourable weather conditions and other socio
economic circumstances. However, the following
issues in management of green manures are to be
considered for future demonstrations:
• Sowing and site selection - Plant populations
were low due to plant destruction by wild a:nimals.
This resulted in very low biomass.
• Fertilizer use - without fertilizing it is not possible
to achieve a closed green stand and biomass
quantities obtained will be low. Farmers considered
that it was not practicable to fertilize fallows.
• Incorporation - rarely was the green manure incorporated
at the best stage. The method of incorporation
was also not ideal because the green
manure was not fully covered and the environmental
conditions were not always good.
• Seed procurement - Seed was not readily
available locally.
The pilot project built a sense of awareness amongst
the farmers. An impact assessment will reveal the
best steps forward.
Grain legumes and Green Manures for Soil Fertility in Southern Africa
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