Crop Productivity and Nutrient Dynamics in a Shrub (Guiera senegalensis)–Based Farming System of the Sahel

Abstract

Piliostigma reticulatum (DC.) Hochst., an indigenous shrub, forms an important vegetative component of parkland cropping systems in the Sahel; however, its biophysical interactions with soil and crops are not well understood. Therefore, the objectives were to determine the impact of P. reticulatum, under varying fertilizer rates, on crop yield response and soil nutrient dynamics. The experiment had a split‐plot factorial design, where the main plot was shrub (presence or absence) and the subplot was fertilizer rate (0, 0.5, 1.0, or 1.5 times the recommended N–P–K fertilizer rate) applied to a peanut (Arachis hypogaea L.)–pearl millet [Pennisetum glaucum (L.) R. Br.] rotation. In 3 of the 4 yr, P. reticulatum improved or had no effect on crop yields when averaged across fertilizer rates. Overall, millet and peanut biomass and N and P uptake by millet increased in the presence of shrubs and with increasing fertilizer rate. Contrary to P, inorganic N in the soils changed very rapidly, reaching very low levels by the end of the growing season. The N content of soil leachates below the rooting zone was generally lower beneath than outside the shrub canopy, suggesting that the shrub conserves N that is otherwise lost through leaching. Piliostigma reticulatum increased particulate organic matter, indicating that this shrub improved soil quality. These results suggest that P. reticulatum, under nonthermal management and a higher density than typically found in farmers’ fields, has ecological benefits with improved soils and reduced loss of N, which has implications throughout the Sahel.

Association of Shifting Populations in the Root Zone Microbiome of Millet with Enhanced Crop Productivity in the Sahel Region (Africa)

“…Millet growth promotion was observed at both study sites in plots intercropped with woody shrubs. For the Keur Matar site, the results of this study are consistent with previous findings (9) in which millet (and groundnut) grown in the presence of G. senegalensis had substantially greater yields over 4 cropping seasons than sole crops. In that study, the application of an intercropping system with the addition of shrub residue took 4 cropping seasons to build the soil organic carbon and alter soil nutrient status.…”

“…This study has shown that intercropping and shrub residue application can have a substantial effect on microbial communities, with individual OTUs expressing high levels of enrichment in intercropping systems (9,10). Moving forward from these associations between individual OTUs and plant health status to the identification of microorganisms which might provide beneficial functions for improved crop growth will require the isolation and functional characterization of strains corresponding to the OTUs identified here.…”

“…Rhizosphere soils around amended shrubs show increased nutrient content (6), improved soil moisture profiles due to hydraulic lift (7), and a more diverse and complex microfauna soil food web (8). Intercropping with G. senegalensis (9) and P. reticulatum (10), with the incorporation of shrub residue, has also been shown to improve crop yields at two long-term field sites in Senegal.…”

The native shrub, Piliostigma reticulatum , as an ecological “resource island” for mango trees in the Sahel

“…Agroforestry, where woody species are allowed to grow in cropped fields, is an approach that improves soils (Lorenz and Lal, 2014;Dossa et al, 2010Dossa et al, , 2009Dossa et al, , 2008, protects against water and wind erosion (Sileshi et al, 2011), and can increase crop yields (Dossa et al, , 2012Sileshi et al, 2012); benefits that collectively increase resilience to climate change, particularly in sub-Saharan Africa (Lasco et al, 2014). Here, farmers have long practiced what is called the parkland system where trees are randomly distributed in fields.…”

“…Hochst. (Fabaceae) -have been shown to have higher soil quality (Dossa et al, 2012 conferring improved crop yields (Dossa et al, 2012 compared to soils where shrubs are absent. Additionally, Kizito et al (2012) showed that G. senegalensis and P. reticulatum perform hydraulic lift; the passive movement of water from relatively moist areas to drier areas in the soil (Caldwell et al, 1998).…”