Soil Acidification in Cocoa (Theobrama cocoa) Agrosystems in Côte d’Ivoire (I): Effect of Carbonate Based Mineral Amendments on Soil Chemical Properties and Growth of Cocoa Seedlings (Theobrama cocoa)

Soil acidification is a major concern in Côte d'Ivoire. The present study examines the effect of an amendment based on crushed carbonate rock (dolomite and limestone) on soil chemistry and cocoa plant growth. To this end, cocoa seedlings were grown under controlled conditions under cover on soils taken from cocoa orchards in Aboisso (south-eastern Côte d'Ivoire). Soils were sampled at 0-20 cm, 20-40 cm and 40-60 cm. A representative composite sample of each horizon was then taken in a soil column. The experimental trial was conducted in total randomization with six repeated treatments (Dolomite 100%, Limestone 100%, Dolomite 50% + Limestone 50%) compared with the control, soil without amendment. After six months, the results showed that the application of carbonate did not induce a significant difference (p > 0.05) in cocoa seedlings growth. However, the amended soil showed improvement chemical properties compared to unamended soil. Soil treatments with limestone improved soil base cation content, CEC and pH, but all these parameters measured still lower to minimum threshold values for good cocoa tree growth. These results showed that the combination of dolomite and limestone appears to be the amendment with the greatest potential for improving the fertility of acid soils under cocoa. Field investigations should then be undertaken to assess the effect of this carbonate combination on soil acidity and fertility under natural conditions.