Variation in wheat yield and soil properties at different landscape positions, nutrient sources, and rates in the tropical cereal-based cropping systems of Ethiopia

Context
There is limited information on how catena features can be used to refine fertiliser recommendations in the undulating landscapes of the east African highlands.

Aims
(1) Determine the effects of landscape positions and soil types on crop-nutrient responses, and rainwater productivity (RWP); and (2) identify wheat yield-limiting nutrients across landscape positions.

Methods
Two sets of on-farm nutrient management experiments with wheat were conducted on foot slope, mid-slope, and hillslope positions over 71 sites in 2016 and 2019. The first experiment were on Vertisols, Nitisols, Regosols, and Cambisols with different levels of N/P2O5, K2O, and SO4. The second experiment were on Vertisols, Nitisols, and Cambisols with different levels of N/P2O5 and Zn.

Key results
NP increased yield across landscape positions. NP × K and NP × S interactions increased total biomass by 5–76%. Zinc × soil type interaction increased total biomass on Vertisols (6%) and Cambisols (9%), but increasing Zn did not improve yield on Nitisols. Zinc × landscape position interaction increased total biomass at foot slope (2%) and mid-slope (13%) positions. Zinc × NP interaction increased biomass yield on Cambisols, Nitisols, and Vertisols. N138P69 significantly increased RWP at foot slope, mid-slope, and hillslope positions. Soil nutrient and water contents decreased with increasing slope regardless of nutrient source and application rate.

Conclusions
Landscape position may be an indicator for targeting site-specific fertiliser recommendations. Farms on hillslopes could be better ameliorated by applying organic amendments with sustainable land management practices.

Implications
Taking into account landscape position can help better manage fertiliser use on undulating land in the east African highlands.