AGRICULTURE FOR SOUTHERN SCHOOLS, 21 
object of making a test ? Why is it important to use clean utensils ? 
Why should the degree of acidity be determined ? The report should 
include the time taken for each test to work and a statement of the 
relative shades of the slips. 
Exercise 20. — Effects of Lime on Soil. 
Purpose: To show that lime will correct the acidity of acid soils 
and aid in the crumbling of clay soils. 
Directions : Mix half an ounce of air-slaked lime with a pound of 
soil which has been found to be acid by the litmus test. Apply the 
test again and note results. 
Treat four pans of clay soil, each pan holding 1 pound, as follows: 
(1) Left as a check, (2) one-half ounce air-slaked lime, (3) 1 ounce, 
and (4) 2 ounces. Mix the lime thoroughly with the soil, leaving no 
lumps. Saturate each with water and leave to dry without stirring. 
After drying note the cracks which have been formed on top and then 
study the physical condition, noting hardness and the tendency to 
crumble. 
Record and report: Each student should report effect of lime on 
acidity, giving reasons. Drawings should be made of the tops of 
the samples of clay soil after they have dried, these drawings to 
accompany a description of the effect of the lime on the physical 
condition of the soil. 
Note. — If the school has the use of land in a section where the soils need 
liming, field tests should be made to determine the amount needed for important 
crops. 
Lesson 34. — A Local Soil Survey. 
1. Value of soil surveys. 
2. Instructions regarding the taking of samples. 
Illustrative material : A map of the county or district showing soil types. 
Lesson 35. — Mechanical Analysis of Soils. 
1. Value of such an analysis. 
2. Methods. 
Illustrative material : Charts or samples showing mechanical analysis. 
Lesson 36. — Chemical and Bacteriological Analyses. 
1. Value of such analyses. 
2. Methods. 
Illustrative material : Charts showing analyses of representative types. 
FIELD CROPS. 
(Fifty-nine lessons, 15 double periods for practical work. Home projects.) 
References: Any of the general texts in field crops. Price List 44, U. S. 
Public Documents Relating to Plant Life. (For sale by the Superintendent of 
Documents, Government Printing Office, Washington, D. C.) 
