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

Four rates of fertilizer N were applied to maize in 10
plots previously under maize or the green manure. (a) Namulonge (b) Jlmma, Ethiopia
10
At Namulonge, mucuna and canavalia produced
maize yields equivalent to about 120 kg-Nlha Ii 8
J:
while, at Jimma, sesbania and crotalaria green ma­ =- 8
~
nures were equivalent to >70 kg-N Iha of fertilizer "
(Figure 2).
;;
>. ~
c 6
~ 0
•
'" • •
6
N
Effects of intercropped legumes on maize produc­ "i
"
:I
4
tion
• Mliiu-m.lize
Table 5 summarizes maize response to green ma­
• Selbllnia maize
... Crotolarla-malze
nure intercrops at three on-station sites over several
years. Although maize responded significantly to N o 40 80 120 o 40 80
fertilizer in 4 out of 6 site-years, the legume inter- Fertilizer N rate (kg/ha) Fertilizer N rate (kg/ha)
crop significantly increased the subsequent season's
maize yield in only one instance (crotalaria at Figure 2. Maize response to fertilizer Nrates following maize
Jimma in 2000). Mucuna, canavalia and crotalaria monocrops or green manure rotations in the preceding season, at (a)
intercropped or relayed with maize in regional on Namulonge, Uganda, and (b) Jimma, Ethiopia
station trials at Jimma, Mlingano and Namulonge
generally had no significant effect on
maize yields in the subsequent season Table 5. Effect of green manure ilitercrops and relay crops on maize grain yields§
(Table 5). This was attributed to low legmanaged
(t/ha) sown with the green manure or alone in the subsequent season - researcher
ume biomass production (and hence N
trials on station
fixation) under the shady conditions of Maize·Green manure system Jimma Mlingano Namulonge
the maize canopy. 2000 2001 1999 2000 2001 2000lR
Sole Maize - fertilizer N 4.89 a 1.95 ab 1.28 2.05 a 3.76 3.11 ab
Mixed results of legume intercrops and Sole Maize + fertilizer N§ 6.02 ab 3.15 c 1.77 4.27 b 3.89 4.54 c
relays were obtained in some 56 on-farm Mucuna intercrop' 5.22 ab 1.60 a 2.12 2.74 a 3.49 3.51 b
trials conducted in Northern and East­
Mucuna relay crop# 4.86 a 2.36 b 2.30 2.28 a 2.84 3.14 ab
ern Tanzania during 2000 and 2001
Canavalia intercrop' 5.96 ab 2.25 bc 1.77 2.40 a 2.53 3.94 bc
(Table 6). In some cases, maize yields
Canavalia relay crop# 5.62 ab 1.88 ab 2.26 1.71 a 2.28 2.57 a
were increased by 60-120% (1-2 t/ha)
while' in others no significant effects Crotalaria intercrop' 6.52 b 2.15 ab
were obtained. On the positive side, nei­ Crotalaria relay crop# 5.34 ab 1.96 ab
ther did intercropped legumes have any Yields within a column followed by the same letter (or no letter) are not
negative impact on maize yields in these significantly different
trials, although experience in other trials § N rate (kg/ha) - 69 (Jimmal. 50 (Mlingano), 70 (Namulonge);
• planted 2 weeks after maize
has found considerable competition
# planted 2 weeks after tasselling
from legumes such as mucuna if not
properly managed.
Discussion and Conclusions
Table 6. Effect of green manure intercrops or relay crops on yield of maize grain§ (tl
hal sown with the green manure or alone in the subsequent season - on farm trials
During the past five years, the Maize·Green manure Tropicallowland ecology
Dry mid·altitude
ECAMA W research network has identi­ system (intercrop or relay) Ngomeni Tanganyika Mlingano
Hai#
fied and characterized several green ma­ 2000 2000 2000 2001 2000 2001
nure and grain legume species that have No. of f~rms 4 4 18 14 8 8
good biophysical adaptation to the Sole Maize - 0 kg·N/ha 1.82 a 3.30 2.22 1.48 a 0.8 2.2 a
moist mid-altitude and tropical lowland Sole Maize - 25 kg·N/ha 2.49 b 3.86
ecologies of Eastern and Central Africa.
Sole Maize - 50 kg·N/ha 3.28 c 3.19 2.49 2.78 b
In monoculture situations, most of these
Maize/mucuna 2.88 bc 3.57 2.32 2.40·b 1.1 4.1 b
legumes were able to biologically fix N
Maize/canavalia 2.92 bc 3.71 2.49 2.31 b 0.0 4.3
much in excess of a maize crop's re­
b
q~irements. However, in intercropping MaizelDolicos lablab 1.1 4.6 b
situations, biomass production and biological
Maize/calopogonium 2.52 b 3.84
nitrogen fixation was severely # green manures relayed into maize in 2000; maize sown alone in 2001
limited by competition for light and § yields within a column followed by the same letter (or no letter) are not significantly
moisture with the maize crop. Further- different
T
Grain Legumes and Green Manures for Soil Fertility in Southern Africa 117