Effect of different manure application rates on the nutritional composition of yam landraces grown under field conditions in Southern Ethiopia

Abstract

Yam is an important tuber crop for food security, income, and medicinal use globally. Its productivity and nutritional quality vary among species and are influenced by agronomic practices such as manure application. This study evaluated the effect of different manure rates on the nutritional composition of six yam landraces under field conditions in Ethiopia from 2023 to 2024. A Randomized Complete Block Design was used with five treatments: control (0 tons/ha), T 1 (10 tons/ha), T 2 (20 tons/ha), T 3 (30 tons/ha), and T 4 (40 tons/ha) of manure, each replicated three times. Proximate analyses (protein, fiber, ash, fat, carbohydrate, and energy) were conducted, and data were analyzed using two-way ANOVA, with mean separation by Tukey’s HSD at p < 0.05. Results showed significant differences ( p < 0.05) in nutritional composition among manure treatments and landraces. Protein content increased with higher manure rates, indicating a significant interaction between manure application and yam landraces proximate composition. Overall, moderate manure rates; T2 (20 tons/ha) to T 3 (30 tons/ha) produced the highest nutritional values. Specifically, Duurundufa, Gebsh, Afri, Ayno, and Qekila recorded highest values for protein (6.75%), fat (3.20%), fiber (7.30%), ash (5.30%), and carbohydrate (72.0%), respectively. These five landraces are recommended for breeding and germplasm conservation due to their superior nutritional profiles and low fat level. Organic manure improved protein content in tuber crops, which are typically high in carbohydrates but low in protein, a critical nutrient in resource-limited regions like Ethiopia. The findings support sustainable manure management to enhance yam productivity and nutritional quality. However, variation among landraces suggests the need for further research across diverse agro-ecologies to optimize manure rates and improve nutritional outcomes in future research settings recommended.