Leaf Vegetable Cultivation in Cameroon: An Overview of the Situation in Njombe and Surrounding Areas

: Over the past ten years, it has been noted that the demand for leafy vegetables in the coastal area of Cameroon is increasing


Introduction
Vegetables in general and especially leafy vegetables are important in the diet of Cameroonian populations; they contribute to food security through their composition and are also an important source of employment and income [1]. Leafy vegetables are rich in mineral elements such as phosphorus (601-9256mg/100g), calcium (430-3495mg/100g) for Solanum scarbrum [20]; Potassium (7887-12861mg/100g), Magnesium (727-1947mg/100g) for Amaranthus hybridus [2]. Solanum scarbrum is also an important source of protein, whose content varies from 25.63 to 72.64% in Cameroon [20]. Amaranthus hybridus, Solanum scarbrum, Corchorus olitorius are leafy vegetables that are good sources of carbohydrates (total and reducing sugars) [2]. In Cameroon, leafy vegetables play an economic role in the food security strategies of urban and peri-urban populations [3]. In the Littoral region of Cameroon, particularly in the Moungo department, leafy vegetables are regularly grown in different production systems. As a result, considerable quantities of vegetables are produced and sent mainly to the markets in the regional capital. In recent years, women have become increasingly involved in the production of leafy vegetables. The scientific works recorded were mainly interested in the production, distribution and conservation of seeds [21,23], as well as in the evaluation of the effect of the environment on the nutritional quality of vegetable leaves [22]. However, few studies have been done on consumption and flows to regional markets. Also, the technical itineraries used are generally not supervised, which raises serious problems regarding the quality of the vegetables produced (health status, presence/absence of pesticide residues, etc.). Moreover, little is known about the origin and quality of the seeds used in the locality. The same applies to the species of vegetables grown and the reasons for their choice. A real lack of knowledge that questions research on the bottlenecks of this vegetable production of capital importance for the household economy and national food security. In a general context of use of fertilisers and phytosanitary products, given the presence of industrial agricultural companies in the study area, a characterisation of vegetable production is urgently needed. It is therefore more than necessary to define the cropping systems practised, the technical itineraries developed and their relevance, as well as the potential risks associated with the consumption of vegetables produced in this highly agricultural area. Therefore, the objective of this study is to clearly define the contours of vegetable production in one of the most important production basins, located in Njombe-Penja, and to measure its impact on the environment.

Study Area
The present work was carried out in Cameroon in the district of Njombe-Penja, Moungo Department, Littoral Region. Njombe-Penja is located approximately between 4°35 and 4°40 North longitude, and 9°39 and 9°41 East latitude. It is a locality in the coastal region with monomodal rainfall. It is a forested area characterised by variable rainfall between 1900 and 3200 mm/year. The landscape is dotted with hills, including volcanic cones and valleys. The soil consists partly of pozzolans, rock structures (from bombs and lapillis), but also in some places of advanced ferralitic soils, etc. The latter are generally clayey or rather sandy-clay along the coast. Cocoa, coffee, cassava, plantain, oil palm and maize, etc. are mainly cultivated [4].

Data Collection
A pre-established, tested and validated semi-structured questionnaire was administered to the targets (farmers and traders). The people to be surveyed were individuals growing leafy vegetables in the locality, regardless of age or gender. They were selected randomly in the field according to their availability. The study took place between March and June 2021 (4 months). The questionnaire was mainly about the individual profile (age, gender, level of education and farming experience (see Table 1), the profile of the land exploited (areas, mode of acquisition of land and cropping system), the technical itineraries used and the management of diseases. The survey was carried out on a population of 100 individuals (Table 1). All questions relating to the farmers' profile were asked directly to them. Questions on varieties, their origins and production constraints were in some cases answered by direct observations of the variety species in the field. For others, the answers were obtained from discussions with the farm manager.

Data Analysis
The data collected was entered into Microsoft Excel, processed and analysed in descriptive statistics using SPSS software. Means and frequencies were calculated and used to construct distribution histograms for each of the production factors analysed.

Respondent's Profile
Of the 100 people surveyed, 96% were women and 4% were men. The overall age range was between 22 and 64 years. More than half of the study population was at least 40 years old.
In terms of education, 64% of the sample have primary education, 28% have lower secondary education and 8% have upper secondary education. A large majority of women are engaged exclusively in subsistence farming (60%), while the others engage in parallel activities such as animal husbandry, small-scale trade and others (sewing, hairdressing, etc.); moreover, 96% of the people surveyed stated that they had inherited knowledge of leafy vegetable cultivation, hence their lack of agricultural training in vegetable cultivation. Only 12% of them belong to an agricultural association such as a GIC, COOP and other farmers' organisations (Table 1).

Parcel Profile
In Njombe area, the surface of parcels dedicated to leafy vegetables varies between 64 and 870 m 2 with an average of 265.84 m 2 . 80% of the exploited land is obtained by renting; the other 20% by inheritance or gifts.

Technical Itinerary
The technical itineraries according to the respondents are almost the same and can be summarised in 4 phases: germination of seeds, transplanting of plants, field maintenance and harvesting of leaves.
Seed germination consists of planting the seeds widespread or in rows (about 15 cm between rows) on beds 80 to 120 cm wide and of variable length, prepared according to their needs (ploughing, burying of organic matter if possible and levelling). After two weeks, the seedlings are ready to be transplanted into the field. Transplanting in the field is done in bulk or in rows on previously prepared beds, respecting a density of about 45 plants/m 2 , which means a spacing of 15 cm x 15 cm. Field monitoring consists of manual weeding, cover fertilisation and treatments with molluscicide or insecticide. Fertilisation takes place two weeks after transplanting, with an average of 3.2 g of fertiliser per plant. Phytosanitary treatment is carried out every two weeks with an average dose of 0.061g of pesticides per plant ( Table 2). The leaves are harvested one month after transplanting and cut every two weeks. After each cut, maintenance operations such as manual weeding, cover fertilisation and phytosanitary treatments are applied. The seeds used for the nursery come from individual production (12%), local markets (60%) and structures in charge of seed production and extension such as IRAD and MINADER (28%). The constraints to obtaining seeds are high cost (56%), poor quality (32%) and low availability (12%). Table 3 shows that fertilisation and the use of plant protection products are essential: ammonium sulphate is the most widely used fertiliser (80%), while chicken droppings are the least used (12%). Pyriforce (Chlorpyriphos-ethyl) is used extensively for insecticide control (28%) and metaldehyde 50g/kg against molluscs (36%). It should also be noted that 56% of the producers monitored do not control the pesticides they use. The peak production season for leafy vegetables in Njombe is from March to October. Leaf harvesting starts 1 month after transplanting and continues every two weeks for 3 months. This process is repeated once until the end of the season. The vegetables harvested are generally destined for the local market (64%), the markets in the mainland (Douala) (28%) and for self-consumption (8%).

Production Constraints
The most frequent constraints are parasitic attacks (Insect larvae) and pests (Caterpillars, snails and insects). The high pest pressure reported by the majority of respondents restricts vegetable production. The pests are 80% insects and 30% molluscs. Insects cause a lot of damage to vegetables, especially on the leaves. They include caterpillars, locusts, whiteflies, ants, termites, aphids, hoppers, cicadas, bugs, ladybirds and thrips. This pest pressure limits the number of harvests and lowers the quality of the vegetables, thus compromising yields and income. Important diseases frequently mentioned are: leaf wilt, leaf yellowing, black spots, rot and perforated leaves (Figure 2). To fight against diseases and pests, 72% of farmers use chemical control, 16% use cultural techniques, 4% use biological control, 8% use both chemical control and cultural techniques.

Discussion
The results of this study showed that the majority of the respondents were female and aged between 22 and 64 years. This is explained by the fact that in Cameroon, it is the woman who is responsible for selling leafy vegetables in the markets. Income generated from the sale of field products contributes to household food security, access to family health care and allows women to achieve a degree of financial independence in the family budget [5,6]. Knowledge of vegetable cultivation is passed on from ancestors who are trained on the job and experience is gained over time in practice. Surveys carried out in Njombe identified six of the most widely grown leafy vegetables. This diversity is lower than that found by Nchoutnji et al. [7] in the northern part of Cameroon. Of this diversity, African nightshade (Solanum scarbum) is the most cultivated leafy vegetable in rural and peri-urban areas, and the most requested in urban areas of Cameroon [6]. It occupies an important place thanks to its nutritional qualities which contribute to the wellbeing of the human organism; the daily consumption of quality vegetables in sufficient quantity would ensure good health and prevent various chronic diseases.  Their richness in trace elements, vitamins and phytocompounds [8,9]. It also provides interesting revenues to the actors [10]. According to the experience of Asian Vegetable Research Development Center (AVRDC), Production systems, seed selection and cultivation techniques are crucial for vegetable cultivation [11].
The technical itinerary for the production of leafy vegetables begins with the establishment and monitoring of a nursery; one month after planting in the nursery, seedlings of between 10 and 15 cm are taken and then transplanted onto previously prepared beds (clearing, ploughing and bed formation). After transplanting, the most important operations that follow are manual weeding, fertilisation and phytosanitary treatments (insecticide, fungicide, molluscicide). These operations have an impact on the production yield of leafy vegetables [20]. As indicated by Asian Vegetable Research and Development Center devenu World Vegetable Centre » (AVRDC) The application rate of chemical fertilisers is 250kg/ha, corresponding to 25g/m 2 ; the average rate of fertilisers used by producers is 90g/m 2 , this rate is three times (3.6 times) higher than the one recommended by this organisation. Over-fertilisation with nitrogen can lead to a high accumulation of nitrates in leaves, especially those used as spinach and lettuce [12,13]. Some of the ingested nitrate can be converted into nitrite, which is responsible for respiratory disorders, especially in young children, resulting in methemoglobinemia [14]. Some studies have proven conclusively that nitrates combine with amines to form carcinogenic compounds called nitrosamines [15]. Phytosanitary problems are one of the constraints that limit the production of leafy vegetables in Njombe.
The stakeholders surveyed reported pest attacks (mites, caterpillars, nematodes) and diseases (rot) on leafy vegetables. Chemical control is the main method used by local producers. Pesticide use practices are most dangerous. Indeed, vegetable growers most often spray vegetables with a variety of insecticides and fungicides at inappropriate doses. These results are the same as those of [16] who worked on cultivation practices and levels of anti-nutritional elements (nitrates and pesticides) in Solanum macrocarpum in southern Benin. In addition, most producers do not observe any protective measures during phytosanitary treatments of crops. The excessive use of fertilisers and phytosanitary products by producers causes numerous problems, the most important of which are: contamination of crops by pesticide residues; pollution of the water table; and the perishability of produce, which leads to numerous post-harvest losses (rotting); as a result, the nutritional and sanitary quality of these vegetables is becoming worrying. The presence of pesticide residues on the leaves of vegetables can lead to food poisoning in the long run. Pesticide use practices are identical in the Njombe locality; these results have also been observed by other authors in some African countries [17][18][19].

Conclusion
This study enabled us to know and identify the different types of leafy vegetables grown in Cameroon, in this case Amaranthus hybridus, Solanum americanum, Corchorus olitorius, Hibiscus sabdariffa, Solanum aethiopicum and Talinum triangulare which are the main ones represented. It allowed us to understand the cultivation practices related to leafy vegetables in the locality of Njombe and surrounding area. The results show that women aged at least 40 are the main actors in this field of activity. The technical itineraries used have similarities, starting with the setting up of the nursery, transplanting to the field, through phytosanitary treatments and fertilisation, to harvesting. Furthermore, the use of fertilisers is not controlled, as they are often applied in inappropriate doses. Moreover, the use of fertilisers is not controlled, as they are often applied in inappropriate doses, and the application of phytosanitary products is hazardous, without any agronomic reference point. This reduces their effectiveness, as recurrent attacks by leaf pests and parasites have been observed despite preventive treatments, with the immediate consequence of reduced harvests and depreciation of vegetable quality. Therefore, an optimisation of the complete technical itinerary of leafy vegetable cultivation is recommended, as well as a reinforcement of the technical capacities of the actors of the leafy vegetable sector of Njombe-Penja and its surrounding areas, through training and recycling sessions.