- 86 — (() Bacteria may be found in diminishing numbers in the subsoil, the number and species present being influenced by the texture of the soil and the amount of water added.

(d) Fungi are numerous in uncultivated soils, and tend to develop in heavily-watered soils.

(e) The introduction of organic matter in the form of green manures is essential for the improvement of the texture of the heavy clay soils, and to provide food for micro-organisms.

(/) The loss of organic matter and nitrogen is rapid in Sudan soils.

{g) So far as can be determined by laboratory methods, the formation of nitrate from proteid via ammonia is feeble.

(A) The amount of nitrogen found in the soil at any one time is considerably below that required for the successful cultivation of a crop.

{i) A short fallow is beneficial to the soil, but after a prolonged fallow soils tend to revert to desert conditions with a deficiency of nitrate-forming organisms and a predominance of fungi and organisms capable of denitrification.

So long, however, as the moisture content has not become too low, the formation of nitrate takes place, but this process is always limited by the rapid desiccation which ensues.

(j) Marked changes can be effected by cultivation and methods of treatment, and these changes are capable of intelligent investigation by the laboratory methods at our disposal.

(k) The resistance, as distinct from the activity, of many organisms to desiccation is very great.