The first four kinds are regularly employed as food, and are found growing as a mixed crop; although the white grains are more appreciated and frequently predominate. Nos. 5 and 6 are not considered so good for human food, but are largely employed for feeding cattle and horses, for which latter purpose they are greatly in demand. No. 7 is used for the same purpose as the last, but is a rarity and of no special value. These seven kinds are grown as six-months’ crops, and are harvested in October when the rains cease. No. 8 is a three-months’ cropping kind, which in this particular resembles “Gero” (_Pennisetum typhoideum_), as its native name indicates. The grain is much smaller than the others, and it is said to be cultivated to some extent in the Sokoto Province. No. 9 is a variety which is said to be cultivated in Bornu in the fertile depressions which retain moisture for long periods, or by means of irrigation from the rivers. (See _Bulletin of the Imperial Institute_, vol. iv. [1906], p. 226.) Guinea corn is permitted to occupy the land for a number of years successively, being often grown with “bulrush millet” (_Pennisetum typhoideum_). In this case the millet occupies the furrow whilst the Guinea corn is on the ridge, and this is reversed when the soil from the ridge has been hoed into the furrow and the previous ridge becomes the furrow. In many parts of the northern districts it is customary to permit the Guinea corn root-stocks to remain in the ground for two or three years, and to fill in the vacancies only with new seed when the old plants die. By this system it is found that the crops are better assured, as the old root-stocks withstand a prolonged drought better than new plants. This custom, if persisted in, would be a direct hindrance to the introduction of ploughing. Manure is applied regularly to this crop in the northern districts, but never in the Niger valley. The method of applying manure varies according to the condition of the crop. Where entirely new plants are to be grown, a shallow bed is made upon the top of the ridge or in the furrow, and the goat, sheep, and cow manure mixed with ashes, and accumulated carefully in the villages, is spread thinly upon the bed before the seed is sown. In other places, where old root-stocks occur, handfuls of manure are applied to the growing plants in May. This is sometimes adopted where young plants only are growing. Manure is so necessary for the system of cultivation adopted in the Kano and Zaria Provinces that every scrap of material which is of manurial value is carefully preserved, being carried to the fields by men and donkeys.