SOIL MANAGEMENT. 43 



(4) Drainage. — The institution of efficient drainage is 

 the only really effective and permanent remedy. In this way 

 the water-table can be kept at a desirable distance from the 

 surface and prevented from rising after irrigation. With good 

 drainage the soluble salts can then be washed out of the 

 soil by successive floodings. When much soluble carbonate is 

 present, the percolation of water may be facilitated by previous 

 application of gypsum or large quantities of coarse straw. 

 While, unfortunately, rather costly good drainage is the secret 

 of brak prevention. 



(5) Avoidance of the Use of Unsafe Irngation Water. — 

 Before being used for krigation, water should always be 

 analysed to determine whether it contains harmful quantities 

 of dissolved salts. 



(6) Growth of Brak-Resistant Plants. — Absence of vege- 

 tation promotes surface accumulation of brak salts ; so it is 

 desirable to maintain some kind of plant growth, even if not 

 very useful. Crops differ greatly in their tolerance for brak 

 salts, some, such as citrus, being extremely sensitive, while 

 others, such as various types of salt-bushes, are highly 

 resistant. 



REFERENCES. 

 » U.S.D.A. Bui. 320. 



- Soils, Their Properties and Management. Lyon, Fippin and Buckman. 



' A Study of the Agricultural Soils of the Cape Colony. Juritz. 



■• Principles of Irrigation Practice. Widstoe. 



^ Soil, Physics and Management. Mosier and Gustafson. 



• Soil Alkali. Harris. 



■> Soils. Hilgard. 



« The Soil. Hall. 



^ Soil Conditions and Plant Growth. Russell. 



