The study was conducted in the commune of Niakhène, located in the Northern Peanut Basin of Senegal ( Figure 1 ). This region, characterized by a Sahelian climate and primarily “Dior” type soils, is suitable for agriculture but faces environmental pressures, particularly drought and erosion. Annual rainfall ranges between 400 and 600 mm, and the dominant vegetation includes species such as Cenchrus biflorus and Faidherbia albida [13] .

This study was conducted between 2020 and 2021 on plots of millet, peanuts, cowpeas, and fallows. A total of 309 surveys were carried out using the “field walk” method, an itinerant survey technique that involves cataloging all weed species encountered while traversing the various areas of the field. This process continues until a new species is only encountered after a significant additional distance has been covered. This approach allows for the identification of rare but agronomically important species, particularly those with a high capacity for dissemination or that are indicative of specific ecological conditions [14] .

For each survey, species were identified, collected, and classified according to an abundance-dominance scale based on the Braun-Blanquet classification [15] .

Species identification was carried out in the field or laboratory using several floras of Senegal, notably [16] , the Illustrated Flora of Senegal [17] - [19] , as well as the work from the Laboratory of Botany and Biodiversity (LBB) at Cheikh Anta Diop University in Dakar (UCAD). The adopted nomenclature follows that of [20] .

The analysis of the weed flora is based on three criteria: taxonomic, biological, and chorological.

Each identified species was associated with its botanical family, allowing for the determination of the total number of species, genera, and families present in the studied weed flora.

To establish the biological spectrum, species were classified according to their life form using Raunkiaer’s classification [18] , adapted for tropical regions where the unfavorable season corresponds to the dry season [21] [22] . This classification distinguishes six (6) biological types: nanophanerophytes (P), chamaephytes (C), hemicryptophytes (H), geophytes (G), therophytes (T), and parasitic plants (Par).

Species were classified based on their geographical distribution, relying primarily on the Illustrated Flora of Senegal [17] [18] . The categories of biogeographical distribution used are: African Species (Af), Afro-American Species (Am), Afro-American and Asian Species (Am As), Afro-Asian Species (As), Afro-Asian and Australian Species (Asu), Afro-Malagasy Species (M), Afro-Malagasy and Asian Species (Mas), Afro-Asian-American-Australian or European Species (Masue), and Pantropical Species (Pt) [23] .

Degree of Similarity

The degree of similarity between floristic surveys was assessed using correspondence factor analysis.

The table below ( Table 1 ) represents the weed flora of rain-fed crops in the northern area of the peanut basin. Each species is characterized by its presence in the house fields and bush fields of crops (millet, peanut, cowpea) and fallow land, as well as by its family, number of genera, biological type, and geographical distribution. The flora consists of 112 species distributed across 78 genera and 34 families.

D = Dicots; M = Monocots; NG = Number of genera; NE = Number of species; Pt = Pteridophytes; TB = Biological type; Therophytes (T); Geophytes (G); Chamaephytes (C); Phanerophytes (P); R.G = geographical distribution; African (Af); Pantropical (Pt); Afro-Malagasy (Ma); Afro-Asiatic (As); Cosmopolitan (Cosm); Afro-Asiatic and American (As Am); Afro-American (Am); Afro-Malagasy, Asiatic, and American (Mas); Afro-American and Australian (Amu). CC = House Fields; CB = Bush Fields; CM = Millet Crops; CA = Peanut Crops; CN = Cowpea Crops; Ja = Fallow.

The table provides information on the taxonomic spectrum of the weed flora of rain-fed crops in the northern peanut basin (Niakhène).

This flora is composed exclusively of angiosperms ( Table 2 ). Within this group, dicots are dominant, comprising 85.29% of the families, 79.48% of the genera, and 78.57% of the species recorded, compared to 14.71% of the families, 21.05% of the genera, and 20.51% of the species for monocots.

Importance of the Families in the Flora of Rain-fed Crops in the Northern Peanut Basin.

The analysis of families present in the weed flora of rain-fed crops in the north of the peanut basin reveals a strong dominance of five main families: Fabaceae (22.32%), Poaceae (15.18%), Convolvulaceae, Malvaceae (7.14%), and Rubiaceae (5.36%). Together, these families account for 57.14% of the recorded species. Additionally, four other families are relatively well-represented: Cyperaceae, Combretaceae, Euphorbiaceae, and Limeaceae (2.68%). The remaining twenty-six families, although present, collectively account for only 42.86% of the species and generally include one or two species each ( Table 3 ).

The remaining twenty-six families, although present, collectively account for only 42.86% of the species and generally include one or two species each ( Table 4 ).

The recorded species are predominantly African (41.07%) and Pantropical (30.36%). The other groups are less represented: Afro-Asiatic and Australian (7.14%), Afro-Asiatic (7.14%), Cosmopolitan (5.36%), Afro-American and Asian (3.57%), Afro-Malagasy and Asian (3.57%) ( Table 5 ).

The analysis of flora based on agricultural crops and field types reveals little influence of the crops and their location on the diversity and abundance of species ( Figure 2 ). Cowpea and peanut crops host 92 species, compared to 82 species for millet. House fields show greater floristic diversity (100 species) compared to bush fields (92 species).

The characterization of the weed flora of rain-fed crops in the northern area of the peanut basin has identified 112 weed species, belonging to 72 genera and 34 families. The number of species in this flora is smaller than that of other weed floras studied in certain areas of the country, both in terms of species and genera. Among these weed floras, we can note that of the food crops in the southern peanut basin with 125 species, 81 genera, and 31 families [2] , the flora of onion crops in the peri-urban area of Dakar with 131 species distributed across 88 genera and 34 families [10] , the weed flora of maize crops in the southern peanut basin with 128 species, 65 genera, and 25 families [24] , the weed flora of irrigated rice crops in the Senegal River Valley with 179 species distributed among 117 genera and 46 families [4] , as well as the weed flora of sorghum and cotton crops in Eastern Senegal and Upper Casamance with 232 weed species belonging to 138 genera and 43 families, and 204 species distributed among 118 genera and 35 families, respectively [25] [26] .

The relatively low number of weed species in the rain-fed crops’ flora in the northern peanut basin compared to other studied crop floras could be explained by differing agroecological conditions prevalent in the various study environments. Indeed, the Casamance region, the peri-urban zone (Niayes), and the southern peanut basin have relatively high rainfall, exceeding 1000 mm/year [27], contrary to the northern peanut basin, where the average annual rainfall is relatively low (700 mm/year). This disparity can also be explained by the nature of the soil, which is sandy and tends not to retain much water, a fundamental element for flora richness [3] [4] .

Within this flora, it emerges that fallow land hosts the largest collection of weeds with 94 species, followed by cowpea and peanut crops, each with 92 species, and finally, millet crops with 82 species. Regarding proximity to dwellings, the flora of house fields is more diverse with 100 species than that of bush fields, which only has 92 species of the overall flora.

In this flora, all encountered species are Angiosperms, divided into 29 families, 60 genera, and 88 species of dicotyledons, as well as 5 families, 16 genera, and 24 species of monocotyledons. This strong dominance of dicotyledons is observed in almost all flora studies across the country, with varying proportions depending on the zones and crops. For this study, the percentage of monocotyledon species relative to dicotyledon species (M/D*100) is 27.27%, a value significantly lower than those obtained in other studies conducted in the country: 43.67% in the food crops of the southern peanut basin [2] , 55.88% in the mixed millet-cowpea crops of the southern peanut basin, 45.77% and 38.12% respectively in cotton and sorghum crops in Eastern Senegal and Upper Casamance [25] [26] .

Furthermore, even though house fields show slightly higher diversity than bush fields, this difference remains minimal. This finding suggests that the proximity to dwellings does not have a significant effect on floristic diversity, in contrast to what is observed in some areas where house fields benefit from greater nutrient inputs related to human activities [28] .

The low floristic variability observed in this study confirms the decisive influence of abiotic factors, such as soil and climate, on the distribution of weeds rather than specific agricultural practices associated with different crops.