https://orcid.org/0000-0001-9457-6382
?Mathematical formulae have been encoded as MathML and are displayed in this HTML version using MathJax in order to improve their display. Uncheck the box to turn MathJax off. This feature requires Javascript. Click on a formula to zoom.ABSTRACT
In the semi-arid regions of southern Africa, around the borders of Angola with Namibia, the Cuvelai seasonal wetland system is formed by floods during the rainy season. The objective of the present study was to assess the effects of introduction of a rice-based mixed cropping system to the seasonal wetlands (ondombe in the local language) from agronomic, social, and economic perspectives. For this purpose, we used a simple methodology with a multidisciplinary approach for yield and household survey and scenario analysis in northern Namibia. The yield survey revealed that in ondombe, rice showed a higher yield performance than that of pearl millet and sorghum, even in a drought year. The farm household survey showed that introducing a rice-based mixed cropping to ondombe could help local farmers enhance crop productivity by reducing labour and providing high rice yield. In addition, scenario analysis based on the yield and household surveys conducted in these regions suggested that the introduction of the mixed cropping system to ondombe could compensate for one-fourth of the governmental urgent food import budget even in drought years. Therefore, this system is an effective option for sustainable agricultural production and environmental management in the studied region.
1. Introduction
In sub-Saharan Africa, agriculture plays an important role in providing food and income for the majority of people, and their livelihood and food security depends to a large extent on smallholder crops (Gassner et al. Citation2019; Stuch et al. Citation2021). However, the impact of climate change on agriculture is expected to be severe in these areas owing to the fluctuating water environments (Altieri et al. Citation2015; El-Beltagy and Madkour Citation2012). The occurrence of floods and droughts in the same locations has become common in sub-Saharan Africa (Bola et al. Citation2014). Moreover, in recent years, there has been an increase in flooding events in semi-arid sub-Saharan Africa owing to high summer rainfall (Bischiniotis et al. Citation2018). Under such weather conditions, effective methods of crop production are required to stabilise agricultural productivity (Awala et al. Citation2016).
Northern Namibia is a semiarid environment with a unique seasonal wetland system, known as the Cuvelai seasonal wetland system (Watanabe et al. Citation2016). The Cuvelai seasonal wetland system, with an aggregate area of 800,000 ha, can store a large amount of water during the summer rainy season from November to April (Awala et al. Citation2021). Many people benefit from the seasonal wetlands through livelihood activities such as livestock farming and fishing (Fujioka et al. Citation2018). These seasonal wetlands also have the potential to produce high yields of pearl millet in drought years because of the suitable water environment and soil fertility (Watanabe et al. Citation2016). More than 90% of the smallholder farmers in the investigated region cultivate drought-tolerant crops such as pearl millet and sorghum as staple food (Awala et al. Citation2016). In northern Namibia, water that accumulates in the lower parts of seasonal wetlands also contributes to the production of drought-tolerant crops (Zegada-Lizarazu et al. Citation2007). In particular, the yield of pearl millet increased when the crop was planted near the lower, wetter slopes of seasonal wetlands in the drought year (Rockström and De Rouw Citation1997). However, the risk of complete failure when growing drought-tolerant cereal crops that are susceptible to flooding may be significantly increased by unpredictable flooding patterns.
In the late 1980s, rice experts from the Philippines were recruited to conduct commercial rice production under the Kalimbeza rice project in the Zambezi Region (Iijima et al. Citation2018). However, this work was later terminated because the large-scale development of irrigation systems was not suitable for the smallholder farmers in the region. Considering the benefit for each smallholder farmer is important for sustainable agricultural production and environmental management. Iijima et al. (Citation2018) proposed the introduction of a rice-based mixed cropping system to the seasonal wetlands (called ondombe in the local language), which recognises the common land features of crop fields in the area (see ). The areas located relatively far from the seasonal wetland system are not flooded under normal circumstances and can therefore be used to grow local upland crops such as pearl millet, sorghum, and maize. In contrast, the areas located relatively close to the wetland system are prone to flooding, making them unsuitable for cultivating upland crops. In a series of basic research trials, under the conditions of flooding and drought events, crop growth and production were reported to be improved by the newly developed technique of a “close mixed-planting technique” (Awala et al. Citation2016; Iijima et al. Citation2016; Izumi et al. Citation2018; Yamane et al. Citation2018). In this technique, when the roots of rice and pearl millet become entangled, air is released from the roots of rice and utilised by pearl millet (Iijima et al. Citation2017). In ondombe, it is necessary that agriculture and rural development start focusing on the introduction of mixed cropping systems for the following reasons: first, to take into consideration environmental conservation, local ecosystems, and biodiversity; second, because they provide cultivation methods and food production systems to cope with certain severe climate events, such as droughts and floods; and finally, to apply “interdisciplinary research” concepts that combine scientific and traditional knowledge, thereby benefitting the local society and its cultural heritage.
Figure 1. Aerial photograph of the rice-based mixed cropping system in ondombe (seasonal wetland).
Source: Aerial photo taken on 10th May 2016 over Onamudindi Village.
The purpose of the present study was to evaluate the system of rice-based mixed cropping in ondombe in the semi-arid area of northern Namibia from three perspectives; (i) agronomic evaluation using a yield measurement survey, (ii) socio-economic evaluation using a farm household survey, and (iii) farm policy evaluation using scenario analysis.
2. Materials and methods
2.1. Environmental and socio-demographic characteristics of study site
The studied area, in northern Namibia, belongs to the savannah climate type according to the Köppen climate classification, and the annual precipitation varies each year. There are two contrasting seasons in a year: the rainy season, which lasts from October to April and has a peak between December and March, and the dry season present during the rest of the year. During the rainy season of 2007/2008, 2008/2009, and 2010/2011, the area received higher amount of rainfall than that in the earlier years, resulting in severe floods in the region. In contrast to these floods, the region experienced severe droughts during the rainy seasons of 2012/2013 and 2014/2015. In the present study, the rainfall pattern of 2015/2016 was different from that in the previous three years (). Rainfall was concentrated in February, and little rain occurred during the rest of the year.
Table 1. Patterns of monthly precipitation in the Omusati region from 200/2001 to 2019/2020 season.
Specific seasonal wetland systems are largely distributed in northern Namibia and include various types of wetlands: seasonal river wetlands (locally known as oshana/oshanas) and small seasonal ponds and large pans (ondombe) (Mendelsohn et al. Citation2000). The soils of these ecosystems are classified into three major groups, namely, Cambic Arenosols, Eutric Cambisols, and Haplic Calcisols, and most of them are characterised as alkali soil or solonetz (Mendelsohn Citation2006).
The population of Namibia is 2.28 million and general net income per person is US$5210. The units of local administration in Namibia are regions with some local authorities, such as cities, towns, and villages. Our target area included the Omusati, Oshana, Oshikoto, and Ohangwena regions. The demographics, socio-economics, and land types of these four regions are similar. The population of these targeted regions was 908,384, and Ovambo, a local language in northern Namibia, was spoken by 86% of the population (Namibia Statistics Agency Citation2019). These regions have more female-headed households and female members in the population, as the regions are characterised by high unemployment and migration rates (Hegga et al. Citation2016). Many of the economically active male inhabitants have migrated to major cities and towns in Namibia.
2.2. Agronomic evaluation by yield measurement survey
We held field lectures to explain the aim and methods of mixed cropping in ondombe (MCO) to the farmers on 23rd and 25th November, 2015 at Onamundindi and Oshiteyatemo villages, respectively. We provided the participants with seeds of rice (Oryza sativa), pearl millet (Pennisetum glaucum), and sorghum (Sorghum bicolor), and invited them to join in the MCO trial programme, which required them to cultivate the three crops on their own ondombe. To support the participants, the programme staff visited and managed each ondombe using tractors and additionally provided paddy seedlings in case there was no germination owing to late rainfall.
The yield survey was conducted on the ondombe of 10 farmers and on upland fields of 42 farmers. In the ondombe, all cultivated crops were harvested, and the cultivated area was measured using a hand-held GPS (GPSMAP 62SJ, Garmin International, Inc., Kansas City). In addition, we recorded the position of the ondombe in the flood year (2013). In each location, rice, pearl millet, and sorghum panicles were harvested from several 4 m2 plots (2 × 2 m). The number of plots on each field depended on the field area. Rice, pearl millet, and sorghum panicles were air-dried and threshed, after which the clean grains were weighed and the grain moisture content was measured by a grain moisture tester (PM-830-2, Kett, Japan). The grain weights were adjusted to 14% moisture content to obtain the total yield per plot. To examine the differences in the results between control and volunteer farmers, t-tests were performed.
2.3. Socioeconomic evaluation by farm household survey
Two villages in the Omusati Region, Onamundindi and Oshiteyatemo, were surveyed in this study (see ). The farmers were divided into two categories: voluntary farmers and control farmers. Voluntary farmers were those participants who carried out the MCO programme, and control farmers were those that did not participate in the programme, but had one or more ondombe in their estates. The household survey was conducted via semi-structured interviews, which contained questionnaires and face-to-face interviews, as needed. The interviews included the household profiles, agricultural activities, labour allocation, on- and off-farm income, and recognition of the MCO project. The household heads or agents of household heads were interviewed as respondents.
Figure 2. Target regions and the two villages, Oshiteyatemo and Onamundindi, in northern Namibia.
Out of a total of 121 farm households surveyed, there were 54 voluntary farmers and 67 control farmers. Eighty-nine farmers who participated in the household survey joined the field lectures. The profiles of the surveyed farm households are shown in . There were no significant differences in the profiles between the two villages. The ratio of men to women in the household heads was 58% to 42%, and the average age was 65.4 years (youngest: 24 years old; oldest: 105; SD: 21.2). The educational background in half of the households was primary school; in 25%, it was secondary school or higher. The average farming experience was 55 years (minimum 6 years; maximum 93 years; SD: 15.6). Sixty percent of the respondents had been in their current houses since 1990, the year of independence. The average number of household members was 12 persons (minimum: 3 persons; maximum: 42 persons; SD: 7.2). The differences in the labour input and time were tested by Tukey–Kramer multiple comparison test. All statistical analyses were carried out using BellCurve for Excel (Social Survey Research Information Co., Ltd. Tokyo, Japan).
Table 2. Profiles of farm households surveyed in the two villages, Onamundindi (n=51) and Oshiteyatemo (n=72).
During May–July 2016, we visited several Omatalas or “open markets” and collected retail price data for pearl millet and rice in the region. Pearl millet and rice grains originated from Angola.
2.4. Scenario analysis
The economic value of MCO for the drought/flood year was estimated by the following scenario analysis. To assess the MCO, we estimated the farm-level net value of the agricultural production system in the drought/flood year as well as the regional increment of economic value in the project-targeted region, Omusati.
Farm-level net value [Fvalue (Namibian dollar (N$) (US$1 = N$15.2)/farm household)] in the ondombe was mainly estimated by the value of pearl millet (PMvalue) and rice (Rvalue) as follows:
(1)
(1) where Cratio is the ratio of input costs (including fertiliser purchase and machine rental) to the total value obtained from the ondombe (pearl millet + rice). The Cratio was provided by the household survey [fixed at 0.076 (7.6%)].
The pearl millet value from the ondombe [PMvalue (N$/farm household)] was calculated using the production [PMproduct (kg/farm household)], milled ratio (PMmill), and local market price [PMprice (N$/kg)] as follows:
(P2)
(P2) where PMmill was fixed at 0.75, and PMprice was provided by the market survey (fixed at 18.5).
The rice value from the ondombe [Rvalue (N$/farm household)] was also calculated using the production [Rproduct (kg/farm household)], milled ratio (Rratio), and local market price (Rprice (N$/kg)) as follows:
(R2)
(R2) where Rratio was fixed at 0.70, and Rprice was provided by the market survey (fixed at 11.5).
The pearl millet production from the ondombe per farm household (PMproduct) was calculated using the yield of the ondombe [PMyield (kg/ha)] and the cultivated area in the ondombe [PMarea (ha)] as follows:
(P3)
(P3) where PMyield and PMarea were measured by the yield survey in 2016.
The rice production in the ondombe per farm household (Rproduct) was calculated using the yield of the ondombe [Ryield (kg/ha)] and the cultivated area in the ondombe [Rarea (ha)] as follows:
(R3)
(R3) where Ryield and Rarea were measured by the yield survey in 2016.
The cultivable area in the ondombe per farm household [Ocrop (ha/farm household)] was estimated using the area of the ondombe per farm household [Oarea (ha/farm household)] and the adjustment ratio of cultivable area in the ondombe in the flood year to that in 2016 (Oratio) as follows:
(4)
(4) where Oarea was calculated from the yield survey in 2016, and Oratio was estimated using a household survey.
The regional-level economic value [Rvalue (N$/village)] was calculated using the Fvalue, the number of farm households per region (Fnumber), and the proportion of farmers with an ondombe and conducting MCO (Fproportion) as follows:
(5)
(5) where the Fnumber of the Omusati, Oshikoto, Oshana, and Ohangwena regions was 30,308, 24,681, 16,350, and 35,138, respectively. The Fratio was calculated from the ratio of farmers who had an ondombe in their estates [fixed at 0.85 (85%)] and the ratio of farmers who actually conducted MCO [fixed at 0.5 (50%)], based on the household survey (fixed at 0.425).
3. Results and policy evaluation
In the ondombe, the yield of rice was much higher than that of pearl millet and sorghum (), even in the drought year. Therefore, when farmers conduct MCO, they can achieve high rice yields. In addition, close-mixed planting with rice might promote the growth of pearl millet and sorghum under flooded conditions (Iijima et al. Citation2016; Awala et al. Citation2016). Ridging in seasonal wetlands might also mitigate the flooding stress for crops (Hirooka et al. Citation2019). The production and yield of pearl millet by control farmers were significantly higher than those by voluntary farmers (). Thus, voluntary farmers may want to increase their levels of crop production and consequently may be willing to adopt the MCO system. We found that the average rice-harvested area in the ondombe was 139.2 m2, and the labour input and time was only 3.0 (%) and 4.8 (person*days: days of labour by a single person), respectively. The labour input and time was significantly lower than upland cultivating and herding (). Although most of the labour input for upland cultivation regionally was in terms of weeding, this activity is not extensively required in rice cultivation. Thus, farmers did not need to spend a lot of time for MCO, and, we concluded that the introduction of MCO in the investigated area would not be difficult for farmers.
Figure 3. Labour input into mixed cropping in ondombe (MCO): (a) share (%) and (b) time (man × date). Means followed by the same lowercase letter were not significantly different at P < 0.05, according to Tukey–Kramer multiple comparison test.
Table 3. Summary of the yield survey in 2016.
shows the differences between the voluntary and control farmers based on the household survey. There was no difference in primary occupation between voluntary farmers and control farmers. In contrast, the number of family members of the voluntary farmers was higher than that of the control farmers. In addition, most voluntary farmers did not feel that their crop production was high enough and that they had access to extension services. In fact, the pearl millet production by voluntary farmers was significantly lower than that by control farmers (). Almost all voluntary farmers wanted to continue the MCO. These results suggested that the introduction of MCO might help the farmers to enhance crop productivity.
Figure 4. Results of the household survey. (a) Number of household members, (b) Primary occupation of the head of the household, (c) Did you or do you expect to produce enough pearl millet to feed your family/household this year, (d) Do you have any access to the Extension Service and Advice, (e) Would you try mixed cropping in ondombe next year.
Source: 2016 Farm Household Survey.
4. Integrated assessment and discussion
Namibia receives an uneven distribution of rainfall, ranging from 50 mm during the dry season in the coastal region to more than 600 mm during the wet season in the northern region (Awala et al. Citation2021). Although the climate of Namibia is characterised by low rainfall, high evapotranspiration rates, and high temperatures (Heyns Citation1991), northern Namibia develops seasonal wetlands during the wet season (November to May) by receiving local rainfall and floodwater from the Angolan highlands. Seasonal wetlands have a high potential for rice production and have been progressively studied (Mizuochi et al. Citation2014). The utilisation of water resources in seasonal wetlands might pose risks such as water depletion and soil salinisation, especially under semiarid conditions. The rainfall pattern in 2016 was different from that in the previous three years: and there was little rain until January, and, a lot of rain only in February. Because of the low amount of rain, the year was considered difficult for cultivating not only rice, but also drought-adapted crops such as pearl millet and sorghum. Indeed, most survey respondents perceived the water status of this year as “too dry” or “dry” and the crop growth as “very bad” and “bad” compared to that in any other year.
Currently, efforts are being made to introduce rice cultivation into the seasonal wetlands formed in northern Namibia (Iijima et al. Citation2018; Suzuki et al. Citation2013), because the pearl millet fields in the area mostly contain small wetlands where rain-fed lowland rice can be cultivated. Flash floods that have become common in this region often adversely affect the harvest of pearl millet, which is a staple food crop. Crop growth and production were reported to have improved through the newly developed techniques of close mixed-planting based on the MCO (Iijima et al. Citation2016; Awala et al. Citation2016). In addition, local farmers often practice mixed cropping of pearl millet and sorghum, and nowadays, these practices include mixed sowing on ridges, as a way of ensuring crop security, because sorghum is relatively more tolerant to waterlogging than pearl millet (Awala et al. Citation2016). This is one of the benefits of MCO when the mixed-planting concept is practically adopted.
Scenario analyses based on yield, household, and market surveys were conducted at the farm household level, village level, and regional level. This research was conducted in 2016, i.e., the drought year. The average net value of MCO in model farmers was N$446/farmer (). By calculating the value and the number of farmers in Omusati, the net value of crop production in the Omusati region after the introduction of MCO was estimated to be N$14.5 million (). Based on the interviews with farmers in the region, the area of seasonal wetlands in the flood year was estimated to be approximately 10 times higher than that in 2016, and the ratio of the harvested area of rice to that of pearl millet was estimated to be 9:1. As a result, the net value of MCO was estimated to be N$2707/farmer and net production in the Omusati region was estimated to be N$34.9 million/farmer (). Fujioka et al. (Citation2018) suggested that seasonal wetlands could be classified according to crop productivity, and further studies, which would include the scenario analysis and consider the classification of seasonal wetlands, are required.
Table 4. Estimation of farm household- and regional-economic value of mixed cropping in ondombe for drought/flood years.
The old-age pension in this region was found to be N$1000/month, and the net value of MCO per farmer was half as much as this value. In addition, this value in the flood year was estimated to be approximately five times higher than that in 2016. From the results of the household survey, we found that most farmers were eager to accept and continue MCO because of the low labour input share and time consumption. The reasons for this positive attitude towards MCO implementation might be not only farmers’ motivation for additional income but also the possibility of utilisation of existing state agency resources and food production even in the drought or flood years. Based on the results from the whole region, fiscal policy of estimated value (drought, N$25.5 million; flood, N$122.5 million) to shortage of production because of extreme climate is avoided. In the drought year, the MCO could compensate for one-fourth of the governmental urgent food import budget (Kahiurika Citation2016), and in the flood years, it could contribute more effectively to farmers’ livelihoods as well as to national food security. During the last decade, northern Namibia has faced drought years (Kahiurika et al. Citation2019) and flood years (Itamalo Citation2017; Van Den Bosch Citation2011), and the introduction and dissemination of rice-based mixed cropping systems are one of the most crucial agricultural and food policy measures for mitigating the negative effects of climate change in the area.
5. Conclusion
Although a simple methodology was used in this study, it has the novelty of empoying a multidisciplinary approach. Our results showed that the introduction of rice-based mixed cropping in ondombe in the targeted area, the Cuvelai seasonal wetlands system, is feasible not only because it offers a household-level survival strategy but also because it offers regional-level food security, additional food production options, and optional resource use in homestead. In addition, farmers’ motivation and expectations were found to be high and positive. The implementation of the system could lead to region-wide reduction in crop failure risk and an increase in food production. Moreover, this system could provide an effective and adoptable method for sustainable agricultural production and environmental management in the studied regions.
Acknowledgements
This study was conducted as part of the project entitled “Flood- and Drought-Adaptive Cropping Systems to Conserve Water Environments in Semiarid Regions” within the framework of the “Science and Technology Research Partnership for Sustainable Development (SATREPS)” funded by the Japan Science and Technology Agency (JST) and Japan International Cooperation Agency (JICA). We thank Ms Vistorina Hango, Dr Yuichiro Fujioka, Mr Kenta Tsuchiya, and the members of the project for their support with the yield and household survey.
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This article has been republished with minor changes. These changes do not impact the academic content of the article.
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