36 AGRONOMY 



of the moist soil for a few minutes. If the paper turns reel, the 

 soil is acid. Litmus paper may be found in any chemical 

 laboratory or at the nearest drug store. Blue litmus paper has 

 the property of turning red in the presence of acids, and red 

 litmus paper will turn blue in alkaline mediums. Acid soils are 

 easily neutralized by the application of lime, marl, or gypsum. 

 Artificial soils. The florist and gardener often find it expe- 

 dient to make artificial soils for their plants. Seedings and cut- 

 tings need a light and porous soil consisting largely of sand ; 

 ferns need a considerable proportion of humus. The grower, 

 therefore, usually obtains peat, sand, leaf mold, and other in- 

 gredients and mixes his soil to suit the needs of the plants. A 

 good potting soil for all ordinary plants is made by building up 

 a mound consisting of a layer of sods from any good soil, a layer 

 of sand, and a layer of stable manure ; then another layer of sods, 

 sand, and manure, and so on. This is allowed to stand until 

 the sods have decayed, after which it is thoroughly mixed and 

 is ready for use. 



PRACTICAL EXERCISES 



1. On a soil map of your region locate such types of sedimentary 

 and drift soils as occur. 



2. What is the name of the soil upon which the school garden is 

 located ? your own home ? 



3. Visit deposits of sand, clay, peat, marl, and humus and collect 

 good samples of each for study. 



4. Weigh a cubic foot of soil from the school garden and estimate 

 the number .of tons in an acre 7 in. deep. 



5. Test the soil in the .school garden and in your own garden for 

 acidity. Make the same test of the soil in the nearest peat bog. 



6. Make a list of the more conspicuous plants in a peat bog. Com- 

 pare with a similar list from a meadow or pasture. 



7. Pour ammonia water through a tube filled with powdered clay and 

 examine that which filters through. What has become of the ammonia ? 



8. Measure out equal amounts of sand and clay and place in sepa- 

 rate vessels. Add measured quantities of water to each until they are 

 saturated. Which absorbs water more rapidly? Which absorbs the 



