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

MUCUNA - MAIZE ROTATIONS AND SHORT FALLOWS TO
REHABILITATE SMALLHOLDER FARMS IN MALAWI
WEBSTER D. SAKALA, IVY LlGOWE and D. KAYIRA
Chitedze Agricultural Research Station, P. O. Box 158, Lilongwe, Malawi
Abstract
An experiment was initiated in the 1999/2000 season to evaluate four different ways of improving maize yields on degraded
and abandoned parts of smallholder farms in Lilongwe, Kasungu and Mzuzu Agricultural Development Divisions
(ADD) in Malawi. Selected sites were farm fields abandoned by farmers due to very low maize yields. In the first
season (2000/2001), two treatments were planted with maize, which was either fertilized with an area specific fertilizer
recommendation or not fertilized. The other two treatments were planted either to a one-year improved fallow of mucuna
or left to a natural fallow. In the second season (2001/2002) maize was planted to all the four plots without fertilizer except
a control where fertilized maize followed fertilized maize. Average maize yields from the four sites ranged from 0.8 t
(at Vibangalala) to 2.0 t ha·1 (at Zombwe). Maize grain and stover yields (3.6 t ha- I and 6.8 t ha- I ) were highest and differed
significantly where maize was fertilized with the hybrid maize. area specific fertilizer recommendation compared
with other treatments. For the non-fertilized plots, maize following mucuna had the highest grain and stover yields of
1.5 and 3.5 t ha- I respectively. Total N yield for both grain and stover followed the trend of maize yield. Nitrogen concentration
in the grain was not significantly different between treatments. These results indicate that resource poor
farmers with abandoned fields who cannot afford fertilizers would benefit by using green manure improved fallows compared
to continuous cropping with maize or leaving the field to a natural fallow.
Key words: Mucuna, maize rotation, short fallow, area specific fertilizer recommendation, smallholder farm, rehabilitation
Introduction
Results from initial assessments of the mucuna-maize
rotation system conducted on-farm and on station in
Malawi from 1997/98 to 1999/2000 showed that
maize yields following unfertilized MUClma
(Kalongonda) were significantly higher than maize
yields after continuous unfertilized maize (up to 3.5 t
ha- 1 vs. 1 t ha- 1 ) (Sakala et al. 2000; Gilbert and Kumwenda,
2001; Sakala et al. 2001; Sakala and Mhango,
2003). Tlle results showed that Mucuna could be a
good alternative source of fertilizer for maize production
in Malawi for farmers who cannot afford fertilizer.
In the same work, it was clear that the best way to
manage mucuna in a maize based cropping system is
through rotation rather than intercropping or relay
cropping of mucuna with maize. The objectives of the
new work descr:ibed here were to i) demonstrate to
more farmers that mucuna can be used for rehabilitating
smallholder farms, ii) collaborate with Non Governmental
Organizations (NGO) on scaling up this
promising technology and iii) measure the yield and
nutrient benefits of the technology on farms.
Materials and methods
The experiment was initiated in the 1999/2000 season
in Ntheu, Kasungu, and Vibangalala Extension
Plarming Areas (EPA) in Lilongwe, Kasungu and
Mzuzu ADDs. The soil characteristics at the sites are
in Table 1. In the first season (~000/2001), two treatments
were planted with maize, which was either
fertilized or not fertilized, and the other two treatments
were either planted to a one year improved
fallow of mucuna or left to a natural fallow. In the
second season (2001/2002), maize without fertilizer
was planted to all the four plots, except the first
treatment where fertilized maize followed fertilized
maize. Crop residues were incorporated at the end
of the first season.
The four treatments were arranged in a randomized
complete block, with farmers as replicates. Each plot
comprised of 10 rows spaced at 90 cm and 10 m
long. Maize seed was planted at 37000 plants per ha
(0.9 m x 0.9 m x 3 plants). The sale crop of maize
received 35:10:0+2S (N:P20s+S) per hectare from
23:21:4S as a basal fertilizer, and from urea as atop
dressing. Maize yield was determined by harvesting
four middle rows (each 9.1 m long) of each plot, and
the yield was adjusted to 12.5% moisture content.
Mucuna was planted at 74407 seeds per hectare (90
m x 15 m x 1 plant) in 2000/2001. Maize yields were
analyzed using GENST AT (Payne, 1978). Analysis
of variance was the main procedure used for testing
significances of differences between means.
Grain Legumes and Green Manures for Soil Fertility in Southern Africa 161