JulJHXAL OF THl<] DkPARTM liXI' OK A(;i! KUTi/i'URK. 



wlieii soil wliicii at the beginning' siiovved no brak ;it the surface becomes 

 brak after irrigation. When this happens and the drainage is good 

 it is because the irrigator has nsed insufficient water to wash the alkali 

 out througli the drainage. Tlie practice of applying water in several 

 light irrigations in place of a fewer number of heavier ones is a 

 ])rolific cause of this kind of trouble. The practice has also the added 

 objection that it tends to make the })lant shallow rooted, which of 

 itself is a considerable handica]). 



It should now be clear that wherevei- brak exists tlie method of 

 irrigation should be such that there is on the Avhole a downward move- 

 ment of water, because, if on the wliole the movement be upward, tlie 

 l)rak of this soil dowii to the depih tlie water penetrates is slowly but 

 suj-ely brought to the surface. 



The reason why brak should not be allowed to lise to the surface 

 is that brak has ils greatest power for injury when it is in the neigh- 

 l)ourhood of the rootcrown of the plant. Illustrative of this is the 

 fact that land too l)rak at the surface to grow anything useful may, 

 l)y a single heavy irrigation, be reclaimed for cultivation at least for 

 a time, the heavy irrigation having the effect of diiving the brak 

 deep into the soil. 



It happens only too frequently that the irrigator has too little 

 water to enable him to keep the brak well down. If this be so much 

 can be done to improve matters by maintaining an efficient soil mulch 

 which not only reduces tlie evaporation of moisture from th.e soil to 

 the air, but also })revents the accumulation of brak at the surface of 

 the soil. The choice of crop is also an ir.iDortant matter. The best 

 crops under the circumstances are those which send their roots down 

 deeply and at the same time shade the soil well, as. for instance, 

 lucerne. 



The deep rooting habit is beneficial in this way. If the crop is 

 deep rooted much of the watei it takes up from the soil enters its roots 

 down in the soil. This being so, the amount of water which can 

 ]iossibly be evaporated at the surface is correspondently reduced, and 

 with it the amount of b'rak. Thus, in the case of lucerne, we have a 

 crop which is often difficult to establish on brak land, but which, once 

 its roots are down and it shades the soil, is able to tolerate brak to a 

 higher degree than most useful crops. 



The appearance of brak at the surface consequent on irrigation is 

 known amongst irrigators as " the rise of brak." Speaking generally, 

 the rise of l)rak is proportionate to the amount of water evaporated at 

 the surface of the soil. Anything that reduces the amount of evapora- 

 tion at the surface of the soil therefore reduces the rise of })rak. 



It must be understood that in no case does all the brak of a soil 

 rise to the surface. Neither must it be forgotten that there may be a 

 rise of bralc of sufficient degree to cause decline in crop yields and yet 

 not sufficient to be discernable. Again, there may be a rise of brak 

 only towards the end of the season. In this case the crop may have 

 done s])lendidly at the beginning, yet indifferently towards the end. 



The effect of cultivation in preventing injury from brak is so 

 gieat that the late Professor Hilgard (than whom no one living has 

 had a wider experience of brak problems) states in his book on soils 

 that deep preparation of the land (to assist the downward movement 

 of water) and the maintenance of an efficient soil-mulch (to prevent 

 evaporation) are the prime essentials to success. 



