150 Report S.A.A. Advancement of Science. 



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. 



I. — 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 £^\i 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 recom- 

 mend that farmers should endeavour to utilise them, especially as this 

 would tend to diminish their number. Though they could probably 



