Soils and Soil Management 57 



of this turbid water into lime water.* What happens to the particles 

 of clay suspended in the water? 



91. Humus is the term applied to partly decayed 

 plant and animal remains, and is well illustrated by 

 the leaf-mold found under the trees in a dense forest. 

 Humus gives to the soil a characteristic blackish color, 

 and adds greatly to its fertility It improves the 

 water-holding power in a noticeable degree, often 

 to double the original water-storing power. It makes 

 clay soils mellow and sandy soils compact. Humus is 

 formed by the decay of the roots, leaves, etc., in virgin 

 soils. The farmer is able to increase the humus in the 

 soil by adding compost directly, and by plowing under 

 straw and green crops, like cow-peas, etc. (See U 131, 

 Green Manuring.) 



92. Examination of Soils.j An experimental study 

 of the several kinds of soils, especially of those occurring 

 in the school district, should be made, and, if a sufficient 

 number of different kinds are not close at hand, others 

 may be secured. These various kinds of soil consist of 

 mixtures of -varying amounts of sand, clay, limestone 

 dust, and half-decayed plant remains. The fertility and 

 water-holding power will bear some relation to the 

 amounts of these separate substances composing the 

 soil. 



*To prepare lime water, secure a large-mouthed bottle or fruit jar. Fill 

 half-full with water. Add lime, a little at a time, until a good handful is used. 

 Cork securely, to keep out the air, and let stand. The lime will settle to the 

 bottom and the clear liquid above is lime water. 



tThe direct examination of the samples of soil, as outlined in this chapter, 

 may be conducted by any boy or girl with little or no assistance from the teacher. 

 A word of caution may be given to the student. He should be reasonably 

 familiar with the theory of the work he is to undertake, and what questions his 

 results may answer. Too often he will want to say that he is "going to prove" 

 so and so. He should be cautioned to " find out" if so and so is true or not true- 

 This is the attitude of the true student. 



