LIME.

This, which is so much needed in most of our soils, is actually useful in the form of carbonate. The best effect, however, is produced by the application of the oxide or hydroxide (quick lime or slaked lime), because these substances, being soluble in the water of the soil, are disseminated far more thoroughly than would be possible with even the most finely-divided carbonate of lime. After addition to the soil they are gradually converted by absorption of carbon dioxide into carbonate, but not until their distribution by virtue of their solubility in water has been effected. So long as the lime remains in the caustic or alkaline state, the soil is not fitted for the growth of plants. Hence lime containing much magnesia (which) absorbs carbon dioxide much more slowly than lime), such as results from burning magnesian limestone, is not suited for agricultural purposes.

THE MANURIAL RESOURCES OF THE COLONY.

1. COMBINED NITROGEN.

A. Nitrogenous Organic Matter. As sources of this valuable substance the Colony has, like all inhabited countries, the excrements of domestic animals and of the human inhabitants, but the quantity of this material is limited, and at present inadequate to supply the needs of the soil. Kraal manure, bucket refuse from towns, waste portions of animal carcasses, and such refuse, should all be carefully utilised on the land, as they contain valuable quantities of combined nitrogen, as well as phosphates, potash and lime. Also valuable for the same reasons are the enormous cave deposits found in many limestone districts. Many of these deposits have been examined in our laboratories, and, while they have proved to be extremely variable in composition, there is no doubt that they form a valuable manurial asset. Some of the more recent deposits are very rich in nitrogen, Specimens containing as much as 9.7 per cent. of nitrogen have come under our notice, but much of the material found in the caves consists largely of fine silt, containing but little fertilising matter. Bones of animals, and excreta of wolves and other animals occur in many of the caves, and thus increase the phosphatic value of the deposits considerably and the nitrogenous value slightly.

The excrement of vultures, which occurs in considerable quantities near the nesting-places of the birds, is exceedingly rich in nitrogen. A specimen examined in our laboratories, obtained from the Orange River Colony, was found to contain about 25 per cent. of nitrogen, and to have a value, when compared with the cost of artificial manures at the coast, of about £17 per ton.

Another product which might be utilised as a nitrogenous manure in this Colony is the locust. In the Transvaal during the past winter locusts have been only too abundant, and I would certainly recommend that farmers should endeavour to utilise them, especially as this would tend to diminish their number. Though they could probably

be more profitably employed as food for pigs, poultry, etc., they have considerable value as manure. If they were collected in sacks by natives easily done at night or in the early morning on their roosting-places-killed by being dipped into boiling water, and then dried in the sun, they could be ground in any ordinary mill. The powder thus formed, if not utilised as food, would form an exceedingly valuable manure. The product from the adult brown locust was examined recently by the writer, and was found to contain 9.5 per cent. of nitrogen, 0.28 per cent. of lime, and 1.59 per cent. of phosphoric acid. Compared with prices of artificial manures at the coast, ground locusts would thus have a fertilising value of about £7 10/- per ton.

It is true that they would probably be somewhat slow in their action as a manure, but they would undoubtedly contribute largely to the fertility of the soil to which they were applied, while the advantage to the country at large resulting from their destruction during the breeding season would be undoubted.

Still another product, possessing value as a local source of nitrogen (and other manurial substances) is the material composing ant-heaps. These are abundant enough in many districts, and when crushed afford a fine-grained soil which is much richer in nitrogen than the soil of the surrounding veld, and could be used with advantage for seed-beds for nurseries and gardens. This plan has been practised by several farmers and others in the Transvaal with great success, and it might be much more largely adopted.

A specimen of such material from an ant-heap, and another of the soil taken three feet away, near Christiana, were examined by the writer, with the following results :

The superiority of the ant-heap material in organic matter, nitrogen, and "available" potash and phosphoric acid over the veld soil shows that it might be used with great advantage on poor soils, though, of course, it is not worth transporting any distance. Probably

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their fine texture and somewhat coherent character would render antheaps too close and impervious to yield a good soil by themselves, but by mixing them with a sandy soil this could readily be remedied.

Ammonium Salts. These, which are in Europe produced as bye-products in the distillation of coal and shale, are not made in any quantity here. Very little coal is used for gas-making, so that the amount of ammonium salts produced in the Colony must be insignificant. Moreover, in the case of many of our soils, deficient as they are in lime, these substances would not be very suitable unless a dressing of lime were previously applied.

C. Nitrates. Unfortunately few authentic cases of the occurence of nitrate deposits are known in the Transvaal. I have had several saline deposits sent from various localities for examination, in the hope that they would be found to consist largely of nitrate of soda or potash, but none have been found to be of any value. A deposit was reported to have been discovered in the Zoutpansberg about a year ago, but I have not been able to obtain any information concerning it. I am told that many of the older farmers in the Colony speak of "saltpetre" occurring in crystals on stones in the neighbourhood of pans, but I have not been able to ascertain whether the substance so called is ever really saltpetre, i.e., potassium nitrate. If such deposits do occur, it is very important, since nitrate of potash or soda would be of immense service in agriculture, provided its price were reasonable. The cost of the imported South American product is very high in this country on account of freight and transport charges.

At present, unless the farmer is willing to pay the very high prices for imported nitrate of soda or sulphate of ammonia, he must chiefly depend for nitrogenous manuring upon organic matter, kraal and stable manure, bucket refuse, carcasses of animals, bats' guano and kindred substances, or adopt the plan of enriching the soil by the growth of leguminous crops and so obtaining nitrogen from the air.

2.-PHOSPHORIC ACID.

A. Bones. There are considerable quantities of bones available in the Colony. In additon to those of animals slaughtered for food, there are the bones and bodies of those which die from disease; unfortunately, these have been only too numerous in late years. Then, too, large quantities of bones occur scattered over the veld as relics of the horses, mules, and oxen which died during the war.

Bones, when reduced to fine powder, form a valuable though somewhat slow-acting manure, and might with advantage be largely employed in agriculture here.

The carcasses of animals which die from disease might, as a preventative of the spread of contagion, be burnt in a suitable furnace, and the residue would form a valuable phosphatic manure. A sample of such "ash" from the crematorium at the Veterinary

Station at Daspoort, was recently examined in our laboratories, and gave the following results :

This substance, compared with the price of manures at the coast, would be worth about £7 9/- per ton.

B. Other phosphatic manures. Unfortunately, deposits of true mineral phosphates are rare in the Colony, and though several specimens of minerals suspected to consist largely of phosphate of lime have been received from various correspondents, none have proved to be of any value.

However, in many limestone districts, caves-really old underground water courses-exist and in many of these deposits containing the excreta of wild animals, wolves, jackals, and others, bones of these animals and their prey, and in some instances, immense quantities of the excrement of bats, mingled with fine silt, occur. These cave deposits always contain some, and often much, phosphoric acid, in addition to nitrogen, potash, and lime. Such deposits are certainly useful as manures.

Large numbers of samples of this material have been examined in the laboratories, and the results show, as might be expected, great variability.

I append a table giving the proportion of the chief manurial constituents in seven samples, which may be taken as typical of such cave deposits

I was a fresh bulky deposit, consisting entirely of bats' dung from Chune's Poort range in the Zoutpansberg.

2 was from caves near Potchefstroom (bats' guano and silt).

3 was from the large cavern at Wonderfontein (bats' guano and

silt).

4 said to consist mainly of wolves' dung (Wonderfontein).
5 contained many bones (Wonderfontein).

6 was a recent deposit, bats' dung and silt (Wonderfontein).
7 a recent deposit from Elandsfontein caves, near Pretoria.

In certain districts it is the custom to employ dried sheep's dung as fuel on the farms. Sheep's kraal manure, used as fuel under the name of "Mest,' was found by Lewis in 1899 to contain (average of 11 samples) :—

While E. H. Croghan, in a paper read last year before the British Association at Johannesburg, found 25 samples from Cape Colony and the Orange River Colony contained :

the ash left when mest is burnt is free from nitrogen, but much richer in potash and phosphoric acid.

While Croghan, in 25 samples, found quantities ranging from :—

In certain parts of the Transvaal are old cattle kraals, used by the natives before the incursions of white men. The deposits overlying these kraals are almost devoid of nitrogen, but still retain considerable quantities of potash and phosphoric acid. A specimen of such deposit, from near Rustenburg, from a kraal said to have been used about a hundred years ago, was found to contain :

This deposit has been largely used by the local farmers with successful results during the last 7 or 8 years, when kraal manure has been scarce.

Another remarkable source of phosphoric acid has come under my notice the ash of certain Transvaal coals. In a specimen of coal ash from one of the Witbank Collieries I found 5.5 per cent. of phosphorus pentoxide.