756 Journal op the Department of Agriculture. 



Humus in the soil is increased (a) by residues of crops and green 

 manures added to the soil; (b) by dung and kraal manure; (c) by 

 leaf mould and turfy material ; (d) by additions of seaweed where it 

 is available. 



In the matter of buildings up the humus-content of the soil the 

 agriculturist has often to fight a losing battle. Where stock have 

 to be fed it is not good practice to plough in green crops. The 

 residues of crops grown and taken away are not sufficient to maintain 

 the humus of the soil. If such parts of the stalks of the nipalie crop 

 as are not eaten by stock were plou.o-hed in, the soil might gain. Very 

 often they are broken up and blown away or burned or otherwise lost 

 to the soil. The farmer might, by a little thought and care, 

 very much increase his stock of organic manure and secure correspond- 

 ing benefit to many crops. 



The conservation of organic matter is a process that helps 

 itself a good deal. Better crops are grown and big-ger residues 

 are left. Some part of each successive application of organic 

 matter resists decay more strongly and persists. These parts 

 accumulate, and in time become a very valuable addition to the 

 soil material, giving it that highly prized quality called " condition," 

 and making it more stable and uniform in crop-production, becoming, 

 in fact, a precious reserve of actual and potential fertility. 



Organic manures which are the origin and sustainers of this 

 highly desirable "condition" should be the subject of thought and 

 study on the part of every farmer, and their augmentation- and use 

 should be the object of continual effort. Bedding ought to be used 

 freely and all residues incorporated in the dung-heap. Applications of 

 the fresh material are highly useful to the potato crop and to other 

 gross-feeding crops, while succeeding grain crops benefit to a notable 

 degree by the residual matters left by such applications. 



Only in very exceptional circumstances ought quicklime to be 

 used in farm practice; where lime is required agricultural lime 

 (ground limestone) should always be chosen. Quicklime (caustic lime) 

 very rapidly uses up the precious luimus ; the carbonate of line is 

 comparatively very mild and economical in this respect. 



II. A second essential is lime; this is often wanting. Some 

 crops, as potatoes, appear to flourish in its absence; some are 

 indifferent, as mealies; while others, like lucerne, depend upon it 

 to make profitable growth. Generally, for the usual purposes of 

 agriculture, the lime in soils requires additions. It performs several 

 functions. 



(a) It is the one available corrective of acidity in soils. Acidity 

 arises from two causes. (1) The oxidation of organic matter gives rise 

 to numerous acid substances. These are neutralized by lime. As 

 oxidntion proceeds simjjler acids are produced, until, finally, carbonic 

 acid is arrived at, and the lime becomes available for further use. If 

 this were the only purpose to be served a small quantity of lime would 

 meet all requirements. The organic acids literally burn themselves 

 out, and the lime is regenerated. (2) The addition of fertilizing sub- 

 stances usually leads to acidity in soil. Superphosphates are strongly 

 acid substances, and when added to soil are dissolved in the soil water, 

 and then precipitated on the soil material. Salts of iron oxide and 

 alumina with phosphoric or sulphuric acid are formed. These are 



