Revealing determinants that affects garlic production in Ethiopia using PRISMA methodology

Abstract Today, garlic productivity in Ethiopia is below its potential which is ranked 15 in the world. This is due to numerous determinants that affect garlic production. Therefore, the study’s main objective was to reveal and sum up determinants affecting garlic production in Ethiopia using PRISMA Method. Preferred reporting items for systematic review and meta-analysis checklist s1 table were employed. Universally accredited and indexed high-quality databases and university libraries; specifically, Scopus, PubMed, Science Direct, University of Toronto Library, and Google Scholar were used for retrieving published data (2000–2022). The titles “Garlic” and Ethiopia” were used to retrieve articles. “Microsoft Excel” was used to summarize results. The present study indicated that a total of 12,000 publications from Google scholar, and 51 publications from the University of Toronto library search engine published on the web of science and Scopus were used. A total of 51 publications were chosen as being the most suitable for this paper. Among the 51 publications, 86%, 6%, 6%, and 2% were articles, Newsletter articles, Text resources, and conference proceedings, respectively. Accordingly, a study revealed that the low production of this crop is due to information obtained via a systematic review discussed and categorized as institutional determinants (15.69%), farmers’ characteristics (9.8%), production and management practice (68.63%), and postharvest (5.88%). Institutional; production and management practices are of the major determinants negatively affecting garlic production in Ethiopia. Moreover, research limitations also were revealed. The recommendation of this paper is therefore not general, specifically, each factor has been recommended.

Gebre Garmame Galgaye is a senior lecturer and researcher at Bule Hora University. He has been teaching horticulture, plant sciences, and environmental sciences students. He has conducted different research activities related to horticulture agronomy, plant physiology, food security, and variety adaptation. Finally, he has an interest in teaching and conducting research related to crop-climate, horticultural agronomy, and postharvest management. He is an independent researcher who has been working with new research designs and methodologies like PRISMA. In this paper, he has independently designed a systematic review, which consists of objectives, hypotheses, and research questions, and written a full original research article.

PUBLIC INTEREST STATEMENT
Garlic is a member of the family Alliaceous, genus Allium, and originated in India, Afghanistan, West China, and Russia, which is generally known as Central Asia. It is mostly used for spicing food as a spice and in modern medicine to treat and cure different diseases. For producing this type of important crop in Ethiopia, there is broad opportunity and potential. However, it has been producing below its potential.
The very low production of this crop is due to several abiotic and biotic determinants. Therefore, the main objective of this paper was to reveal determinants that affect garlic production in Ethiopia using the preferred reporting items for systematic review and meta-analysis (PRISMA) method. The study revealed that garlic production in Ethiopia was determined by institutional, farmer characteristics, production and management; and post-harvest technology determinants. Therefore, these determinants should be adjusted based on appropriate garlic production practices.

Introduction
Garlic (Allium sativum L.) is the second most commonly produced and consumed horticultural crop of the cultivated Alliums next to the onion in the world (Rubatzky & Yamaguchi, 1997;Singh & Chand, 2003). According to reference (James, 2008) garlic is a member of the family Alliaceous, genus Allium and originated in India, Afghanistan, West China, and Russia which is generally known as Central Asia. It is distributed and spread to other countries of the world through trade and colonization (Panthee et al., 2006;Tindal, 1986).
It is mostly used to spicing food as a spice and in modern medicine to treat and cure different diseases (Labu & Rahman, 2019). Garlic has been used as a paramount medicine started from ancient Egyptians which is stated in the medical text Codex Ebers (ca.1550 BC). Mostly it is a remedy for different ailments such as tumors, headache, heart problems, worms, and bites (Tattelman, 2005;Thomson, 2007). According to reference (Bongiorno et al., 2008) garlic has antibacterial, antifungals, anti-viral, and antioxidant capacities. Moreover, anti-cancer and antiatherosclerotic properties have also been observed (Bongiorno et al., 2008). Currently, intensive review article revealed that the major biologically active ingredient of garlic (allicin) with its derivatives have been used therapeutic use and potential for drug discovery worldwide (Azene, 2021).
Garlic grows very-well at sub-tropical to temperate or high lands (1500-3456 mal), well-drained sandy, silty-clay soils, pH of 7, and excellent storage condition [Alemu et al., 2016, Table 1-13]. The significant importance of garlic has been known as a cultivated spice and medicinal plant for over 5000 years (Bizuayehu, et al., 2021). Therefore, Garlic have been a big demanded crop both locally and internationally (Alemayehu & Abate, 2021). Consequently, garlic is one among the most paramount economic crops of low income smallholder producers of highland area of Ethiopia (Alemayehu & Abate, 2021;Diriba, 2016). The highest net returns of Ethiopian Birr 518,409 and 626,814 per hectare had obtained in 2017 and 2018, respectively (Alemayehu & Abate, 2021). Thus, most of Ethiopian smallholder farmers around highland area produce garlic partially for home self-consumption and mainly for marketing as an income generation (Diriba, 2016).
Ethiopian agro-ecology has been ample opportunity and potential for garlic production. According to central statistical agency (2017), garlic production declined from coverage hectare of 16,411.19, during 2013/14 to production coverage hectare of 15,381 during 2016/17 having a total production of bulb yield (159,093.58 and 138,664.3 tons) with the average garlic productivity of 9.7 and 9.02 t ha-1, respectively, while current garlic productivity in Ethiopia is below potential (CSA (Central Statistical Agency), 2018; FAO, 2015; FAOSTAT (Food and Agriculture Organization of the United Nations Statistics), 2011; FAOSTAT (Food and Agriculture Organization Statistics), 2018; (AW Worku & Mehari, 2018), Shege et al., 2021). Internationally, Ethiopia has ranked 15 (FAOSTAT (Food and Agriculture Organization Statistics), 2018). While, China is the first ranked country accounting for over 78% of world total production (22.27 million tons) (Bizuayehu, et al., 2021). Following china, other ranked counties were India, Bangladesh, Republic of Korea, Egypt, Spain, USA, Uzbekistan, Russia, and Myanmar, respectively (FAOSTAT (Food and Agriculture Organization Statistics), 2018). Worldwide, the production of garlic during 2018 was 28.49 million tons from 1,546,741 hectares of land (FAOSTAT (Food and Agriculture Organization Statistics), 2018). Among this, only 124,801 tons from 12,429 hectares of land was the total production of Ethiopian with a mean productivity of 10.04 tons/ha (FAOSTAT (Food and Agriculture Organization Statistics), 2018). This indicates Ethiopian garlic production is very low when compared to world average 18.4 tons/ha (FAOSTAT (Food and Agriculture Organization Statistics), 2018).
However, these factors have been factors that affect the production of garlic across part of the country. Indeed, a several detail of factors influences garlic production has been studied across the country, however, there are some more poorly conducted studies which have not been published and not used in this paper yet. I collected and extracted the published literature (from high quality indexed journals like web of science, Scopus, ScienceDirect, PubMed and Google scholar databases) on garlic production factors. Therefore, the general objective of this paper is to better reveal the determinants that affecting garlic production in Ethiopia. Specifically, the first one is to systematically review entire government institution determinants and farmers characteristics affecting garlic production; second, to reveal production and management practices determinant that affects garlic production. Then finally, to gather and show the post-harvest practices that affects garlic yield/production. This findings could help to sum up to date evidences concerning factors affecting garlic production in Ethiopia and to exploit different existing production influences with in a single paper to fill gaps and improve future research prospect by indicating pillars where more scientific focal point might be sighted.

Hypothesis
• H0: A government institution, farmer's characteristics, production and management practices; and post-harvest technology have not determined garlic production in Ethiopia.
• H1: A government institution, farmer's characteristics, production and management practices; and post-harvest technology have determined garlic production in Ethiopia.

Research questions
(1) What are the government institutions determinants that affects garlic production in Ethiopia?
(2) What are the farmer's characteristics that determines garlic production in Ethiopia?
(3) What are the production and management determinants that affects garlic production in Ethiopia?
(4) What are the post-harvest determinants that affects garlic production in Ethiopia?

Study design
This study was designed and done according to the provided guidelines by Mother D. et al. (Moher et al., 2009) of PRISMA meaning preferred reporting items for systematic review and metaanalysis. As indicated by reference (Moher et al., 2009), it is not as an essay or term paper or normal literature review, but it is a review of a clearly prepared questions that utilizes systematic and explicit tools to identify, choose, and deeply appraise appropriate research, and to gather and analyze data from the articles that are included in the systematic review. It may or may not include statistical method to analyze and condense the findings of the included articles/ research report (Moher et al., 2009). Furthermore see the official website interpreting the methodology (www.prisma-statement.org). Other detail protocol for conducting this study was not used. The Preferred Reporting Items for Systematic Review and Meta-Analysis check list S1 Table is submitted in the supporting information section.

Searching strategy
Universally accredited and indexed high quality databases and university library; specifically, Scopus, PubMed, Science Direct, University of Toronto library and Google Scholar were used for retrieving published data . The searching strategy was to retrieve and download high quality published original research and review articles revealing government institution, farmer's characteristics, production and management practices; and post-harvest determinants affecting garlic production. The detail keywords including "Garlic", "Clove size", "Clove weight", "Spacing", "Watering", "Irrigation", "variety", "Ethiopia", and "Fertilizer" were used.

Exclusion/inclusion criteria
Published Original research and review articles reporting factors that affect garlic production were included in this paper. Specifically, studies indicating limitation of irrigable land problem, improved and high yielder varieties, cultivar and germ plasm, agricultural practices and organic and inorganic fertilizer type and rate, mulching, location, disease, spacing or plant population, propagation method like clove size and weight, and irrigation were included. Moreover, lack of research, dissemination and extension, and entire government institutional (concerns garlic development) constraints in production of garlic were consisted. Post-harvest factors like harvesting time, curing, storage method, storage site, storage season and storage conditions were also included. However, articles written with out of English languages were excluded. Generally, the following reasons were as follow; Reason 1, the articles (record) must contain both garlic and Ethiopia that has been published data from 2000-2022.
Reason 2, the article (record) must be from universally high indexed journal or database, and Reason 3, the article (record) must discuss about factors that affect garlic production in Ethiopia.

Selection of study
In PRISMA, commonly known method called Endnote (San Francisco, Thomson Reuters, CA, and United State of America) was employed to assemble materials (compile) the articles. First, the author assessed titles and executive summary (abstracts) of the retrieved articles for inclusion criteria. Next, the appropriate, and relevant full published studies (articles) were assessed and reviewed. Information such as factors used, treatments levels, the name of the specific areas in which the trial (experimental) work was conducted were also taken in to account during the selection process.

Method of data analysis
Non-parametric, descriptive quantitative statistic were used to summarize the articles. Quantitative, and qualitative data were employed due to their suitability for PRISMA. Software including "Microsoft Excel" was used.

Result
Country wide (Ethiopia), scholars revealed that garlic is a major spicing component of almost all dishes. Moreover, it is a paramount economic cash crop which could treat various human, plant and animal diseases. However, Production of garlic is affected by biotic (living things) and abiotic (non-living things) stresses. These could categorized as government research and economic institutional determinants, farmers characteristics, production and management practices including variety development and adoption, location, inappropriate propagation (clove size and weight), planting density, mulching, irrigation schedule or shortage of rainfall, and using appropriate, and type of irrigation, diseases management, and postharvest technology factors ( Figure 1).
This paper was designed to reveal those factors affecting garlic production in Ethiopia. A total of 12,000 publications from Google scholar and 51 publications from the University of Toronto library search engine which is published on the web of science and Scopus were searched ( Figure 2). After take-off irrelevant and duplicated articles, a total of 51 publications were carefully chosen as being most suitable for this paper. Among the 51 publications, 44, 3, 3, and 1 were articles, Newsletter articles, Text resources, and conference proceedings, respectively ( Figure 3).
The result of this review indicates that most 35(68.63%) of the study focused on production and management practices factors including variety, clove size, clove weight, spacing, mulching, irrigation, diseases, and insects management [ Figure 3, Table 3-5]. Next to this, 23(45.1%) articles revealing about two or more determinants that affect garlic production (findings deals about two or more subjects under one experimental setup like variety and fertilizer; location, spacing, and variety . . . etc) [ Table 1 -4, 13]. There were very low studies focused on post-harvest factors (5.9%) and farmers' characteristics (9.8%), respectively [ Figure 3, Table 2 and 13].

Institutional determinants, and farmers' characteristics
Among institutional factors shortage of finance service for input like improved variety seed, chemical, pesticides, and irrigation facilities purchase were indicated [ Table 1]. Moreover, Low supply of improved seed varieties, and fertilizers including poor extension service, poor market linkage, Low entire institutional support(institutional procurement of production inputs, extension services, financing institutions, market institutions) and market information's(supply, demand, price, market absorption) were observed as a major problem by different survey scholars [ Table 1].
Poor knowledge and skill gap of farmer (57.14%) were highly studied farmer among farmer's characteristics, while low attitude of farmers towards improved technology like low usage of improved seed varieties, low supply, and use of fertilizers (14.29%) were the lowest studied problem in Ethiopian context [ Table 2]. Furthermore, this systematic review indicated that poor knowledge and skill gap of farmer, and low attitude of farmers towards improved technology like low usage of improved seed varieties, low supply, and use of fertilizers were observed as a major problem which affects garlic production in Ethiopia. Whereas farmers experience (28.57%) was medium problem to wards reduction of garlic production [ Table 2].

Production and management practices
Variety/germ plasma/accession/cultivar were found to be the most frequently used, being the part used in 31% of the studies production and management factors, followed by fertilization especially nitrogen and phosphorous fertilization (19%), diseases (11%), location (8.6%), spacing (8.6%), mulching (8.6%), irrigation (8.6%). While the lowest researched production and management practices of garlic was about planting material like size, weight of clove, time of dormancy, and other vegetative or seed propagation or generally how to multiply seedlings of garlic either sexually or asexually (5.01%). Report of this systematic review revealed that research on garlic propagation in Ethiopia is very low [ Table 1-12].

Post-harvest factors
Country wide, research on garlic harvesting, curing, storage method, storage sites, storage season storage was found to be the least researched areas, being the part used in 5.9% of the studies [ Figure 3, Table 13]. Report of this systematic review revealed that garlic post-harvest research was narrowed. Harvesting time, sorting, curing, storage method, site, duration and season, and transportation of garlic bulbs are the determinants that contributes great value in increasing product Reports assessed for eligibility (n =4) Reports excluded: Reason 1 (n =0), the article must contain both garlic and Ethiopia.
Reason 2 (n =0), the article must be from universally high indexed journal or database Reason 3 (n =0), the article must discuss about factors that affect garlic production in Ethiopia Studies included in review (n =51) Institutional factors (n=8) Farmers perception (n=5) Agronomic factor (n=35) Post-harvest factors (n=3)

Identification Screening
Included Figure 3. Article selection procedures for this paper using PRISMA flow diagram.
value and price stabilization. While as the base the researchers and research output users may use this review for further research work.

Publication-region wise
Most of the study was conducted at Oromia (35.94%), Amahara (25%), and Tigray (20.31%), SNNNPR (17.19%), respectively [ Table 1-13]. Only one study reported 1.6% from Dire Dawa. While even a single study was not reported from other parts of the country. The output of the study revealed that most of the studies /researches were focused on Oromia, Amahara and Tigray due to most of the production potential area of the country was Oromia, Amahara and Tigray. Besides, most of the researchers choose the areas to conduct garlic production trails. Furthermore, international projects focus these areas and research at these areas were accessible as compared with other areas. However, other part of the country like Afar and Somali has not been researched for garlic production due to the areas are not suitable for garlic production. Even though the environment is not suitable, other technological options should be researched and funded to increase the productivity of garlic in the country. This indicates there were research gaps in the country.

Institutional determinants affecting garlic production
Several scholars revealed that institutional factors could affect garlic production. In this systematic review, about 15.69% institutional determinants. According to these articles institutional determinants are discussed as follow. Among them a study conducted in the Amahara region, Yilmana Densa district by shege  indicated that no companies are producing improved planting material. As a result, farmers have been using only local garlic varieties either purchased from 29 local markets (in his sample 66.7 %) or used their own saved seed (30%) for garlic production. Similarly, lack of access to pest and disease-resistant varieties, lack of a functional seed Seed 1 is any planting material used for propagation certification/regulatory system which ultimately results in the use of uncertified poor quality seeds by farmers are indicated as a major institutional factor in SNNPR 2 and Oromia, specifically Kaffa, Sheka, and West-Omo zones, West shewa zone, Gurage, Hadiya, Yemi special district , Table 1]. Reference (Diriba et al., 2020) also indicates that horticultural crops including garlic producing farmers in Arsi oromo areas had no access to any of the modern inputs from NGO, 3 research and university institutions except improved seed from NGO. Their study revealed that 20.6%, 38.8%, 43.1%, and 44.4% of the sample identified limited access to transport, limited supply of credit, high cost of credit/interest, and huge bureaucracy are the causes of limited access to finance access, respectively for more production. Moreover, a study conducted at SNNPR and Oromia, shows that the lack of private seed company engaged in the seed supply and distribution channel, and lack of institutional coordination in the seed supply system at some districts such as Guder and Ambo has been also eliminated as constraints for the production of vegetable crops including garlic , Table 1]. In the Kaffa, West-Omo, Sheka, and Bench-Sheko zones of southwest Ethiopia, during the 2015/16 and 2018/19 production periods, no supply of inputs such as improved varieties and fertilizer had been delivered to the farmers which negatively influenced the productivity of crops including garlic   Table 1]. The government planned to engage in small-scale irrigation. However, there is inadequate irrigation water in some other potential mid to highlands of Ethiopia, resulting in conflict between farmers in irrigation water use. Limited organized market information, linkages, lack, and unapplied government policy and initiatives to overwhelm the issue are major institutional factors [20, Shege et al., 2021, Shibabaw et al., 2017, Singh & Chand, 2003, Siyoum & Yesuf, 2013, and G Tabor et al., 2004. In 1986, garlic research was started at Debre Zeit (Bishoftu) and 5 varieties have been released so far . Currently, several organizations collaborate in backstopping, fundraising, technology dissemination, and offering feedback to the vegetable research . However, the collaboration among organizations engaged in the vegetable sub-sector including EHDA 4 and EHPEA, 5 while they are not strong as expected [HS Tabor et al., 2021, Table 1].

Farmer's characteristics affecting garlic production
Although in this systematic review, about 9.8% articles has been discussing farmers characteristic. Accordingly, farmers characteristic are discussed as follow. A study conducted in the Amahara region by Shege et al.  shows that most farmers are with less than 5 years of experience in the participation of garlic production. Farmers with less experience produce less garlic production and the vice versa which indicates garlic production directly proportionated with years of experience in garlic production. The use of poor agricultural practices (traditional technologies) is distributed and practiced in this sector. The current work shows that the use of improved variety and fertilizer by farmers have been very weak and negatively viewed in some part of the country particularly, Arsi, West-Omo zone, Sheka, Bench-Sheko, Kaffa, West shewa zone, Gurage, Hadiya and Yemi special district , Shibabaw et al., 2017, Table 2]. Due to the farmer's background in traditional agricultural production, they are still farming with poor agricultural practices and are not familiar with good agricultural practices (modern farming) yet. The farmer's education level is less and influences the ability, skill, and perception of farmers to adopt good agricultural practices (new technologies) to boost production. In the study reported by reference (Benyam et al., 2021) about 100%, 97%, 63%, and 60% of the sample in West-Omo zone, Bench-Sheko, Sheka, and Kaffa respectively, indicated that lack of knowledge and skill showed a statistical difference on crop production including garlic production. As revealed by reference (Benyam et al., 2021), except for maize variety, all farmers has been used local seed variety and no application of fertilizer in sheka zone, south-west Ethiopia. From 2015/16 to 2018/ 19, the average land coverage was 48,135.7 ha, while the average improved variety usage for this entire land was only 1,335.5 qt. Consequently, it has been revealed that improved seed variety usage behavior of the West-Omo zone is weak and needs further intervention and training. Moreover, it could indicate that there is a lack of skill, knowledge, poor knowledge dissemination and extension service, and accessibility (Benyam et al., 2021).

Production and management practices
In Ethiopia, vegetative (clove) means of propagation is common. Farmers has been using local cultivar, improved variety, hybrids, imported varieties in local and modern commercial production system based on accessibility. Any appropriate production and management practices, including propagation method/ planting material, plant population density/spacing, mulching, fertilizing, and watering/irrigating, disease, and insect control vary across different environments and varieties. Improved and high yielding variety with wide agroecology adaptability is the main target of breeders for which genotype by environment combination evaluation is paramount important for variety selection, cultivar, and germplasm recommendation leading to identifying potential production in several areas of the country [Bizuayehu, Kebede, et al., 2021, Bongiorno et al., 2008, Debebe, 2022, Debebe et al., 2017, Dessie, 2020, Dessie & Mulat, 2019, Diriba et al., 2020, Diriba et al., 0000, Diriba et al., 2015, FAO, 2015, Mohammed et al., 2014, HS Tabor et al., 2021, Tadesse, 2015, Tattelman, 2005, Table 3-12].
Worldwide, garlic is grown in all temperate to subtropical as well as in hilly low land areas (tropical) (Pandey, 2012). However, In Ethiopia, garlic is produced mostly in the sub-tropical (midland) and temperate (highlands) of the country (Dessie & Mulat, 2019;Fasikaw et al., 2020;J Mohammed et al., 2021). As indicated under [ Table 6] Angot followed by Ginaza had recommended for high garlic yield production due to overall higher yield obtained from Angot and Ginaza, respectively. It is not surprising that the yield of cultivars at location Angot had statistically higher as compared to the two locations revealing variations in agro-ecology conditions for the production of garlic (Dessie & Mulat, 2019). Similarly, Fasikaw Belay et al. [Taffesse et al., 2012, Table 6] experimented with different locations including, Hagere Selam, Ofla, Hatsebo, Ahferom, Hagere Selam, Ofla, Hatsebo, Ahferom with an altitude 2632,2133,2107,2027,2632,2133,2100,2027, respectively. Among these locations, Ofla and Ahferom with an altitude of 2107 and 2027 respectively had produced higher garlic yields than other locations   Table 6]. However, a study at Gursum and Kombolcha reported statistically similar garlic yields which might be due to close environmental factors [Bizuayehu, Kebede, et al., 2021, Table 6]. The variation of yield across locations is mainly attributed to the suitability of edaphic and environmental conditions for the revelation of the genetic code of different genotypes, accessions, varieties, and cultivars. Moreover, this emphasizes the effect of varied environmental (climate) factors on the yield of garlic.
Several study revealed that different varieties response differently across areas [Bizuayehu, Kebede, et al., 2021, Bizuayehu, et al., 2021, Bongiorno et al., 2008, Debebe, 2022, Debebe et al., 2017, Dessie & Mulat, 2019, Diriba et al., 2020, Diriba et al., 0000, FAO, 2015, Tadesse, 2015, Tamene et al., 2017, Tattelman, 2005. For an instance, an evidence to the GGE 6 and AMMI 7 biplot models, G9 (Bora-1/16) and G7 had observed as high yielder and stable genotypes. Thus, these genotypes had released for the study area and others with the same agro-ecologies to boost the production of garlic [Bongiorno et al., 2008, Table 3]. According to reference (J Mohammed et al., 2021) an experiment had also conducted during the rainy season for 2 consecutive years (2019 and 2020) at Gursum and Kombolcha districts on farmers' farms, Eastern Hararghe zone, Oromia region state, Ethiopia with an altitude of 1200-2460 m.a.s.l. 8 Consequently, Tsedey 92 had produced 13.3% and 54.3% yields more than the local and Chelenko I, respectively. At that agro-climate, therefore, Tsedey 92 had recommended having sustainable garlic production. During 2010/2011, in Beresa watershed, Mesqanworeda, Guraghie Zone of the SNNPR, Ethiopia, with an altitude of 1960 m.a.s.l, two varieties namely Tsedey 92 and local had tested at farmers' fields by using supplementary irrigation   Table 3]. Accordingly, Abreham Mulatu et al. [Tamire et al., 2007, Table 3] reported that Tsedey 92 variety had a superior yield over the local one. However, the study conducted at three locations of the south Gondar zone of Amhara Region in Ethiopia revealed that Tsedey 92 (40.88 q/ha) statistically recorded as ranked 3rd next to Holleta (42.74 q/ha) and Cultivars Adizemene local (55.44 q/ha), respectively in descending order (Dessie & Mulat, 2019). Similarly, Ayalew et al. [Bongiorno et al., 2008, Table 3] study conducted at Dabat district of north Gondar with altitude ranges from 1500 to 3200 masl revealed that the lowest fresh bulb weight (5.57 t•ha−1 and 16.70 g per plant) had recorded from the Tseday 92. While the local variety had yielded high (16.56 t•ha−1 and 49.72 g per plant) followed by Kuriftu (35.36 g per plant and 11.78 t•ha−1). The varied yield from different studies indicates the genetic variation of the genotypes, and the alteration of altitude and other environmental factors of the areas.
An appropriate planting method is paramount important in garlic production. It affects garlic growth and development thereby yield. Most farmers use cloves varying in weights/sizes, which might affect plant stand, vegetative growth, bulb yield, and even its quality (Semira & Tefera, 2017;Shege et al., 2021). Garlic clove size used for propagation significantly affects the marketable bulb of garlic. According to the report by (Semira & Tefera, 2017) consistent increased marketable bulb size had revealed in response to an increased weight of garlic cloves. Therefore, the largest-width cloves (with the thickest) had produced from the plot where the largest weigh cloves were planted. Contrarily, plots planted with small-weight garlic cloves produced small-sized garlic cloves [Moher et al., 2009, Table 6]. The highest bulb diameter and bulb length had recorded from mediumweight garlic cloves (1.5-2 g) planting material. Large-sized garlic cloves (2-3 g) weight garlic cloves significantly varied when compared with small-weight garlic cloves (1-1.5 g) cloves in bulb yield. Several scholars indicated that smaller-weight garlic cloves negatively affected its yield , Bewuketu et al., 0000, Moher et al., 2009, Motuma et al., 2020, Tesfaye & Merah, 2021]. This reveals the failure of the small weight garlic seed cloves in the development of higher bulb size due to low storage food when compared with large weight garlic cloves. While, in the large weight garlic cloves, there might be the presence of a higher quantity of contained food which boosted cell division, cell elongation, and growth resulting in larger bulb yield than the medium and smaller sized (Nasir, 2018). Similarly, Bizuayehu Desta et al. , Table 6] the longest bulb length (4.03 cm) had recorded by using 3-3.5 g weighted   garlic cloves planting material. While the shortest bulb length (3.45 cm) had recorded from 1-1.49 g weighted garlic cloves planting material. Consequently, it is shown that the longest bulb length recorded is due to large-sized garlic cloves planting material might be regarded quality as belongs to the higher presence of stored nutrients that resulted in high leaf area index, seems high storage of photoassimilates and translocation to bulb yield.
Plant population/ spacing is one of the production and management practices affecting the yield of a plant. Consequently, inappropriate spacing significantly reduces the yield and yield components of garlic. According to the reference , the assessment report indicated that farmers had planted cloves in a double-row arrangement with 34.8 cm between double-rows, 26.8 cm between rows, and 11.8 cm between plants, which is not in line with the recommendation by researchers. In 2007, EIAR, 9 cited in  recommended that planting space is 30, 15, and 10 cm between double rows, rows, and plants for improved garlic clove varieties, respectively. However, spacing can be varied from location to location, season to season, and variety to variety since it affects the yield of garlic. In different areas, scholars recommended different spacing between plants (intra row spacing) which significantly affect bulb yield and yield components. Mengesha, and Tesfaye [Kalkidan et al., 2021, Table 7] indicated that the high garlic yield (7.87 t/ha) had been recorded from 10 cm spacing between plants (intra row) while the low garlic yield (4.85 t/ha) had observed from 20 spacing (intra row). The study conducted at Aksum University, Selekleka research and demonstration center, Tigray, elucidated that the highest garlic bulb yield had recorded from the combinations of 5 cm spacing (intra-row) with Tsedey 92 and Bishoftu Netch improved varieties due to the absence of statistical difference with the yield recorded from combinations of same intra-row spacing (5 cm) [Dessie & Mulat, 2019, Table 7]. This reveals to utilize effectively a given land through a dense population. Wide spacing between plants has been employed by the producers/farmers resulting in a low bulb yield of garlic. Thus, having appropriate garlic plant density or spacing as recommended by researchers is paramount important to enhancing the production of garlic.
Mulching is one of the good agricultural practices which involves placing inorganic or organic materials on the soil plants to provide a suitable environmental condition for the growth and development of a plant. It reduces soil moisture loss by preventing evaporation, breaking winds, and regulating the temperature of the soil which regulates the effect of encouraging root growth and there determines the yield of the garlic. Black polyethylene (plastic) and different plant straws are mostly used in Ethiopian vegetable farms or fruit nurseries. Bark chunks, pine needles, and wood chips are suitable mulching materials. A review by Ousman (Yimer, 2020) indicated that fine mulches, such as wood shavings, buckwheat hulls, bark granules, and cocoa shells are attractively used in beds. Figuratively, a study conducted by [Pandey, 2012, Table 7] showed that wheat straw mulch had positively influenced the total yield of garlic (68.6 qt/ha) which had a real (p < 0.05) difference than without mulch total yield (62.8 qt/ha) plots. This revealed that the increased yield is due to wheat straw mulch effectively conserving soil moisture and retrieving other functions of mulching. Weldemariam Seifu et al. [Tesfaye et al., 2021, Table 7] also reported that black polyethylene and grass mulch boosts garlic leaf number by 5.466 and 4.166 respectively when compared with no mulching. In Ethiopia, there are limitations in the published research conducted on mulching materials and mulching-related works. Further research and publication therefore kindly be suggested.
Regularly, watering garlic throughout the growth is required for its maximum potential production. Irrigation/watering are paramount since garlic root depth is shallow. Insufficient watering or lack of irrigation (rainfall) when garlic reaches the bulbing stage, will result in few bulbs which cause early maturation. Water stress during plant growth and development deducts potential yield. A study by Dessie Gieta (Dessie, 2020) reported that the level of soil moisture affects not only the yield of garlic but also its bulb quality which is kindly affected by irrigation system/method [ Table 8]. The trickle irrigation system/method is advantageous over the gravity irrigation method since the trickle system uses water efficiently and also high yield production. Reference [Thomson, (G Tabor et al., 2004) 2007, Table 7] also revealed that the drip method saved 27.20% and 29.40% of water during Kharif &Rabi periods, respectively. In another setup, Ashebir Haile et al. (Ashebir et al., 2021) indicated that garlic production with varied irrigation methods at different levels of depletion had statistically affected the bulb yield. Accordingly, 7.45 t/ha marketable yield had observed from the frequently irrigated plot as the highest record compared to the yield (4.68 t/ha) of the wider interval which was 40% plus of allowable soil moisture level [ Table 8]. Mandefro Chala and Shoeb Quraishi (Mandefro & Shoeb, 2015) concluded that the application of 80%ETc can produce a comparatively high garlic yield than that of full irrigation which saves water efficiently to boost the yield of garlic [ Table 8]. In Ethiopia, only survey reports and publications on the impact of small-scale irrigation schemes, data acquisition and modeling of Irrigation strategies in a Smallscale irrigation scheme, and wastewater irrigation is indicated [Nasir, 2018, Tindal, 1986, Weldemariam et al., 2017, Workat et al., 2018, Table 8]. However, watering or irrigation method/ system research and publication is very limited which needs holistic support for research and publications to work.
In Ethiopia where garlic has been produced, low soil nutrients are the 2nd main factor affecting the production of garlic next to moisture stress. According to reference , garlic can be cultivated in a variety of soil types including black heavy soils and red soils. Suitable soil contains organic matter, adequate moisture-holding capacity, pH of 6.5-7.5, and is well-drained is ideal for garlic production in Ethiopia highlands. Fertilizing garlic medicinal plants is an important production and management practice like any vegetable production for those fertilizers needed as promote yield. Worldwide including in Ethiopia, as it is investigated by several scholars, in-organic and organic fertilizers have a significant impact on garlic yield and yield-related traits (Diriba, 2016). In Ethiopia, urea and diammonium phosphate (DAP) fertilizer had been utilized for a long time as nitrogen and phosphorus for maximum yield (Bewuket, 2021). Consequently, a new inorganic fertilizer (NPS) to replace DAP, consisting of phosphorous (P2O5), nitrogen (N), and sulfur (S) by the ratio of 38%, 19%, and 7%, respectively, had introduced by Ethiopian Ministry of Agriculture. In the country, several studies have been studied for optimum rate recommendation. Accordingly, Fikru and Fikreyohannes [Habtu et al., 2019, Table 9-10] indicated that garlic clove weight had significantly risen by 18.47% due to increasing the rate of nitrogen from control (without N-fertilizer) to 130 Kg ha-1. In their study, nitrogen fertilizer application revealed very high significant effects on fresh biomass which is increased by 73.80% over without N fertilizer application (control). Economically, about 398,701 ETB 10 ha-1(highest net benefit) had been obtained from the application of 130 kg nitrogen fertilizer per hectare, whereas 336,800 ETB ha-1(the least net benefit cost) had been obtained from unfertilized (Fikru & Fikreyohannes, 2018). Verma et al.  also reported that nitrogen fertilizer increases the net returns of garlic[ Table 4]. Testing this, a maximum marginal rate of return % (1,976.36%) with an application of 130 kg N ha-1 had been recorded, whereas the minimum (336,800, 1,127.07%) had indicated with nil nitrogen application. Similarly, a study from northern Ethiopia indicated that 7.11 t ha−1 of bulb yield is obtained from a land fertilized with a nitrogen rate of 92 nitrogen kg ha−1 followed by 46 nitrogen [ Table 9-10] While other levels of nitrogen rates had shown a declining trend in bulb yield and the least mean yield (4.8 t ha−1) had been recorded from a plot without nitrogen fertilizer (Workat et al., 2018). Reference [Habtewold et al., 2019, Table 9-10] also revealed that nitrogen fertilization highly (p < 0.01) influenced garlic yield dry weight, the maximum dry weight had been recorded at 278.33 kg N per hectare. (Diriba et al., 2015) reported a similar pattern which indicates that nitrogen fertilizer increases the growth, yield, and yield components of the garlic [ Table 9-10].
Phosphorus is another essential nutrient for the development of roots which affects the growth, development, and yield of plants including garlic due to its involvement in a lot of biochemical and physiological processes (Guta, 2019;Workat et al., 2018). Alemu Degwale et al. [AW Worku & Mehari, 2018, Table 9-10] revealed that phosphorous application at the rate of 92 kg P2O5 ha-1 has risen the mean garlic clove weight by 20.7% more than the control (without application of phosphorous fertilizer). Reference (Diriba et al., 2015) also shows that phosphorus application on both Vertisols and Andosols at the rate of 40 kg P ha-1 led to the production of maximum garlic clove compared with application of zero kg per hectare.
Sulfur and Potassium uptake imbalance to nitrogen and Phosphorous can incline to dangerous plant disease and insect damage (Diriba et al., 2015). As a result, the crops tend to have less shoot growth and low yields as well as the quality which minimizes the viability of such precious crops. Therefore, NPS fertilizer is currently stabilizing the gap between the interaction of nitrogen, phosphorous, and Sulfur which significantly affects the yield of garlic in Ethiopia. Alemayehu Getachew and Abate Asefa [Ashebir et al., 2021, Table 9-10] reported that application of the combined NPS inorganic fertilizers with 112-37-16 kg ha−1 had provided the highest yield, net returns, and MRRs which is recommended for garlic producer farmers in the northwest Ethiopian highlands. The study from Gurage zone, southern Ethiopia revealed that the bulb yield of garlic had significantly affected by the various rates of NPS fertilizer, the highest yield (14.91 ton ha−1) was recorded from 57: 114: 21 kg/ha NPS which is 65% higher than no application of NPS fertilizer (Bewuket, 2021). However, reference  point out that 78.75-69-12.75 N-P-S ha-1 had recommended for fresh garlic production as it shows significantly higher fresh yield and quality. The varied recommendation is due to different experimental setup and other agro-ecological contributions [ Table 9-10].
Organic fertilizer like compost is often used as an option for inorganic fertilizers. As cited in reference (Alemu et al., 2016) reported by Hargreaves et al., (2008) bio-fertilizers application including vermicomposts had been known as an effective means for modifying soil structure, aggregation, and fertility, rising microbial populations, and diversity increasing Cation Exchange Capacity (CEC) of soil, improving soil moisture-holding capacity and thereby increasing crop yields. According to Alemu Degwale et al. (Alemu et al., 2016) report, risen application of vermicompost from 0 to 5 t per hectare significantly had increased the total bulb yield of garlic by 9.57%. Cattle manure application can result in significant improvement of physic-chemical properties of soil. In agreement with the (Alemu et al., 2016) results, Alemayehu Getachew and Abate Asefa (Alemayehu & Abate, 2021) also revealed that applications of different levels of organic fertilizer improved the Physico-chemical properties of crop soils and thereby significantly influenced the yield of garlic.
carlaviruses and allexiviruses is a pain for the producers. Supporting this, K. Jemal et al  investigated that common symptoms are stunting of the plants, strip, and yellow mosaic. GV-B is the most frequently occurred virus followed by OYDV which indicated that both Allexivirus and Potyvirus are common in Ethiopia (Abel, 2017;Debebe et al., 2017;Kero et al., 2015;Yohanis et al., 2020). Reference (Abel, 2017;Debebe et al., 2017) revealed that Potyvirus is widely spread across a garlic-producing area of Ethiopia by infecting either improved varieties like Tseday, Kuriftu, and Bishoftu nech, improved cultivars, or frequently used local accessions.
According to Habtewold Kifelew et al. [Yimer, 2020, Table 11] Propiconazole and Rex Duo had found to be a superior solution in controlling garlic rust and contribute to the highest yield of 1913 kg/ha and 1881 kg/ha in 2017 and 2018 respectively. It is revealed that about 106% yield advantage had obtained from Rex Duo sprayed treatment in 2017, while 37.8% in the 2018 producing season [Yimer, 2020, Table 11]. At the Kabe area (Kassaw & Ayalew, 2021) it was also reported that the maximum 8047 kg ha −1 yield is recorded from treatment treated with 1.25 Litter of propiconazole by three times spraying frequency, while, at Segno, a similar 8047 kg ha −1 yield had reported from 1.5 L by three times spraying frequency. Oppositely, the lowest yield (4660 and 4740 kg ha −1) had been found from untreated plots from Kabe and Segno, respectively (Kassaw & Ayalew, 2021). However, It has been indicated that spraying frequency is an economically paramount factor in rates of propiconazole for the management of rust disease in which the highest (6896.36%) marginal rate of return had obtained at the average plot treated with 0.5 L with two times spraying of propiconazole fungicide [ Table 4]. According to [Worku & Dejene, 2012, Table 11-12] the highest severity of garlic rust level (82.77%), was recorded in the unsprayed fungicide garlic plantation which tends to total garlic yield losses of 58.75%. Moreover, reference [Worku et al., 2016, Table 11-12] indicates that among the garlic plantation treated with 4 fungicides (propiconazole, mancozeb, ridomil, and bayleton, garlic plantations treated with propiconazole lowered disease severity (3.72%), whereas greater disease severity (73.47%) had observed from garlic plantations treated with bayleton which is not significant compared with the control/no chemical spray (83.45%) at the 128 days. Consequently, a very low (5.59 t ha-1) yield had harvested from the plantation with high severity of the garlic rust which is treated with bayleton, whereas the highest yield from garlic plantation treated with ridomil and mancozeb had recorded 7.35 t ha-1 and 6.43 t ha-1, respectively, which is near to the best fungicide (propiconazol) resulted in higher (8.28 t ha-1) garlic yield. Worku  cost-benefit analysis supported that using propiconazole forges a high net return of 139,050 Ethiopian birr ha-1 due to fungicide effectiveness. Generally, it has been revealed that garlic rust disease could cause more than 49.33% yield loss if garlic plantations are not protected. Thus, propiconazole is suggested to protect against garlic rust disease.
White rot garlic disease is caused by Sclerotium cepivorum Berk (Tamire et al., 2007). Garlic marketable yield production has been significantly reduced due to White rot . According to [Abrha et al., 2015, Table 11] in both seasons, white rot could be reduced by different management chemicals, hot water, chemical + hot water. Traditionally, hot water followed by chemical treatment lowered the incidence and severity of white rot which tends to result in a high yield. However, the lowest marketable yield and the highest infected yield had recorded from the control plantation due to higher incidence and severity of white rot. Therefore, hot water treatment is important to manage the incidence and severity of white rot disease which seems to result in higher marketable yield and is preferable by farmers in easiness accessibility and environmentally sustainable. But, in the Simret Kebele, even though white rot disease incidence had 100% in the garlic plantation, relatively the highest garlic yield had observed from the chemical treated plantation in the second season [Table 11].
Siyoum Z, and Yesuf M (Siyoum & Yesuf, 2013) reported that tebuconazole, capatan and mancozeb treatment reduced final garlic white rot disease incidences by 74.33%, 34.45%, and 31.25%, respectively, as compared to no treatment of chemicals [Table 11]. Besides, different levels of tebuconazole treatment of garlic cloves resulted in significant differences in white-rot incidence and severity thereby varying the yield of garlic. According to  treating garlic plantation with tebuconazole at the rate of 2.1 ml kg_1 and spray at 0.25 l ha_1 at stem bases resulted in a significant reduction of white-rot incidence, progress rate, and severity on bulbs [ Table 11-12]. Comparatively, benomyl at 5.2 g kg_1 and Captan at the rate of 4.17 g kg_ 1 had resulted in a significant reduction by 24% and 16% respectively, compared with control at Bakelo, while at Debre Zeit these fungicides decreased the garlic white rot disease incidence by 40-44% (Tamire et al., 2007). As a result, it had revealed that the highest marketable yield had recorded from garlic treated with captan (48-77%), tebuconazole (43-73%), and benomyl (42-64%) over the control, while Thiram subsequently had not proven effective [ Table 11-12]. Generally, the Garlic yield of varieties or cultivars could be improved by fungicide application depending on the season, location, and general setup.
The best garlic cultivation technology method is holistic and comprehensive by applying appropriate production and management practices like propagation, spacing, mulching, irrigation, fertilization, integrated pest and disease control, and suitable production area with monoculture and intensive cropping system depending on varieties.

Post-harvest factors
Post-harvest handling is the branch of horticultural science which addresses issues of harvesting time, handling, curing, storage method, site, duration and season, and transportation of the crops. This affects planting material of garlic lends to influence germination, growth and bulb yield production of garlic. According to (Debebe, 2022). The extent of post-harvest losses for fruit and vegetables is 33.38%. To reduce post-harvest losses appropriate management of post-harvest factors including harvesting, curing, and storage condition is paramount. Garlic maturity is depending on its intended utilization. When garlic is to be harvested, the proper time of physiological and commercial or horticultural maturity is a primitive for an appropriate clove to plant. Early and/or delayed harvesting of garlic gloves causes post-harvest losses in the field of horticulture. It leads to yield small bulbs that boost rapid weight loss, cracking of the bulbs, and shrinking skins, whereas beyond harvesting time results in discolored, split, burned, and sprouted bulbs. Therefore, searching for appropriate post-harvest practices is mandatory to maintain quality and prolong the shelf life of garlic. [Bizuayehu, et al., 2021, Table 12] revealed that the largest weight loss had been recorded in bulbs harvested at 60% of top fall followed by 100% top fall harvest. The study also indicated that the minimum bulb weight loss (22.10%) and some sprouted bulbs (8.33%) had been observed in bulbs harvested at 80% top fall, respectively. Curing is the technique that exposes garlic to dry off the necks, roots, and outer scale leaves of the bulbs, and runoff moisture from the outer layers of the garlic bulb before storage. Cured garlic bulbs are more advantageous by 23.52% than noncured bulbs and bulbs stored on a shelf or in a net bag maintain the quality and prolong shelf life over floor storage. [Diriba-Shiferaw et al., 2016, Table 12] reported real differences in weight losses of stored garlic bulbs as influenced by storage season. It indicates that higher bulbs weight loss had observed in the dry storage season than in the rainy season which implies that storing garlic bulbs in the dry season risen bulbs' temperature, and rate of respiration and in turn boosts garlic bulb's weight loss that reduces shelf life and quality under normal storage environment [Table 12]. Regarding sprouting, (G Tabor et al., 2004) it has been revealed that even if garlic cloves are stored for twelve weeks, additional 6.5 weeks is required to attain maximum sprouting time [ Table 12]. These additional weeks determine the time to maturity of the garlic crop. Uniformity of garlic maturity and harvesting, therefore, after harvesting longer than 12 weeks is recommended under Ethiopian ambient conditions to maintain quality and enhance the yield of the garlic crop.

Summary, conclusion and recommendation
Nationally and internationally, Garlic has been a big demanded crop due to its medical and economical contribution. Even though Ethiopian agro ecology has been an opportunity and potential for garlic production, currently garlic productivity in Ethiopia is below potential due to several abiotic and biotic factors. To solve these problems several scholars have been tried to investigate; assessing constraints of garlic production including institutional and farmer's characteristics, selection of appropriate locations, variety, propagation, spacing, mulching irrigation or watering, fertilization, pests and diseases, harvesting time, and method, curing, storage site, storage season and storage duration. Additionally, the interaction of those factors has been also considered. However, it could be concluded that findings published in reputable journals discussing determinants affecting garlic production are limited. Specifically, studies concerned about insect pests, farmer's characteristics, location, propagation (clove size and weight), spacing, mulching, watering/irrigation methods, and post-harvest practices like harvesting time and methods, curing, storage (storage site, methods, duration and season), value chain management and transportation are very low. Research institutions and universities; and agricultural office have not been multiplied and provided enough planting materials, training and extension service about entire production and management; and post harvesting technology for farmers who engaged garlic production which is negatively affected garlic production in the country. Besides, finance institutions has not been provided sufficient credit access for the farmer's. Farmer's characteristic like garlic production experience, farmer's perception, farmer's knowledge and skill regarding with garlic production strongly influenced garlic production. This study also shows the lack of accessibility for producers by the market information institutions. Therefore, firstly, the current systematic review study revealed a gap (limitation of the published research work) of research focused factors affecting garlic production. Secondly, the presence of poorly done and unpublished research works was also observed, in bachelors, masters, and doctorate 11 degree students and researchers from at least 30 Government universities and research institutions have been conducting research. Finally, based on ten year strategy of agriculture transformation agency, it is also concluded that government research affairs haven't specific strategic plan to wards factors affecting garlic production in Ethiopia. Thus, based on this systematic review, the following suggestions are pointed out as recommendations.
• To have opportunity, potential, bases and use different agricultural innovation and technology, research on national wide (Ethiopian country-wide) institution determinants and farmers' characteristics that affects garlic production should be investigated. There might be unknown opportunity and potentials to boost garlic production in Ethiopia.
• Especial movement for scientific research and publication on insect pests, farmer's characteristic, location, propagation (clove size and weight), spacing, mulching, watering/irrigation methods, and post-harvest practices like harvesting time and methods, curing, storage (storage site, methods, duration and season), value chain management and transportation should be initiated and engaged by national research and publication affairs.
• Unpublished quality research should be published and researcher who poorly conducts research should follow a web of science, Scopus/Elsevier, and PubMed research principles and methodologies.
• Ethiopian agriculture research institutions, universities, national research directorate, Ethiopian horticulture producers and export association, Ethiopian horticulture association, and horticulturists should focus on factors that affect the production of garlic and play their role in the gaps pointed out via this systematic review.
• Extension and Capacity building training for farmers or producers should be given by research institutions, universities, associations, and horticulturists to set up farmers' or producers' perceptions.
• Variety/cultivars/germplasm/accessions/ should be cultivated in the preferable weather condition (location) to boost the production and productivity of garlic.
• Since scholars reported high yield from other spacing than national recommended spacing, specific area research-based spacing is recommended.
• Black polyethylene mulching followed by the grass (straw) mulching is optionally suggested.
• 60%, 80%, and 100% of ETc (Crop evapotranspiration) and Trickle irrigation method is available as a suggestion based on the weather condition of the area.
• Scholars revealed higher yields from other fertilization rates and types than national recommendation and it is also highly varied over locations. Thus, a specific area of research-based fertilization is suggested.
• Spraying Rex Duo twice at 21-days intervals starting from the onset of the disease, 0.5 liters propiconazole two times, and hot water treatment is used to control garlic rust diseases based on location and other production and management practices.
• Tebuconazole (Folicur 25 EC 2.1 ml kg-1) and captan are the most effective chemotherapy used to control garlic white rot.
• Harvesting at 80% top fall, top-curing, wooden shelf and net bag, rainy season storage with more than 12 weeks of ambient temperature, and RH storage are suggested to maintain quality and prolong the shelf life of garlic. Furthermore, research and publication on garlic are too limited, thus it is kindly recommended to do so.
• It is also an important problem that there is no specific journal for garlic production, garlic products, traditional, technological and molecular techniques used in garlic products, and the use of garlic in medicine. Therefore, the author suggests that specific journal for garlic production, products, traditional, technological and molecular techniques used in garlic products, and the use of garlic in medicine should be established.
• For the future climate change might challenge garlic production in Ethiopia. Therefore, garlic breeders should be stand up for garlic improvement program.