Influence of landscape position on sorghum yield response to different nutrient sources and soil properties in the semi-arid tropical environment

Understanding the response of crops to nutrient applications in undulating landscapes is imperative to improve nutrient use efficiency and crop yield. This study aimed to identify sorghum yield-limiting nutrients and characterize soil properties targeting landscape positions. The field experiments were conducted across 52 sites in four districts, covering three distinct landscape positions during the 2020 and 2022 cropping seasons. The treatments were All-blended, All- compound, All- individual, 150% of All- blended, All- blended-K, All- blended-S, All-blended-Zn, All -blended-B, recommended NP, 50% of All -blended, and control (no fertilizer). Treatment sequencing was randomized using a complete block design under foot slope (FS), mid-slope (MS), and hillslope (HS) positions. Results revealed that landscape position significantly affected the growth and yield of sorghum. Significantly higher yields were obtained from foot slopes than mid-slope and hillslope positions. Yield response to the application of nutrients significantly decreased with increasing slope. Overall, yield among all landscape positions was in the decreasing order of FS>MS>HS. The application of nutrients at different rates significantly improved sorghum total biomass and grain yield. Raising the all-blended treatment rate by 50% increased sorghum yield by 44% and 147% over the application of 50% of all nutrients and the unfertilized control treatment, respectively. Statistically significant yield differences were not observed among blended, compound, and separate applications of nutrients. The omission of K, S, Zn, and B did not show a significant variation in yield over the recommended NP fertilizer. The results of soil analysis results revealed that N and P are the most commonly deficient nutrients in sorghum-growing areas. The mean average volumetric soil moisture content ranged from 5.9-28.7% across landscape positions, with the highest at the foot slope and lowest at the hillslope position. Further research is suggested to determine economically optimum N and P rates across the three landscape positions

Landscape-based nutrient application in wheat and teff mixed farming systems of Ethiopia: farmer and extension agent demand driven approach

Introduction: Adapting fertilizer use is crucial if smallholder agroecosystems are to attain the sustainable development goals of zero hunger and agroecosystem resilience. Poor soil health and nutrient variability characterize the smallholder farming systems. However, the current research at the field scale does not account for nutrient variability across landscape positions, posing significant challenges for targeted nutrient management interventions. The purpose of this research was to create a demand-driven and co-development approach for diagnosing farmer nutrient management practices and determining landscape-specific (hillslope, mid-slope, and foot slope) fertilizer applications for teff and wheat. Method: A landscape segmentation approach was aimed to address gaps in farm-scale nutrient management research as well as the limitations of blanket recommendations to meet local nutrient requirements. This approach incorporates the concept of interconnected socio-technical systems as well as the concepts and procedures of co-development. A smart mobile app was used by extension agents to generate crop-specific decision rules at the landscape scale and forward the specific fertilizer applications to target farmers through SMS messages or print formats. Results and discussion: The findings reveal that farmers apply more fertilizer to hillslopes and less to mid- and foot slopes. However, landscape-specific fertilizer application guided by crop-specific decision rules via mobile applications resulted in much higher yield improvements, 23% and 56% at foot slopes and 21% and 6.5% at mid slopes for wheat and teff, respectively. The optimized net benefit per hectare increase over the current extension recommendation was $176 and$333 at foot slopes and $159 and$64 at mid slopes for wheat and teff (average of $90 and$107 for wheat and teff), respectively. The results of the net benefit-to-cost ratio (BCR) demonstrated that applying landscape-targeted fertilizer resulted in an optimum return on investment ($10.0 net profit per$1.0 investment) while also enhancing nutrient use efficiency across the three landscape positions. Farmers are now cognizant of the need to reduce fertilizer rates on hillslopes while increasing them on parcels at mid- and foot-slope landscapes, which have higher responses and profits. As a result, applying digital advisory to optimize landscape-targeted fertilizer management gives agronomic, economic, and environmental benefits. The outcomes results of the innovation also contribute to overcoming site-specific yield gaps and low nutrient use efficiency, they have the potential to be scaled if complementing innovations and scaling factors are integrated