.244 IWO METHODS OF l-AK.M IRRIGATION. 



iind I have often seen great hules in the ground three to four feet 



.deep from which material had been taken for dammin^g^ the water. 



I'his sort of work is bad, and there is no need for it. It is infinitely 



(better to build permanent sluice-gales along the furrow, and others 



at the lowest ends of the basins to let out the surplus water. These 



gates should be well bedded, and the frames should run well into 



the banks on both sides. If this is not done you will have trouble 



from the water working- its way round or under, and some day 



\\ hen you are not expecting it, a sluice may easily be washed out. 



In extensive irrig-ation works it is absolutely necessary to build 

 permanent sluice-gates across the large canals for dividing the 

 water ; but with small canals this is not necessary. An excellent 

 .arrangement is a sheet of iron semicircular in shape. 

 This is a \ery handy arrangement, as it can be quickly carried 

 ftom place to place. But it is only suitable for small canals, and 

 should not be used for the openings into the basins, as the water 

 would cut round it very soon. Another excellent method for 

 quickly, easily, and cleanly blocking a canal is to use a piece of 

 canvas cut roughly to the shape of the letter \', ha\ing a bar or 

 narrow strip of wood fastened to the broad end. 



The bar is placed across the top of the canaj, and the loose end 

 of the canvas laid upstream in the bed. If the edges of the canvas 

 are pressed into the sides and bottom of the canal, it will hold 

 for quite a long while. Some people drive a long spike through 

 the small end of the canvas to help to hold it in position. These 

 canvas sluices are very useful and handy; but they cannot be set 

 if there is a large flow of water. They are suitable for moderate- 

 sized furrows that are too large for the cheese-knife sluice mentioned 

 above, and too small to make it necessary to build permanent 

 sluices. But all the same, as soon as you have your canal in 

 working order, and have decided how you are going to irrigate, 

 I strongly advise you to put in permanent sluices ; and this refers 

 to any method of irrigation that may be employed. 



After you have irrigated and sown you will probably see a 

 crop come up bearing a look of promise ; but suddenly it begins 

 to look sickly, and as days go on the growth is patchv, being fair 

 in some places, scanty, weak, or absolutely at a standstill in 

 others. Most beginners think the remedy is to pour on more 

 water as soon as the top of the ground looks dry, and the more 

 they pour it on the less things may improve. Perhaps they have 

 put on too much water, packed the ground too closely, and shut 

 out the air that the roots require. It is not easy to sav w^hy stand- 

 ing water injures, more or less, so many plants by simply touching 

 the stalks ; but it is a fact. 



The following points should be borne in mind, but they are 

 only general, and subject to many exceptions depending upon soil, 

 climate, and crop : — 



(i). Nearly all plants are more or less injured by flooding when 

 they are very young. 



(2). A layer of fine mud may prevent many seedlings from com- 

 ing to the surface. 



(3). The deeper the water and the longer it stands the worse it 

 is, especially with muddy water. 



