336 Irrigation and Drainage 



and occupied the soil, the shading, the firming and 

 the root binding all conspire to prevent puddling 

 and baking, so that flooding may then be practiced 

 with less danger of harm ; and so grass lands, alfalfa 

 and clover may always be flooded with little danger 

 of injuring the texture of t'he soil, because the exten- 

 sive root systems prevent it. 



When water is applied in furrows without wash- 

 ing, so that it rises and spreads through the soil 

 between the furrows by capillarity, it then has the 

 opposite effect from puddling, and tends rather to 

 improve the texture by drawing the loosened soil 

 grains together into clusters by an action of surface 

 tension like that which rolls drops of water into spheres 

 on a dusty floor. As the soil crumbs become satu- 

 rated with capillary water the loose dust particles which 

 have been formed in tilling are drawn to them and 

 bound closely by the pull of the surface film ; but 

 so soon as the whole soil becomes immersed in water, 

 as in the case of flooding, and as happens in the bottoms 

 of the furrows, there is then no surface tension, and 

 the soil grains fall apart under the water of their own 

 weight, and compacting and puddling are the results. 



It follows, therefore, that all crops where the 

 ground is not covered by them, and where cultivation 

 is resorted to to prevent loss of water by evaporation, 

 should so far as practicable be irrigated by the fur- 

 row method ; and since the bottoms of the furrows 

 must be subjected to the conditions which puddle, 

 it follows that the furrows should always be as far 

 apart as other conditions will permit, 



