Person: Sida, T.S.
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Sida
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T.S.
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Sida, T.S.
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0000-0001-6482-2669 3 results
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- Should fertilizer recommendations be adapted to parkland agroforestry systems? Case studies from Ethiopia and Rwanda(Springer Verlag, 2019) Sida, T.S.; Baudron, F.; Ndoli, A.; Tirfessa, D.; Giller, K.E.Aims This study aimed to disentangle tree-crop fertilizer interactions in agroforestry systems, which has been suggested as an entry point for sustainable intensification of smallholder farming systems in sub-Saharan Africa (SSA). Although tree-crop systems generate multiple economic and ecological benefits, tree-crop competition commonly occurs. We hypothesized that mineral fertilizers affect facilitative and competitive interactions differently in tree-crop systems. Methods Tree-crop-fertilizer interactions were explored for wheat growing under Faidherbia albida, and maize growing under Acacia tortilis and Grevillea robusta through omission trials of nitrogen (N) and phosphorus (P) in open fields and fields under tree canopy, using a split plot design. The experiments were conducted in Ethiopia and Rwanda, replicated four times, and over two seasons. Results Our results demonstrated that the presence of F. albida significantly improved N and P use efficiencies, leading to significantly higher (P < 0.001) grain yields in wheat. This tree species contributed around 64 kg ha−1 yr.−1 of mineral N. The P use efficiency of wheat under F. albida was double that of open field wheat. By contrast, G. robusta and A. tortilis trees lowered nutrient use efficiencies in maize, leading to significantly less maize grain yields compared with open fields receiving the same fertilization. Probabilities of critically low crop yields and crop failure were significantly greater for maize growing under the canopy of these species. Conclusions Our results showed that recommended fertilizer rates led to facilitative interaction only with F. albida, highlighting that fertilizer recommendations need to be adapted to agroforestry systems.
Publication - Excessive pruning and limited regeneration: are Faidherbia albida parklands heading for extinction in the Central Rift Valley of Ethiopia?(John Wiley and Sons, 2018) Sida, T.S.; Baudron, F.; Dejene Adugna Deme; Motuma Tolera; Giller, K.E.Scattered Faidherbia albida trees provide multiple ecological and production benefits across the Sahel. The intensive management and use of this important tree may impede its regeneration. Regeneration bottlenecks were explored and population dynamics modelled. On experimental plots in which seed of F. albida was sown, exposure to the first 2 months of dry season resulted in a quarter of seedling mortality. Exposure to season-long free grazing and browsing caused significantly greater seedling mortality. Results from monitoring 100 permanent plots scattered over the landscape showed that adult population density was 4.2 ± 0.3 (mean ± SE) trees ha?1 and dominated by old age classes. Sixty percent of the total population were older than 30 years. The mean density for juveniles was 1.4 ± 0.2 (mean ± SE) individuals ha?1. The annual rates of decline were 1.2%, 51.3%, and 63.2% for adults, seedlings, and saplings, respectively. Our model predicted that the F. albida population will start to decline within 1?2 decades to eventually fall below 1 tree ha?1 within 60 years under current management. The model highlighted that the limited seed source, caused by excessive pruning, was the main constraint for recruitment. Appropriate land management policy to ensure adequate seed production would avert current trends in decline of F. albida population.
Publication - Conservation agriculture with trees amplifies negative effects of reduced tillage on maize performance in East Africa(Elsevier, 2018) Ndoli, A.; Baudron, F.; Sida, T.S.; Schut, A.G.T.; Heerwaarden, J. van; Giller, K.E.Conservation agriculture (CA) is widely promoted in sub-Saharan Africa both in open fields and in agroforestry where the practice is known as ‘conservation agriculture with trees’ (CAWT). Although advantages and disadvantages of CA are well studied under sole cropping, less is known about its impact in agroforestry systems. The performance of open pollinated maize varieties under CA, CAWT, sole maize under conventional tillage (CT) and conventional tillage with trees (CTWT) was compared on-farm in equatorial savannah areas over four consecutive seasons in Rwanda and two seasons in Ethiopia. The tree species considered in the study were mature Grevillea robusta (A. Cunn.) and Senna spectabilis (DC.) in Rwanda and mature Acacia tortilis (Forssk.) in Ethiopia. Both CA and the presence of trees consistently reduced maize emergence, leaf area (LA), plant height, and maize yields. Crop emergence was significantly reduced under CAWT compared with CTWT. Maize emergence rates in CAWT and CTWT were respectively 46.9% and 70.1%, compared with 74.7% and 79.8% in sole maize under CA and CT. Grain yield in CAWT and CTWT were respectively 0.37 t dry matter (DM) ha−1 and 1.18 t DM ha−1 as compared with 1.65 t DM ha−1 and 1.95 t DM ha−1 in CA and CT. We conclude that CAWT strongly reduces crop yield in the equatorial savannah of East Africa. CA is incompatible with agroforestry under the conditions of our study. There is an urgent need for rigorous research to revisit if, when and where CAWT can generate benefits for smallholder farmers.
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