Mapping Bioavailability of Mineral Elements under Sugarcane Cultivation: Case of the Soils of the Integrated Agricultural Unit of Zuenoula (Centre-West Cote d'Ivoire)
Abstract
The knowledge of the bioavailability of mineral elements in the soil to plants is of great agronomic interest for the improvement of agricultural production. For this purpose, soil samples were taken from the top 60 cm of the soil in the three different sectors of the sugarcane plantations at the Zuenoula integrated agricultural unit. These samples underwent physico-chemical analyses in the laboratory according to standard procedures. The results of the soil analyses are compared with the reference values for sugarcane. All these values were georefrenced through the coordonates of the corresponding sample. These georeferenced values were processed by interpolation methods with ArcGis software to obtain thematic maps of the bioavailability of these nutrients. The results obtained show that the texture was silty in all soil layers considered. They are not very acidic. nitrogen levels are low. Organic carbon and Phosphorus contents are low to moderate. The mineralisation of organic matter is relatively normal. The adsorbent complex was slightly to moderately saturated. Various ratios (Ca/Mg and Mg/K) point to nutritional imbalances. Thematic mapping of these different parameters showed a deficiency in mineral elements, at high percentages (≥ 90%) in the different soil layers. This reflects the expression of a generally low to medium soil fertility status. This would require the correction of these limiting factors for optimal mineral nutrition of sugarcane. Thus, sustainable soil fertility management requires a good knowledge of the physico-chemical parameters of soils cultivated with sugarcane. Spatial information technology leading to detailed mapping of soil, is an important tool to achieve this.
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Introduction
Soil is a fundamental aspect of land resources and is the foundation for agricultural development and environmental sustainability. It is an important factor for the survival of organisms in all living environments (Fox et al., 2008). Its evolution is linked to the combined action of climate and vegetation, leading to both geochemical and structural evolution. To this 'natural' effect adds the influence of the type of land use on its properties (Bigorre, 2000). Maintaining and even increasing soil fertility is an important issue (Sanchez, 2002). A study by Tittonell et al (2007) clearly demonstrated the impact of soil fertility, climatic conditions and soil fertility management models on crop yields in Africa. In sub-saharan Africa, widespread loss of soil fertility is one of the main causes of declining agricultural productivity and food insecurity (Pieri, 1989; Stoorvegel and Smaling, 1990; de Ridder et al. 2004), so improving soil fertility and agricultural productivity are two priority objectives of agricultural policy in West Africa (CORAF/WECARD, 2008). Thus, the recent decline in sugar production in Côte d'Ivoire is thought to be due to a decline in soil fertility in sugarcane cultivation (Bouadou, 2014; Yao, 2017). Sustainable management of soil fertility in industrial sugarcane farming would therefore require a good knowledge of the physical, chemical and hydrodynamic characteristics of soils. Spatial information technology, including mapping, would be an important tool to achieve this. The updated mapping of nutrient availability in soils under sugarcane crops was carried out on the plots of the Sucrivoire at the integrated agricultural unit in Zuénoula with the aim of making new fertilisation recommendations. This study specifically aims at the sustainable management of soil fertility, through the knowledge and geolocation of soil fertility levels. This required knowledge of physical and chemical parameters, as well ascertain balances between mineral elements. These observations were made according to soil depth levels corresponding to the progression of the volume of soil explored by the roots according to the phenological stages of the plant.
Conclusion
After the study related to the mapping of the bioavailability of nutrients in sugarcane cultivation at the Integrated Agricultural Unit of Zuenoula, the results show that the soil texture was loamy over the first 60 centimeters of soil depth. The soils are slightly acidic. Nitrogen levels are low over at least 95% of the site area. The phosphorus content is also low, over about 30% of the extent of the zone. And the potassium content is acceptable over most of the zone. But the decrease with depth of the different contents of these mineral elements requires a special attention to avoid a significant deficit, mainly when the roots of the crop access the deeper layers of the soil.This could be accentuated by certain ratios (Ca/Mg and Mg/K) which point to nutritional imbalances. Knowing the spatial evolution of soil nutrients is important to determine the amount of fertilizer to apply to correct fertility levels and increase production, in order to be able to meet the standards of rational fertilization in sugarcane cultivation.