168 



CALIFORNIA FRUITS: HOW TO GROW THEM 



levees. This causes the water to flow through the furrows from side 

 to side and distribute itself evenly over the whole ground. The number 

 of furrows which can be passed before connecting with the bank de- 

 pends upon the slope of the land the nearer level the land the greater 

 the distance that can be left between the connections, and vice versa. In 

 this way the water is taken slowly down a grade where it would flow 

 too rapidly were it admitted to furrows in the direction of its flow. 



Another combination of the check and furrow system is found 

 where the lowest spaces of a slope irrigated by furrows are laid off in 

 checks to catch the overflow from the furrows and compel its percola- 

 tion at a point which would otherwise receive too little water. The parts 

 of a furrow system which lie farthest from the source of supply are 



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Combined check and furrow irrigation. 



obviously least supplied, because long flow can not be maintained there 

 without much loss from overflow. Holding the water in checks at the 

 lower end usually for two rows of trees is quite a help toward even 

 distribution. 



The Basin System. The term basin should be restricted to in- 

 closures which do not aim at covering the whole surface, but only a 

 small area immediately surrounding the tree. The check system is 

 clearly a more rational and perfect method of flooding. When basins 

 were used on ground capable of irrigation by the check or furrow sys- 

 tems, it was probably due to a misconception which has prevailed also 

 in the practice of fertilization, that the tree derived its chief benefit from 

 the soil immediately surrounding and beneath its bole, and that distant 

 applications were likely to be wasted. Years ago it was held that the 

 lateral root extension of a tree was equal to the spread of its branches, 



