A comparison between legume technologies and fallow, and their effects on maize and soil traits, in two distinct environments of the West African savannah

Abstract

Legume-maize rotation and maize nitrogen (N)-response trials were carried out simultaneously from 1998 to 2004 in two distinct agro-ecological environments of West Africa: the humid derived savannah (Ibadan) and the drier northern Guinea savannah (Zaria). In the N-response trial, maize was grown annually receiving urea N at 0, 30, 60, 90 and 120 kg N ha -1. In Ibadan, maize production increased with N fertilization, but mean annual grain yield declined over the course of the trial. In Zaria, no response to N treatments was observed initially, and an increase in the phosphorus (P) and sulphur (S) fertilizer application rate was required to increase yield across treatments and obtain a response to N applications, stressing the importance of non-N fertilizers in the savannah. In the rotation trial, a 2-year natural fallowmaize rotation was compared with maize rotated with different legume types: green manure, forage, dualpurpose, and grain legumes. The cultivation of some legume types resulted in a greater annual maize production relative to the fallow-maize combination and corresponding treatments in the N-response trial, while there was no gain in maize yield with other legume types. Large differences in the residual effects from legumes and fallow were also observed between sites, indicting a need for site-specific land management recommendations. In Ibadan, cultivation of maize after the forage legume (Stylosanthes guianensis) achieved the highest yield. The natural fallow-maize rotation had improved soil characteristics (Bray-I P, exchangeable potassium, calcium and magnesium) at the end of the trial relative to legume-maize rotations, and natural fallow resulted in higher maize yields than the green manure legume (Pueraria phaseoloides). In Zaria, maize following dual-purpose soybean achieved the highest mean yield. At both sites, variation in aboveground N and P dynamics of the legume and fallow vegetation could only partly explain the different residual effects on maize.

Impacts of heterogeneity in soil fertility on legume-finger millet productivity, farmers’ targeting and economic benefits

“…2) and had stronger effects in the poor fertility fields which were often P deficient (Table 1). Millet yields increased following legumes, as is commonly found in legume cereal cropping systems (Osunde et al 2003;Ncube 2007;Franke et al 2008). The yield responses were larger when larger amounts of legume biomass were incorporated.…”

Nitrogen rhizodeposition from soybean (Glycine max) and its impact on nutrient budgets in two contrasting environments of the Guinean savannah zone of Nigeria

“…At both locations, aboveground soybean residues were fed to steers over the dry season and the manure was collected and applied in the field at subsequent planting. Plant residue and manure analyses suggested that the carry-over rate of N from residues at harvest to manure at planting was 0.50 (Franke et al 2008), and this rate was used in N budget (3).…”

“…The crop accumulated 55 kg aboveground N ha -1 . Soybean was heavily infested with diseases in Ibadan (Franke et al 2008) and as a result, biomass production was reduced and leaves prematurely shattered.…”

“…Furthermore, more information is needed on the transfer of rhizodeposited N to the next crop and the influence of management on rhizodeposition and N transfer. This is especially relevant since aboveground legume N dynamics are often poorly correlated with yield dynamics of subsequent cereals (Sanginga et al 2002;Ncube et al 2007;Franke et al 2008).…”

“…Driving factors behind this rapid adoption have been the availability of new, well-adapted, varieties, the high market value of soybean grain, and the positive impact of soybean on subsequent cereal crops. Soybean in rotation may increase maize yield by as much as 140% compared to continuous maize cultivation (Carsky et al 1997;Sanginga et al 2002;Osunde et al 2003;Franke et al 2004Franke et al , 2008. Maize yield gains are largely due to increased soil N availability following soybean cultivation (Giller 2002).…”