M L Kusekwa, R S Kyamanywa and M D Ngowi
Livestock Production Research Institute (LPRI)
Ministry of Agriculture
PO Box 202, Mpwapwa, Tanzania
ABSTRACT
Forage legumes were grown as intercrops with maize, sorghum and bullrush millet, and maize was planted in alleys of Leucaena for two growing season (1988/89 and 1989/90) at Mpwapwa, Tanzania. The objective was to determine the best entry points of these legumes into the crop-livestock systems of semi-arid Tanzania.
Cereal grain yields were not significantly depressed by the presence of forages, pointing to the possibility of introducing forages to the cereal-cropping systems existing in semi-arid Tanzania, through such methods as intercropping and alley cropping.
RESUME
Introduction de légumineuses fourragères dans les systèmes agraires de la zone semi-aride en Tanzanie
Des essais ont été effectués en vue de déterminer la meilleure manière d'introduire des légumineuses dans les systèmes agraires mixtes de la zone semi-aride de la Tanzanie. Dans le cadre de ces travaux, des légumineuses fourragères ont été intercalées entre des cultures de mais, de sorgho et de mil chandelle et du mais a été semé entre des haies de Leucaena pendant deux saisons de croissance (1988/89 et 1989/90) à Mpwapwa (Tanzanie).
Il ressort des résultats enregistrés que la présence de plantes fourragères n'entraînait aucune baisse significative de la production de céréales, ce qui signifie que l'on peut introduire ces espèces végétales dans les systèmes à base de céréales de la zone semi-aride de la Tanzanie en utilisant la technique des cultures intercalaires ou en couloirs.
INTRODUCTION
It is common practice, in semi-arid Tanzania, for grazing lands to be taken for crop growing and so for livestock production to be pushed out to poorer, less productive lands, where rainfall is unreliable. In these areas, sound land-use practices, aimed at economically using the land resources at a sustainable level, need to be developed and employed. One such practice is to produce more good quality forage feed within the existing crop-livestock systems.
Forage legumes have played an important role in raising the productivity of farming in temperate areas, a role which has yet to be clearly demonstrated for the tropics. The primary role of the legumes is fixation of atmospheric nitrogen; this leads to improved soil fertility, enhanced forage and mulching quality (Tothill, 1986), and also to a supply of high quality feed for ruminants. In Tanzania, semi-arid areas are characterised by small-scale mixed crop-livestock farming systems. In such systems, forage legumes could be integrated into both the crop and the livestock components. In the crop phase, legumes can reduce the rate of decline of soil fertility, or even enhance crop yields, and can also reduce the length of the fallow period. In the pastoral phase, legumes contribute to better quality and use of crop residues and of natural forages on fallow land (Kusekwa, 1990).
This paper discusses the testing of best-bet legumes for semi-arid Tanzania under two cropping systems with a view to determining their possible entry points into the crop-livestock farming systems in the area.
MATERIALS AND METHODS
The work was carried out at the Livestock Production Research Institute, Mpwapwa, Tanzania (6° 20' S; 36° 30' E; altitude 1100 m). Annual rainfall here is 700 mm, with 90% of the rain falling during December-April. Maximum and minimum temperatures are 27.5 and 15.5°C, respectively.
The cereals used in the study were varieties of maize, sorghum and millet commonly grown in the area. The maize and sorghum varieties used were early maturing (80 days): the millet (a local variety) took about 100 days to mature.
The legumes used were best-bet forage legumes: Stylosanthes hamata (Verano stylo): S. scabra (Seca stylo); Lablab purpureus (Rongai and Red); Macroptilium atropurpureum (Siratro). Neonotonia wightii (Tinaroo glycine) and Leucaena leucocephala (Peru).
Intercropping trial
The six forage legumes were grown as intercrops with the three cereal crops commonly grown in central Tanzania, during the 1988/89 growing season. The cereals and legumes were planted 30 cm apart, in rows 90 cm apart. The split plot design was used, with the cereals making up the main plots and the legumes the subplots; the control was cereal with no legume. In anticipation of severe competition for nutrients by the intercrops, phosphorus and nitrogen fertilisers were applied as recommended for the area, 40 kg P/ha as triple superphosphate (46% P2O5) and 42 kg N/ha as calcium ammonium nitrate (26% N). Nitrogen was split-applied at active vegetative growth and then at the pre-ear-emergence stages of the cereals.
During the 1989/90 growing season, two legumes were dropped from the study: Rongai lablab because of severe smothering effects on the cereals; and Seca stylo because of its poor survival, caused by termite damage. The established legumes were slashed to ground level before the cereals were sod-seeded at the usual spacing of 30 x 90 cm.
Alley-cropping trial
For the alley-cropping study, an area was selected from a previously established 5-ha Leucaena field, in which rows of Leucaena were spaced 3, 4, 5 and 6 m apart; maize was sown in the alleys at 30 x 90 cm spacing. The rows of Leucaena were cut back to stubble heights of 25, 50 and 75 cm, making the study a four alleys x three cutting heights combination of treatments. Maize was fertilised with phosphorus and nitrogen in the first year of the study (1988/89), but in the subsequent year (1989/90) fertiliser N was withdrawn as fertility build-up was anticipated from the effects of mulching. During the 1989/90 growing season, interface competition was also investigated by looking at yields of grain and stover in relation to distances of the maize rows from the Leucaena rows.
Statistical analysis
Statistical analysis was performed with Instat (PC version, June 1987: Statistical Service Centre, University of Reading, UK).
RESULTS AND DISCUSSION
Intercropping trial
In 1988/89, grain and stover yields of the different cereals were significantly (P<0.05) different (Table 1). However, the type of cereal did not significantly effect legume dry-matter (DM) production, which was about 3 t/ha in each case. Millet and sorghum yielded higher (P<0.05) total forage (stover + legume herbage) than maize. The trends in yield of cereal grain and stover and legume forage during the 1989/90 growing season were similar to those in the 1988/98 growing season.
Table 1. Effects of intercropping forage legumes cereals on grain-stover and legume herbage yields, 1988/89 and 1989/90 growing seasons
|
Cereal |
Yield (t/ha) |
||||
|
Cereal grain (air dried) |
Cereal stover (DM) |
Legume herbage (DM) |
Total forage (stover + legume) (DM) |
||
|
1988/89 growing season |
|||||
|
|
Maize |
5.6 |
3.9 |
3.2 |
7.1 |
|
|
Sorghum |
2.0 |
5.0 |
3.4 |
8.4 |
|
|
Millet |
3.7 |
5.7 |
3.2 |
8.9 |
|
|
Mean |
3.77 |
4.87 |
3.27 |
8.07 |
|
|
LSD (5%) |
0.69 |
0.64 |
ns |
133 |
|
1989/90 growing season |
|||||
|
|
Maize |
4.5 |
3.4 |
3.5 |
6.9 |
|
|
Sorghum |
3.1 |
5.5 |
2.9 |
8.4 |
|
|
Millet |
3.9 |
6.0 |
2.9 |
8.9 |
|
|
Mean |
3.83 |
4.97 |
3.10 |
8.07 |
|
|
LSD (5%) |
0.59 |
0.79 |
0.46 |
1.41 |
The grain yield did not seem to be depressed by the presence of intercrops as the yields were high compared with the area averages which, according to the Mpwapwa District Agricultural Officer, are 3.0 t/ha for maize, 1.5 t/ha for sorghum and 2.5 t/ha for millet. This result points to the possibility of introducing forages to the cereal cropping systems of the area, especially dual-purpose legumes such as lablab. Traditionally, agropastoralists in this area usually intercrop cereals with grain legumes. This could be realised if and when farmers can be shown that overall productivity of the land is increased when forage from stover and legume is put to proper use such as maintaining a productive animal.
Table 2 shows the effects of forage legumes on grain and stover yields and legume herbage production when intercropped with cereals. Rongai lablab appeared to depress grain yield of the cereals the most, probably as a result of smothering effects of the lablab on any companion plants, while Siratro and Verano and Seca stylo seemed to enhance grain yield, which indicated that there was some soil fertility build-up in plots under these legumes. In general, the more DM produced by the legume the more the depressing effect on grain yield.
It is evident that the inclusion of forage legumes in cereal plots led to increased quantity and quality of the total forage (stover + legume herbage) produced. Stovers alone had an average crude protein (CP) content of 2.4% while legumes averaged 13.9% CP. Such an improvement in the quantity and quality of the feed resource is seen as the key to improved nutrition of the ruminant livestock during the extended dry season of six to seven months in semi-arid central Tanzania.
Table 2. Effects of forage legumes on grain, stover and legume-herbage yields when intercropped with cereals, 1988/89 and 1989/90 growing seasons
|
Cereal |
Yield (t/ha) |
||||
|
Cereal grain (air dried) |
Cereal stover (DM) |
Legume herbage (DM) |
Total forage (stover + legume) (DM) |
||
|
1988/89 growing season |
|||||
|
|
No legume |
3.7 |
5.1 |
- |
5.1 |
|
|
Verano stylo |
4.2 |
5.8 |
1.0 |
6.8 |
|
|
Lablab (red) |
3 4 |
5.1 |
2.1 |
7.2 |
|
|
Lablab (Rongai) |
2.8 |
4.3 |
9.8 |
14.1 |
|
|
Siratro |
4.2 |
5.8 |
4.7 |
10.5 |
|
|
Tinaroo glycine |
3.7 |
5.2 |
1.1 |
6.3 |
|
|
Seca stylo |
4.1 |
5.6 |
1.0 |
6.6 |
|
|
Mean |
3.73 |
5.14 |
3.28 |
8.09 |
|
|
LSD (5%) |
0.25 |
ns |
0.93 |
0.78 |
|
1989/90 growing season |
|||||
|
|
No legume |
3.6 |
5.3 |
- |
5.3 |
|
|
Verano stylo |
4.2 |
5.3 |
1.7 |
7.0 |
|
|
Lablab (red) |
3.4 |
5,0 |
3.0 |
8.0 |
|
|
Siratro |
4.3 |
5.0 |
4.9 |
9.9 |
|
|
Tinaroo glycine |
3.5 |
4.8 |
3.3 |
8.1 |
|
|
Mean |
3.80 |
5.10 |
3.10 |
7.66 |
|
|
LSD (5%) |
0.23 |
ns |
0.52 |
0.91 |
Further work is needed on some aspects of soil fertility build-up and animal feeding in order to determine the extent of improvement in productivity when forage legumes are introduced into the crop-livestock farming systems of semi-arid Tanzania.
Alley-cropping trial
Table 3 shows the effects of the width of Leucaena alleys on maize grain and stover yields and Leucaena leaf-meal production. Grain yield tended to increase with increase in alley width, but the increases were not significant. During the 1989/90 growing season grain and stover yields were lower than in the previous year. The lower yields could be attributed to withdrawal of fertiliser nitrogen.
Table 3. Effects of width of alleys Leucaena on maize grain and stover yields and Leucaena leaf-meal production, 1988/89 and 1989/90 growing seasons
|
Alley width (m) |
Yield (t/ha) |
|||||
|
Maize grain (air dried) |
Maize stover (DM) |
Leucaena leaf meal (DM) |
||||
|
1988/89 |
1989/90 |
1988/89 |
1989/90 |
1988/89 |
1989/90 |
|
|
Control |
4.3 |
2.71 |
6.8 |
4.00 |
- |
- |
|
3 |
2.8 |
2.53 |
4.7 |
3.48 |
3.0 |
3.60 |
|
4 |
2.7 |
2.41 |
5.0 |
2.10 |
2.5 |
3.20 |
|
5 |
3.0 |
2.65 |
5.5 |
3.28 |
2.3 |
3.00 |
|
6 |
4.0 |
2.52 |
6.9 |
2.99 |
2.1 |
3.10 |
|
SE |
0.55 |
0.30 |
0.62 |
0.34 |
0.37 |
0.39 |
Increases in Leucaena stubble height tended to progressively decrease maize grain and stover yields (Table 4), but the effects were not significant. The effects of distance of maize rows from Leucaena alleys were not clear (Table 5).
Table 4. Effects of stubble height of Leucaena rows on maize grain and stover yields, 1989/90
|
Leucaena stubble height (cm) |
Yield (t/ha) |
|
|
Maize grain (air dried) |
Maize stover (DM) |
|
|
Control |
2.71 |
4.00 |
|
25 |
2.66 |
3.06 |
|
50 |
2.48 |
3.10 |
|
75 |
2.44 |
3.39 |
|
SE |
0.26 |
0.30 |
Table 5. Effects of distance of maize rows from Leucaena on maize grain and stover yields, 1989/90
|
Distance from Leucaena rows (cm) |
Yield (t/ha) |
|
|
Maize grain (air dried) |
Maize stover (DM) |
|
|
Control |
2.71 |
4.00 |
|
90 |
2.49 |
3.16 |
|
180 |
2.56 |
3.21 |
|
SE |
0.22 |
0.24 |
These results indicate that it is feasible to introduce Leucaena into the cropping system, using the alley-cropping approach. The additional production (forage) from the Leucaena rows could serve to supply mulch and supplement forage feed, particularly during the dry season.
CONCLUSIONS
Results from these two cropping studies, intercropping and alley cropping, show that including legumes in the cropping systems in semi-arid central Tanzania can increase the productivity of these systems. Grain as well as fodder for mulch and livestock feed are produced with negligible or no adverse effects on grain yield. It would be even more useful if dual-purpose legumes, such as lablab, were used. Screening for more suitable multipurpose legumes is required to cater for fitting legumes into the cropping systems. The total produce would then include grain from both cereals and legumes, forage, stover and nitrogen from N-fixation.
ACKNOWLEDGEMENTS
We acknowledge the support of the International Development Research Centre and the International Livestock Centre for Africa, through the Pasture Network for Eastern and Southern Africa, in funding these studies. We are also grateful for the assistance given by scientific and technical staff of the Livestock Production Research Unit, notably R N Hero, C R Ulime and Ms T S R Mrema for data processing and analysis, and R R Chibindu for typing the manuscript.
REFERENCES
Kusekwa M L. 1990. Pastures and forages. National agriculture and livestock research masterplan. Ministry of Agriculture and Livestock Development, Tanzania. 27 pp.
Tothill J C. 1986. The role of legumes in farming systems of sub-Saharan Africa. In: Haque I, Jutzi S and Neate P J H (eds), Potentials of forage legumes in farming systems of sub-Saharan Africa. Proceedings of a workshop held at ILCA, Addis Ababa, Ethiopia, 16-19 September 1985. ILCA (International Livestock Centre for Africa), Addis Ababa, Ethiopia. pp. 162-185.
