LEGUME–MAIZE ROTATION OR RELAY? OPTIONS FOR ECOLOGICAL INTENSIFICATION OF SMALLHOLDER FARMS IN THE GUINEA SAVANNA OF NORTHERN GHANA
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Date
2018
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Cambridge University Press
Abstract
Soil nutrient constraints coupled with erratic rainfall have led to poor crop yields and occasionally to crop
failure in sole cropping in the Guinea savanna of West Africa. We explored different maize-grain legume
diversification and intensification options that can contribute to mitigating risks of crop failure, increase
crop productivity under different soil fertility levels, while improving soil fertility due to biological N2-
fixation by the legume. There were four relay patterns with cowpea sown first and maize sown at least
2 weeks after sowing (WAS) cowpea; two relay patterns with maize sown first and cowpea sown at least
3 WAS maize in different spatial arrangements. These were compared with groundnut-maize, soybean–
maize, fallow-maize and continuous maize rotations in fields high, medium and poor in fertility at a site
each in the southern (SGS) and northern (NGS) Guinea savanna of northern Ghana. Legumes grown
in the poorly fertile fields relied more on N2-fixation for growth leading to generally larger net N inputs
to the soil. Crop yields declined with decreasing soil fertility and were larger in the SGS than in the
NGS due to more favourable rainfall and soil fertility. Spatial arrangements of relay intercrops did not
have any significant impact on maize and legume grain yields. Sowing maize first followed by a cowpea
relay resulted in 0.18–0.26 t ha−1 reduction in cowpea grain yield relative to cowpea sown from the onset.
Relaying maize into cowpea led to a 0.29–0.64 t ha−1 reduction in maize grain yield relative to maize sown
from the onset in the SGS. In the NGS, a decline of 0.66 and 0.82 t ha−1 in maize grain yield relative to
maize sown from the onset was observed due to less rainfall received by the relay maize. Groundnut and
soybean induced 0.38–1.01 t ha−1 more grain yield of a subsequent maize relative to continuous maize,
and 1.17–1.71 t ha−1 more yield relative to relay maize across both sites. Accumulated crop yields over
both years suggest that sowing maize first followed by cowpea relay is a promising ecological intensification
option besides the more common legume–maize rotation in the Guinea savanna, as it was comparable with
soybean–maize rotation and more productive than the other treatments.
Description
This article is Published by Cambridge University Press, 2018 and is also available at doi:10.1017/S0014479718000273
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Citation
Expl Agric. (2019), volume 55 (5), pp. 673–691