LABORATORY EXERCISES 



223 



To Demonstrate the Beneficial Effect of Active Organic Matter in Soils. 



Procedure. Mix with 16 quarts of a light, sandy soil an amount of green 

 clover equivalent to 3 tons of clover hay per acre. Put the mixture into 2 

 two-gallon jars, and plant one to corn and the other to grain. Fill two other 

 jars with the same soil, but without the green clover, and plant one to corn 

 and the other to grain. Observe results. 



Questions. (a) Why are legumes generally the best green manuring crops? 



(6) Mention ways in which organic matter improves soil fertility. 



To Demonstrate the Fertilizer Needs of an Unproductive Soil by a Pot 

 Fertilizer Test. Procedure. Thoroughly mix a quantity (enough to fill 8 

 two-gallon jars) of an unproductive soil and fill 8 two-gallon jars. (Provide 

 each jar with an opening at the bottom for drainage.) Number the jars and 

 treat them as follows: 



Jar No. 1 Give no treatment. 

 Jar No. 2 Add 3 grams sodium nitrate (N). 

 Jar No. 3 Add 3 grams sodium acid phosphate (P). 

 Jar No. 4 Add 3 grams potassium sulfate (K). 



Jar No. 5 Add 3 grams each of sodium nitrate and sodium acid phosphate. 

 Jar No. 6 Add 3 grams each of sodium nitrate and potassium sulfate. 

 Jar No. 7 Add 3 grams each of sodium acid phosphate and potas- 

 sium sulfate. 

 . Jar No. 8 Add 2 grams each of the three fertilizing salts. 



The fertilizing salts may be pulverized and mixed with the soil. Plant 

 each jar to corn, place all in a favorable place, and observe results after about 

 4 or 5 weeks. 



To Show that Ammonia is Given off from Fermenting Manure. Pro- 

 cedure. Put some moist horse dung into a quart Mason jar and keep it covered 

 in a warm place for about 2 days. Then hold a piece of moistened red litmus 

 paper over the mouth of the jar. Note odor of the escaping gas, and note 

 change in the color of the litmus paper. (Ammonia gas turns red litmus 

 paper blue.) 



To Show How the Loss of Ammonia from Manure May be Reduced or 

 Largely Prevented. Procedure. Fill a quart jar about two-thirds full of horse 

 dung; wet with water, and tamp down well. Place in a warm place for about 

 2 days. Make similar tests as in the previous experiment. 



Laboratory Exercises. Material Needed. Four-quart samples of at least 

 four of each class of commercial fertilizers; 3 tumblers; several strips of blue 

 litmus paper; a saucer; a little sulfuric acid; 5 one-gallon jars; enough loam 

 or silt loam to fill 5 one-gallon jars; a handful of corn; one-half cupful pulverized 

 peat; 2 flasks or vinegar bottles; and a few ounces of ammonium carbonate. 



To Learn to Know the Common Commercial Fertilizers. Procedure. 

 Study the samples of fertilizers provided, and record observations, etc., in 

 tabular form as follows: 



(Keep in mind local conditions). 



