EXERCISE 24 



THE POWER OF SOILS TO TAKE UP PLANT FOOD FROM SOLUTION 



Statement. A farmer frequently applies barnyard manure to the surface of the soil in winter, and 

 at other times when it is not convenient to turn the manure under immediately. The soluble portion 

 of the manure is carried down into the soil by the rain as it percolates through the soil. 



Object. To learn whether the plant food is carried through the soil and lost in the drainage 

 water or whether it is taken up by the soil and held there until the plants can use it. To determine 

 whether all soils have equal power of absorbing plant food and whether they all give it up equally 



fully and generously. To determine whether 

 the presence of organic matter in a soil 

 affects its power to absorb soluble plant 

 food. 



Materials. Four lamp chimneys ; four 

 glass tumblers ; sand ; loam ; clay ; dry, finely 

 pulverized barnyard manure ; cheesecloth ; 

 string. 



Directions. Cover the bottoms of the 

 lamp chimneys with cheesecloth and fill one 

 a fourth full of clay, another a fourth full of 

 loam, and another a fourth full of sand. Fill 

 the fourth lamp chimney one-fourth full 

 of a mixture of equal parts of sand and 

 finely pulverized manure. Place the lamp 

 chimneys in the percolation rack (Fig. 27) 

 and place tumblers under each. Prepare 

 a solution to pour over the soil in each as follows: Fill a gallon vessel one-fourth full of dry, 

 finely pulverized barnyard manure. Fill the vessel three-fourths full of water and stir until the soluble 

 part ctf the manure has colored the water. Let the organic matter settle, pour off the water, and 

 use it to water the soil in the lamp chimneys. Observe the color of the water which percolates through 

 the various types of soils. Record the amount of manure water which will be clarified by each 

 soil before the drainage water begins to show color and explain the practical significance of this 

 difference. 



Questions. What was the color of the first water that percolated through each type of soil ? Which 

 soil showed percolation water when the least amount of water had passed through it? Which soil 

 retained the most coloring matter? What was the effect of adding organic matter to sand on the amount 

 of coloring matter retained ? Discuss the value in this respect of applying all organic matter possible to 

 the soil. Which soil — clay, loam, or sand — is most retentive of plant food when a manure or fertilizer 

 is applied, and why ? As between a soil which admits water readily and one which admits water slowly, 

 what difference would there be in the application of barnyard manure in winter ? As between a sloping 

 surface and one which is only slightly rolling? As between a time when the ground is covered with 

 ice or is frozen and when it is not ? Prepare a statement giving your views as to the proper time and 

 method of applying manure. Compare the merits of hauling it out frequently, and composting and 

 applying just before planting. 



References. Waters, H. J. Essentials of Agriculture, pp. 72-73, 75. Ginn and Company. Mosier and 

 Gustafson. Soil Physics and Management, pp. 163-168. J. B. Lippincott Company. Lyon, Fippin, Buck- 

 man. Soils, their Properties and Management, pp. 349-373. The Macmillan Company. 



[48] 



Fig. 20. Percolation rack 



