Soils, liming and salinity in cocoa production

Sandy clay loam to clay loam soils are the most productive and high organic matter levels of at least 3% are preferable. The tap root can grow to 2m depth, but the majority of the lateral roots are concentrated within the top 30cm of soil and well over half in the top 10cm. Therefore, good, even water and nutrient supply is the foundation for vigorous trees and a high bean yield.

Short term waterlogging is tolerated, but high water tables, especially if salty, as in the Mekong Delta of Vietnam, will limit root development and hence production. The soil pH range should be between 5.0-7.0 in the top 10-20cm. Production is severely limited below pH 4.5 and also above 8.0. Low soil pH at depth can also be a problem, particularly in established crops.

When the soil pH drops below 5.5, magnesium, calcium, phosphorus and molybdenum availability drops. At pH levels above 7.5, zinc, manganese and iron can become deficient. Cocoa has low tolerance to high concentrations of aluminum and, as a consequence, once pH drops below 4.5, dry matter production declines. Base saturation should be at least 50- 60%. The optimum exchangeable bases as a percentage of the total should be about K:Ca:Mg = 8:68:24. 

In trials, use of lime has been shown to improve growth, increase the number of pods per tree and produce up to a 70% increase in fresh bean yield/tree.

Cocoa has a low tolerance of chloride and production will decline when grown in saline soils. Care is needed when planting close to the seashore.

Here, wind breaks are used to reduce seaspray damage and in areas where the water table becomes seasonally saline, leaf burn can be an issue. Sulfate of potash fertilizers should be used in areas where chloride levels are high.

Note: All soil pH values shown are measured in water.