Legume–maize Rotation or Relay? Options for Ecological Intensification of Smallholder Farms in the Guinea Savanna of Northern Ghana

Abstract

SUMMARYSoil 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 N 2 -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, soybeanmaize, 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 N 2 -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.

Growth, Yield and Nutritional Performance of Sweet Sorghum and Legumes in Sole and Intercropping Influenced by Type of Legume, Nitrogen Level and Air Quality

“…Intercropping provides alternatives and multiple advantages with increasing efficiencies of land use [1], solar radiation [2], irrigation water [3], and nitrogen [4]. Cereals combined with legumes in intercropping increases total productivity per unit area and improves quality of output [5,6].…”

Improvement of Maize Productivity and N Use Efficiency in a No-Tillage Irrigated Farming System: Effect of Cropping Sequence and Fertilization Management

“…The effect of variable legume-cereal crop sequences on the yielding potential of the terminal maize crop in a rotation is well documented by several researchers [ 11 , 16 , 17 ], yet it is greatly dependent on the species and order of the break crops in the sequence. Legume crops are recognized with three main functions in the cropping sequences: (1) provide protein-rich food and feed, (2) supply N to the system through the symbiotic N 2 fixation, and (3) maintain the essential diversification to the cropping system (as break crops) that would uplift the productivity of the system, compared to cereal-cereal rotations [ 40 ].…”

“…This adds value to the inclusion of soybean in the crop sequences and suggests that the positive effects associated with CS5 were most probably because of the inclusion of soybean rather than the late sown faba bean. [ 11 ], highlighted the positive impact of the preceding soybean crop in increasing the yield of succeeding maize crop, through increasing the N uptake in maize, to the extent that N became a non-limiting factor in maize productivity. Similar results were reported by [ 10 ], who documented the significant effect of soybean, occupying different sequential orders in rotation with cereals, on the performance of the succeeding maize crop.…”

“…In addition, it contributes to weed and pest control [ 7 ] and improves the soil’s physical and nutritional qualities by reducing soil erosion, improving soil water holding capacity [ 8 ], and fortifying the soil organic matter [ 9 , 10 ]. The presence of both cereals and legumes is very common in a crop rotation that is designed to enhance productivity and increase the economic value of the farming system [ 11 , 12 ].…”

“…Crop rotation is identified as one of the most important factors affecting maize yield [ 15 ]. The significant influence of the preceding crops in determining maize growth and productivity is well documented in many parts of the world [ 11 , 16 , 17 ]. However, few studies have been conducted on the effect of crop rotation on maize yield under arid irrigated conditions [ 18 ].…”