
==== Front
Heliyon
Heliyon
Heliyon
2405-8440
Elsevier

S2405-8440(24)13184-2
10.1016/j.heliyon.2024.e37153
e37153
Research Article
Effect of harvesting time on root yield and nutritional composition of orange-fleshed sweet potato [Ipomoea batatas (L.) Lam] varieties in East Hararghe
Bedassa Chala Begna begnachala@gmail.com
chala.begna@ambou.edu.et
a⁎
Gebeyehu Setegn b
Mohammed Wassu c
Gelmesa Dandena d
Neme Getachew e
a Department of Horticulture, Ambo University, Ambo, Ethiopia
b International Potato Center (CIP‐SSA), Addis Ababa, Ethiopia
c Department of Plant Science, Haramaya University, Haramaya, Ethiopia
d Economic Security Department, International Committee of the Red Cross ‐ ICRC, Bole Kifle Ketema, Kebele 13, Addis Ababa, Ethiopia
e Department of Food Science and Postharvest Technology, Haramaya Institute of Technology, Haramaya University, Haramaya, Ethiopia
⁎ Corresponding author. P.O.Box: 19 Ambo, Ethiopia. begnachala@gmail.comchala.begna@ambou.edu.et
30 8 2024
15 9 2024
30 8 2024
10 17 e3715326 3 2024
27 8 2024
28 8 2024
© 2024 The Authors. Published by Elsevier Ltd.
2024

https://creativecommons.org/licenses/by-nc-nd/4.0/ This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
In eastern Ethiopia, sweet potato is a vital food and nutrition security crop; moreover, orange-fleshed sweet potato (OFSP) varieties are rich in beta-carotene content and have the potential to alleviate chronic Vitamin A malnutrition in the region. However, the unavailability of adaptable varieties and lack of information on production and post-harvest handling practices have limited its production and utilization in eastern Ethiopia. The research was conducted to identify the proper harvesting stage of OFSP varieties for optimum yield and nutritional compositions at Rare and Babile research stations of Haramaya University during the main rainy season of 2022. Three varieties (Alamura, Kabode, and Bakule) and four harvesting periods (120, 150, 180, and 210 days after planting (DAP) in factorial combinations were evaluated in randomized complete block design with three replications. Data were collected for growth, yield, and physicochemical composition-related parameters. Combined analysis of variance revealed the interaction effect of harvesting time and varieties had a significant (p < 0.05) effect on yield, yield-related parameters, and physicochemical components. Alamura variety produced comparable above-ground biomass (28.99 t ha−1) and the highest marketable root yield of 36.40 t ha−1 at 150 DAP, with dry matter content of 33.01 and 30.58 % at 150 and 120 DAP, respectively. Harvesting Alamura at 150 DAP also had the highest ꞵ-carotene, zinc, and iron contents of 11809 μg/100 g, 3.79, and 14.47 mg/100 g, respectively. It was concluded that growing the Alamura variety and harvesting at 150 DAP was better for obtaining higher root yield with good nutritional compositions in the study area.

Keywords

Days after planting
Marketable root yield
Dry matter content
Beta-carotene content
Zinc content
Iron content
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pmc1 Introduction

Sweet potato [Ipomoea batatas (L.) Lam] is a perennial herbaceous plant in the Convolvulaceae family [1,2]. It is the source of a staple for human nutrition and welfare as it can assist the developing food security in vulnerable communities [3]. It is a significant economic crop in many countries and after potato and cassava, the world's third-largest root crop [4]. In Ethiopia, sweet potato plays a key role in maintaining food security and household income generation [[5], [6], [7]]. Under marginal conditions in Ethiopia, the crop requires few inputs, grows quickly, and produces a consistent yield [8]. The dominant white-fleshed sweet potato cultivars are commonly consumed; however, they do not provide the nutritional benefit that orange-fleshed variants do [9].

Orange-fleshed sweet potato (OFSP) varieties, in particular, produce the ꞵ-carotene source of storage roots and are important in fighting Vitamin A Deficiency (VAD) and developing more resilient farming systems in Sub-Sahara Africa (SSA) countries as a consequence of the high amount of naturally bio-available ꞵ-carotene [10,11]. It is regarded as the most successful biofortification of a staple crop to address VAD [12] and the different varieties of sweet potato contain significant quantities of essential micronutrients for women of childbearing age or who are pregnant and preschool children [3]. Orange-fleshed sweet potato cultivars are the cheapest and most readily available year-round source of dietary vitamin A for disadvantaged families in SSA [13].

Early-maturing sweet potato varieties can be harvested 3–4.5 months after planting, providing a vital source of food during the ‘hunger season’ in many Sub-Saharan African countries. However, sweet potato varieties have flexible harvesting and planting time with high-temperature tolerance character that adapts to different environments [14] Sweet potato is generally harvested at 150 DAP, however, maturation stages vary between varieties [15]. In Ethiopia, the sweet potato harvesting time often lasts 2–3 months after maturity [16], increasing the danger of sweet potato weevil attack, particularly during the dry period. This is due to farmers storing roots in the soil in the absence of storage facilities and technologies [17]. Weevil and other root damage are typically associated with drought and rose drastically as harvesting was delayed [15].

In Ethiopia, sweet potato was produced by 1,510,779 farmers on 39939.1 ha of land and the cultivated land (16.58 %) for sweet potato was the third largest among root and tuber crops only exceeded by potato and taro (godere). Oromia regional state had the largest share in terms of cultivated land (49.32 %), number of holders (53.72 %), and total production (55.22 %) of the country during the 2021/22 Meher season. East and West Hararghe administrative zones accounted for the largest share of cultivated land (36.55 %) and the number of holders (40.54 %) in the Oromia regional state of which East Hararghe sweet potato producers and cultivated land had 27.16 and 31.58 % share in Oromia regional state, respectively [18]. This indicated that sweet potato is a vital food and nutrition security crop in East and West Hararghe. In line with more than 90 % of eastern Hararghe households subsist primarily on a monotonous sorghum diet and consume almost no meat and limited vitamin-rich foods, such as fruit and vegetables [19]. In this regard, OFSP varieties rich in beta-carotene content have the potential to combat Vitamin A malnutrition in the region. However, the unavailability of OFSP varieties and lack of recommendations on production and post-harvest handling practices have limited its production and utilization in eastern Ethiopia. This is supported by the finding of [20] that the harvesting stage had a significant impact on the carotenoid and phytochemical concentrations of 10.13039/501100002329 OFSP varieties. The limited information and understanding of parameters that determine the production and quality of OFSP roots in stallholder farmers’ fields demands research on OFSP varieties in eastern Ethiopia. Therefore, this research was conducted to identify the proper harvesting stage of OFSP varieties for optimum yield and nutritional compositions in East Hararghe.

2 Materials and methods

2.1 Description of the experimental site

The research was conducted at the Rare and Babile experimental sites of Haramaya University (Fig. 1) starting from June 20, 2022, the main cropping season, and harvested based on the treatments designed (DAP). The site has a latitude and longitude of 9°24′N 42°01′E/9.400°N 42.017°E with an elevation of 2047 m above sea level (masl) and is located on the university's main campus. The area receives an average annual rainfall of 790 mm. The site experiences mean minimum and maximum temperatures of 8.3 and 25 °C, respectively, with an average annual temperature of 17 °C. The rainy season of the area is bimodal where the short rainy season stretches from March to May and the main rainy season from June to September. The soil is categorized as an alluvial deposit with a sandy loam texture [21]. The Babile research site is located at 09°13′ N 42°20′ E latitude and longitude respectively, with a height of 1648 masl in the eastern lowlands of Ethiopia. Two separate seasons exist for the distribution of rainfall: the first rainy season, which runs from March to May, and the second rainy season, which runs from June to September. The area's mean annual minimum and maximum temperatures ranged from 15.4 to 28.8 °C, with an average annual rainfall of 731 mm and an average annual humidity of 33–38 %, according to Ref. [22].Fig. 1 Shows the sites of Haramaya (Rare) and Babile districts in Eastern Hararghe, Oromia, Ethiopia.

Fig. 1

2.2 Description of sweet potato varieties

Two improved OFSP varieties, Alamura and Kabode, and a farmer's cultivar called Bakule were used as experimental materials (Table 1). The planting materials of OFSP varieties were collected from Awassa Agricultural Research Center, while Bakule cultivar cuttings were collected from a farmer's field in the Kersa district. The vines of the varieties were further multiplied at Haramaya University's research farm sites to obtain enough planting materials needed for establishing the trials.Table 1 Description of sweet potato cultivars evaluated at two locations of East Hararghe in 2022 cropping season.

Table 1Variable	Alamura (Ukr/Eju-10)	Kabode (NASPOT 10 o)	Bakule	
Year of release	2019	2019	nif	
Adaptation area	Low to mid altitudes (700–2200 masl)	Low to mid altitudes (700–2000 masl)	nif	
Maturity days	120 to 150	90 to 120	nif	
Growth habit	Twining & spreading	Non-twining & semi-erect	nif	
Predominant root skin color	Cream	Purple red	White	
Predominant root flesh color	Deep orange	Intermediate orange	White	
Root yield (t ha−1)	23 to 28	20 to 25	nif	
Dry matter content (%)	31.5	30.3	nif	
β-Carotene content of roots (mg/100g)	12.4	8.5	nif	
Resistance to sweet potato virus diseases	Moderately resistant	Resistant	nif	
Breeder center	AwARC/SARI	HawARC/SARI	nif	
Source: [23], HawARC/SARI = Hawassa Agricultural Research Center of South Agricultural Research Institute (SARI), nif = no information found.

2.3 Treatments and experimental design

Three sweet potato varieties (Alamura, Kabode, and Bakule) and four harvesting times (120, 150, 180, and 210 days after planting (DAP)) in a factorial combination and a total of 12 treatments were used in the experiment. The experiment was laid out in Randomized Complete Block Design (RCBD) with three replications. Thirty-centimetre cuttings from healthy and middle vigorous growing vines of these varieties were prepared and used for planting. The 12 treatments are each assigned in one plot in each replication. Five ridges, each containing seven cuttings, were planted in each plot. Thirty-centimetre-long sweet potato cuttings were planted 40 cm apart from each other or spacing between plants and 80 cm between ridges.

2.4 Experimental procedure and field management

The experimental land was physically cleaned, then plowed, disked, and harrowed twice with tractor power, and then leveled by hand before planting. Three replication blocks and twelve plots were prepared. Five ridges and seven plants per ridge were arranged in a 4 × 2.8 m (11.2 m2) area. Weeding, cultivation, and other management practices were carried out as per recommendations for sweet potato crops uniformly for all plots [24]. Harvesting was done carefully and manually without damaging the roots based on treatment arrangements.

2.5 Data collection and measurement

2.5.1 Growth, yield, and yield components

Growth parameters, including vine length, leaf area index, and above-ground fresh biomass, were recorded at 120, 150, 180, and 210 DAP. Vine length was measured from seven randomly selected plants and the average was recorded in cm. The LAI was determined using a CI-202 Area meter (CID, Inc. made in the USA) which calculates the leaf area and LAI of the sample plants. Using a weighing balance (CAMRY Mechanical Hanging Scale with a weight capacity of 100 kg), above-ground fresh biomass was gathered from the three middle rows of a plot by cutting the vegetative sections of the plant back to 2 cm at harvest time.

Root parameters like root fresh weight, root length and diameter, marketable and non-marketable root number, marketable, unmarketable, total root yield, and weevil damage were also measured at each harvesting time from both sites. From each of the seven sample plants, three roots were taken, and the average fresh weight of the roots was determined at harvest time using a sensitive balance and presented in grams. Similarly, from these three roots of the seven sample plants, root diameter at the center of its broad region (using a caliper) and root length (using a centimeter) were measured and the average was recorded. Marketable root numbers per plant/hill were calculated by detecting and averaging insect and disease-free roots, under and over-sized roots, and damaged roots from the seven sample plants. All diseased, infected, under and over-sized roots were considered under non-marketable root number per plant. After sorting harvested roots into clean and uninfected ones weighing 100–500 g, marketable root yields (t ha−1) were measured using a weighing scale and expressed on a hectare basis. Those roots not considered under marketable root yield were taken to non-marketable root yield and expressed on a hectare basis. Total root yield (t ha−1) was computed and expressed in hectares by combining marketable and non-marketable root yields. The degree of weevil infestation was assessed by rating the harvested storage roots in each plot on a scale from 1 to 9 as stated by Ref. [25].

2.5.2 Nutritional composition and quality parameters

The samples of sweet potato roots from both sites and each plot at each harvesting time (120, 150, 180, and 210 DAP) were carefully harvested, labeled, covered with plastic, and taken to the laboratory for further physicochemical analysis. In the laboratory, the sample roots were washed with tap water twice, piled, and sliced into pieces.

The dry matter content (%) of storage roots of each variety at various harvesting stages was determined as stated by Ref. [26]. According to Ref. [27], Atomic Absorption Spectro-photometric analysis was used to determine the analysis of Fe and Zn contents. The gravimetric method as reported by Ref. [28] was used to determine the crude fiber content. The UV Spectrophotometric technique, as reported by Ref. [29], was used to determine the reducing sugars. Using high-pressure liquid chromatography (HPLC) following [30] guidelines, the beta-carotene content of each cultivar was assessed.

2.6 Data analysis

The data was subjected to a two-way analysis of variance (ANOVA) using SAS Version 9.4 statistical software [31]. Fisher's Least Significant Differences (LSD) for main factors effects and The Tukey honestly significant difference (HSD) test were used to compare treatment means of interaction effects at a 5 % (p < 0.05) level significance. Path coefficient analysis was carried out to determine the direct and indirect effects of growth and yield-related parameters on marketable root yield at 150 DAP.

3 Results and discussion

3.1 Effect of sweet potato varieties and harvesting time on growth parameters

The combined analysis of variance over the two locations showed a significant (p < 0.05) impact on major growth parameters like vine length, leaf area index, and above-ground fresh biomass due to the interaction effect of variety with the harvesting stage (Table 3). The interaction effect of variety by location also had a significant effect on leaf area index (Table 2).Table 2 The interaction effect of variety over location on LAI of sweet potato at Rare and Babile in East Hararghe during the 2022 main cropping season.

Table 2Treatment	Location	
Variety	Rare	Babile	
Alamura	2.92b	2.99b	
Kabode	1.75c	1.31d	
Bakule (local)	3.31a	3.12ab	
LSD (5 %)	0.27	
CV (%)	12.72	
The means in this table that are followed by the same letter do not differ statistically at the 5 % level of significance.

Table 3 Interaction effect of variety and harvesting time on vine length, LAI, and above-ground fresh biomass of sweet potato at Rare and Babile in East Hararghe Zone, Ethiopia.

Table 3Factors	Growth traits	
Variety	HT (DAP)	Vine length (cm)	LAI (%)	AGFB (t ha−1)	
Alamura	120	96.06e	2.64cd	20.27b	
150	122.10cd	3.33ab	28.99a	
180	119.80cd	3.19abc	27.09a	
210	106.94de	2.66cd	21.05b	
Kabode	120	44.69f	1.92ef	14.93c	
150	43.27f	1.70fg	13.83c	
180	37.12f	1.39fg	8.78d	
210	32.59f	1.11g	7.56d	
Bakule (Local)	120	139.61b	2.35de	13.88c	
150	179.27b	3.11bc	21.90b	
180	207.39a	3.59ab	30.33a	
210	214.19a	3.80a	30.31a	
Tukey (5 %)	21.01	0.65	4.25	
CV (%)	9.45	12.72	10.74	
The same letter in the column does not differ statistically at the 5 % level of significance, HT = Harvesting time, DAP = days after planting, LAI = Leaf area index, AGFB = Above-ground fresh biomass.

3.1.1 Vine length (cm)

The interaction effect of location, variety, and harvesting time on vine length was non-significant (p ≥ 0.05), however, the interaction effect of variety and harvesting time was significant (p < 0.05) for vine length (Appendix Table 1). At 210 and 180 DAPs, the local cultivar Bakule had the longest vine lengths of 214.19 and 207.39 cm, respectively (Table 3). The Kabode variety had the shortest vine length (44.69, 43.27, 37.12, and 32.59 cm) at early to last harvesting times, respectively. This finding corresponded with the reports of [32], where the local variety measured the longest vine (149.94 cm) from a trial established in Ethiopia's southern region. According to Ref. [33], substantial variations in vine length were identified across the examined OFSP cultivars at Malawi and Bangladesh Agricultural Research Institute (BARI), Pahartali, and Chittagong, respectively. Variations in vine length could be related to variations in genotypes due to genetic variations and their interaction with the environment [34].

3.1.2 Leaf area index (LAI)

The interaction effect of variety with location and variety by harvesting time interaction showed a significant (p < 0.05) difference for LAI (Appendix Table 1). As a result, the Bakule variety had the highest LAI (3.31 and 3.12), at Rare and Babile respectively (Table 2). Similarly, the Bakule variety at 180 and 210 DAP and the Alamura variety at 150 and 180 DAP measured the highest LAI (3.59, 3.80, and 3.33, 3.19), respectively (Table 3). On the other hand, the lowest LAI (1.31) was measured from the Kabode variety at the Babile site. The lowest LAI (1.11, 1.39, and 1.70) was also measured from Kabode at 210, 180, and 150 DAP, respectively. The difference in LAI of these varieties is due to the Alamura and Bakule varieties having broader leaves than the Kabode variety. The result is supported by the finding of [35] that the optimum LAI (4.40–7.23) was observed after the entrance of 3 MAP and the variations are due to morphological characteristics of the varieties in sweet potato, especially the shape and size of the leaves can affect the LAI.

3.1.3 Above-ground fresh biomass (t ha−1)

The combined analysis of the two locations (Rare and Babile) showed that the interaction effect of harvesting time and varieties was significant for above-ground fresh biomass (Appendix Table 1). Bakule variety at 180 and 210 DAP and Alamura variety at 150 and 180 DAP gave the highest above-ground fresh biomass (30.33, 30.31 and 28.99, 27.09 t ha−1), respectively. The combined result of three sites studied for two years at Gedeo Zone Southern Ethiopia also showed that the Alamura variety yielded (29.90 t ha−1) similar above-ground biomass [36]. The lowest above-ground fresh biomass yield (7.56 and 8.78 t ha−1) was recorded from Kabode at the late harvesting stage (210 and 180 DAP), respectively (Table 3). This indicates that the above-ground fresh biomass yields of the Kabode variety decrease as the harvest time extends due to thin and narrow leaves drying faster than the broad leaves of the other two varieties. The decrease in above-ground fresh biomass with delayed harvest stages is the consequence of senescence and leaf abscission, plant death, and reverse allocation of photoassimilates from tuberous roots to shoots at later harvest stages than at earlier harvest stages [37].

3.2 Effect varieties and harvesting time on root yield and related traits

3.2.1 Root length (cm)

The analysis of variance showed that the three-way interaction effect of location, variety, and harvesting stage was not significant (p ≥ 0.05) for root length. However, the interaction effect of variety with location, harvesting time with location, and variety with harvesting time showed significant differences (p < 0.05) (Appendix Table 2). Alamura variety at both Rare and Babile sites measured the longest root length (19.14 and 19.94 cm) whereas the Bakule variety at both sites and Kabode at Rare site measured the shortest root length (Table 4). Similar root lengths were measured at all harvesting stages and both sites except for the Rare site at 120 DAP which was significantly lower than the others (Table 5). Alamura variety resulted in the longest root length (21.01 and 20.19 cm) at 150 and 180 DAP, respectively. However, the shortest root length was measured from Bakule at 120 and 150 DAP (14.09 and 16.17 cm) from Kabode variety at 210 DAP (15.70 cm) (Table 9). This result is consistent with the reports of [38] that there is an increasing linear correlation concerning harvesting age to commercial root length reaching 15.27 cm at 150 DAP, indicating that the increase of the field period promoted greater root growth.Table 4 Interaction effect of variety and location on root length of sweet potato at Rare and Babile in East Hararghe during 2022 main cropping season.

Table 4Treatment	Location	
Variety	Rare	Babile	
Alamura	19.14ab	19.94a	
Kabode	16.72c	18.38b	
Bakule (local)	16.63c	16.55c	
LSD (5 %)	1.36	
CV (%)	6.25	
The same letter in this means does not differ statistically at the 5 % level of significance.

Table 5 The interaction effect of harvesting time over location on root length of sweet potato at Rare and Babile in East Hararghe during the 2022 main cropping season.

Table 5Treatment	Location	
HT(DAP)	Rare	Babile	
120	16.16b	18.50a	
150	17.92a	19.11a	
180	18.31a	18.04a	
210	17.59ab	17.51a	
LSD (5 %)	1.67	
CV (%)	6.25	
The means in this table that are followed by the same letter do not differ statistically at the 5 % level of significance, HT = Harvesting time, DAP = days after planting.

3.2.2 Root diameter (cm)

The interaction effect of location, variety, and harvesting time showed a significant difference (p < 0.05) for root diameter (Appendix Table 2). As a res ult, the wider root diameter (from 12.20 to 14.93 cm) was measured from the Alamura variety harvested at 150 and 180 DAP from both sites which were not significantly different from Alamura at 210 DAP from Rare and 120 DAP from Ref. [38] Babile. Kabode at 120 DAP from both sites and Bakule variety at late harvesting time (180 and 210 DAP) at both sites were also statistically similar to the above result in root diameter (Table 6). The smallest root diameter (8.60–10.34 cm) was measured for the Kabode variety at late harvesting time (180 and 210 DAP) and for the Bakule variety at early harvesting time (120 and 150 DAP) at both sites. This result is in agreement with the findings of [38], where the diameter of roots increased with delay in the harvest stage from 90 to 150 DAP.Table 6 Mean of root diameter as affected by interaction effects of variety, harvesting time, and location at Rare and Babile during the 2022 main cropping season.

Table 6Location	Rare	Babile	
Treatment	HT(DAP)	
Variety	120	150	180	210	120	150	180	210	
Alamura	11.25b-h	14.93a	14.80a	12.20a-e	12.98a-c	14.84a	12.62a-d	11.72b-f	
Kabode	12.20a-e	11.20b-h	9.07f-i	8.60hi	12.28a-e	11.44b-g	10.34c-i	9.66e-i	
Bakule (local)	7.97i	9.60e-i	12.84a-c	13.36ab	8.74g-i	10.03d-i	13.35ab	13.67ab	
Tukey (5 %)	2.80	
CV (%)	7.61	
Means that are followed by the same letter do not differ statistically at the 5 % level of significance, HT = Harvesting time, DAP = days after planting.

3.2.3 Marketable root number

The interaction effect of harvesting time and variety had a substantial effect on the marketable root number per plant (Appendix Table 2). At 150 and 180 DAP, Alamura (8.43 and 6.80), respectively, had the greatest number of marketable roots per plant followed by Kabode variety at 120 and 150 DAP Alamura at 120 DAP. However, the local variety (Bakule) at 120 and 150 DAP and Kabode at 210 and 180 DAP gave the lowest number of marketable roots (3.16–3.80) (Table 9). Similarly, a significant marketable root number was observed from the finding of [39] conducted at the Daro Labu and Habro districts during the 2016–2017 cropping season with the highest mean value (6.67) of root number per plant.

3.2.4 Non-marketable root number

The interaction effect of variety and harvesting time showed a significant (p < 0.05) difference in non-marketable root numbers (Appendix Table 2). Bakule variety at 120 and 150 DAP and Kabode variety at 210 DAP resulted in the highest number of non-marketable roots (11.71, 10.17, and 10.19), respectively (Table 9). The lowest number of non-marketable roots (5.37–7.42) was recorded from the Alamura variety at 150 DAP which was statistically non-significant with this variety at 180 and 120 DAP, Kabode at 120 and 150 DAP and Bakule at 180 and 210 DAP. The finding of [40] revealed that a higher number of non-marketable roots per plant was recorded at early harvest stages due to a greater number of immature tuberous roots and at later harvest stages due to weevil damage and oversized tuberous roots.

3.2.5 Total root number per plant

The interaction effect of variety and harvesting time over location showed significant differences (p < 0.05) for the total root number per plant (Appendix Table 2). Hence, the highest value (12.14–14.87) was recorded from Alamura and Kabode varieties at all harvest stages and Kabode at 120, 150, and 180 DAP. This implies that varieties harvested at different stages having higher marketable root numbers gave lower non-marketable root numbers showing comparable total root numbers per plant. Whereas the Kabode variety harvested at 210 DAP resulted relatively lower number of total roots (11.84) per plant (Table 9) [23]. also reported that there was significant differences were among OFSP varieties tested in the total number of roots per plant.

3.2.6 Root fresh weight (g)

The interaction effect of variety with location and variety with harvesting time was significant (p < 0.05) for root fresh weight (Appendix Table 3). Alamura variety at both the Rare and Babile sites and the Kabode variety at the Babile site gave the highest root fresh weight (871.73, 872.00, and 820.57 g), respectively (Table 7). On the other hand, the Alamura variety harvested at 150 and 180 DAP (1011.40 and 899.30 g) and the Kabode variety harvested at 120 DAP (868.30 g) recorded the highest root fresh weight. According to Ref. [13], variations in root fresh weight of sweet potato could be due to genetic variations of the varieties and environmental effects. The lowest root fresh weight was observed from the Bakule variety at the early stage (120 and 150 DAP) and from the Kabode variety at the late harvest stage (210 DAP) (Table 9).Table 7 The interaction effect of variety and location on root fresh weight of sweet potato at Rare and Babile in East Hararghe during the 2022 main cropping season.

Table 7Treatment	Location	
Variety	Rare	Babile	
Alamura	871.73a	872.00a	
Kabode	657.83b	820.57a	
Bakule (local)	636.37b	657.40b	
LSD (5 %)	90.96	
CV (%)	9.96	
Means that are followed by the same letter do not differ statistically at the 5 % level of significance.

Marketable root yield (t ha−1).

The interaction effect of location, variety, and harvesting time showed a non-significant (p ≥ 0.05) difference for marketable root yield (Appendix Table 3). However, the interaction effect of variety and harvesting time resulted in a significant (p < 0.05) difference in marketable root yield. As a result, the Alamura variety gave the highest marketable root yield at 150 DAP (36.40 t ha−1) followed by the Kabode variety at 120 DAP (32.45 t ha−1) and Alamura at 180 DAP (32.22 t ha−1). The lowest marketable root yield was recorded from Bakule harvested at 120 DAP (19.67 t ha−1) (Table 9). This result is consistent with the findings of [15], who discovered that tuberous root yields were lower at 90 DAP compared to 120, 150, and 180 DAP. According to Ref. [41], the highest marketable root yield was recorded from BD45, BD-38, and BD-15 sweet potato clones, with no differences among themselves, but higher than the other clones at 150 days of harvest.

Non-marketable root yield (t ha−1)

Interaction effects of location with variety and variety with harvesting time showed significant (p < 0.05) differences in non-marketable root yield (Appendix Table 3). The highest non-marketable root yields (2.07–2.42 t ha−1) were recorded from the Bakule and Kabode varieties at both sites. However, the lowest non-marketable root yields (1.56 and 1.78 t ha−1) were obtained from the Alamura variety at both Babile and Rare sites, respectively (Table 8). This indicates that the Alamura variety showed consistency and the least non-marketable root yield at both sites. Bakule variety at 120 and 150 DAP and Kabode at 180 and 210 DAP showed higher non-marketable root yield (2.43–2.97 t ha−1). However, the lowest non-marketable root yields (1.39–1.90 t ha−1) were recorded from Alamura at 120, 150, and 150 DAP, from Kabode at 120 and 150 DAP, and Bakule at 180 and 210 DAP (Table 9). It is supported by Ref. [15] results that combined analysis of data across the harvesting periods showed that genotype had a highly significant effect on both commercial and non-commercial root yield.Table 8 The interaction effect of variety and location on non-marketable root yield of sweet potato at Rare and Babile during the 2022 main cropping season.

Table 8Treatment	Location	
Variety	Rare	Babile	
Alamura	1.78bc	1.56c	
Kabode	2.14ab	2.07ab	
Bakule (local)	2.16a	2.42a	
LSD (5 %)	0.36	
CV (%)	14.59	
This means that are followed by the same letter do not differ statistically at the 5 % level of significance.

Total root yield (t ha−1).

Table 9 Interaction effect of variety and harvesting time on root length, marketable, non-marketable, and total root number, root fresh weight, marketable, non-marketable, and total root yield of sweet potato at Rare and Babile in East Hararghe Zone, Ethiopia.

Table 9Factors	Root Yield and Related Traits	
Variety	HT (DAP)	RL (cm)	MRN	NnMRN	TRN	RFW (g)	MRY (t ha−1)	NnMRY (t ha−1)	TRY (t ha−1)	
Alamura	120	18.50b-d	6.35b-d	6.43de	12.78ab	775.50b-e	29.76cd	1.47e	31.23cd	
150	21.01a	8.43a	5.37e	13.81ab	1011.40a	36.40a	1.39e	37.79a	
180	20.17ab	6.80ab	6.86de	13.66ab	899.30ab	32.22bc	1.69de	33.91bc	
210	18.48b-d	4.86d-f	8.47b-d	13.33ab	801.20b-d	27.02ef	2.15b-d	29.17de	
Kabode	120	19.40a-c	6.57bc	6.83de	13.40ab	868.30a-c	32.45b	1.52e	33.97b	
150	18.37b-e	5.91b-d	7.42c-e	13.33ab	799.50b-d	29.18de	1.71de	30.89d	
180	16.73d-f	3.78e-g	9.28bc	13.06ab	686.40d-f	26.44fg	2.43a-c	28.86de	
210	15.70fg	3.42fg	10.19ab	13.61ab	602.60fg	24.25gh	2.76a	27.01ef	
Bakule (Local)	120	14.09g	3.16g	11.71a	14.87a	487.00g	19.67i	2.97a	22.65g	
150	16.17e-g	3.80e-g	10.17ab	13.97ab	628.10e-g	22.41h	2.50ab	24.91fg	
180	17.63c-f	5.11c-e	7.03c-e	12.14ab	743.40c-f	27.33d-f	1.90c-e	29.23de	
210	18.47b-d	5.43b-e	6.41de	11.84b	729.00c-f	28.65d-f	1.79de	30.44d	
Tukey (5 %)	2.22	1.67	2.40	2.94	148.83	2.59	0.59	2.73	
CV (%)	6.25	15.81	15.08	11.12	9.96	4.67	14.59	4.59	
The same letter in the column does not differ statistically at the 5 % level of significance, HT = Harvesting time, DAP = days after planting, RL = Root length, MRN = Marketable root number, NnMRN = non-marketable root number, TRN = Total root number, RFW = Root fresh weight, MRY = Marketable root yield, NnMRY = non-marketable root yield, TRY = Total root yield.

The combined analysis of variance revealed that the interaction effect of variety with harvesting time had a significant (p < 0.05) impact on total root yield (Appendix Table 3). Across harvesting times compared for the three varieties, the Alamura variety at 150 DAP (37.79 t ha−1) gave the highest total root yields followed by the Kabode variety at 120 DAP (33.97 t ha−1) and Alamura at 180 DAP (33.91 t ha−1). However, the lowest total root yield (22.65 and 24.91 t ha−1) was recorded from the Bakule variety at 120 and 150 DAP (Table 9). Similar average attainable fresh root yields ranging from 18 to 32 t ha−1 were reported for different varieties [11] and when grown in different conditions [42]. In general, Alamura variety at 150 DAP gave higher marketable and total root yields showing consistency at both sites with minimum non-marketable root yield.

3.3 Path coefficient analysis

The path coefficient analysis of growth and yield-related parameters collected at 150 DAP was carried out to identify direct and indirect effects on the marketable root yield of the crop. As a result, the marketable root number per plant has the maximum direct positive effect (0.90) on marketable root yield. This is followed by non-marketable root number per plant (0.64), LAI (0.33), root length (0.20), root fresh weight (0.20), above-ground biomass (0.16), and non-marketable root yield per hectare. Total root number per plant (−0.57), vine length (−0.48), and root diameter (−0.03) have a negative direct effect on marketable root yield. Marketable root number per plant, root diameter and length, and root fresh weight showed higher indirect positive effects on marketable root yield through other characters except root diameter, non-marketable root number, and yield. The indirect effects of vine length, LAI, above-ground biomass, non-marketable and total root number per plant, and non-marketable root yield on marketable root yield through most parameters are observed to be negative (Table 10). The result obtained from this path analysis strongly indicates that marketable root number per plant, root diameter and length, and root fresh weight should be considered as indices for selecting a high-yielding sweet potato variety.Table 10 Path coefficients showing direct and indirect effects for marketable root yield.

Table 10S. No.	Character	r with MRY	Direct effect	Indirect effect	
VL	LAI	AGBM	RL	RD	MRN	NMRN	TRN	RFW	NMRY	
1	VL	−0.38	−0.48	−0.48	0.25	0.08	−0.06	0.006	−0.28	0.24	−0.10	−0.06	0.03	
2	LAI	0.12	0.33	−0.37	0.33	0.12	0.02	−0.008	0.10	0.05	−0.13	0.01	0.002	
3	AGBM	0.44	0.16	−0.25	0.25	0.16	0.08	−0.015	0.32	−0.20	0.02	0.09	−0.01	
4	RL	0.89	0.20	0.15	0.03	0.06	0.20	−0.03	0.74	−0.49	0.10	0.17	−0.04	
5	RD	0.88	−0.03	0.09	0.09	0.08	0.17	−0.03	0.77	−0.46	0.05	0.16	−0.04	
6	MRN	0.88	0.90	0.15	0.04	0.06	0.16	−0.03	0.90	−0.44	−0.07	0.15	−0.04	
7	NMRN	−0.79	0.64	−0.18	0.03	−0.05	−0.15	0.02	−0.62	0.64	−0.36	−0.15	0.03	
8	TRN	−0.13	−0.57	−0.08	0.08	−0.005	−0.03	0.002	0.12	0.40	−0.57	−0.05	0.001	
9	RFW	0.89	0.20	0.15	0.02	0.08	0.17	−0.02	0.68	−0.49	0.14	0.20	−0.04	
10	NMRY	−0.80	0.05	−0.24	0.01	−0.04	−0.15	0.02	−0.70	0.40	−0.01	−0.14	0.05	
Where, VL = Vine length, LAI = Leaf area index, AGBM = Above-ground biomass, RL = Root length, RD = Root diameter, MRN = Marketable root number, NMRN = non-marketable root number, TRN = Total root number, RFW = Root fresh weight, NMRY = non-marketable root yield, MRY = Marketable root yield.

3.3.1 Weevil damage

The three and two-way interaction effect of location, variety, and harvesting time showed a non-significant (p ≥ 0.05) difference for weevil damage. However, the main effects of location, variety, and harvesting time showed significant (p < 0.05) differences (Appendix Table 3). A higher sweet potato weevil infestation (4.56) was recorded at the Babile site than at Rare (Table 11). This could be because Babile has warmer weather conditions than Rare, which favors weevil multiplication and infestation. On the other hand, the Alamura variety showed a lower weevil damage record (3.50) as compared to the Kabode and Bakule varieties. This result is in line with the finding of [43] where sweet potato roots are highly affected as harvesting time is delayed and at the early harvesting stage less damage to roots by sweet potato weevils. As harvesting time extends from 120 to 210 DAP, the incidence of weevil damage increased from no damage (1) to heavy damage (7.67), respectively (Table 11). Harvesting time had a major impact on weevil damage to sweet potato roots, especially at the Babile site. The results concur with those of [15], who discovered that sweet potato root injury increases with harvesting time increase from 90 to 180 DAP, which leads to an increase in non-marketable root yield.Table 11 Main effect of location, variety, and harvesting time on weevil infestation of sweet potato roots at Rare and Babile during the 2022 main cropping season.

Table 11Treatment	Sweet potato weevil infestation	
Levels	Mean	
Location	Rare	3.83b	
Babile	4.56a	
LSD (5 %)	0.47	
Variety	Alamura	3.50b	
Kabode	4.42a	
Bakule (Local)	4.67a	
LSD (5 %)	0.57	
HT (DAP)	120	1.00d	
150	2.67c	
180	5.44b	
210	7.67a	
LSD (5 %)	0.66	
	CV (%)	23.46	
This means that is followed by the same letter and does not differ statistically at a 5 % level of significance for each factor, HT = Harvesting time, DAP = days after planting.

3.4 Varietal and harvesting time effects on root nutritional compositions

3.4.1 Dry matter content (%)

The three-way interaction effect of location, variety, and harvesting time showed a non-significant (p ≥ 0.05) difference for root dry matter content. However, the interaction between location and variety, location and harvesting time, and variety and harvesting time had a significant (p < 0.05) impact on the root dry matter content (Appendix Table 4). The highest root dry matter content (30.48 and 29.52 %) was measured from the Alamura variety at both the Babile and Rare sites. The lowest root dry matter was recorded from the Bakule variety at both sites and Kabode at the Babile site (Table 12). The highest root dry matter contents of 28.32 and 27.69 % were recorded at 150 and 180 DAP from the Rare site, respectively, whereas starting from 120 DAP to 180 DAP resulted in significantly higher root dry matter at the Babile site. Conversely, the lowest root dry matter (25.17–27.01 %) was measured from Rare at 210 and 120 DAP and from the Babile site at 210 and 180 DAP (Table 13). Alamura variety harvested at 150 and 120 DAP resulted in the highest dry matter content (33.01 and 30.58 %), respectively. However, the lowest root dry matter content was recorded from the Bakule variety at 120 and 150 DAP (21.53 and 23.86 %) and from the Kabode variety at 210 DAP (22.58 %) (Table 14). This outcome is consistent with the research conducted by Ref. [15], who found that the dry matter content rose from planting to harvest up to 150 DAP but not to 180 DAP. Similarly [38], also revealed that as harvesting time increased from 90 to 150 DAP, the total dry mass of roots showed rising responses with delay in the harvest stage.Table 12 Interaction effect of variety and location on dry matter content of sweet potato roots at Rare and Babile in East Hararghe during the 2022 main cropping season.

Table 12Treatment	Location	
Variety	Rare	Babile	
Alamura	29.52a	30.48a	
Kabode	26.93b	25.68bc	
Bakule (local)	24.24c	25.73bc	
LSD (5 %)	1.54	
CV (%)	4.68	
Means that are followed by the same letter do not differ statistically at the 5 % level of significance.

Table 13 The interaction effect of harvesting time and location on dry matter content of sweet potato roots at Rare and Babile during the 2022 main cropping season.

Table 13Treatment	Location	
HT(DAP)	Rare	Babile	
120	26.40b-d	28.11ab	
150	28.32a	28.25ab	
180	27.69a-c	27.01a-d	
210	25.17d	25.81cd	
LSD (5 %)	1.90	
CV (%)	4.68	
Means that are followed by the same letter do not differ statistically at the 5 % level of significance.

Table 14 Interaction effect of variety and harvesting time on dry matter content, crude fiber, reducing sugar, zinc, iron, and β-carotene content of sweet potato root at Rare and Babile in East Hararghe Zone, Ethiopia.

Table 14Factors	Root Nutritional Compositions	
Variety	HT (DAP)	DMC (%)	Crude fiber (%)	RS (g/100g)	Zn (mg/100g)	Fe (mg/100g)	β-carotene (μg/100g)	
Alamura	120	30.58ab	2.19cd	5.27ef	2.54cd	9.91d	7895c	
150	33.01a	3.18a	10.60a	3.79a	14.47a	11809a	
180	29.80bc	3.05ab	9.92ab	3.48ab	13.68a	10478b	
210	26.60ef	2.88ab	8.83b	3.28a-c	13.36ab	7614cd	
Kabode	120	29.66b-d	2.67a-c	8.57bc	3.23a-c	13.01a-c	8179c	
150	27.99c-e	2.73a-c	7.13cd	3.37ab	13.09a-c	7391cd	
180	24.99fg	2.62a-c	5.73d-f	2.98a-c	11.84bc	6772d	
210	22.58gh	2.59a-c	4.49f	2.83bc	11.76c	5487e	
Bakule (Local)	120	21.53h	1.51e	2.22g	0.97f	2.42f	1222g	
150	23.86gh	1.89de	2.63g	1.44ef	3.64f	1457g	
180	27.27d-f	2.46b-d	5.57d-f	1.62ef	5.84e	2492f	
210	27.29c-f	2.44b-d	6.73de	1.83de	5.82e	2956f	
Tukey (5 %)	2.52	0.61	1.69	0.82	1.60	983.01	
CV (%)	4.68	12.29	13.13	15.79	8.11	8.05	
The same letter in the column does not differ statistically at the 5 % level of significance, HT = Harvesting time, DAP = days after planting, DMC = Dry matter content.

3.4.2 Crude fibre content (%)

The interaction effect of variety and harvesting time gave a highly significant (p < 0.01) difference in crude fiber content (Appendix Table 4). The larg est amount of crude fiber (2.59–3.18 %) was recorded for the Alamura variety harvested at 150, 180, and 210 DAP and from the Kabode variety harvested at all harvesting times. However, the lowest fiber concentration was found for the Bakule variety harvested at 120 and 150 DAP (1.51 and 1.89 %) (Table 14). This result is consistent with [44], who reported that there was an increase in fiber content with a delay in harvesting stages from 90 to 150 DAP for all sweet potato cultivars examined. Similarly [45], also noted that the dietary fiber of OFSP roots was higher as harvesting time extended 90 DAP. The increase in fiber content as harvesting time extends is due possibly to the conversion of other nutrients with time. The variation in dietary fiber is caused by several factors, such as nutritional composition, maturity, and genotype [15].

3.4.3 Reducing sugar (g/100g)

Similar to crude fiber, the interaction effect of variety and harvesting time showed a highly significant (p < 0.01) difference for reducing sugar content (Appendix Table 4). The highest amount of reducing sugar (10.60 and 9.92 g/100g) was recorded for the Alamura variety harvested at 150 and 180 DAP, respectively, followed by the Kabode variety at 120 DAP and the Alamura variety at 210 DAP. Whereas, the lowest reducing sugar (2.22 and 2.63 g/100g) was found for the Bakule variety harvested at 120 and 150 DAP (Table 14). [46], also reported that the reduced sugar contents of two sweet potato varieties increased at the 16th week's harvest compared to the roots harvested at the 12th week.

3.4.4 Zinc contents (mg/100g)

The effect of variety by harvesting time interaction was a highly significant (p < 0.01) difference in the zinc content of sweet potato roots (Appendix Table 5). The highest zinc content was found for Alamura harvested at 150, 180, and 210 DAP (3.79, 3.48, and 3.28 mg/100g) and for Kabode harvested at 120, 150, and 180 DAP (3.23, 3.37, and 2.98 mg/100g), respectively. The lowest amount of zinc (0.97–1.62 mg/100g) was recorded from Bakule harvested at 120, 150, and 180 DAP (Table 14). This result is also closely related to the observation of [15], where root zinc content stabilized from 120 to 180 DAP.

3.4.5 Iron contents (mg/100g)

The interaction effect of variety with harvesting time showed a highly significant (p < 0.01) difference in root iron content (Appendix Table 5). Root iron content also followed a similar trend with zinc with the highest amount found for the Alamura variety harvested at 150, 180, and 210 DAP and for the Kabode variety harvested at 120 and 150 DAP ranging from 13.01 to 14.47 mg/100g. The lowest amount of iron (3.42 and 3.64 mg/100g) was recorded from the Bakule variety at 120 and 150 DAP, respectively, (Table 14). This finding reveals that the local white-fleshed variety (Bakule) contains less zinc and iron content than the two orange-fleshed varieties. Furthermore, the results are consistent with the findings of [15], that the root iron contents were stabilized as harvesting times were delayed.

3.4.6 Beta-carotene (μg/100g)

The effect of location with variety and harvesting time was non-significant (p ≥ 0.05) for β-carotene contents of roots (Appendix Table 5). However, the interaction of variety with harvesting time showed a significant (p < 0.05) difference in root β-carotene level. As a result, the highest amount of root β-carotene level (11809 μg/100g) was measured for the Alamura variety harvested at 150 DAP, which was followed by this variety at 180 DAP (10478 μg/100g). As expected, the lowest β-carotene levels were found for the white-fleshed local variety, Bakule, harvested at 120 and 150 DAP (1222 and 1457 μg/100g), respectively, (Table 14). The two OFSP (Alamura and Kabode) varieties showed higher β-carotene contents than the local variety and can overcome the problem of VAD identified in the study area. Therefore, harvesting the Alamura variety at 150 DAP produces better β-carotene content with consistently higher tuberous root yield at both sites. This result is in line with the finding of [15], that the β-carotene content of OFSP varieties remained constant from 90 DAP to 150 DAP and then increased to 180 DAP (15.3–19.0 mg/100g). According to Ref. [33], report, the highest vitamin A (919.2 μg/100 g RAE) or (11,030 μg/100g of β-carotene) fresh weight basis was recorded in CIP 440267.2 variety and recommended in Bangladesh based on yield and quality. [47], also discovered that OFS from Kelantan contained a relatively high concentration of β-carotene followed by α-carotene and zeaxanthin. According to Ref. [48], the amount of β-carotene found in sweet potatoes ranged from 9195 μg/100g DW (dry weight) in white-fleshed to 37,603 μg/100g DW in orange-fleshed sweet potato cultivars. However, the value of this result is slightly lower than what was reported by researchers might be due to environmental effects and varietal differences. The β-carotene content of Alamura and Kabode varieties tends to decrease as harvesting time extends beyond 150 DAP possibly due to relatively early maturing varieties and conversion of carotenoids into other nutrients as colour changes.

4 Conclusion

The combined analysis of variance over the two sites showed that the interaction effect of variety with harvesting time had a significant (p < 0.05) impact on growth, yield, and yield-related traits as well as on nutritional components of sweet potato crops. As a result, the two OFSP varieties (Alamura and Kabode) gave higher root yields at an earlier harvesting stage than Bakule (local) with higher micronutrients (Zn and Fe) and other nutritional components. More specifically, the Alamura variety harvested at 150 DAP is even better than the Kabode variety in many components. Having the advantages of root yields and physicochemical compositions, the Alamura variety yields comparable vine and above-ground fresh biomass to the local cultivar that is used for animal feed. Path coefficient analysis showed that marketable root number per plant, root diameter and length, and root fresh weight have a strong positive direct effect on selecting a higher marketable root-yielding variety. Thus, from this result, the Alamura variety harvested at 150 DAP gave better above-ground fresh biomasses, marketable root yield, and physicochemical composition than Kabode and local varieties. Therefore, it has a high potential to combat malnutrition and food insecurity problems that are prevalent in eastern parts of the country with its higher root yield, beta-carotene content, and other essential micronutrients.

Data availability statement

Agronomic and nutritional data are included in the supplementary file submitted with the manuscript.

Funding statement

This work was supported by the 10.13039/501100003081 Ethiopian Ministry of Education , especially the fieldwork and laboratory activities supported by 10.13039/501100004845 Haramaya University . However, this work had no special grant that supported the grant budget.

CRediT authorship contribution statement

Chala Begna Bedassa: Writing – original draft, Visualization, Validation, Methodology, Investigation, Formal analysis, Data curation, Conceptualization. Setegn Gebeyehu: Writing – review & editing, Visualization, Validation, Supervision, Methodology, Conceptualization. Wassu Mohammed: Writing – review & editing, Supervision, Methodology, Conceptualization. Dandena Gelmesa: Writing – review & editing, Visualization, Validation, Supervision, Methodology, Conceptualization. Getachew Neme: Writing – review & editing, Supervision, Methodology.

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.

Appendix Tables ANOVA Table for Yield, Yield-related, and Physicochemical ParametersAppendix Table 1 Combined mean square of ANOVA for vine length, LAI, and fresh biomass of sweet potato at Rare and Babile

Appendix Table 1Source	Df	Vine Length (cm)	LAI	Biomass (t/ha)	
Loc	1	323ns	0.61*	0.80ns	
Var	2	127374***	19.72***	1342.53***	
HT (DAP)	3	2857***	0.71***	120.50***	
Loc*Var	2	124ns	0.39*	9.23ns	
Loc*DAP	3	144ns	0.08ns	1.32ns	
Var*DAP	6	2552***	1.65***	222.93***	
Loc*Var*DAP	6	80ns	0.14ns	3.47ns	
Error	46	112	0.11	4.57	
Where *** = significant at 0.001, ** = significance at 0.01, * = significant at 0.05, ns = non-significant, Df = degree of freedom, Loc = location, LAI = Leaf Area Index, DAP = Days after planting, Var = Variety, and HT = Harvesting Time.

Appendix Table 2 Combined mean square of ANOVA for root length, root diameter, marketable root number, non-marketable root number, and total root number of sweet potato at Rare and Babile

Appendix Table 2Source	Df	RL (cm)	RD (cm)	MRN	NMRN	TRN	
Loc	1	11.46**	1.66ns	0.002ns	125.27***	126.35***	
Var	2	54.38***	43.37***	32.71***	28.30***	0.24ns	
HT (DAP)	3	5.40**	5.82***	6.60***	2.58ns	3.40ns	
Loc*Var	2	4.52*	1.46ns	0.26ns	2.37ns	4.21ns	
Loc*DAP	3	6.71**	0.77ns	0.74ns	0.67ns	0.66ns	
Var*DAP	6	21.29***	28.07***	13.90***	30.25***	5.43*	
Loc*Var*DAP	6	0.36ns	1.83*	1.37ns	0.82ns	1.93ns	
Error	46	1.25	0.79	0.70	1.46	2.19	
Where *** = significant at 0.001, ** = significance at 0.01, * = significant at 0.05, ns = non-significant, Df = degree of freedom, RL = Root length, RD = Root diameter, Loc = location, DAP = Days after planting, Var = Variety, and HT = Harvesting Time, MRN = Marketable root number, NMRN = Non-marketable root number, TRN = Total root number.

Appendix Table 3 Combined mean square of ANOVA for root fresh weight, marketable, non-marketable, and total root yield per hectare, and weevil damage of sweet potato at Rare and Babile

Appendix Table 3Source	Df	RFW (g)	MRY (t/ha)	NMRY (t/ha)	TRY (t/ha)	Weevil damage	
Loc	1	67735**	28.51***	0.03ns	30.29***	9.39**	
Var	2	306950***	280.48***	2.39***	232.65***	9.06***	
HT (DAP)	3	46446***	27.35***	0.42**	21.96***	156.94***	
Loc*Var	2	46913***	0.60ns	0.36*	0.93ns	1.39ns	
Loc*DAP	3	561ns	1.01ns	0.03ns	1.16ns	1.39ns	
Var*DAP	6	94976***	124.49***	2.08***	97.26***	1.50ns	
Loc*Var*DAP	6	5988ns	1.87ns	0.05ns	1.85ns	0.50ns	
Error	46	5616	1.71	0.09	1.89	0.97	
Where *** = significant at 0.001, ** = significance at 0.01, * = significant at 0.05, ns = non-significant, Df = degree of freedom, RFW = Root fresh weight, MRY = Marketable root yield, NMRY = Non-marketable root yield, TRY = Total root yield, Loc = location, DAP = Days after planting, Var = Variety, and HT = Harvesting Time.

Appendix Table 4 Combined mean square of ANOVA for root dry matter, crude fiber, and reducing sugar content of sweet potato at Rare and Babile

Appendix Table 4Source	Df	Dry matter (%)	Crude fiber (%)	Reducing Sugar (g/100g)	
Loc	1	2.89ns	0.58*	0.76ns	
Var	2	162.03***	3.67***	114.34***	
HT (DAP)	3	24.50***	1.30***	10.57***	
Loc*Var	2	12.70**	0.13ns	0.06ns	
Loc*DAP	3	4.75*	0.02ns	0.38ns	
Var*DAP	6	62.12***	0.59***	35.49***	
Loc*Var*DAP	6	2.01ns	0.09ns	0.97ns	
Error	46	1.61	0.10	0.72	
Where *** = significant at 0.001, ** = significance at 0.01, * = significant at 0.05, ns = non-significant, Df = degree of freedom, Loc = location, DAP = Days after planting, Var = Variety, and HT = Harvesting Time.

Appendix Table 5 Combined mean square of ANOVA for root zinc, iron, and beta-carotene contents of sweet potato at Rare and Babile

Appendix Table 5Source	Df	Zn (mg/100g)	Fe (mg/100g)	β-carotene (μg/100g)	
Loc	1	1.76**	6.33**	2893171**	
Var	2	23.91***	540.34***	3.419E+08***	
HT (DAP)	3	1.24***	17.07***	9066119***	
Loc*Var	2	0.37ns	0.40ns	88354.4ns	
Loc*DAP	3	0.03ns	0.55ns	136259ns	
Var*DAP	6	0.81***	13.87***	1.380E+07***	
Loc*Var*DAP	6	0.06ns	0.71ns	53048.1ns	
Error	46	0.17	0.65	245006	
Where *** = significant at 0.001, ** = significance at 0.01, * = significant at 0.05, ns = non-significant, Df = degree of freedom, Loc = location, DAP = Days after planting, Var = Variety, and HT = Harvesting Time.

Appendix A Supplementary data

The following is/are the supplementary data to this article:Multimedia component 1

Multimedia component 1

Acknowledgments

The authors express their appreciation and thanks to the Ministry of Education of the Federal Democratic Republic of Ethiopia for funding the research work and Haramaya University for additional fund support and facilitating the release of the budget for the work. We would also like to thank the staff and laboratory technicians of 10.13039/501100004845 Haramaya University for their technical and material support in the analysis of physicochemical parameters.

Appendix A Supplementary data to this article can be found online at https://doi.org/10.1016/j.heliyon.2024.e37153.
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