SOIL WATER 95 



soil which has had some sand mixed with it. A 

 comparison of these three samples should point 

 a profitable lesson. If you have a very sandy soil 

 find the influence of adding humus to it in like 

 manner. If accurate measurements are desired, 

 weigh the dry soil and the same soil after it is 

 thoroughly saturated. A good soil should be able 

 to absorb at least one-half its own weight of water; 

 humus often holds almost twice its own weight of 

 water, and sand from 15 to 25 per cent. 



Testing the Water-moving Ability of Soils. The 

 ability of a soil to move water by capillary action, 

 and to draw upon the free water to supply the 

 needs of plants, may be determined with a fair 

 degree of accuracy in the following manner. Take 

 chimneys of fire-dried and well-packed clay, sand 

 and humus, as in the previous test, and stand 

 them in a pan. Cover the bottom of the 

 pan with half an inch of water. Note the water 

 creep up into the chimney by capillary attraction. 

 It rises very rapidly in the sand at first, but is carried 

 only three or four inches high and then stops 

 the spaces between the grains are too large for it to 

 be drawn higher. Humus takes the water up more 

 slowly but eventually the soil at the top of the 

 chimney is wet with the film water drawn up from 

 below. The clay absorbs water even more slowly 

 than humus, but the surface soil of the chimney of 

 clay is wet in a few hours. Now test in a similar 

 manner the farm soils which you have to handle. 

 See what effect mixing a little sand or humus with 

 the clay has upon its water-drawing power, and 

 what influence mixing a little humus with the 

 sand has upon its capillary power. Compare 

 the capillary power of sand when it is put into 

 the chimney loosely, and when it is packed 



