Cocoa - nutritional summary

Macronutrients

A cocoa plantation with about 1075 trees per hectare contains about 212kg N, 53kg P2O5, and 385kg K2O in the roots, stem, leaves and pods when it reaches the first year of production (Table 5). Significant amounts of CaO, MgO and micronutrients are also important.

In the early production years, considerable quantities of nutrients are accumulated and immobilized within the canopy. Newer hybrids that come into production earlier may require more nutrients than older varieties. 

After seven years, the mature tree contains almost double the level of most major nutrients it had in the first year of production. Held within the tree, these nutrients are needed to ensure strong flowering and pod production. Balanced nutrient application is particularly important in the early years in order to ensure fast, even growth and development in nurseries, and during the immature phase. A proportion of these nutrients are provided through nutrient recycling from leaf litter and pod husks if they are evenly spread across the field. Fertilizer use is needed to supply the additional nutrients, not provided by these sources, as well as balancing the nutrient input from all sources.

Nitrogen is a major component of the tree and needs to be continuously available over the life of the plantation. In mature plantations around 400-450kg/ha are present in the tree and almost 50% of it is in the leaves to support growth. Around 35kg/ha of N is removed in every tonne of bean and husk that is harvested. 

Phosphorus – although needed in much smaller quantities, P is required to maintain a range of growth processes. Only small amounts of phosphorus are removed at harvest. Because phosphorus is held strongly by the soil and is poorly available, regular fertilizer use is required to support canopy growth, pod production and build soil phosphorus reserves.

Potassium is present in a mature crop at much higher levels than nitrogen – – at over 700kg K2O/ha. About 50% of this potassium is located in the wood of the stem and branches. With potassium playing a major role in pod production, around twice as much K is removed at harvest, compared to nitrogen and most of this found in the husk. As with nitrogen, regular applications are required to maintain crop growth and fruiting. While many plantations will look to return potassium to the system by allowing leaves and husks to rot down, these methods of recycling are not always distributed evenly across the field, thereby creating areas of high and low potassium availability. 

Nitrogen, phosphorus and potassium requirements need to be carefully balanced and a shortage of any one of these nutrients will restrict the yield of the crop.

Calcium and magnesium are also required to support the stem, branches, leaf canopy and pod production. Very high levels of calcium (110-140kg/ ha) are required as the tree is developing and also to maintain good fruit production. Although similar amounts of CaO and MgO (around 10kg) - are removed at harvest, nearly three times the amount of calcium is needed to support the mature tree canopy, compared to magnesium. All nutrient uptake figures in this section are given in oxide forms. 

Micronutrients

Much lower amounts of micronutrients are required to support growth. 
Manganese is required at around 7kg/ha and is primarily needed to support leaf development. 
Zinc and boron deficiencies are common and must be corrected to maintain tree growth and fruit health. 
Boron working with calcium and potassium, has a direct effect on pod health and survival and in particular in minimizing VSD.