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

Materials and Methods
On farm experiments were carried .out on soils with
different characteristics to cover soils of different
texture, C content, P content, pH and CEC in Zambia
and Zimbabwe. The legumes were planted in a
randomized block design, together with fertilized
and unfertilized maize as treatments.
Zambia
Four legumes, Mucuna, Crotalaria juncea, Glycine max
and Vigna unguiculata, were planted on six farms in
Zambia in Choma, Magoye, Kabwe, Muswishi, Kasarna
and Mungwi. Choma and Magoye are in medium
rainfall areas with annual rainfall of 600-800
mm, while Kabwe and Muswishi were in high rainfall
areas (800-1000 mm annual rainfall), and Kasarna
and Mungwi receive 1000-1200 mm rainfall
annually. Kabwe and Misamfu were on sandy
loamy soils, while Mungwi was on a loamy sand
and Muswishi on a sandy clay loam (Table 1). All
the sites had ~ow .contents of available P oH~~ than
7 ).lg P g-I SOlI WIth the exception of Kabwe which
had .40 ).lg P g-I soil available P. CEC was less than
10 cmol+kg-I except for Muswishi, which was on.a
sandy clay loam and had a CEC of 39 cmol+kg-I
(Table 1).
ZImbabwe
The experiment was carried out at 24 sites in two
districts, Murewa and Shurugwi. Murewa was a
high rainfall area, receiving up to 1000 mm rainf~ll
Table 1. Initial soil characterization of Zambian sites
Site pH (KCI) %sand %clay %silt Textural class
Kabwe 6.3 77 9 14 Sandy loam
Misamfu 4.2 70 15 15 Sandy loam
Muswishi 5.5 58 22 21 Sandy clay loam
Mungwi 5.1 82.1 9.8 8.1 loamy sand
apnually while Shurugwi was in a low rainfall area
receiving around 650 mm annual rainfall. Six legumes
were planted; Mucuna, Crotalaria juncea, Crotalaria
grahamiana, Glycine max, Cajanus cajan and Vigna
unguiculata.
The sites in Murewa covered red and black clays,
loamy sands and sands (Table 2). The coarse textured
soils had low C contents with most of the sites
on coarse textures having less than 0.8% C, while
sites on heavier soils had C cQntents of up to 3% C
(Table 2). All the sites in Murewa had low contents
of available P and low. CEC with most of the sites
having less than 3 ).lg P g-I available P and less than
6 cmol+kg-I CEC.
All the sites in Shurugwi were on coarse textured
soils, all with It;sS than 7% clay content (Table 3). pH
at the sites in Murewa averaged around 5.5 (Table
2) and were lower than those in Shurugwi which
had a mean of 7 (Table 3). The sites in Shurugwi
were of low soil fertility status than those in
Murewa and Zambia. Most of the sites in Shurugwi
had less than 0.6% C, 3 ).lg P g-I available P and less
than 3 cmol+kg-1 CEC (Table 3).
Results and Discussion
_Biomass yield of different legumes in Zambia and
Zimbabwe
At all the sites, green manure legumes had larger
biomass yields compared with the grain legumes,
%C %N iJg g"P Mgme% Ca me% Na me% Kme% CEC
1.48 0.11 40 2.3 5 0.9 10.1
0.86 0.06 7 0.8 0.08 0.36 5.8
1.44 6.2 2.3 4.15 0.05 0.48 39.1
0.7 0.03 5 0.7 2.1 0 0.1 5.8
Table 2. Initial soil characteristics of sites in Murewa, Zimbabwe
Farmer pH (H2O) %sand %silt %clay Textural class
Nzvere 5.3 86 6 7 loamy sand
A.Oarare 5.4 32 15 52 Clay
Kwari 5.6 30 20 49 Clay loam
Mutsago 5.4 46 14 37 Sandy clay
Chokurongerwa 5.3 82 6 11 loamy sand
Matambanadzo 5.4 82 6 11 Sand
Mandebvu 5.3 82 6 11 Sand
Kaitano 5.2 84 6 9 loamy sand
Musegedi 5.4 86 6 7 loamy sand
Mugwagwa 5.3 86 6 7 loamy sand
Takarova 5.5 84 6 9 loamy sand
Ndoro 5.6 42 16 41 Clay
B.Oarare 5.5 32 18 49 Clay
Gwara 5.5 46 20 33 Sandy clay loam
%C %N iJg g'P Mg me% Ga me% Na me% Kme% CEC
0.44 0.08 2.12 0 0.1 0.03 ·0 0.13
1.98 0.17 2.27 0.89 1.35 0.05 0.04 2.33
2.28 0.21 2.07 0.87 1.53 0.03 0.05 2.48
1.26 0.11 2.02 0.87 1.35 0.05 0.05 2.32
0.46 0.08 2.02 0.01 0.09 0.03 . 0 0.13
0.77 0.11 2.96 0.11 0.37 0.08 0.03 0.59
0.7 0.1 3.11 0.07 0.26 0.02 0.02 0.37
0.45 0.07 2.57 0 0.05 0.02 0 0.07
0.39 0.08 2.22 0.01 0.06 0.03 0 0.1
0.64 0.14 1.63 0 0.06 0.02 0 0.08
0.49 0.07 2.81 0.04 0.22 0.04 0 0.3
3.06 0.27 1.63 2.45 2.92 0.04 0.03 5.44
2.96 0.26 3.56 2.78 3.61 0.05 0.04 6.48
2.81 0.38 1.78 1.59 2.29 0.06 0.02 3.96
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Grain legumes and Green Manures for Soil Fertility in Southern Africa