Evaluating Alternative ISFM Practices on Soil Fertility, Crop Productivity, Soil Carbon Stock, and Nutrient Balances in Humid Highland of Central Ethiopia
No Thumbnail Available
Date
2025-02
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Addis Ababa University
Abstract
Smallholder farmers in the Dire and Legedadi watersheds face challenges with declining soil fertility and crop productivity exacerbated by limited adoption of integrated soil fertility management (ISFM) practices. Therefore, the main objective of this PhD work was to explore the effect of ISFM practices on crop yields, soil fertility, soil C stock and soil NPK balance. The study included eight treatments (sole wheat, sole faba bean, wheat with 100% recommended NPS, wheat with 100% recommended VC, wheat with 50% recommended rate NPS and 50% VC, wheat and faba bean intercropping with 50% recommended NPS and 50% VC, wheat and faba bean intercropping with 50% NPS, and wheat and faba bean intercropping with 50% VC). In NPS added treatments Urea fertilizer was applied as a supplemental dose to satisfy the N recommendation. The treatments were tested in two farmers' fields using a randomized complete block design with three replications for two consecutive rain-fed cropping years (2021-2022). Crop productivity was evaluated by grain yield and biomass yield explained by partial budget/economic analysis using marginal rate of return (MRR). Intercropping indices, including the land equivalent ratio (LER), crowding coefficient, and system productivity index, were assessed. Selected soil physicochemical properties were determined following standard protocols, and soil carbon stock, nitrogen stock, and carbon sequestration were calculated according to Donvan’s equation. The MonQI toolbox was used to analyze full and partial nutrient balances. The data were subjected to analysis using SAS/STAT software. The highest mean wheat grain yield (4000 kg ha-1 at Dire and 4151.7 kg ha-1 at Legedadi and straw yields (8827.7 kg ha-1 at Dire and 8548.3 kg ha-1 at Legedadi) were obtained from the application of a full dose mineral fertilizer. Wheat faba bean intercropped treatments exhibited the highest net benefits of (USD 5598.1ha-1, 5690.8 ha-1) at Dire and Legedadi sites, respectively. The combined application of VC and NPS fertilizers resulted in higher agronomic efficiency of N (40% and 42%), and LER 1.89 and 1.76 at Dire and Legedadi sites, respectively. These treatments also significantly (p< 0.01) increased total nitrogen (TN), available phosphorus (Pav), exchangeable bases (Ca2+, Na+, and Kexc), and Cation exchange capacity. The results revealed significant variations of soil chemical properties between Dire and Legedadi sites for the TN (p=0.003), Pav (p=0.0001), Kexc (p=0.0001), and SOC (p=0.001). The application of a full dose of VC resulted in the highest soil carbon stock and carbon sequestration at both sites. Wheat-faba bean intercrop showed a greater NPK deficit, attributed to the higher nutrient uptake by both the wheat and faba bean crops. Combined fertilizers application had better PK balances than the sole application of mineral fertilizer.
Description
Keywords
Crop Productivity, ISFM, Intercropping, Nutrient Balance, Monqi Toolbox, Soil Fertility, Soil Carbon and Nitrogen Stock