Crop production: Consider the carob

Until recently, only a few livestock farmers have used pods from the carob tree to feed their stock, but agricultural researchers are now encouraging commercial plantings because of their feeding potential.

Pods from the carob tree (Ceratonia siliqua) – commonly known as St John’s bread – can be used directly by humans and animals and don’t necessarily have to be processed. Usually, pods are ground and strained through a 10 mm strainer before being added to growth rations for livestock.

Because the feeding values are high, and the pods are a good source of easily digestible sugars, they are a valuable source of energy in a diet. In economic terms, the value of carob is 85% of that of barley.

In an experiment run at Elsenburg in South Africa’s Western Cape Province, ground carob pods were included in the starter and growth rations of bull calves. The calves that had carob in their diet displayed higher feed intake and body mass increases than those that didn’t get the carob ration.

Pods ground without the seeds can be very useful. The powder can be dissolved in milk to make an energy drink, or mixed with a little flour and included in bread or breakfast cereals. Glue can be produced from the seeds (10% to 15% of the pod).

The powder is also used as a commercial stabiliser and thickener in ice cream, salad dressings, cheese, salami, canned meat and fish, jelly, mustard and a few other products.

CLIMATE

The carob tree is Mediterranean in origin and extremely hardy.
The trees are best suited to a climate that has cool (but not too cold) winters, a moderate to warm spring and warm to very warm summers, with little rain.
An annual rainfall of 350 mm to 600 mm is sufficient for commercial production, but additional irrigation will be needed in drier areas.
Trees are sensitive to frost, especially when young.
Adult trees can handle low temperatures, but fruit set can be compromised by frost.
Pods that get too much rain sometimes ferment, so the tree isn’t suitable for summer rainfall areas.

SOIL

Most soil types, from rocky ridges to deep sandy or heavy loamy soils, are suitable for carob cultivation, provided that drainage is good.
Trees will grow better if the soil is loosened before planting and, because they have a strong tap root, deep root growth should be possible.
Very wet, sour soil is not suitable.

REPRODUCTION

Fresh seeds sprout quickly and can be planted directly into the soil.
Dry, hard seeds have to be scarified and then soaked in water.
Dry seeds can also be planted directly into the soil in a seed tray, but must then be kept moist for 6 weeks.
A seed tray is needed to ensure the tap root doesn’t develop too soon.
When trees are about 30 cm high, they can be planted out in 0.5 m x 0.5 m by 1 m deep holes.
Plant them in the top 15 cm of soil.
They will need 2 litres of water twice a week.
When the trunk is about 1 cm thick, you can graft a well-known cultivar on to it.
There’s a relatively long period between the sprouting of seeds and the delivery of meaningful production.
This is partially due to the fact that the trees are unisexual, so it is possible that an orchard can deliver a very poor harvest because there are mainly male trees (that don’t produce pods).

GROWTH PATTERN

Recently planted carob trees grow slowly for the first year.
Bigger trees that are in black bags, may have problems because the tap root has grown out of the bag and twisted in the process.
Trees sometimes break during planting, and if this happens, they won’t grow.
Trees are planted in rows 10 m apart, and spaced 10 m apart within the rows.
Grafted trees will produce pods within 6 years, and can stay productive for 80 to 100 years.

HARVESTING PODS

Pods ripen in summer.
They’re ripe when they turn brown and fall from the trees.
You can pick them up from the ground or shake the branches.
If the pods are still slightly moist, leave them in the sun until the moisture level is less than 10%.
Pods can be ground to make livestock rations; for other uses, the pods and seeds have to be separated.

YIELD

When trees reach the age of six, you can expect to harvest 2 kg to 3 kg per tree.
Production will increase to 40 kg to 50 kg per tree by the time the tree is 12 years old.
After 25 years, trees will produce about 100 kg a year, so you can expect a harvest of about 10 t/ha.
Individual trees have been noted that produce 300 kg to 400 kg.
The size of the tree is the most important factor to influence how many pods it will produce.
Shallow soil produces smaller trees, and smaller yields.

Although the carob tree is still far from being a great commercial success; its potential cannot be overlooked.