Relationship between Soil Fertility Indices under Coffee and Cocoa Fallows in Daloa, Côte d'Ivoire

Abstract

In the department of Daloa in Côte d'Ivoire, many coffee and cocoa plantations that have fallen into decline and been left fallow are in the process of being reclaimed by their former or new users. In order to prevent the failure of the planned new crops, this study was initiated to determine how the soils under these fallows function, which is essential for developing sustainable management strategies for them. Thus, seven fallows older than ten years were identified. In each of them, a 10,000 m2 plot was delimited and three soil pits were set up. In one pit, three soil samples were taken. After analysis of these samples in the laboratory, correlations and balances between certain physico-chemical soil components were calculated. The results show that organic matter contributes in some places to the constitution of the CEC (r ˃ 0.70) and thus participates in the soil's function as a reservoir of nutrients. On the other hand, when the soils are leached, the organic matter binds to the sand remaining in the profile and, because of its coarse particles, it hardly contributes to the constitution of the CEC (r = -0.70). However, whatever the case, the stability balances between the soil nutrients are globally favourable due to the long duration of the fallows (Ca/Mg close to 2 while K/Mg, (Ca+K)/Mg and C/N varied from 0.10 to 0.50, 15 to 30 and 9 to 12, respectively). Pending consideration of the functioning of the biological component of the soils studied, organic matter appears to be the most determining factor in their overall functioning.