Soil fertility is an indicator of good agricultural production and consequently of the agricultural activity of a locality. In the Sahel and in particular in the basin of the Thies region, soils gradually lose their production capacity. Desertification caused by the combined and simultaneous action of climatic and anthropogenic factors continues to progress. However, studies by the National Agency for Statistics and Demography (ANSD) reveal that the extent of farms in the different regions of Senegal is not correlated with the potential of land production. The objective of this study is to determine whether the areas cultivated in the groundnut basin of the Thies region are related to soil fertility. The methodology adopted is based on a physico-chemical soil analysis to determine a possible relationship between soil fertility and the extent of agricultural land. Field studies were also carried out on the adaptation strategies developed by local producers in the face of this decline in soil fertility. The Bernoulli formula was used for the selection of the study sample. The results of the soil physico-chemical analysis reveal that the areas cultivated by farmers are larger in the less fertile lands. Therefore, the control methods undertaken in the face of declining soil fertility have been fruitful.