— 102 — Where superphosphate is applied in conjunction with farmyard manure or nitrate the yield has been proportionately reduced.

Where nitrate of soda is applied alone the yield shows an extraordinary advance on that of the check plot. The application of farmyard manure has a similar effect.

It will be readily admitted by all who have come into contact with Sudan cotton soil that an increase in the amount of humus is very necessary. This is most readily and economically provided in the shape of green manures.

The limited production of farmyard manure, and its extensive employment in the form of " zibla," for the plastering of mud-brick buildings, coupled with its speedy deterioration in so arid a climate, render this source of organic nitrogen little available for extensive agricultural operations.

Lubia afin {Dolichos lahlab) is without doubt the best green manure for this district. It is a legume, and thus increases the nitrogen content of the soil during growth ; it is extremely hardy, grows luxuriantly, and requires little cultivation or attention. It is a profitable crop to grow either for fodder, provided a contract for its disposal in a green form has been concluded ; or for the manufacture of hay, when a forage baler is necessary, as there is always a ready sale for the hay in Khartoum provided it is in a portable form ; or as a seed crop, the grain constituting an article of native diet.

If ft is to be used as a green manure it may be cut just as flowering starts and converted into hay or sold green. The stubble should then be watered immediately after cutting, when a new growth will develop. This may be watered twice and then ploughed under. Care should be taken not to cut the plant off too near with the ground, but to leave a 6-inch stubble to carry the second growth.

The improvement in the physical qualities of the soil due to the introduction of green manure is not so noticeable or so lasting in this country as in others, as all visible traces of roots, stalks, etc., disappear in a very short time.

As explained elsewhere, however, such destruction is in reality a process of nitrification, and if accompanied by crop growth and irrigation does not fail in its purpose. Periodic treatment of this nature is almost indispensable to successfxxl cotton cultivation, and must ultimately result in a marked and permanent improvement in the soil.

Sheep-feeding Experiments.—Restorative crops are by nature feeding crops, and the necessity of their inclusion in any rotation opens the question of the place of livestock in any local system of agriculture. While a regular market exists for small quantities of green forage and lubia hay, profitable disposal of large acreages of the few leguminous crops which flourish on our heavy cotton soil must be based on the general introduction of dairy or butchers' stock.