Issue 2 (202)/2025

ALSE and ACS Style
Igbadun, H.E.; Cofie, O.; Kpakpo-Sraha, M.A.; Onwuegbunam, D.O.; Tilahun, S. Effect of water management strategies on two vegetable crops under a Bhungroo irrigation technology in Upper East Region, Ghana. Journal of Applied Life Sciences and Environment 2025, 58 (2), 189-214.
https://doi.org/10.46909/alse-582172

AMA Style
Igbadun HE, Cofie O, Kpakpo-Sraha MA, Onwuegbunam DO, Tilahun S. Effect of water management strategies on two vegetable crops under a Bhungroo irrigation technology in Upper East Region, Ghana. Journal of Applied Life Sciences and Environment. 2025; 58 (2): 189-214.
https://doi.org/10.46909/alse-582172

Chicago/Turabian Style
Igbadun, Henry E., Olufunke Cofie, Michael A. Kpakpo-Sraha, Donatus O. Onwuegbunam, and Seifu Tilahun. 2025. “Effect of water management strategies on two vegetable crops under a Bhungroo irrigation technology in Upper East Region, Ghana.” Journal of Applied Life Sciences and Environment 58, no. 2: 189-214.
https://doi.org/10.46909/alse-582172

Effect of water management strategies on two vegetable crops under a Bhungroo irrigation technology in Upper East Region, Ghana

Henry E. IGBADUN^1*, Olufunke COFIE², Michael A. KPAKPO-SRAHA³, Donatus O. ONWUEGBUNAM⁴ and Seifu TILAHUN²

¹Department of Agricultural and Bioresources Engineering, Ahmadu Bello University, Zaria, Nigeria

²International Water Management Institute (IWMI), West Africa Regional Office, Accra, Ghana; e-mail o.cofie@cgiar.org; s.tilahun@cgiar.org

³Ghana Irrigation Development Authority, Accra, Ghana; e-mail: micadetey@gmail.com

⁴Forestry Research Institute of Nigeria / Federal College of Forestry Mechanization, Afaka, Kaduna, Nigeria; e-mail: donancy2001@yahoo.com

*Correspondence: igbadun20@yahoo.com 

Received: Jan. 19, 2025. Revised: Apr. 09, 2025. Accepted: May 05, 2025. Published online: Jun. 18, 2025

ABSTRACT. Exploring options to access water for irrigation and water management strategies at the field level is pivotal for improving crop yield and water productivity. Farmer-participatory field trials were conducted in Gorogo and Sepaat communities, Upper East Region, Ghana, in the 2020/2021 and 2021/2022 irrigation seasons to evaluate the yield response of tomato and onion crops to varied levels of deficit irrigation using Bhungroo irrigation technology. The experimental factor was water application depth at four levels: 65, 85, and 100% of crop water requirement (CWR) and farmers’ discretion. Irrigation water productivity (IWP) was computed as a function of the yield and water applied. Seasonal water used in the tomato fields ranged from 232 to 502 mm, while the onion trials varied from 358 to 750 mm. The fresh fruit yield of tomato ranged from 6.0 to 17.5 t ha⁻¹ in the two seasons, while the dry onion bulb yields ranged from 15.2 to 25.4 t ha⁻¹. The IWP ranged from 2.11 to 3.61 kg m⁻³ for tomato and from 2.05 to 4.51 kg m⁻³ for onion. The lowest values were obtained from the least water applied, while the highest values were obtained from the highest. The deficit irrigation schedules significantly decreased both yield and IWP compared to 100% CWR in tomato and onion, while the farmers’ discretion led to over-irrigation in both study locations. It is recommended that tomato and onion crops be irrigated to meet the full crop water requirement in the study areas.

Keywords: deficit irrigation; drip irrigation; onion; tomato; water productivity.

 

INTRODUCTION

Water scarcity has become a growing concern worldwide (Saud et al., 2020), threatening food security (Ouda and Zohry, 2020). The United Nations Sustainable Development Goal (SDG) target 6.4, which focuses on improving water use efficiency (WUE), expects that by 2030 nations should substantially increase their WUE across all sectors, ensure sustainable withdrawals and supply of freshwater to address water scarcity, and substantially reduce the number of people suffering from water scarcity irrigation (FAO, 2021). Agriculture, which withdraws about 70% of global freshwater (FAO, 2021), is expected to take the lead towards achieving this target. Although agriculture should produce food to meet the demand of the world’s growing population to guarantee food security, it is to do this within the confines of sustainable water withdrawal. This means that agriculture produces more crops with less water or sustains production without increasing the freshwater demand. Rainfed agriculture is based on a natural water supply; therefore, water withdrawal from freshwater bodies for crop production is largely about irrigation agriculture. To achieve SDG target 6.4, agricultural water use requires continued exploration of supplementary water sources and strategies that minimise water utilisation while optimising crop productivity to ensure food security and sustainability. This is achievable using efficient irrigation systems (Eissa et al., 2018) and deficit irrigation strategies (Ouda and Noreldin, 2020).

Irrigated agriculture in Ghana thrives more on vegetable production. Crops commonly cultivated include tomato, onion, pepper, okra, and cabbage. One of the leading regions in vegetable production under irrigation is the Upper East Region (UER). The dry season, which spans from November to April in the area, favours two or three cycles of intensive production of vegetable crops under irrigation. Small-scale farmers who abstract water from shallow dug wells, streams, and small dams and dugouts largely dominate the practice. The prevailing threat is the rate at which these water sources dry up, making it difficult for farmers to complete one cycle of crop production. The drying up of the water sources may be associated with the impact of climate variability on these resources. This can also be associated with a lack of effective water management strategies. Exploring supplementary sources of water and strategies for effective water management to enable sustainable intensification of crop production in the dry season has become imperative when the regions will continue to lead in dry season agriculture and enhance the country’s quest for food and nutrition security.

The Upper East Region has a unimodal rainfall pattern, and effective rainfall occurs between June and September. In some parts of the region, rain also occurs with flash floods, especially between August and September. Flood water could rise to about 50 cm in prone areas (Mante et al., 2018) and make farmlands inaccessible or unusable. Flood water can be converted to irrigation water if it is harvested and stored in systems where it can be retrieved at a future date for irrigation. Harvesting floodwater for irrigation is a water conservation technique and a supplementary source of water for irrigation. This practice was developed in India in the early 2000s and is referred to as Bhungroo irrigation technology (BIT) (Biplap, 2013).

Bhungroo is Gujarat-India’s native name for an access tube that serves as both a conduit for infiltrating flood water and a tube for extracting water from the aquifer (Owusu et al., 2017). The uniqueness of BIT is its ability to infiltrate water down to the aquifer and provide access to recover water when needed. Thus, it is an aquifer storage and recovery technology. Unlike conventional irrigation water storage techniques, such as reservoirs, check dams, and farm ponds, Bhungroo wells recharge groundwater directly, reducing evaporation and ensuring a steady water supply. Surface reservoirs and check dams are effective for runoff capture but suffer from high evaporation and land-use challenges. Farm ponds provide local water storage but require significant maintenance and space. Bhungroo technology offers a compact, efficient alternative by directing rainwater underground. This approach enhances groundwater reserves while minimising water loss (Owusu et al., 2017; Mante, 2020). Few studies have evaluated the aquifer characteristics of Bhungroos (Mante, 2020; Mul et al., 2018). Mante et al. (2018) assessed the potential of Bhungroos to store flood water and recover stored water for use during the dry season. Their study also evaluated the water quality of Bhungroos and their suitability for irrigating vegetable crops. A knowledge gap that stands out from their investigation is the water management strategies for the optimal use of Bhungroo water to ensure sustainability. There is a need to investigate optimal water application regimes under gravity drip irrigation systems to ensure maximum vegetable production and irrigation water productivity (IWP).

Studies on irrigation strategies have shown their impact on crop yield and water productivity. Dehkordi (2020) examined Arachis hypogaea L. under pressurised irrigation in Iran and found that moderate irrigation frequency with optimal water use improved peanut yield). The partial root-zone drying (PRZD) method outperformed traditional deficit irrigation, reducing yield losses while maintaining water efficiency. PRZD also enhanced yield using the same moisture levels across different irrigation frequencies. These results underscore PRZD’s potential for optimising crop water productivity and IWP in water-scarce areas.

Tomato (Solanum lycopersicum) and onion (Allium cepa L) are two major vegetables highly consumed in Ghana. According to Van Asselt et al. (2018), tomato is a key component in the diets of Ghanaian households, and approximately 440,000 tonnes of tomatoes are consumed annually, which is about 40% of household vegetable expenditure. In addition, onions constitute a significant proportion (approximately 20%) of household vegetable expenditure, mainly due to their extensive use in stew and soup preparation (MoFA-IFPRI, 2020). According to FAOSTAT (2020), the annual production of tomatoes in Ghana is 395,755 metric tonnes, harvested from a cultivated area of about 92,000 ha. Onion production was set at 155,402 metric tonnes from 8013 ha.

Abdul-Ganiyu et al. (2015), Abdul-Ganiyu and Gbedzi (2010), Abubakari and Abubakari (2014), and Yenihebit et al. (2020) reported the production of tomato and onion in the Upper East Region, but there is a knowledge gap regarding the response of these crops to varying water application regimes under gravity drip irrigation systems in the region. Abdul-Ganiyu et al. (2015) reported the effect of varied water application schedules on onion growth and yield in the Golinga Irrigation Scheme in the Northern Region and considered water application regimes with 100% daily crop evapotranspiration in the morning hours only, evening hours only, and two split applications with half applied in the morning and the other half in the evening. However, the irrigation system used was not specified in the report.

Adimassu (2020) carried out a field investigation on the response of yield and water productivity of onion and tomato to drip irrigation using Bhungroo and solar irrigation systems in Gorogo and Sepaat communities in the Upper East Region of Ghana. The study was carried out for only one irrigation season. The results presented were not sufficient for an in-depth analysis and deduction of the subject. It is important to know the response of these vegetables to different water regimes between seasons to establish a pattern. Kuşçu et al. (2014) studied the response of tomato to different irrigation regimes using a drip system on a clay–loam entisol in Bursa Province, Turkey, and reported that full irrigation throughout the growing season was preferable for higher yield and net income. However, this is not so in some regions in which water for irrigation is scarce, as irrigation managers opt for deficit irrigation practices to optimise crop production for economic viability and sustainability (Ouda and Noreldin, 2020). Çömlekçioğlu et al. (2016) reported that the water saved with deficit irrigation in tomato did not compensate for the yield reduction that resulted under their experimental conditions. In Syria, Mubarak and Hamdan (2018) found that onion yield, dry matter, and water productivity were higher under full irrigation compared to deficit irrigation. In Egypt, Taha et al. (2019) examined the impact of drip irrigation on onion response, applying water at varying levels (as percentages of the reference evapotranspiration (ETo)) and concluded that, under limited water supply, irrigating onions in calcareous soil with 100% ETo (rather than 120% ETo) conserves 17% of irrigation water but with an 8% yield reduction.

Water productivity (WP) is defined as a measure of gains per unit of resource use (Zwart and Bastiaanssen, 2004). Key indicators for agricultural purposes comprise biophysical, economic, and social gains, which are typically assessed based on land and water usage. Specifically, yield is the most widely used metric for quantifying biophysical productivity per unit area of land. WP has gained interest due to increasing concerns about available water resources (FAO, 2022). Although some stakeholders might consider water used as water consumed by the plant (Delft, 2020), others might consider the irrigation water that is applied or even water diverted from the source for irrigation. Attention is required regarding the denominators used when calculating water productivity, especially when values from different sources are compared (FAO, 2022).

These reports amplify the need to study the response of crops to water management strategies and water application regimes for different locations, soil types, and irrigation systems to enhance WUE for sustainable crop production and save water that can be released to other users, thus working towards achieving SDG target 6.4.

The specific objective of this study was to evaluate the growth stages, yield, and IWP of tomato and onion crops as affected by deficit water application regimes under drip irrigation with Bhungroo as a water source. The study was carried out to identify how best the Bhungroo water can be managed to achieve the desired outcomes. There was no attempt to compare the response of tomatoes to the onion because they are two different crops; however, a comparison of the outputs of the individual crops between the two study locations was carried out.

 

MATERIALS AND METHODS

Study location

This research was carried out during the 2020/2021 and 2021/2022 irrigation seasons in Gorogo (10°42’1.404” N, 0°51’8.244” E) and Sepaat (10°42’0.282” N, 0°51’8.604” E) communities of the Talensi District, Upper East Region, Ghana. The region exhibits a semi-arid climate characterised by an average annual rainfall of 921.0 mm (Liebe et al., 2005; MoFA, 2020). The rainfall follows a unimodal wet season, starting in June and ending in late September. During peak rainfall (August and September), localised flooding occurs in flat, low-lying areas, where water can stand for long periods (from a few days to weeks). The rainy season is followed by a hot and dry season in October and November and the harmattan cold season between December and February. After that, a hot and dry season occurs from March to May. During the dry season (November to May), total irrigation activities occur in the region. The mean monthly maximum temperature of the study locations ranged from 29.6 to 38.3°C with the lowest values in December and the highest values in March, while the minimum temperatures ranged from 18.8 to 25.5°C.

Owusu et al. (2017) reported that the soils at the study locations are sandy clay loam at a 0–15 cm depth and sandy loam and sandy clay at a 15–30 cm depth, based on the USDA soil classification system (Table 1). The soil pH values are near neutral, with the lowest value of 6.14 and the highest value of 7.03. The soil salinity, measured by the electrical conductivity, indicated that none of the soil samples were saline, as all concentrations were well below 2 dSm⁻¹. Hence, the soils are favourable for vegetables, and the available water with the top 30 cm soil depth is adequate to meet the water requirement of fruit and vegetable crops. Soil fertility shows low values of cation exchange capacity (CEC), averaging below 5 cmol kg⁻¹, indicating low soil fertility.

 

Table 1
Soil physical properties of Gorogo and Sepaat

Parameter		Sepaat		Gorogo
Depth Soil (cm)		0-15	15-30	0-15	15-30
Particle size Distribution (%)	Sand	54	58	76	82
	Silt	14	6	2	2
	Clay	32	36	22	16
Texture (USDA)*		SCL	SC	SCL	SL
Field Capacity (% Vol)		23.9	31.7	19.5	14.8
Permanent Wilting Point (% Vol/)		19.3	21.6	13.1	9.4
Available Water Capacity (%)		4.6	10.1	6.4	5.4

*SCL = Sandy clay loam; SC = Sandy clay; SL = Sandy loam
Source: Owusu et al. (2017)

 

Description of the Bhungroo and solar pump facilities in Gorogo and Sepaat

The Bhungroo wells in Gorogo and Sepaat were drilled in December 2016 in flood-prone areas, which are waterlogged annually during the wet season. Typical floodwater depths occurring in the areas are between 100 and 500 mm (Mul et al., 2018). The fields are constantly flooded between August and September. Although farming activities, including rice cultivation in the flooded plain, take place during the wet season, no dry season irrigation is practised in the area because, after harvesting rice, the residual soil moisture depletes so fast that the topsoil surface becomes dry and cracks due to evaporation. There were no close sources of water for irrigation in the study location. This is where Bhungroo technology becomes a valuable water resource for irrigation.

The Bhungroo well at Gorogo was 60 m deep, while that at Sepaat was 42 m deep when the wells were drilled. The recharge floodwaters laden with high turbidity go through an infiltration bed to reduce contamination in the underlying aquifer and clogging of the wells. At both study locations, the wells were solar powered, being equipped with a submersible pump powered by a Lorentz Solar panel PS2-1800C-SJ5-12 (Max: 70 m, 7.6 m³ h⁻¹, 200 V), which pumps water into two water storage poly-tanks reservoirs of a 5000-L capacity each.

Gravity drip irrigation system setup

The drip irrigation system is gravity based, and the water supply to the driplines was from raised water storage tanks of 6-m height. The layout comprised a mainline (40 mm diameter uPVC pipe) from the water reservoir, which delivered water to the two experimental fields in each location. The sub-main lines were 32-mm diameter high–density polyethylene pipes connected to the main line and fitted with a control valve so that the flow of water into each sub-main could be controlled. The operational performance of the drip irrigation system was carried out after setting up to evaluate the system’s field emission uniformity according to the procedure described by Jamrey and Nigam (2018). This was necessary to determine whether the emitters were dripping efficiently and uniformly across the field. Hence, field emission uniformity was determined as expressed by Keller and Karmeli (1974) (Equation 1).

where Q_ave is the average emitter flow rate, EU_f is emitter flow uniformity, and Q_{4th ave} is the average lowest quarter volume of water caught.

The average emitter flow rate was determined following Keller and Karmeli (1974) (Equation 2).

where V_ave is the volume of water dripped into the can, and T is the time of flow. An EU_f greater than 85% is considered very good (Jamrey and Nigam, 2018).

Experimental design

Two sets of trials (one on tomato crop and the other onion crop) were set up in both the Gorogo and Sepaat fields in the 2020/2021 and 2021/2022 irrigation seasons. Each trial consisted of four treatments replicated three times and laid out in a randomised complete block design (RCBD), with water application depth as the experimental factor. The experimental setup, which includes four water application levels − 100, 85, and 65% of the crop water requirement (CWR) as well as a level based on farmers’ discretion or experience − is presented in Table 2. Each treatment plot was 4 m × 6 m and spaced 1.0 m apart. The spaces between the replicate blocks were 1.5 m wide to mitigate the lateral flow of water between adjacent plots/treatments. The two trials in each study location were separated by a space of 2.0 m. Adimassu (2000) set up a similar experiment in the same study location to examine the response of tomato and onion to a similar water application regime. In that setup, however, while the other treatments were irrigated using the gravity drip irrigation system, the farmer’s plot, which was regarded as the control treatment, was under surface/flooding irrigation and not under the drip irrigation system. In this study, all treatments were placed under the drip irrigation system, including the treatment under the farmers’ discretion (Drip + FD). The Drip + FD treatments for both crops were purposively carried out by a group of farmers in each study location: 15 farmers (5 males and 10 females) in Gorogo and 10 farmers (5 males and 5 females) in Sepaat. These farmers were trained before the season on the working principle of the drip irrigation system. They also took part in setting up and operating the drip systems. In administering the Drip + FD treatment, the farmers allowed the drip to run until a time that they collectively agreed that the treatment plot was well irrigated. The irrigation time was documented for each irrigation event.

 

Table 2
Description of experimental treatments

Treatment label	Description*
Drip + CWR100 %	Water application to meet 100 % CWR
Drip + CWR85 %	Water application to meet 85 % CWR.
Drip + CWR65 %	Water application to meet 65 % CWR.
Drip + FD	Water application is based on farmers’ discretion

*The same treatments were administered in both tomato and onion crop trials
CWR is the crop water requirement

 

The potential sources of variability that might affect the results were identified as soil variability, climate fluctuations, farmer decision-making (in the Drip + FD treatment), crop variety and management, and irrigation system performance.

To ensure consistent treatment-based water application across the field, the irrigation schedules were controlled − that is, predefined irrigation frequencies and durations for each treatment − except for the farmer-discretion approach. In addition, all study locations had competent technicians to monitor and implement the irrigation treatments correctly. Furthermore, uniform drip irrigation lines (emitters), lateral spacing, and pressure regulation were maintained to ensure consistency. Soil and environmental variabilities were controlled by grouping similar plots (blocks) and randomly assigning treatments within each block, that is, an RCBD.

Irrigation scheduling

A 2-day fixed irrigation interval (FAO, 2002) was maintained throughout the crop growing season and the crop water requirement was based on the ETo of the study areas and the crop coefficients (Kc) of the test crops. For each treatment, the driplines were run for the length of time required to apply the needed water depth.

A control valve was installed to open and shut the water flow into the driplines for each treatment according to the irrigation time. For Drip + FD treatment, irrigation was applied through the drip system and continued until the farmers, using their discretion, collectively determined that the treatment plots had received sufficient water. The crop water requirement, gross water application depth, and irrigation time for the test crops were computed using Equations (3-5). The drip irrigation efficiency was taken as 90% (Panigrahi et al., 2010):

where CWR is the crop water requirement (mm/day); ETo is the reference evapotranspiration (mm/day) computed from climatic data based on the Penman–Montieth models (Allen et al., 1998); Kc is the crop coefficient (Allen et al., 1998); GWR is the gross water requirement (mm/day); and Wp is the wetted percentage for tomato taken as 50% (Panigrashi et al., 2010).

The seasonal water applied (SWA) in each treatment was a summation of the depths of water applied over the season.

Agronomic practices

Seedlings of tomato (‘Tropimech’) and onion (‘Bawku Red’) were raised in open-field nurseries and transplanted in the trial plots after 6 and 4 weeks in the 2020/2021 and 2021/2022 seasons, respectively. In the 2020/2021 season, the crops were transplanted on 6^th January, 2021, while in the 2021/2022 season, transplanting was done on 6^th December, 2021. Seedling transplant was delayed by 2 weeks in 2020/2021 due to logistical challenges in setting up the drip system caused by the COVID-19 pandemic.

The Tropimech tomato cultivar was selected for the study, as it is early maturing with a growth cycle of 70–90 days after transplant (DAT) and tolerant to nematode and tomato yellow leaf curl disease, which has infested tomato production in the UER (Robinson and Kolavalli, 2010). Tomato seedlings were transplanted 60 cm apart along the driplines. Each drip line had 10 plants, which gave a total of 70 plants per experimental plot (about 29,200 plants ha⁻¹). Bawku red onion, commonly planted in the area, were used for the study. It is tolerant of moisture stress and matures between 100 and 125 DAT (Danje et al., 2019). The onions were spaced at 20 cm between drip lines by 30 cm intervals between emitter spacing, with 20 onion stands per drip line, equivalent to 400 stands per experimental unit (about 166,670 plants ha⁻¹).

In both seasons and locations, weeding was carried out at 3 and 6 weeks after transplant (WAT) in the tomato plots and at 4 and 7 WAT in the onion plots. Inorganic fertilisers – NPK 23-10-5 and ammonium sulphate – were applied at a rate of 180 kg N ha⁻¹ 3 WAT and 100 kg ha⁻¹ as top dressing at 6 WAT in the tomato trials. Golan 20 SL (Acetamiprid 200 g L⁻¹) pesticides were sprayed every 2 weeks during the full vegetative and flowering growth stages at a rate of 12 mL/14 L, as recommended by Boateng and Cornelius (2013), to control aphids and grasshoppers.

The onion plots were fertilised with NPK 23-10-5 at a rate of 200 kg N ha⁻¹ after the first weeding and with ammonia sulphate at a rate of 100 kg ha⁻¹ as a top dressing after the 2^nd weeding. In the 2021/2022 season, the onion in Gorogo was attacked by beet armyworm (Spodoptera exigua), which was controlled with Belt Expert 480SC pesticide twice per week at a rate of 20 mL/16 L applied with a knapsack sprayer for 3 weeks to eradicate the pests and redeem the crop.

Agronomic data collection

Agronomic data obtained from the field include crop phenology and yield. The changes in growth stages of the crops were carefully observed, and the number of days after transplant was recorded when these changes became obvious. Records were taken when the transplanted tomato seedlings became established: early vegetative stage (up to 50% plant spacing cover), full vegetative stage (over 75% plant spacing cover), 50% flowering, fruiting, and ripening and harvest. In the onion trials, the number of days from transplant to the establishment, full vegetative stage, bulb initiation, bulb development, and bulb maturity stages were noted.

At ripening, tomato fruit was picked in sequential harvesting in both seasons and locations until the fruit was exhausted. In the 2021/2022 season, ripe tomato fruit was picked four times in Gorogo and three times in Sepaat. The masses of fruit harvested per 18 m² area (plot size) were measured and extrapolated to tonnes per hectare. The onion bulbs were harvested at maturity when the head leaves had fallen over, senesced and allowed to cure in the open air for 3 days before yield measurements were taken. The bulb yields per sampled plot size (18 m²) were weighed and extrapolated to tonnes per hectare.

Computation of irrigation water productivity

IWP is the relationship between crop yield produced per unit volume of irrigation water applied in the fields (FAO, 2003). It was computed using Equation (6):

Data analysis

An analysis of variance test was carried out on the yield and seasonal water application data, and the mean values were ranked using the least significant difference test. The growth stage duration and IWP were analysed based on the percentage difference.

 

RESULTS AND DISCUSSION

Operational performance of the drip irrigation system

The performance indices of the drip irrigation system set up for the trial fields in the 2020/202 and 2021/2022 seasons are shown in Table 3. The emitter flow uniformity was very good, being greater than 90%. According to Hakiruwizera (2024), drip irrigation systems with uniformity rates between 85 and 95% are considered acceptable, while those ranging from 75 to 85% are deemed fair, and below 75% require improvement. The EU_f showed that the drip system setup was adequate and that water was uniformly emitted on the fields within the treatments.

Crop phenology

Figure 1 shows the growth stage duration of tomato crops for the two seasons in the study locations. The tomato growth cycle (from transplant to the end of harvest) was 74 days in Gorogo and 64 days in Sepaat in the 2020/2021 season, while in the 2021/2022 season, the growth duration was 92 and 85 days in Gorogo and Sepaat, respectively. The growth duration of the tomato crop in Gorogo was consistently longer than in Sepaat, being 10 days in the first season and 6 days in the second season. While this difference in the growth duration may not be significant between the two locations, the growth duration between the two seasons was highly significant (p < 0.01). This difference in the seasonal growth duration (about 20 days) may have been caused by the late transplanting of tomato in the 2020/2021 season. The delay pushed the late vegetative, flowering, and fruiting stages into the heat period in late February and March. The heat stress from high night temperatures (varying from 24 to 27⁰C) and the daytime heat in those months could have hastened the length of the flowering, fruiting, and ripening stages. The lengths of the growth stages were shorter than those given by Allen et al. (1998) for tomato (105 − 115 days). Since the lengths of crop growth stages are influenced by several variables, including crop variety and agroecological and environment-induced variables, including heat and moisture stress (Taiz and Zeiger, 2010), the length of the growing season obtained for tomato may be specific to this study.

Figure 2 shows the growth stages and duration of the onion crops in Gorogo and Sepaat in the two seasons. The growth stage durations were similar in both locations and seasons. This suggests that the difference in transplant date did not affect the duration of the phenological changes. This could have been because the Bawku Red onion is known to be tolerant to heat stress (Danje et al., 2019). The leaves of the onion crops began to fall (leaf senescence) about 105 DAT. The lengths of the different growth stages of the onion crop agree with those given by Allen et al. (1998). The entire growth duration also agrees with Adu-Dapaah and Oppong-Komadu (2004), who reported that the Bawku Red onion variety matures between 100 and 120 days.

 

Table 3
Operational performance indices of the drip irrigation setup

Emitter Performance	2020/2021 Season				2021/2022 Season
	Gorogo		Sepaat		Gorogo		Sepaat
	Tomato	Onion	Tomato	Onion	Tomato	Onion	Tomato	Onion
Qavg (L hrv−1)	0.45	0.38	0.77	0.73	0.42	0.40	0.81	0.70
EUf (%)	91.0	84.8	93.6	92.0	91.9	88.8	93.6	92.0

Q_avg is average emitter discharge; EU_f is field emission uniformity

 

 

 

Seasonal water applied

Table 4 shows the SWA in the tomato trials in the Gorogo and Sepaat fields in the 2020/2021 and 2021/2022 seasons. Water applied in the Gorogo field varied from 251.7 to 439.1 mm in the 2020/2021 season and from 314 to 502 mm in 2021/2022.

In both seasons, the highest values were recorded in the Drip + FD treatment. Similarly, in Sepaat, the water applied varied from 232.2 to 392.1 mm in the 2020/2021 season and from 288.0 to 460.2 mm in 2021/2022. The SWA in the Drip + FD treatments in both seasons was highest because farmers applied more water, especially during the fruiting and ripening stages. The difference in water applied was due to the increased number of irrigation events in the 2021/2022 season compared to the 2020/2021 season, mainly because the latter season was longer than the former.

The 2020/2021 growth season was shorter because the tomato seedlings were transplanted in January 2021. The SWA in the two seasons was lower than that reported by Adimassu (2020), which ranged from 445 to 684 mm in the two study locations. Ahmed et al. (2022) reported a seasonal water requirement of 360–386 mm in Ikara, Nigeria. Biswas et al. (2015) computed a seasonal water requirement of 363 mm for tomato crop grown in 115 days. Ubi and Osodeke (2009) also reported that tomato transplanted between November and January in the tropics required 440–520 mm of water/season.

When tomato is transplanted in January and harvested in March/April, the seasonal water required ranges from 232 to 418 mm.

In the onion trial (Table 5), SWA varied from 368.5 to 749.6 mm in the 2020/2021 season and from 354.7 to 614 mm in the 2021/2022 season. The highest SWA occurred in the Drip + FD treatment. There was no statistically significant difference in SWA between the two study locations. The water applied by the farmers in the Drip + FD treatment in Sepaat in the 2020/2021 season was higher than that in Gorogo by 20%. In the 2021/2022 season, the difference between the SWA by the farmers in both locations was about 5%; the farmers in Sepaat then had better discretion in scheduling irrigation. The SWA agreed with those reported by Genemo and Seyoum (2021) in Ethiopia, ranging from 416 to 694 mm. Pérez-Ortola and Knox (2015) stated that onions need 225 to 1040 mm to produce 10 to 71 t ha⁻¹ while the FAO (2022) reported that the seasonal water requirement of onions ranges from 350 to 550 mm. Adimassu (2020) also reported a range of 447 to 526 mm. Generally, the seasonal water requirement of any crop depends largely on the crop agroclimatic location and season of cultivation. The irrigation method or system can also influence the depth of water required to grow a crop. Although water must be applied to meet the evaporative demand on the crop (net irrigation requirement), additional water may be required to compensate for losses due to irrigation efficiency.

Some key observations were made about the Drip + FD treatment. First, the yield from this treatment was second only to the 100% crop water requirement (Table 6 and Table 7), showing effective farmer intuition. The farmers adapted irrigation based on observation, demonstrating practical water management skills. Although individual farmers’ efficiency might vary, with some over- or under-irrigation, their collective scheduling judgment was relatively good. It was, however, evident that they were not mindful of deficit irrigation, given that the water applied under Drip + FD was more than that of the full irrigation treatment. The results suggest that, with training and monitoring tools, farmers could further improve efficiency. Positive results from farmer-managed drip irrigation build trust and encourage the adoption of optimised practices.

 

Table 4
Seasonal water applied (mm) in tomato trials in the 2020/2021 and 2021/2022 season

Treatment	2020/2021 Season		2021/2022 Season
	Gorogo (mm)	Sepaat (mm)	Gorogo (mm)	Sepaat (ccm)
Drip + FD	439.1a	392.2a	502a	460.2a
65% CWR	251.7d	232.2d	314.6c	288.0c
85% CWR	329.1c	303.6c	411.6b	376.6b
100% CWR	387.2b	357.1b	484.2a	443a

Mean values with the same letter in the same column are not significantly statistically different at a 0.05% level of significance

 

Table 5
Seasonal water applied in onion trials in the 2020/2021 and 2021/2022 season

Treatment	2020/2021 Season		2021/2022 Season
	Gorogo	Sepaat	Gorogo	Sepaat
Drip + FD	623.5a	610.0a	749.6a	641.0a
65% CWR	368.5c	354.0c	354.7d	363.5d
85% CWR	481.9b	478b	478.8c	475.4c
100% CWR	556.9a	563a	563.3b	559.3b

Mean values with the same letter in the same column are not significantly statistically different at a 0.05% level of significance

 

Table 6
Fruit yield of tomato crops in Gorogo and Sepaat during the 2020/21 and 2021/2022 seasons

Treatment	Tomato fruit yield (t ha−1)*		Tomato fruit yield (t ha−1)*
	Gorogo	Sepaat	Gorogo	Sepaat
	2020/2021	2020/2021	2021/2022	2021/2022
Drip + FD	10.61a*	9.11a	15.11a	11.55a
65 % CWR	6.02c	4.90c	9.96c	7.13c
85 % CWR	8.04b	6.62b	12.78b	8.44b
100% CWR	12.60a	9.21a	17.46a	11.83a

*Means with the same letter in the same column are not statistically different at a p < 0.05 level of significance.

 

Table 7
Onion bulb yield in the 2020/2022 and 2021/2022 seasons

Treatment	Onion bulb yield (t ha−1)*		Onion bulb yield (t ha−1)*
	Gorogo	Sepaat	Gorogo	Sepaat
	2020/2021	2020/2021	2021/2022	2021/2022
Drip + FD	23.6a	23.6b	15.34a	22.23a
65 % CWR	15.2c	14.2d	9.73c	13.37b
85 % CWR	20.7b	19.5c	12.68b	14.31b
100% CWR	24.2a	25.4a	15.59a	22.56a

*Mean with the same letter in a column are not significantly different at a p < 0.05 level of significance

 

Combining farmer flexibility with scientific guidance improves both productivity and water conservation. Training and peer influence play key roles in scaling sustainable irrigation methods tailored to local conditions.

The findings of this study contribute to sustainable irrigation practices in a number of ways. Farmers’ participation enhances adoption and long-term sustainability. Familiarity with, and the use of, precision irrigation techniques, such as drip irrigation, reduce water waste and improve efficiency. Scalable approaches can be adapted to various agroecological zones.

Policy recommendations can be derived from this study to improve water management strategies for vegetable production in Ghana. Drip irrigation practice should be promoted for adoption and its cost subsidised. Farmer training on optimised irrigation practices should be expanded and community-led water governance systems should be strengthened.

Yield response of tomato to irrigation strategies

The fruit yield of tomato in the two seasons and locations are presented in Table 6. The treatment irrigated at 65% CWR recorded the lowest yield at the two locations and during both seasons, while the treatment irrigated at 100% CWR recorded the highest yield. The trend was expected since deficit irrigation tends to reduce crop yield, and applying water to meet full water requirements results in the optimum yield. Irrigation treatments significantly affected tomato yield in both seasons and locations (p < 0.001). In the 2020/2021 and 2021/2022 seasons, 65% CWR treatment consistently produced lower yields compared to all other treatments (p = 0.001). The 85% CWR treatment resulted in lower yields than the Drip + FD and 100% CWR treatments (p ≤ 0.004), but a higher yield than the 65% CWR treatment (p = 0.001). No significant differences were found between Drip + FD and 100% CWR (p = 0.999), indicating similar performance under full irrigation. It implies that for optimal tomato yields, full irrigation (Drip + FD or 100% CWR) should be adopted, 65% CWR treatment should be avoided due to significantly lower yields, and 85% CWR should be considered for water conservation with a slightly reduced yield.

The average percentage increase was 52.2 and 32.2% for Gorogo and Sepaat, respectively. The difference can be associated with the effect of the late transplant of tomato seedlings in the 2020/2021 season. The results suggest that transplanting tomatoes in January instead of early December in the study locations would lead to significant yield losses of 30–50%.

A comparison of treatments in the same year showed that there were no significant differences at the p < 0.05 level of significance between the Drip + FD treatment and 100% CWR, implying that the farmers’ discretion may have led to SWA more than the CWR without a corresponding increase in yield. The results also showed that reducing water application by 35% (65% CWR) reduced tomato yield in Gorogo and Sepaat by 43.0 and 40.0%, respectively. Additionally, a reduction in water application by 15% (85% CWR) reduced tomato yield by 26.8 and 30.0% in Gorogo and Sepaat, respectively.

The yield recorded in both seasons of the 2020/2021 trials is poor compared to the global average fruit yield of 20–25 t ha⁻¹ (Robinson and Kolavalli, 2010). However, they were within the range of fruit yield of tomato in Ghana, reported as 6–17 t ha− (Adu-Dapaah and Oppong-Konadu, 2004; Robinson and Kolavalli, 2010). The yields in the 2020/2021 season were lower than in the 2021/2022 season largely due to flower abortion occasioned by the high temperatures, which began in late February into early March. Night temperatures above 23°C have been reported to cause low flowering, poor fruit setting, and flower abortion in tomato plants (Adams et al., 2001; Yang et al., 2016).

Yield response of onions to irrigation strategies

Table 7 shows the onion yields from the trials in Gorogo and Sepaat. The onion yields ranged from 15 to 24 t ha⁻¹ in Gorogo and from 14.2 to 25.4 t ha⁻¹ in Sepaat. The lowest values were obtained from the treatment irrigated at 35% deficit (65% CWR), and the highest from the treatment irrigated at 100% CWR. Across both locations and seasons, irrigation treatment had a significant effect on onion bulb yield (p < 0.001). The 65% CWR treatment consistently produced the lowest yields, which was significantly lower than all other treatments (p = 0.001), and 85% CWR showed intermediate performance, yielding significantly less than 100% CWR and Drip + FD (p ≤ 0.004) and significantly more than 65% CWR (p = 0.001). No significant differences were observed between Drip + FD and 100% CWR in the 2021/2022 season for onions in either Gorogo or Sepaat (p = 0.999). In Sepaat in 2020/2021, all treatments differed significantly (p = 0.001). The practical implications of these results are that for optimal onion yields, full irrigation (100% CWR) or Drip + FD should be applied. Severe water stress (65% CWR) should be avoided, and 85% CWR should be considered for water conservation. The yields in 2021/2022 were about 50% lower than in the 2020/2021 season. This difference may be associated with the effect of pest attack on onion in Gorogo in the 2021/2022 season. The results not with standing, the trend showed that deficit irrigation, achieved by reducing water application by 15% and 35% below the CWR, led to dry bulb onion yield reductions of 18.7–23% and 37–40%, respectively, across both study locations. The yield reduction effects of deficit irrigation were consistent across both seasons.

The yields obtained from these experimental trials were higher than the 10.05–15.65 t ha⁻¹ reported by Enchalew et al. (2016) by applying water equivalents of 50, 60, 70, 80, and 90% of CWR using gravity drip irrigation in Ethiopia. The yields from this study were also well above the ranges for onions in Ghana.For example, the DAI-Nathan Association (2014) reported yields of 10 t ha⁻¹ for the Bawku red variety. Van Asselt et al. (2018) estimated average yields of 3.3 t ha⁻¹. Balana et al. (2020) reported yields of 3.7 t ha⁻¹ under rainfed production and 12.0 t ha⁻¹ under irrigation, while official statistics (MoFA, 2020) put current yields at about 19 t ha⁻¹.

Irrigation water productivity (IWP)

Figure 3 shows the IWP of the tomato trials in Gorogo and Sepaat in the two seasons. IWP varied from 2.11 to 3.61 kg m⁻³ across all treatments. The results implied that between 2.11 and 3.61 kg of tomato was produced from every m³ of irrigation water applied. On a mean basis, the lowest IWP values were observed in Sepaat (2.21 kg/m³) under 85% CWR and in Gorogo (2.71 kg/m³) under the Drip + FD treatment. Conversely, the highest IWP values, 2.63 and 3.43 kg/m³, were recorded in the full irrigation treatment (100% CWR) for Sepaat and Gorogo, respectively, across both seasons. A comparative analysis between locations revealed that the IWP values for Gorogo exceeded that of Sepaat by approximately 22%, mainly due to the higher tomato yields in Gorogo compared to Sepaat. Within treatments and in both seasons, the IWP of the 100% CWR treatment was significantly higher (p < 0.05) than the other treatments. In the 2020/2021 season, the tomato yield was affected by the heat stress and moisture stress, which resulted from the deficit water application at 65% CWR, reducing IWP.

The practical implication of the results for both locations is that for optimal water use and higher tomato yields, irrigation scheduling should prioritise meeting full crop water demands.

The tomato IWP values for both locations are slightly lower than those recorded by Wondatir et al. (2013) in the Kobo Girana Valley irrigation system in Ethiopia, with an IWP of 3.81 kg m⁻³ and fruit yield of 20.03 kg m⁻³ at 100% CWR irrigation depth and an IWP of 3.87 kg m⁻³ and fruit yield of 20.48 kg m⁻³ at 80% CWR irrigation depth. In Kaduna, Northwest Nigeria, Onwuegbunam et al. (2023) obtained a mean maximum IWP value of 3.96 kg m⁻³ for UC 82B tomato at 60% CWR.

Figure 4 shows the pooled IWP of the onion trials in Gorogo and Sepaat during the two seasons. IWP was highest when 100% CWR was applied; the mean IWP at this level was 3.56 and 4.27 kg m⁻³ in Gorogo and Sepaat, respectively. The least IWP occurred in the Drip + FD treatment, being 2.92 and 3.67 kg m⁻³ in Gorogo and Sepaat, respectively, and these IWP values were 14–18% lower than those obtained under 100% CWR. The IWP values implied that 3.56 and 4.27 kg of onion were obtained as the highest bulb yields per unit volume of water applied in Gorogo and Sepaat, respectively. The IWP of onion obtained in this study is higher than the range of 2.18–3.42 kg m⁻³ obtained by Terán-Chaves et al. (2023) but lower than that obtained in the Kobo Girana Valley Irrigation Project, Ethiopia, by Wondatir et al. (2013) for an unspecified cultivar, that is, 5.5 and 6.93 kg m⁻³ at 100 and 80% CWR for 20.14 and 20.01 t ha⁻¹ of bulb yields, respectively. Across irrigation treatments, the yield output due to a determined irrigation amount plays a significant role in IWP. The onion IWP for Gorogo is less than the range obtained by Igbadun et al. (2012), but that of Sepaat is within the range. Between the two seasons, the IWP of onion at Gorogo was not significantly different from that at Sepaat in 2020/2021. However, in 2021/2022, the IWP at Sepaat exceeded that at Gorogo by 39%, mainly due to pest-inflicted yield losses during the vegetative stage in Gorogo. The lowest IWP values among the treatments were observed in 65% irrigation treatment during the 2020/2021 season. However, the Drip + FD treatment yielded the lowest IWP in the 2021/2022 season, likely due to the reduced crop yields resulting from infestation. One significant finding of this study is that the IWP of onion decreased with increasing deficit irrigation levels, contrary to expectations based on previous research, such as that of Terán-Chaves et al. (2023). Importantly, it is difficult to set a global benchmark for the IWP of crops, as their values are highly variable, differing among crop cultivars, locations, and irrigation methods. This explains why this parameter must be determined for a particular crop variety, location, and irrigation method.

 

 

 

Although some studies have suggested that deficit irrigation can reduce crop yield and water use under water-limiting conditions while increasing water productivity and saving water in tomato and onion production (Sujeewa et al., 2020), this study revealed that deficit irrigation reduced both the yields of tomato and onion and that IWP was not improved. Water productivity depends largely on crop responses to the magnitude of stress caused by the water deficit imposed at any given time. The magnitude and consequences of water stress on crops depend on the morphological and phenological characteristics of the crop and the agronomy-enabling environment, as well as the climatic evaporative demand at the time of the application of the deficit, the level of the deficit, and the soil water characteristics. Under conditions of high evaporation and limited available soil water, even moderate irrigation deficits can trigger severe moisture stress, significantly affecting crop yield, particularly during critical growth stages. If there is weed competition or crop health is threatened by pests and diseases, irrigation deficits will result in low water productivity. The findings of this study may have been influenced by two major factors. First, the late transplant of tomato and onion seedlings, particularly in the first season, potentially compromised the crops’ response to deficit irrigation. Second, pest infestation in the second season, though brought under control, may have further impacted the crops’ yield response to deficit irrigation.

Significant differences may occur in the yield of the same crops between two growing seasons, as year-to-year variations in temperature, humidity, and wind can impact evapotranspiration rates, affecting crop growth despite consistent irrigation. Differences in solar radiation and nighttime temperatures influence photosynthesis and energy storage, thus impacting tomato and onion yields.

This study concluded that deficit irrigation significantly decreased both yield and IWP compared to 100% CWR. However, given the increasing global focus on water conservation, deficit irrigation is still a viable strategy for vegetable crop production in water-scarce regions if drought-tolerant vegetable varieties are chosen (Geerts and Raes, 2009), as some tomato and onion cultivars can withstand water stress while still producing reasonable yields. Strategic irrigation during critical growth stages, such as the reproductive stage, helps to maintain productivity while reducing total water use (Kirda, 2002). Precision irrigation methods, such as drip irrigation, enhance water efficiency by delivering moisture directly to the root zone, minimising waste.

Yield–water use relationships

The graphical relationships between tomato fruit yield and SWA for the pooled values (2020/2021 and 2021/2022) are presented in Figures 5a and 5b for Gorogo and Sepaat, respectively. The relationship between the yield and SWA for Gorogo was best described by the curvilinear relationship (Figure 5a), expressed by Equation (7) as:

Equation (7) implies that the fruit yield was initiated only after a threshold of 162 mm of seasonal irrigation was applied. The fruit yield would peak at a SWA of 560 mm, after which it would decline with additional SWA. Applying seasonal water over 560 mm would result in losses, mainly deep percolation, with drip irrigation being the water application method. Similar yield–SWA trends were obtained by Igbadun et al. (2012) for onion and Alghamdi et al. (2023) for tomato.

The yield–SWA relationship for tomato in Sepaat (Figure 5b), however, was best described by a linear relationship (Equation 8):

Equation (8) implies that tomato fruit yield was initiated after a threshold SWA value of 59 mm was attained in Sepaat. Thereafter, for every 100 mm of water applied, the fruit yield increased by 2.89 t ha⁻¹. Hence, at 560 mm SWA (optimum SWA for Gorogo), the expected yield in Sepaat would be 14.5 t ha⁻¹, which is about 8% less than the maximum yield for Gorogo. The limitation of the linear function in analysing the SWA–yield relationship is that the maximum value of SWA is indefinite, but it is known that this is not the case, as each crop has a water requirement beyond which water applied is lost to evaporation, deep percolation, or runoff, depending on the irrigation method employed.

Greaves and Wang (2017) obtained a similar (linear) SWA–yield relationship for maize under deficit irrigation using flat basins.

Figures 6a and 6b graphically represent the onion yields and the SWA for the pooled values (2020/2021 and 2021/2022) for Gorogo and Sepaat, respectively.

The relationship between the bulb yield and SWA for Gorogo, best fitted by the curvilinear relationship (Figure 6a), is expressed by Equation (9) as:

The implication of Equation (9) is that the onion bulb yield was initiated after the SWA threshold value of 189 mm. Hence, the maximum bulb yield would be 18.6 t ha⁻¹, corresponding to a SWA of 620 mm. Thereafter, the bulb yield would decrease, even with additional SWA.

 

 

 

 

 

Therefore, applying seasonal water in excess of 620 mm would result in irrigation water losses. Alghamdi et al. (2023) reported similar trends for tomato grown in a greenhouse under deficit irrigation with fresh and saline irrigation water.

The yield–SWA relationship for onion in Sepaat (Figure 6b) was best described by the linear relationship (Equation 10):

Y = 0.0394 × SWA – 0.5465, r² = 0.87

(10)

Equation (10) implies that onion bulb yield was initiated after a threshold SWA value of 14 mm in Sepaat. Thereafter, for every 100 mm of water applied, the bulb yield increased by 3.94 t ha⁻¹. Hence, at 620 mm SWA (optimum SWA for Gorogo), the expected bulb yield in Sepaat would be 23.9 t ha⁻¹, which is about 22% more than the maximum yield for Gorogo.

 

CONCLUSIONS

Field trials were conducted in the Gorogo and Sepaat communities, Upper East Region, Ghana, to evaluate the yield and IWP responses of tomato and onion crops under varying water application regimes. The trials, managed by local farmers, also served as learning platforms for the adoption of drip irrigation and the understanding of irrigation scheduling impacts.

The results showed that irrigation level significantly influenced both yield and IWP. Full irrigation at 100% CWR consistently outperformed deficit irrigation (65 and 85% CWR) across both locations and growing seasons. Deficit irrigation led to significant yield losses without corresponding gains in IWP, contradicting expectations from previous studies.

Although irrigation based on farmers’ discretion yielded better results than deficit irrigation, it remained less effective than full irrigation, partly due to overapplication beyond crop water requirements. Environmental stressors, such as late transplanting, high temperatures, and pest infestations, further reduced crop performance under deficit conditions.

Full irrigation is recommended for optimal tomato and onion yields and maximum IWP at both Gorogo and Sepaat. However, applying 85% CWR may be considered a viable water-saving option under constrained water availability, acknowledging its moderate yield losses. Early season transplanting is critical to avoiding heat-related stress and yield reductions. Prompt pest management is also essential for preserving water productivity.

 

Author contributions: Conceptualization: HEI; Methodology: HEI, OC and MAK; Analysis: HEI and DOO; Investigation: HEI and MAK; Resources: OC; Data curation: HEI; Writing: HEI and DOO; Review: DOO and ST; Supervision: OC. All authors declare that they have read and approved the publication of the manuscript in this present form.

Funding: International Water Management Institute (IWMI), Accra Regional Office, Ghana.

Acknowledgments: This article was developed from field work carried out under the Africa Research in Sustainable Intensification for the Next Generation (AfricaRISING) Project Outcome 1: GH1221-20 executed by the International Water Management Institute (IWMI), Accra Office, Ghana.

Conflicts of interest: Authors declare that there are no conflicts of interest with respect to this publication.

 

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