Brak in its Relation to Irrigation. \'-'> 



BRAK IN ITS RELATION TO IRRIGATION. 



By Arthur vStead. B.vSc, F.C.S., Lectiuer in Chemistry, 

 Grootfontein vScliool of ARricultiiie. 



[This article was originally delivered in the form of a lecture at a meeting of the Cradock 

 Farmers' Association and was printed iu a section of the Press. In view of the 

 importance of the subject, the lecture is published in full together with illustrations 

 furnished by Mr. Stead. — ACTING Editor.] 



The result of long experience lias led me to tlie belief tJiat brak is mudi 

 more widespread, and its deleterious eft'ects of much greater economic 

 importance than is generally supposed ; of economic importance, 

 because cjuantities too small to be visible or detectable by taste are 

 yet able to depress the yields of crops, thereby discounting* the value 

 of irrigation works to a degree that demands attention. 



I propose to deal with the subject in a simple way, and yet, at 

 the same time, somewhat fully, even at the risk of touching on aspects 

 that may not be of particular local application. I feel sure that your 

 patient attention can be relied upon. 



The Variable Effect of Brak. 



The same c^uantity of the same kind of brak affects the yield of no 

 two different crops to the same degree ; and indeed this varying- effect 

 applies also to different varieties or strains of the same crop. This 

 means that plants possess varying powers of resistance to brak. A 

 similar condition of affairs is to be found in the animal kingdom, for 

 do we not all know that, given the same adverse conditions, the 

 resistance of dift'erent animals to them differs enormously, that 

 different breeds of the same animal resist to quite different degrees, 

 and also that animals of the same breed may show varying powers of 

 resistance. 



This at once suggests that wherever brak conditions obtain it may 

 be possible, by growing the right strain of the right crop, to reduce 

 the evil effects of the brak of any particular soil to a minimum. 

 Probably the best way to get the best lesisting strains is by selecting 

 seed from plants which are found to be much superioi' to the average. 



Declining Yields following Irrigation. 



Let us inquire why it is that our wheat crop, for instance, gives 

 poor yields in comparison with those obtained in Europe. 



The farmer when questioned on this point generally replies that if 

 he had the water when he wanted it he could equal the European 

 average every time. My experience is that he cannot continuously 

 do so. 



I know of instances in which lands, situated in areas of too little 

 rainfall to produce any crop, have been, brought under permanent 

 irrigation and have yielded as much as ten bag's of wheat per acre ; 

 while the most that could be got out of them a few years later was five 



