Abstract
The objective of this study was to assess the contribution of the spatial organization of cropping systems and the physicochemical properties of surface layers of the agricultural zones soils in tropical hydrosystems to the spatial availability of nitrogen and pesticides during the wet season, such as the Béré watershed (BW) in C?te d’Ivoire. For this purpose, after mapping the spatial distribution of the BW cropping systems based on the likelihood classification methodology of satellite images of the study area, 27 samples from the 0 - 20 cm horizon of the soil surface layers of the agricultural areas were taken during the wet and agricultural season of the year 2016. The Kjeldahl method has been used to evaluate the total nitrogen concentration and high-performance liquid chromatography (HPLC) chain made it possible for the analysis of pesticide residues in the soil solutions. Geostatistical analysis and processing of spatial data and physicochemical and agrochemical soil parameters revealed that two major agricultural areas stand out in the BW, namely the Béré upstream watershed (BUW) dominated at 32.65% by annual croppings (maize, cotton, rainfed or lowland rice, market gardening, etc.) and the Béré downstream watershed (BDW) by large areas of perennial croppings (cashew nuts, cocoa, etc.), i.e. 21.47%. Agricultural soils in BW are usually of the moderately desaturated ferralitic type with a low acid pH and a quite strong temperature, such as those of tropical soils’ characteristics. However, agricultural soils in the BUW are characterized by higher proportions of sand and coarse sand. The parameters such as total porosity, cation exchange capacity, clay, organic matter, silt, fine silt, coarse silt, and potassium ions, are higher in the soils of the agricultural area of the BDW. Moreover, soils in the agricultural areas of the BUW are less rich in total nitrogen (0.84 g·kg-1) in contrast to those of the BDW (1.2 g·kg-1). On the other hand, the median concentrations of total pesticides remain very high in the BUW (193.80 μg·kg-1) in front of those of the BDW (94.81 μg·kg-1). In addition, the biological family of herbicides was the most notable in BW. The chemical families of triazines (100% detection; 79.37 μg·kg-1) are the most important in the agricultural area of the BUW with the very significant presence of active molecules of pesticides such as simazine (92.86% detection; 13.17 μg·kg-1). However, in the BDW, urea substitute (100% detection; 44.02 μg·kg-1) dominate, including the active substance chlortoluron (84.62% detection; 10.12 μg·kg-1). The presence and abundance of nitrogen and pesticides in the soils of the agricultural areas of BW are strongly linked to the intensive use of these agrochemicals in cropping systems in recent decades in West African countries, even though most of the active molecules found are forbidden in several countries, especially in European countries. These are applied to tropical agricultural soils with physicochemical characteristics favorable to their retention in wet weather, as confirmed by the case of BW’s agricultural soils. Therefore, the BW’s water resources present worrying risks of contamination during rainy events that deserve to be assessed and monitored. Hence the need to take mitigating measures to this effect in order to preserve the quality of the environment.
Highlights
In recent decades, in addition to the expansion of cropping systems, most modern methods of cropping protection in the world and especially in West Africa have increasingly relied on the use of plant protection products and chemical fertilizers for rapid development and an increase in agricultural production to meet the food needs linked with high population growth in developing countries [1] [2] [3] [4] [5]
Almost half of the Béré watershed (BW) territory (45.9%) was made up of large farming areas divided into two distinct large farming areas, the Béré upstream watershed (BUW) (30.14%) and the Béré downstream watershed (BDW) (15.76%) in the agricultural zone of the BUW (Marandallah, Sarhala, Tiéningboué, and Mankono), the majority of the agricultural exploitations of annual types were developed, i.e. about 32.65% of its 2268.85 km2 surface area
This study shows that the BW has large areas of farms divided into two large agricultural areas, the Béré upstream watershed (BUW) dominated by annual croppings and the Béré downstream watershed (BDW) by perennial croppings
Summary
In addition to the expansion of cropping systems, most modern methods of cropping protection in the world and especially in West Africa have increasingly relied on the use of plant protection products and chemical fertilizers for rapid development and an increase in agricultural production to meet the food needs linked with high population growth in developing countries [1] [2] [3] [4] [5]. In view of this worrying situation, it was necessary to ensure the quality of BW’s soils in order to take measures to prevent environmental risks linked to the contamination of water resources by diffuse agricultural pollution To this end, the public authorities needed to know the level of contamination of the agricultural soils of BW by nitrogen and pesticides. This work is of great interest and constitutes a prerequisite for good preservation of the environment through proposals for more rational use of these agrochemicals in the agrosystems of developing countries It is with this in mind that this study was initiated in order to assess the contribution of the spatial organization of cropping systems and the physiochemical characteristics of the surface layers of soils in the agricultural zones of tropical hydrosystems to the spatial availability of nitrogen and pesticides in wet season soils such as the BW in Côte d’Ivoire. The aim was to 1) establish the spatial distribution of the agricultural areas of the BW; 2) characterize the physicochemical parameters of the soil surface layers of the agricultural areas; 3) establish the spatial distribution of the concentrations of total nitrogen and pesticides available in these areas; 4) determine the influence of the spatial distribution of cropping systems and the physicochemical properties of the soils of the agricultural areas of the BW on their availability of total nitrogen and pesticides
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
