THE WOBK OF ROOTS 129 



results in the formation of a pasty mass impervious to 

 water, as can be easily seen by kneading a little wet 

 clay. Such a soil is called a puddled soil, and its 

 properties are illustrated in the making of reservoirs, 

 the bottoms of w^hich are sometimes lined with wet 

 clay, which is then kneaded by driving sheep into the 

 enclosure: the result is a layer which is water-tight. 

 To a certain extent, puddling of the soil is caused by the 

 beating action of rain, as well as by baking in the sun 

 and the deposition of salts by evaporation. (Mulches 

 prevent this action; so also does a covering of plants, 

 which explains why the soil of meadows, natural 

 pastures, woodlands, etc., remains in good tilth.) 



It is interesting to note that puddling may also be 

 caused by tilling the soil when it is too dry, the effect 

 being to reduce it to a fine powder, which forms a 

 pasty mass on becoming wet. 



Puddled soil is improved by mixing manure, burnt 

 clay, straw, coal ashes or sand with it. Try an experi- 

 ment to test this. The addition of lime is also beneficial, 

 since it tends to form floccules (see page 152). 



The texture of the soil is more important than its 

 richness, and it is almost useless to apply manures to 

 soil which is in poor tilth: tillage is of more importance 

 than manuring.^ 



1 See King : "The Soil," and "Irrigation and Drainage": Bailey : "Princi- 

 ples of Agriculture," Chaps. II, III and IV. See articles in the Ycar-Book of 

 the U. S. Dept. of Agriculture, for 1894 by Whitney, Galloway and Woods; for 

 1895 by Whitney ; for 1900 by Briggs ; for 1903 by King. 



