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

Table 1. Soil characteristics of some selected parameters across
four sites at the end of the second season in 2002
Treatment pH OM (%) NOl (ppm) NH4 (ppm)
Fertilised maize 5.5 3.0 1.3.8 99.7
Unfertilised maize 5.5 3.5 14.1 84.2
Maize after 5.5 3.8 13.3 65.1
mucuna
Maize after 5.5 4.1 12.1 66.3
natural fallow
SED Prob SED Prob SED Prob SED Proo
Site 0.13 < 0.001 0.49 < 0.001 2.39 < 0.037 15.4 < 0.001
Treatment 0.13 NS 0.494 NS 2.39 NS 15.4 NS
Site xTrt. 0.264 NS 0.988 NS 4.78 NS 30.2 NS
Results
Soil chemical characteristics of the treatments
There were no significant differences at the end of
the second season on soil chemical characteristics,
although organic matter tended to be higher following
the natural fallow and mucuna compared to unfertilized
and fertilized maize monocultures (Table
1).
Effects of mucuna on soil cover compared to natural
fallow
No measurements were taken on soil cover in plots
with the short term fallow of mucuna and the plots left
to natural fallow. However, farmers in the study sites
observed that where mucuna was planted there was a
good soil cover compared with the plots left to natural
fallows.
Effect of treatments on maize grain and stover
yield
Average maize grain yield was highest where maize
was fertilized with the area specific fertilizer recommendation.
For the non-fertilized plots, maize following
mucuna had the highest grain yield (1.5 t
ha·1) and highest stover yield (with 3.5 t ha- 1 )
(Tables 2a and b). The lowest inaize grain yield (0.4
t ha- 1 ) was from plots where unfertilized maize followed
unfertilized maize (Tables 2a and b). Among
the -twenty-six sites, Vingalala site had the lowest
average maize yield of 0.8 t ha- 1 but had similar
maize yield trends to the other sites.
Figure 1. Grain and stover nitrogen across sites for four maize­
mucuna systems in Malawi
Effect of treatments on grain and stover N yield
Nitrogen yield for both grain and stover (Figure 1)
was highest for the fertilized treatments followed by
the maize following mucuna treatment, with the
least grain and stover yield obtained from maize
that followed the natural fallow. There were significant
differences in nitrogen concentration in the
grain due to sites; the lowest nitrogen concentration
was obtained from Vibangalala and the highest
from Kasungu. The N.in the maize crop after mucuna
was almost double that from unfertilized
maize.
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Effect of sites and treatments on N concentration
There were significant differences in nitrogen concentration
in the grain due to sites_ The lowest nitrogen
concentration was obtained from Vibangala site
and the highest concentration was from Kasungu
(Table 3). The N in the maize crop after mucuna was
almost double that from unfertilized maize.
Conclusion
Similar yield trends were obs~rved at all four sites
and strongly indicate that resource poor farmers
who cannot afford fertilizers would benefit a lot by
Table 2a. Maize grain yield (t hal) from 26 farms located at four
sites in 2001/2002
Site No. of Fert- Unfert· Maize Maize Mean
farms ilized ilized after after (t hal)
Maize Maize Mucuna Fallow
Ntcheu 6 3.6 1.1 1.6 1.4 1.9
Kasungu 5 1.7 0.8 1.2 0.9 1.1
Vangalala 6 1.4 0.4 0.7 0.6 0.8
Zombwe 5 3.6 0.9 2.4 1.3 2.0 .
Mean 2.6 0.8 1.5 1.0 1.5
SED Prob.
Site 0.248