A UNIT IN AGRICULTURE 3? 



Ex. 16. Field Lesson. 



Material: a suitable field as near the schoolhouse as possible. Do 

 you find any ledges of outcropping rock? li' you do, break off a small 

 piece and compare the freshly broken surface with the outside or 

 weathered surface. Note carefully any difference. Do you find any 

 boulders or pebbles ? Break one open and compare the freshly broken 

 surface with the outside surface as before. Are the boulders and 

 pebbles of the same material as the rock in the ledge ? Select a piece 

 of each different rock you find to take to school for future study. 



Look along the bed of a stream for pebbles. (If there is no stream 

 at hand, this work may be done at another time and place by indi- 

 vidual pupils.) How do the pebbles in the bed of the stream com- 

 pare in size and shape with those back from the stream? How do 

 you account for the difference ? 



Find some good rich soil and dig a hole about 18x12 inches and 

 18 inches to 2 feet deep. Observe closely the material and the color 

 at different depths. Notice especially the amount of black soil. 



Make a drawing of one side of the wall. Repeat this exercise by 

 digging the hole on a steep slope. Account for any differences in 

 the soil at the two places. What is subsoil? Which do you think 

 will grow the better crop, the side hill or the lowland? Why? From 

 your observation of farm crops, can you state whether this is gen- 

 erally true? 



Ex. 17. Soil Texture. 



Material : sand, clay, and loam two small fruit jars full of each, 

 from the farms in the neighborhood of the school, if possible. Label 

 each jar and set one jar of each aside for use in Exercise 18. Com- 

 pare the three kinds of soil as to color, texture, and amount of humus. 

 Put some of each kind in a large test tube, cover with water, shake 

 thoroughly and set aside. Which settles most rapidly ? Most slowly ? 

 Which contains particles that float ? If these soils were poured into a 

 running stream which would be carried farthest ? Put a little hydro- 

 chloric acid on each and note the result. Mix the three samples in a 



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