%O The authors are grateful to E George for his constructive
comments, to A Moussa,MBachir, A Thiombiano
and I Oumarou for their technical help at sampling and
sample analysis, to H Traoré (INERA, Burkina Faso)
and ICRISAT Sahelian Centre for logistical support
and to the Deutsche Forschungsgemeinschaft (DFG)
and the Gesellschaft für Technische Zusammenarbeit
(GTZ) for funding.
%K cowpea, cropping systems, groundnut, pearl millet, sorghum
%A M Bagayoko
%A A Buerkert
%A G Lung
%A A Bationo
%A V Romheld
%I Kluwer
%V 218
%L icrisat1919
%J Plant and Soil
%N 1-2
%P 103-116
%D 2000
%X Yield increases of cereals following legumes in rotation have been previously reported for West Africa, but little
progress has been made to explain the mechanisms involved. At four sites in Niger and Burkina Faso, field trials
with pearl millet (Pennisetum glaucum (L.) R. Br.), cowpea (Vigna unguiculata (L.) Walp), sorghum (Sorghum
bicolor (L.) Moench) and groundnut (Arachis hypogaea L.) were conducted from 1996 to 1998 to investigate
the role of soil mineral nitrogen (Nmin), native arbuscular mycorrhizae (AM) and nematodes in cereal/legume
rotations. Grain and total dry matter yields of cereals at harvest were increased by legume/cereal rotations at
all sites. Soil Nmin levels in the topsoil were consistently higher in cereal plots previously sown with legumes
(rotation cereals) compared with plots under continuous cereal cultivation. However, these rotation effects on
Nmin were much larger with groundnut than with cowpea. Roots of rotation cereals also had higher early AM
infection rates compared to continuous cereals. The dominant plant-parasitic nematodes found in all experiment
fields were Helicotylenchus sp., Rotylenchus sp. and Pratylenchus sp. In sorghum/groundnut cropping systems,
nematode densities were consistently lower in rotation sorghum compared to continuous sorghum. Continuous
groundnut had the lowest nematode densities indicating that groundnut was a poor host for the three nematode
groups. In millet/cowpea cropping systems with inherently high nematode densities, crop rotations barely affected
nematode densities indicating that both crops were good hosts. These results suggest that on the nutrient poor
Sudano-Sahelian soils of our study, total dry matter increases of rotation cereals compared with continuous cereals
can be explained by higher Nmin and AM infection levels early in the season. The site-specific magnitude of these
effects may be related to the efficiency of the legume species to suppress nematode populations and increase plant
available N through N2-fixation.
%T Cereal/legume rotation effects on cereal growth in Sudano-Sahelian West Africa: soil mineral nitrogen, mycorrhizae and nematodes