TEXTURE AND STRUCTURE OF SOILS 



47 



Procedure. — Examine the texture of each of the labeled soils 

 both under the hand lens and by the feel. Observe the color and 

 estimate the amounts of organic matter by the darkness of the color. 

 Be able to identify samples if unlabeled. 



Observe the plasticity and cohesion of each soil when enough 

 water has been added to develop maximum plasticity. Make small 

 marbles of sand, clay and muck respectively when each is at its 

 maximum plasticity. Dry and observe relative cohesion and 

 plasticity. Be able to state the relation of texture, moisture and or- 



9 CLAY 



SAND5 



APPARATU5 FOR FILTERING 5AND3 



Fig. 7 — Apparatus for a simple mechanical analysis of soil. Shaker 

 bottle, funnel, filter, beaker and stand. 



ganic matter to cohesion and plasticity. What is the practical im- 

 portance of texture and class ? 



Obtain set of unlabeled samples for identification of class. If 

 possible, pupils should also identify samples in the field. As mois- 

 ture variations and tillage operations often make great differences 

 in the general appearance of a soil, skill in quickly and accurately 

 determining the class of any soil in the field is a valuable asset in 

 all agricultural work. 



Exercise V. — Determination of soil class from a mechanical 

 analysis. 



Materials. - — Figure on page 35. 



