Over 75% of the world’s cocoa is grown within eight degrees of the equator. Outside this climate zone, temperatures and rainfall can limit production. Typically, cocoa is grown in areas where temperatures range between 18-32˚C. Cocoa will withstand temperatures of 30-32˚C for up to a month, but long periods of high temperatures will affect tree growth. At monthly mean temperatures below 24˚C flower production is limited.
Cocoa Agronomic Principles
All farmers – no matter how smallscale – should look to manage trees to produce as many pods of good quality beans as possible.
Effective use of inputs can help to maximize production given the specific growing systems and climatic/soil conditions.
Growth Characteristics
Seedlings are grown for the first 7-8 months in a nursery before they are transplanted to the field. Here, they need to be weed free and under moderate shade. Young trees will require lime where soils are too acidic and best growth occurs in soils with a high potassium to nitrogen ratio and where phosphorus is provided to support root growth. After a year when the tree starts to branch, it needs to be shaped to encourage multi-branch development. Any cocoa fruit set is normally removed for the first two-three years to encourage strong plant development. The use of grafted seedlings can help provide an earlier fruiting. Leaves develop as groups or ‘flushes’. Leaves from one flush will mature before the next flush occurs.
Nutrients for a flush of growth are drawn from the older leaves and stem. If soil fertility is low, flush growth can cause major defoliation of the tree. The extent of this defoliation is often used as a guide to the soil’s fertility status. Generally, 8 to 10 healthy leaves are required for the development of one pod. Typically, the cocoa tree develops a vertical stem known as a chupon and forms 3 to 5 more horizontal exposed branches called jorquettes or fans. Leaves form at the growing end of the chupon and on the fan branches. Leaves on fan branches grow alternatively in series of groups known as flushes.
Traditionally two jorquettes were allowed to develop, but modern pruning practices allows only one to form. Experience suggests that Nitrate-N is particularly important in speeding jorquette formation. After two to three years, flowers develop on the leafless, older wood of the chupon and jorquette. The flowers open overnight and are pollinated the next morning. With new hybrid varieties, flowering occurs earlier, often within the first 18 months.
Cocoa fruit develop after pollination which is largely by insects. Normally only 5% of the flowers are successfully pollinated, the rest will drop within a day or two of opening. There is a high correlation between the level of available phosphorus in the soil and flowering, as well as pod yield. Over the first four to six weeks, fruit expansion is extremely slow. It then accelerates and reaches peak expansion at around 75 days when the size of pod is just over 10cm in diameter. These small, developing fruit are known as ‘cherelles’ and over the first three months around 80% dry on the branch, becoming unproductive and dropping from the tree.
This abortion of pods, known as ‘cherelle wilt’, is a physiological disorder which is influenced by moisture stress and nutrient stress. After three months, hormones produced in the fruit will prevent further wilting. Calcium and boron applications have been shown to reduce cherelle wilt and increase the number of pods held on the tree. Fruit pods mature after 5-6 months taking on a yellow or darker red color. Pods normally contain 20-50 seeds containing 55-60% cocoa butter.
Growth Requirements
Annual rainfall across this region is commonly between 1150 and 3000mm and it is only in the lowest rainfall regions that irrigation is practiced.
Cocoa prefers an even spread of rainfall combined with high humidity – around 80%. Flowering occurs during the months of heavier rainfall. Periods of drought – of less than 100mm/month - will severely limit production. No flowering will occur in the dry season unless irrigation is provided.
