58 SOIL AN IMPORTANT FACTOR 



To Demonstrate the Need of Nitrogen and the Six Essential Mineral Ele- 

 ments in Plant Growth. Procedure. Place 50 kernels each of wheat and oats 

 between moist blotters, and germinate. When the seedlings are well started 

 transfer the best ones to culture solutions (Fig. 19). By means of pins fasten 

 at least 3 of each kind of seedlings in each cork. Start four cultures, as follows: 



(1) Distilled water, (2) full nutrient solution, (3) nutrient solution with- 

 out phosphorus, (4) a culture without iron. Place in favorable place and 

 observe growth. 



Prepare full nutrient solution as follows: 



Potassium acid phosphate .... 8 grams in Yz liter distilled water. 



Calcium nitrate 6 grams in y% liter distilled water. 



Magnesium sulf ate 15 grams in Y^ liter distilled water. 



Ferric chloride 0.05 grams in Yi liter distilled water. 



For use take 50 c.c. of each of the first three solutions and 4 c.c. of the ferric 

 chloride solution, mix, and dilute to 500 c.c. with distilled water. 



For nutrient solution without phosphorus use 10 grams of potassium 

 chloride instead of potassium acid phosphate. 



For nutrient solution without iron omit the ferric chloride solution. 



Cover each jar with brown paper. Keep jars full by using distilled water. 

 Renew culture solution if plants are allowed to grow a long time. Observe 

 the character of growth and root development. 



Laboratory Exercises. Material Needed. A handful each of corn, beans, 

 oats and wheat seeds; 2 tumblers; 18 one-gallon crocks; a small amount of 

 tincture of iodine; one mortar and pestle; 8 quarts dry fine sand; 8 quarts 

 moist fine sand; 8 quarts wet fine sand; 4 quarts dry silt loam; 4 quarts 

 moist silt loam; 4 quarts wet silt loam; 4 quarts black sandy loam; 4 

 quarts light colored sandy loam; a small amount pulverized muck and lime; 

 12 thermometers. 



To Demonstrate That Oxygen is Necessary for Germination. Procedure. 

 (a) Place some corn, beans and wheat seeds in two tumblers of water. 

 Change the water in one tumbler each day, but do not change the water in 

 the other. (6) Plant some corn, wheat and bean seeds in each of two one- 

 gallon crocks. Maintain favorable moisture conditions in one, and keep the 

 other soil saturated and flooded with water. Record results. 



Questions. (a) Why cannot seeds germinate in stagnant water? 



(6) Why do corn and beans often rot in wet, cold soils? 



(c) Why is oxygen necessary for germination? 



To Demonstrate the Importance of Good Contact Between the Soil and 

 the Planted Seed. Procedure. Fill a two-gallon crock with a loam and tamp 

 so as to make a good, firm seed bed. Make two shallow furrows with a stick 

 and sow radish seeds in each. Cover seeds in one furrow with moist soil, press 

 soil down on seed, then cover with loose dirt. Cover the seeds in the second 

 furrow with moist soil but do not press the soil on the seed. (Before preparing 

 the seed bed see that the soil is moist or contains a favorable moisture 

 supply, Figs. 20 and 21.) Place the crock in a favorable place do not water. 

 Observe results. 



Questions. (a) Why is it necessary to have good contact between the 

 seed and soil? 



(6) What is the meaning of tilth? 



(c) What is good tilth? 



To Study the Effect Produced When a Clay or a Heavy Clay Loam is 

 Worked When Very Wet. Procedure. Place a cupful of clay or a heavy clay 

 loam upon a pie tin or saucer. Add sufficient water to form thick mud. Mold 

 the mud into a ball and allow it to dry out in the sun. Repeat, using a sand. 

 Note results. (Save hard clay ball for next exercise.) 



