This section is from the book "The Planting, Cultivation And Expression Of Coconuts, Kernels, Cacao And Edible Vegetable Oils And Seeds Of Commerce", by H. Osman Newland. Also available from Amazon: The Planting, Cultivation And Expression Of Coconuts, Kernels, Cacao And Edible Vegetable Oils And Seeds Of Commerce.
The high price of butter in this country is leading now to the establishment of a new industry in Great Britain-i.e., the crushing of monkey-nut or ground-nut kernels for the extraction of a pale yellow oil, which is of great value in the manufacture of margarine, for which, with butter at so high a price, there is an increased demand. Ground-nut oil is also used for preserving sardines and as a lubricant and illuminator. Inquiries are being made at the leading seed-crushing centres for the establishment of his new branch of the oil-extracting industry, and a movement has also been started to erect mills in Scotland to forward the industry. The kernel of the monkey-nut contains about 50 per cent, of oil, which belongs to the non-drying class of oils, of which up to 40 per cent, can be extracted by crushing machinery. As India, Egypt, the West Coast Protectorates, both British and French, East and Central Africa, Rhodesia, etc., are able to supply large quantities of these monkey-nuts, there is every promise of the development of a large export trade in the commodity. The annual exports from India and West Africa alone amount to about £5,000,000 ; and in the United States, every large town has its " pea-nut " factory. Our French Allies pay great attention to the crushing of monkey-nuts, and extensive crushing businesses are established at Marseilles, and they will probably do their utmost to encourage the Colonial industry.
Other countries which express this oil are China, Java, the United States, and Japan.
The ground-nut, earth-nut, monkey-nut, or pea-nut, as different nuts of the same species are variously called, is the fruit of a yellow-flowered herbaceous plant belonging to the Nat. Ord. Leguminosce, which is cultivated extensively in Gambia, Senegal, Hong Kong, India, Nigeria, East Africa, and the United States. The value of the nut largely depends on its oil content, which in a good sample will average 40 per cent, of the seed by weight after extraction. At the same time, the leaves and branches of the plant form an excellent fodder for cattle and sheep, and should always be utilised after harvest.
The flowers are peculiar and worthy of consideration, as they have a considerable bearing on the successful cultivation of the crop. After fertilisation the torus or seed stalk of the flower becomes elongated, rigid, and deflexed, and forces itself into the ground where the ovary at its extremity begins to enlarge and develop into a yellow wrinkled one to three-seeded pod. If the ground be so hard as to prevent the seed stalk from burying the developing ovary, the whole part withers and no fruit is formed, hence the necessity for keeping the soil in a friable condition until the flowers be set.
The highest percentage of marketable nuts is produced in sandy loams; soils deficient in lime, if rich in nitrogen, will produce luxuriant plants but little fruit, and clay soils are always unsuitable, producing small pods of low quality.
In ordinary field conditions, the soil should not be cultivated to a greater depth than 6 inches, but the tilth must be thorough ; deep cultivation adds considerably to the cost of harvesting.
If the soil be carefully selected, little after-cultivation is necessary ; three hoeings before the crop covers the ground are generally sufficient.
The plants should be so close as to completely cover the ground when full grown, and protect the soil and roots from direct sun ; 15 inches by 15 inches is a suitable distance.
The quantity of shelled seed required per acre depends on the system of planting, but 30 to 35 lbs. per acre is ample with a planting distance of 15 inches by 15 inches.
The proportion of shell to kernels varies, some varieties of nuts give 66 per cent, kernel and 34 per cent, shell, and others up to 80 per cent, kernel and 20 per cent, only of shell. A good ground nut should give, apparently, 48 per cent, to 50 per cent, of oil in the kernels. The following table of yields of dried nuts per acre is given by the Imperial Institute Bulletin :-
Carolina running, ....
„ „ (selected), Gambia, ......
Local variety, .....
Red Tenessee, .....
Virginia running, ....
Lbs. 1,706 1,548 1,479 1,254 1,670 765
2,041 2,027 1,789 1,846 1,836
The sandy plains in Bida or Kano in Northern Nigeria, according to its able Director of Agriculture, offer an ideal soil for ground-nut production. A yield of over a ton of freshly harvested nuts per acre was being generally obtained at Kano, and at Bida at least 1,400 lbs. of kernels per acre were obtained in the 1912-13 season. A superior variety of ground-nut is grown in the neighbourhood of Pategi, Ilorin Province, which might be useful to draw upon for seed elsewhere.
In the Gold Coast Colony, where the Hongkong as well as the native variety is cultivated, at least in some of the centres, crows and rodents seem able at times to secure more than their fair share of the crop, in spite of its being underground.
In Gambia, ground-nuts- which form by far the most important article of cultivation in that colony- alternated with the staple food crops of the country- viz., guinea corn, maize, millet, and cassava, offer a fairly useful form of rotation.
At the beginning of each season, "strange farmers" appear in Gambia, and take up the cultivation of the ground-nut area, doing planting and harvesting on a percentage system, so much going to the owner of the land. After harvesting and selling, the strange farmer disappears with his good profit, and may not perhaps be seen again. There is never, however, any dearth of such farmers.
Harvesting the crop is by far the most expensive operation, and no system yet devised can do away with the large amount of hand labour necessary for gathering the crop. In Nyassaland it is dug and gathered in a manner very similar to that employed for the Irish potato crop.
After harvesting, the nuts are usually sun-dried for about a week, and not shelled until required for shipment, but machines can now be secured to dry the nuts artificially.
Under ordinary field conditions 4 acres to the ton of shelled nuts would be an average for Nyassaland, and the following figures, taken from a 6 1/2 -acre block grown at Namiwawa on unmanured land in 1915, show the cost of production and value of the crop, the figures being based on actual working expenses :Cost of Production per Acre aNd Value oF Crop.