THE WATER OF SOILS. 24! 



irrigate again within a much shorter time than will be neces- 

 sary if deep-furrow irrigation be used. 



A similar experiment with deep and shallow furrows was 

 made at the Southern California station near Pomona in 1901, 

 as reported in Bulletin 138 of the California Station. The 

 results as far as they went were' precisely similar, and upon 

 the basis of these the writer earnestly advocated deep-furrow 

 irrigation, and had the satisfaction of seeing it strongly 

 approved by orange-growers at Riverside and elsewhere, by 

 putting it into practice. 



In addition to the saving and better utilization of the 

 water used, this mode of application has the advantage of 

 preventing the roots from coming too near the surface ; it will 

 also largely eliminate " irrigation hardpan " or plowsole. 



The results produced by long-continued shallow plowing and 

 irrigation in shallow furrows is well illustrated in the last of 



& 



the irrigation profiles, which shows the observations made on 

 the same land as the others, but where rational cultivation and 

 deep-furrow irrigation had not yet been introduced. It will 

 be seen that after applying, and of course paying for, the 

 water for three days, its average penetration was only about 

 eighteen inches ; so that the trees of the orchard received very 

 little benefit, and were supposed to be needing fertilization 

 when in fact they were simply suffering from lack of water 

 at the lower roots. 



One somewhat unexpected point is shown by these dia- 

 grams, viz., the slight sidewise penetration of the water; the 

 wetted areas having a nearly vertical lateral outline. This 

 means, of course, that unless the furrows run very near the 

 trees of an orchard, the soil immediately beneath the trees 

 will remain dry; thus inducing the roots to spread sideways 

 and losing depth of penetration and soil. It will be noted 

 especially in the lower figure that here again the deep furrow 

 offers a material advantage over the shallow, the sidewise 

 spread being much more pronounced than in the shallow fur- 

 row alongside. 



Distance Between Furrows and Ditches. The distance be- 

 tween the furrows must, of course, be proportioned to the 

 readiness with which the water penetrates, being less as the 

 land is of closer texture. The distance between head ditches 

 16 



