Climate change and variability pose significant challenges in Cameroon's Far North Region. Relying predominantly on rainfed agriculture, this region faces heightened rainfall fluctuations and droughts, severely impacting agricultural output and pushing farmers into precarious socioeconomic conditions. Despite other adaptive strategies, access to water remains a challenge, prompting this study to assess the impact of rainwater harvesting (RWH) on crop yields in the Diamaré area. In a farm experiment, the growth of okra, cucumber, lettuce, and cowpea grown purely under rainfed conditions was compared to those that were rainfed as well as supplemented with harvested rainwater during the dry spell of the rainy season. A rooftop RWH system was adopted for irrigation, and data on crop growth and final yields were collected. Statistical analysis revealed a statistically insignificant yet positive influence of rainwater on the growth, development, and ultimate yield of okra, lettuce, and cucumber. The insignificant impact was due to minor differences in means of crop growth parameters. Despite minimal differences in means, the study underscores the positive impact of RWH on crop yields in Diamaré. The findings advocate for the adoption of rooftop and other cost-effective RWH techniques to enhance farmers’ resilience and long-term economic benefits.

  • The impact of rainwater harvesting (RWH) on crop yields has not been largely explored in Cameroon.

  • The study outlines the role of RWH in meeting crop water needs in drought-affected areas.

  • It shows the positive impact of RWH on the growth, development, and output of crops.

  • The results suggest RWH is economically beneficial in the long run.

  • Crop water requirement is a crucial determining factor for RWH.

Since the 1800s, human activities have been the main driver of climate change, primarily due to the burning of fossil fuels such as coal, oil, and gas (UN 2023). In fact, according to the most recent Intergovernmental Panel on Climate Change Sixth Assessment Report (IPCC 2023), human activities, principally through emissions of greenhouse gases, are unequivocally responsible for global warming with the global surface temperature reaching 1.1 °C above pre-industrial levels.

About 15% of today's anthropogenic greenhouse gas emissions are believed to come from agricultural sources (Akinnagbe & Irohibe 2014). While being a major contributor to climate change, agriculture is the most vulnerable to climate disasters (FAO 2011). Nowhere are its impacts more evident than in the agricultural sector. Climate change results in increasing temperatures, changing rainfall patterns, and more frequent and intense extreme weather events such as droughts, cyclones, and floods, which hamper agricultural productivity in several ways (Fakava 2012). These extreme weather events have direct effects on crop growth and their need for water, groundwater recharge, and the water cycle, as well as soil fertility, water supply for irrigation, and the prevalence of pests and diseases, which causes a huge loss in agricultural production (Yadav et al. 2020).

Climate change and variability have significantly intensified in the Sudano-Sahelian agroecological zone of Cameroon (Eze et al. 2021). With agriculture being predominantly rainfed, a disruption in rainfall patterns directly affects crop production, leading to food insecurity, loss of jobs, and poverty. The Far North Region is facing notable climate variability (World Bank 2022), leading to hazards such as heatwaves, dry spells, floods, droughts, and decreasing rainfall significantly affecting rainfed agriculture. Njoya et al. (2022) reported a 50% reduction in rainfed crop yields due to these conditions and a projected 90% decline in net income from crops by 2100. Farmers in this region are mostly concerned about droughts and decreases in rainfall (Figure 1), which are the main factors contributing to decreasing crop yields (Njoya et al. 2022).
Figure 1

Variability and trends of precipitation across seasonal cycles, 1951–2020 in the Far North Region of Cameroon.

Figure 1

Variability and trends of precipitation across seasonal cycles, 1951–2020 in the Far North Region of Cameroon.

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Figure 2

Map showing Diamaré Division.

Figure 2

Map showing Diamaré Division.

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Figure 3

Experiment farm location map.

Figure 3

Experiment farm location map.

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Figure 4

Rooftop RWH system.

Figure 4

Rooftop RWH system.

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Within the context of scarce water resources for agriculture, rainwater harvesting (RWH) constitutes a promising alternative that has been studied by different disciplines in recent years (Njoya et al. 2022). It guarantees a reasonably constant supply of water to crops by harnessing rainfall over a catchment surface and storing it for use at deficient periods. However, RWH appears to not have been widely adopted by farmers in the Far North Region of Cameroon (Cheo et al. 2014). There is limited literature on the impact of RWH on crop yields in Cameroon. This study therefore seeks to investigate the feasibility of RWH as an adaptation mechanism in the Far North Region of Cameroon. It was hypothesized that RWH has a significant impact on crop yields in the Diamaré Division, Far North Region of Cameroon. The study objectives were as follows: (i) to determine the current water sources used by farmers in Diamaré, (ii) to determine the degree of RWH adoption by farmers in Diamaré, (iii) to ascertain the various types and levels of RWH practiced by farmers in Diamaré, (iv) to identify the challenges faced by farmers in the adoption of RWH, in Diamaré, (v) to estimate the fraction of crop water requirements deficit met through RWH, in Diamaré, and (vi) to assess the impact of RWH on crop yields in order to develop a strategic framework for improving access to water in Diamaré Division, Far North Region of Cameroon.

Study area description

Diamaré Division, situated in the plains of the Far North Region of Cameroon at coordinates 10°35′37″N and 14°18′52″E, spans an area of 4,665 km2 with a population density of 137.7/km2 (Figure 2). It comprises nine sub-divisions, namely, Bogo, Dargala, Gazawa, Maroua I, Maroua II, Maroua III, Meri, Ndoukoula, and Petté with Maroua as its capital (City Population 2017). Maroua I, II, and III are urban settings. The Diamaré plains fall within the Sudano-Sahelian ecological zone of Cameroon, characterized by a semi-arid climate (Molua & Lambi 2006). This climate exhibits a dry season extending from October to May and a brief rainy season from June to September, with an annual rainfall average of 700 mm. Temperature differentials ranging from 27 to 41 °C are significant, and the rainy season and dry season nights (December–January) generally experience cooler conditions. Relative air humidity varies with altitude (Fita Dassou et al. 2015).

Study design and data collection

Questionnaire survey

The study concentrates on rural smallholder farmers in the Diamaré Division, Far North Region of Cameroon. Using a purposive sampling method, Meri, Gazawa, Bogo, and Petté sub-divisions were used for the study, given they are entirely agriculture-based. In order to determine the current water sources used by farmers, the degree of RWH adoption by farmers, the types and levels of RWH practiced by farmers, and the challenges faced by farmers in the adoption of RWH, a total of 150 farmers were surveyed. Questionnaires were administered by interviewers with the help of a research assistant to counter language barriers.

Farm experiment

In order to assess the impact of RWH on crop yields, a farm experiment was conducted in Maroua I. A 500 m2 parcel of farmland was chosen based on convenience as well as its favorable characteristics (Figure 3). The nature of the soil lithology was homogeneous vertisol for the entire plot. Vertisols are tropical soils with good agricultural and engineering potentials and cover over 1,200,000 hectares in North Cameroon (Tamfuh et al. 2018). The piece of land used for the study was covered in clay soil with a clay-loamy soil type that is ideal for garden plants.

Rooftop RWH system in the farm area

While other water harvesting techniques such as infiltration pits or recharge aquifers exist, a rooftop collection and tank storage technique was preferred for the experiment because it allows for the measurement and control of water supply, which are crucial for the experiment. An existing building located at the edge of the farm was used to establish a rooftop RWH infrastructure with an approximate catchment area of 15 m2 (Figure 4). A 6-m-long gutter was installed to collect the rainwater. Using a Poly Vinyl Chloride (PVC) pipe, the collected water was conveyed into a 1000-L plastic tank for storage.

Cultivation of crops under RWH and no RWH conditions

Four crops, namely, okra (Long Clemson), cucumber (Poinsett), lettuce (Blonde de Paris), and cowpea (PBR) were chosen for the experiment. These crops were chosen based on their water requirement characteristics, growth period, and their production and consumption rates in the study area (Table 1). Cucumber and lettuce are garden crops that are mostly grown for market purposes by farmers in Maroua. Cowpea is a drought-resistant crop that is suitable for cultivation in semi-arid areas and commonly cultivated by local farmers. Okra is mostly grown by farmers for home consumption. For the experiment conditions, the parcel of land was partitioned into two such that one of the portions was cultivated under rainfed conditions only (no RWH), while the other was rainfed but supplemented with harvested rainwater during the dry spell of the rainy season (RWH). All other factors, such as soil type, climatic conditions, application of pesticides, and farming techniques used, were identical for both the control and experiment sections during cultivation. Manual tillage was applied with very small mounds or furrows created for planting seeds. During the growth process, pesticides were applied to fight attacks and infection from insects. Okra, cucumber, and cowpea were planted on 9 June 2023. Lettuce seeds planted around the same time were transplanted to the experiment farm on 1 July 2023. The first harvest of cucumber was done on 29 July 2023. The second harvest was done on 1 August, the third was done on 8 August, the fourth on 15 August, and the last on 22 August. Lettuce and cowpea were harvested on 21 August 2023. For data collection, 6 okra plants, 12 cucumber plants, 11 lettuce plants, and 20 cowpea plants were sampled from each section. Data on crop growth and development were collected on a 10-day interval for the lifetime of the crops from both sections. The number of leaves, stem diameter, leaf area, fruit length, and fruit diameter were the major growth indices measured at different stages of crop growth and development (Figure 5). The data were collected by a trained Agriculture Expert. These data were used to make a comparative analysis of crop growth rate between crops that received harvested rainwater and crops that did not. The quantity of the final yield for each crop type was also measured from the respective crop portions and their weights were recorded.
Table 1

Experimental crops used and their water requirements

Crop typeSpecieQuantityDaily water requirement (mm) (FAO 2022) Maturity (days)Optimal growth period
Okra Long Clemson 3 packets (10 g each) 60–80 Days Rainy season (June–September) 
Cucumber Poinsett 3 packets (10 g each) 8.1 60–70 Days Rainy season (June–September) 
Lettuce Blonde de Paris 3 packets (5 g each) 60–70 Days Dry season (November–February) 
Cowpea PBR 2 cups 5.8 60–90 Days Rainy season (June–September) 
Crop typeSpecieQuantityDaily water requirement (mm) (FAO 2022) Maturity (days)Optimal growth period
Okra Long Clemson 3 packets (10 g each) 60–80 Days Rainy season (June–September) 
Cucumber Poinsett 3 packets (10 g each) 8.1 60–70 Days Rainy season (June–September) 
Lettuce Blonde de Paris 3 packets (5 g each) 60–70 Days Dry season (November–February) 
Cowpea PBR 2 cups 5.8 60–90 Days Rainy season (June–September) 
Table 2

Cost–benefit analysis parameters for cucumber cultivation

RWHNo RWH
Initial investment $110.58 $20 
Annual revenue (B$203.92 $191.04 
Annual cost (C$82.72 $82.72 
Discount rate (x5% 5% 
Period years (n15 Years 15 years 
RWHNo RWH
Initial investment $110.58 $20 
Annual revenue (B$203.92 $191.04 
Annual cost (C$82.72 $82.72 
Discount rate (x5% 5% 
Period years (n15 Years 15 years 
Figure 5

Monitoring of crop development.

Figure 5

Monitoring of crop development.

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Estimating irrigation water requirement met through RWH

To determine the irrigation water requirement met through harvested rainwater, data on the water requirement of each crop used was collected from secondary data sources. According to FAO (2022), the standard grass crop grown in a semi-arid climate with a mean temperature above 25 °C needs approximately 9 mm of water per day. Based on these parameters, crop water needs for the four crops concerned were estimated as follows.

A rain gauge was installed on the farm for the measurement of daily rainfall. This was validated with rainfall data from a recognized agency for authenticity. Rainfall data were collected on a daily basis. Holding all other factors such as the evapotranspiration constant, the following equation was adopted to determine the irrigation water need supplemented by harvested rainwater:
(1)
A 10-L watering was used to collect water from the tank and efficiently water crops based on their irrigation water needs, especially during periods of short dry spells, as determined by the deficiencies recorded in rainfall. Figure 6 shows the quantity of water available in the tank at different time periods.
Figure 6

Harvested rainwater stored in tank.

Figure 6

Harvested rainwater stored in tank.

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Data analysis

Quantitative data from questionnaires and the farm experiment were analyzed using the Statistical Package for the Social Sciences. Data analysis was done using descriptive statistics to establish the impact of RWH on the yield of the selected crops in quantitative terms. Qualitative data were interpreted and regrouped into common themes in order to be represented as quantitative data. Results were represented with the use of appropriate summary tables, bar charts, and pie charts. Observations of changes at different stages of crop growth and development were also presented in photos. Analysis of variance (ANOVA) was used to establish a significant difference or otherwise in the performance of the two scenarios simulated during the experiment. All analyses were performed at a 95% confidence level. The results were presented using summary tables and charts. A cost–benefit analysis was also performed in order to determine the economic feasibility of rooftop RWH for smallholder farmers in the study area, compared to cultivating under purely rainfed conditions. The discounted net present value was calculated as follows to show the net present value of the future benefits of adopting RWH:
(2)
where NPV is the net present value; R is the revenue, r is the discount rate, n is the years.

As depicted in Table 2, the initial investment for RWH consists of renting farmland, the cost of acquiring a used water tank, the cost of installing a rooftop water harvesting system and acquiring a watering can. For crops grown without RWH, the initial investment consists of renting farmland only. The annual cost consists of the costs of seeds, manure, pesticides, and cost of labor, which was the same for both cultivation under RWH and no RWH conditions. The annual revenue was determined by multiplying the quantity of cucumber output from each section by the unit price (price per kg of cucumber). The discount rate adopted represents the operational interest rate in Cameroon. The water harvesting system adopted is assumed to serve for a period of 15 years.

Water sources used by farmers for agriculture in Diamaré division

Farming in Diamaré is practiced both during the rainy season and the dry season. In the rainy season, the results from the survey reveal that all farmers (100%) depend on rainfall for agriculture. These results are compatible with the study by Ntali et al. (2023), who pointed out that agriculture is primarily rainfed. During this season, the main crops cultivated are maize, millet, cotton, sorghum, beans, groundnuts, cowpeas, rice, and potatoes. During the dry season, the main crops cultivated are onion, sorghum, pepper, tomatoes, okra, carrots, and other vegetables. The farmers mainly used collected rainwater, boreholes, and wells to meet their crop water needs. However, this is effectively the case only in the rainy season. Dry season farming capitalizes on other water sources such as boreholes and wells, which has rarely been discussed by previous researchers. It is therefore crucial to take into consideration water sources used by farmers in the dry season, as over 41.3% of farmers in Diamaré are involved in counter-season farming.

Degree of adoption, types, and levels of RWH in Diamaré

Results from the survey show that 85.3% of farmers practice either rooftop and/or surface RWH. This drifts away from most other works that present contrary findings. Mtyelwa et al. (2022) have it that RWH adoption by smallholder farmers is very low in the rural areas of Ethiopia and South Africa. Furthermore, while most farmers (74.7%) practice rooftop RWH, just 42% of farmers practice surface runoff water harvesting. The findings also reveal that factors that greatly influence farmers' adoption of RWH are income/finance, level of technology, and complexity of RWH systems. This perfectly complements the results of Nji & Fonteh (2002) as concerns factors influencing RWH adoption in the Mandara Mountains of the Far North Region of Cameroon.

For rooftop water harvesting, the findings reveal that farmers mostly use the rooftops of their existing buildings with aluminum sheets to harvest rainwater. The water is usually collected and reserved in bowls, buckets, and drums and can last up to 3 days (Figure 7). Unlike rooftop RWH, the most common methods of collecting surface water in Diamaré are through the use of canals, existing waterways, and terrace systems. These, of course, are common traditional technologies, as can be seen in the works of Mfitumukiza et al. (2022). The results showed terrace farming to be very common in Meri, which is ideally due to its mountainous nature. This proves that geographical locations influence the technique of RWH adopted by farmers in Diamaré, as already revealed by Sayl et al. (2020).
Figure 7

Traditional mode of RWH in Diamaré.

Figure 7

Traditional mode of RWH in Diamaré.

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Challenges faced by farmers in adopting RWH for agriculture in Diamaré

Just like in the work of Mwenge Kahinda & Taigbenu (2011), finance is the most common challenge limiting the widescale adoption of RWH for agriculture in Diamaré. A greater number (71.3%) of the farmers surveyed revealed that RWH for agriculture is an expensive investment that they cannot afford. Furthermore, a majority (56%) of the farmers point out that their water storage capacity is limiting their ability to store rainwater. A significant proportion of farmers also find it difficult to realize (55.3%) and maintain (48.7%) RWH infrastructures. Another striking challenge is that over 41.3% of the farmers do not know what RWH technique to use in their farms.

Crop water requirement met through RWH

The farm experiment demonstrated that RWH effectively supplemented crop water needs for all crops except cowpeas (Table 3). This aligns with the finding of Sacolo & Mkhandi (2021) that RWH could meet 45% of crop water requirements in the Lubombo Plateau. Okra had an approximate growing period of 81 days during which its water requirement was 738 mm. Owing to insufficient rainfall, okra had an irrigation water need of 144 mm, which was met through RWH. Cucumber had an approximate growing period of 81 days, during which its water requirement was 664.2 mm. Owing to insufficient rainfall, cucumber had an irrigation water need of 70.2 mm, which was met through RWH. The lettuce was transplanted after attaining 2 weeks of growth. It therefore had an approximate growing period of 60 days on the experiment farm, during which its water requirement was 558 mm. Rainfall was however limited to 324 mm. Thus, lettuce had an irrigation water requirement of 234 mm, which was met through RWH. Cowpeas, conversely, had a lower water requirement. While it had a water requirement of 475.6 mm, rainfall during its growing period of 81 days was 594 mm. This means the crop had sufficient water with the support of RWH. Excess water has a negative impact on the crop's growth, as will be seen in the following section.

The impact of RWH on crop yields in Diamaré

Crop growth and development parameters

Number of leaves

From Figure 8, it can be seen that the six okra crops that were sampled from both crop sections had an equal number of leaves on the 24th day of growth. However, when the crops were approaching maturity on the 64th day of growth, the six crops that received harvested rainwater had an average of 43 leaves, while those that did not receive harvested rainwater had an average of 39 leaves. RWH therefore had a positive impact on the growth of okra. However, ANOVA results show that this impact was insignificant (p = 0.529) at a 95% confidence level.
Figure 8

Effect of rainwater supplementation on the development of plant leaves.

Figure 8

Effect of rainwater supplementation on the development of plant leaves.

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Parkash et al. (2021) reported that cucumber plants with a smaller number of leaves will have reduced yield due to reduced photosynthesis ability. Vide et al. (2023) have shown that cucumber yield is affected by irrigation. It can be deduced from Figure 8 that RWH has a positive impact on the growth and development of cucumbers. On the 24th day of growth, crops from both sections had an average of about eight leaves each. However, on the 54th day, cucumber crops that received harvested rainwater had an average of 36 leaves each, while those that did not receive rainwater had an average of 34 leaves each. The impact is, however, insignificant given the minimal difference between the means of crops that received rainwater and crops that did not, with a p-value of 0.732 at a 95% confidence level.

Furthermore, for lettuce crops, there was no significant difference between the number of leaves for crops that received harvested rainwater and those that did not receive harvested rainwater at a 95% confidence level (p = 0.937).

Cowpeas, conversely, have a very low water requirement, hence their suitability for the Diamaré region. As a result, they received just a little harvested rainwater during the first days of growth after which they were left to grow under normal conditions. Figure 8 shows that on the 24th day of growth, the crops that received harvested rainwater had an average of 9 leaves, while those that did not had an average of 8 leaves. By the 44th day of growth, neither of the crops was receiving harvested rainwater but there was still a difference in the number of leaves. Crops that did not receive rainwater had more leaves than those that did. This suggests that more water than required was supplied. The impact was however insignificant given the minimal difference between the means of crops that received rainwater and crops that did not. The insignificance is justified by the p-value (0.709), which is greater than 0.05 at a 5% level of significance.

Stem diameter

From Figure 9, it can be seen that on the 34th day of crop growth, okra crops that received harvested rainwater had an average stem diameter of 9.1 cm, while those that did not receive rainwater had an average stem diameter of 8.5 cm. As the crops approached maturity on the 64th day of crop growth, crops that received harvested rainwater had an average stem diameter of 29 cm, while those that did not had an average diameter of 26.63 cm. Hence, RWH had a positive impact on the growth of okra. However, as in the case of a number of leaves, the difference in stem diameter of solely rainfed okra plants and those with supplemental water supply from rooftop harvested rainwater was not significant (p = 0.455) at a 95% confidence level. Gunawardhana & Silva (2012) reported that okra has a high yield when grown under high temperature and irrigating at field capacity. Dhankhar et al. (2012) also reported a high correlation (r = 0.76) between okra yield and soil relative humidity.
Figure 9

Effect of rainwater supplementation on stem diameter (okra, cucumber, and cowpea) and leaf size (lettuce).

Figure 9

Effect of rainwater supplementation on stem diameter (okra, cucumber, and cowpea) and leaf size (lettuce).

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From Figure 9, it can be seen that cucumber crops that received harvested rainwater had an average stem size of 13.01 cm, while those that did not had an average stem size of 10.98 cm. Therefore, crops that received additional harvested rainwater had comparatively larger stems than those that did not. The difference was significant given the p-value (0.008), which is less than 0.05 at a 5% level of significance. The results presented in Table 4 show that cucumber crops that received harvested rainwater produced fruits with an average length of 21 cm and diameter of 76.7 cm, while cucumber crops that did not receive harvested rainwater produced fruits that had an average length of 19.5 cm and diameter of 72 cm. This means that RWH has a positive impact on the size of the fruit produced as well. Despite the obvious positive effect of RWH on cucumber, the impact was not significant (0.218) at a 95% confidence level.

Table 3

Crop water requirement, rainfall, and irrigation water need

 
 

Unlike the other plants, the effect of supplemental water supply on lettuce plants through RWH was measured using leaf size. From Figure 9, it can be seen that on the 10th day of crop growth, lettuce crops that received harvested rainwater had an average leaf area of 30.38 cm2 each, while those that did not receive harvested rainwater had an average leaf area of 28.83 cm2. This was the case until the 40th day of the crop growth. Lettuce plants that received harvested rainwater had an average leaf area of 110.32 cm2, while those that did not had an average leaf area of 106.71 cm2. RWH, therefore, had an impact on the yield of lettuce plants. However, further analysis using ANOVA revealed that the difference in the sizes of lettuce leaves was not statistically significant at the 95% confidence level (p = 0.751).

On a qualitative level, lettuce plants that received supplemental water supply through RWH had richer and greener leaves than the leaves of those that were solely rainfed, which had a somewhat pale appearance (Figure 10).
Figure 10

Pictorial depiction of the effect of rainwater supplementation on lettuce.

Figure 10

Pictorial depiction of the effect of rainwater supplementation on lettuce.

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For cowpeas, Figure 9 shows that crops that received harvested rainwater on the 34th day of growth had an average stem diameter of 8.23 cm, while those that did not, had an average of 9.16 cm. By the 44th day of growth, neither of the crops was receiving harvested rainwater but there was still a difference in the stem diameter. Cowpea crops that did not receive rainwater had larger stems (10.29 cm) than those that did (9.95 cm). This impact was, however, insignificant given the minimal difference between the means of crops that received rainwater and crops that did not. The insignificance is justified by the p-value (0.557), which is greater than 0.05 at a 5% level of significance. These results complement the works of Wanjira & Peris (2016), which revealed that RWH is more suitable for dry season farming through irrigation of the land. Thus, the decline in rainfall amounts in the study area is not significant enough to result in impaired growth of cowpea.

Quantity of output

Based on the results presented in Table 4, cucumber plants that received harvested rainwater produced about 135 fruits, of which 34 became rotten on the farm. The remaining 101 good fruits that were harvested weighed 50.98 kg. For those that did not receive harvested rainwater, the plants produced about 120 fruits, of which 16 became rotten on the farm, leaving a net of 104 good fruits with a total weight of 47.76 kg. Even though crops that received additional harvested rainwater had a lower number of good fruits, their total weight was higher than those that did not receive harvested rainwater. Cucumber fruits cultivated under warm temperatures and high humidity levels are vulnerable to several fungus-like organisms of the genus Pythium (Sultana et al. 2023). The cucumber fruits that became rotten developed the cucumber fruit rot Pythium. Its symptoms start as water-soaked, brownish lesions that quickly enlarge and turn big, watery, squishy, and rotting. The rot generally appears on the portions of fruit in contact with the soil. Rotten tissues can be seen to have white cottony mycelium, especially under humid conditions, as seen in Figure 11.
Table 4

Weight and size of cucumbers produced

 
 
Figure 11

Rotten cucumber fruit.

Figure 11

Rotten cucumber fruit.

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Cost–benefit analysis of adopting rooftop RWH for cucumber cultivation in the rainy season by smallholder farmers in the study area

From Table 5, it can be seen that adopting rooftop RWH for the cultivation of cucumber in the rainy season is worthwhile given it has a higher net present value of $1,147.43, unlike cultivation under no RWH conditions. Thus, adopting rooftop RWH for cucumber cultivation in the rainy season by smallholder farmers is economically viable in the long run.

Table 5

Cost benefit analysis for cucumber cultivation (net present value)

RWH
No RWH
Discounted annual costDiscounted annual revenueDiscounted annual costDiscounted annual revenue
Total discounted value $858.61 $2,116.62 $858.61 $1,982.93 
Initial cost $110.58  $20.00  
Total present value $969.19 $2,116.62 $878.61 $1,982.93 
NPV $1,147.43 $1,104.32   
RWH
No RWH
Discounted annual costDiscounted annual revenueDiscounted annual costDiscounted annual revenue
Total discounted value $858.61 $2,116.62 $858.61 $1,982.93 
Initial cost $110.58  $20.00  
Total present value $969.19 $2,116.62 $878.61 $1,982.93 
NPV $1,147.43 $1,104.32   

This study aimed to assess the impact of RWH on crop yields toward food security in Diamaré, Far North Region of Cameroon. Experimental results show that the crops grown under RWH conditions have better and faster growth and development rates while producing larger outputs, except for cowpea which revealed contrasting results. Cowpea is a drought-resistant crop that is suitable for cultivation in semi-arid regions. It has a low water requirement and will not produce well if given much water. Therefore, the crop water requirement is a crucial determining factor for the adoption of RWH for agriculture. Farmers should only consider RWH when their crop water needs cannot be met by direct rainfall. Based on a cost–benefit analysis performed for cucumber cultivation, the study found rooftop water collection and storage in tanks for irrigation to be economically viable in the long run for smallholder farmers. Therefore, rooftop RWH by farmers to supplement crop water needs in the rainy season during dry spells is recommended. Moreover, smallholder farmers can also adopt other cost-effective RWH technologies such as half-moon, contour bunds, terracing, and infiltration pits.

The authors wish to acknowledge support from the African Union and the Pan African University of Water and Energy Sciences, Including Climate Change (PAUWES) for awarding study scholarship to the primary author. The authors express profound gratitude to the Global Water Partnership–Central Africa (GWP-CAf) Regional Secretariat for their continuous support during the research project. Acknowledgment is also extended to Alliance Citoyenne pour le Développement et l'Éducation à l'Environnement (ACEEN), for facilitating access to rural farmers and aiding in data collection in the Far North Region.

All relevant data are included in the paper or its Supplementary Information.

The authors declare there is no conflict.

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