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Teff is the most dominant staple cereals in Ethiopia, but yield levels are extremely low (1.2 t/ha) because of declining soil fertility, resulting in widespread national food insecurity. The aim of this study was to explore the effect of potassium (K) fertilization on teff yield and nutrient uptake in Vertisols in the central highlands of Ethiopia. Five levels of K (0, 30, 60, 90, and 120 K2O kg/ha) were applied as muirate of potash (KCl) arranged in RCBD with three farm fields as replicates. At crop maturity, a plot of 3 m × 3 m was harvested to measure teff yield and yield components and subsampled for laboratory analysis to determine nutrient uptake. Results showed a highly significant (p < 0.01) response of teff to K fertilizer application and significant differences among locations. When averaged across locations, the highest mean grain (1,875 kg/ha) and straw yields (6,774 kg/ha) were obtained with the application of 90 and 120 kg K2O/ha, respectively. However, the lowest grain (1,576 kg/ha) and straw (5,798 kg/ha) yields were harvested from control plots. This is about a 20% increase over the control. When averaged for all treatments, the highest mean grain (2,641 kg/ha) and straw (7,794 kg/ha) yields were obtained at Moretina Jiru and the lowest grain (1,280 kg/ha) and straw (4,210 kg/ha) yields were obtained at Sululta. Contrary to the popular view that Ethiopian Vertisols are rich in K, there are sites in the central highlands where K deficiency is limiting teff production. In sites where K-soil level was low and rainfall distribution was adequate, the application of K fertilizer along with the government recommended zinc blend fertilizer – NPSZn: 17.7 N + 35.3 P2O5 + 6.5 S + 2.5 Zn – significantly improves nutrient uptake, agronomic efficiency, and teff yields.

The pectin was extracted using H 2 SO 4 , HNO 3 , and HCl from the pulp of four coffee varieties (Harar, Sidama, Jimma, and Guji) collected from different regions of Ethiopia. The effect of extraction temperature, time, solid-to-liquid ratio, types of acid and coffee varieties on the physiochemical properties and yield of pectin were studied. A maximum pectin yield, which was 12.7 %, was obtained from Harar coffee pulp treated with H 2 SO 4 . The equivalent weight of the extracted pectin varied from 1111 to 1667 g/mol. The methoxyl contents of the extracted pectin ranged from 4.23 to 7.13 %. The degrees of esterification and anhydrouronic acid of the pectin ranged from 53 to 68.5 % and 35.5 to 68.8 %, respectively. The results show the yield and physiochemical properties of the coffee pulp pectin depend on extraction parameters, acid types, and coffee varieties. Moreover, the pectin extracted from coffee pulp showed strong gelling properties., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Pectin was extracted from coffee pulp using 0.1 M H2SO4. The Box Behnken Design based Response surface methodology was applied to optimize pectin yield. The impact of extraction time (45-75 min), temperature (80-100 °C), solid to liquid ratio (SLR) (1:20, 1:27.5, and 1:35), and pH (1.5, 2, and 2.5) on pectin yield were studied. Under optimal extraction conditions (84 °C, 75 min, SLR of 1:20 and pH: 1.5), physical, chemical, structural and antioxidant properties of pectin were examined. The results of the physicochemical analysis are: acetyl value: 1.10 ± 0.05 %, equivalent weight: 1429 ± 54 g/mol, anhydrouronic acid: 57.1 ± 0.9 %, degree of esterification: 78.5 ± 1.8 %, moisture content: 8.5 ± 1.5 % and ash content: 4.3 ± 0.9 %. FTIR analysis indicated the (-OH) peak of pectin was lower and shifted left compared to treated and untreated coffee pulp powder. SEM analysis shows a smoother surface, whereas XRD shows a less amorphous structure of pectin. The total phenolic and flavonoid content of coffee pulp pectin was found to be 26.7 μg Gallic Acid Equivalent/mg and 0.8957 μg Quercetin Equivalent/mg, respectively. Antioxidant analysis showed significant antioxidant properties (IC50 = 642.31 ± 30.43 μg/mL). The predicted and actual pectin yields at the optimal extraction condition were 14.39 and 13.7 %, respectively, with R 2  = 0.95 that indicate the model can represent the experiment. Therefore, achieving a maximum pectin yield with improved antioxidant and other physicochemical qualities ensures that coffee pulp can potentially serve as a viable commercial source of pectin., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)