THE IRRIGATION AGE. 135 



of the mulched cylinder and 3.17 per cent drier in that of the un- 

 mulched one. 



There are several very important principles demonstrated by these 

 experiments. (1) Water in ordinary soils may rise to the surface from 

 depths as great as 10 feet so that in climates like California, having a 

 wet and dry season, if there is enough rainfall to charge the surface 

 10 feet with capillary moisture much of this may become available to 

 crops, even if their roots do not penetrate to that depth. (2) The 

 coarse textured soils, while they may not retain as much moisture, will 

 not lose it as rapidly, by surface evaporation, nor so deeply, as the 

 finer grained soil will. (3) When the surface of even unstirred soil 

 once becomes very dry the loss of water upwards through it becomes 

 very slow. I hope during another year to repeat these experiments 

 but to periodically wet the surface to imitiate the conditions of humid 

 rather than of arid climates, and I expect to demonstrate that although 

 frequent wetting of the surface has taken place the soil will in the end 

 have become much drier in the deeper layers. 



I have this winter succeeded in measuring a capillary rise of 

 water exceeding 44 inches on the level in 24 hours through a height 

 of a little more than 6 inches of coarse sand with its surface kept wet 

 when the same sand, with the surface air dry, failed to lift an amount 

 equal to one half inch. These facts go a long way toward explaining 

 the high duty of water in California and Washington and their much 

 lower duty in humid climates. They teach, with the force that noth- 

 ing else can, the great importance of the dry soil mulch wherever soil 

 moisture is deficient. They teach that if in the sub-humid and semi- 

 arid regions of the United States moisture can be gotten into the soil 

 by any means in sufficient quantity to produce a crop it may be pre- 

 served there by soil mulches long enough for crops to utilize it, if only 

 the proper conditions for development in the moist soil exists. 



The old system of intertillage introduced by Jethro Tull in Eng- 

 land, and modified by Hunter and still later by Smith, at Lois-Weedon, 

 has much to recommend it on fertile soils, in which there is a defici- 

 ency of soil moisture, as is the case in the sub-humid regions of this 

 country. Tull was a close observer, and early learned to appreciate 

 the great advantage of thorough tillage, not only in conserving soil 

 moisture, but also in developing available plant-food. He strongly 

 advocated planting in drills, so as to admit of thorough and frequent 

 stirring of the soil and with the aid of the horse. 



Hunter modified Tull's system by laying out his fields in strips 

 about 9 feet wide, every other one of which was sown, while the inter- 

 mediate ones were left naked and were frequently cultivated through 

 the season, and kept free from weeds. In the fall of the year the 

 bare strips were sown, and the others, which had borne the crop, 

 were plowed up and tilled in a similar manner. His method amounted 

 -to a system of summer fallowing, as that practice is now generally 



