224 NITROGEN, PHOSPHORUS AND POTASSIUM 



Questions. (a) Which of these fertilizers are true salts? 

 (6) Which of these fertilizers should be used with special caution when 

 applied in the hill? Why? 



(c) What is the difference between acid phosphate and rock phosphate? 



(d) Which of the phosphate fertilizers is the most available? 



(e) Is all the material composing acid phosphate soluble in water? (Try it.) 

 (/) How should rock phosphate be used for best results? 



To Continue the Study of Acid Phosphate. Procedure. A. Place about a 

 teaspoonful of acid phosphate in a dish and pour on about a tablespoonful 

 of water. Mix thoroughly. Now dip a piece of blue litmus paper into the 

 mixture. What does this indicate? (Soluble phosphate salts are acid in char- 

 acter.) Should lime be mixed with acid phosphate and applied as a mixture? 

 (Consult text.) Why? Should acid phosphate and agricultural lime be 

 applied to the same soil the same season? Explain. 



B. Weigh out five grams (the weight of a nickel) of rock phosphate. 

 Place it in a porcelain dish and add 5 grams of hot (130 F.) sulfuric acid. 

 (Handle acid with great care.) Stir well with glass rod, and note changes. 



Questions. (a) How is acid phosphate usually made? 



(6) How does the resulting material compare with the acid phosphate on 

 the market? 



(c) Tell briefly the steps in the manufacture of acid phosphate. (Consult 

 any book on fertilizer manufacture.) 



(d) Should a farmer attempt to make his own acid phosphate from 

 rock phosphate? 



To Study the Effect of Applying Commercial Fertilizers on the Seed in 

 the Hill. Procedure. Fill 5 one-gallon jars with loam or silt loam and plant 

 two hills of corn in each jar. Treat jars as follows: 

 Jar No. 1 No treatment. 



Jar No. 2 Apply one-half an ounce of muriate of potash on the seed in 

 one hill, and one-half an ounce of a mixed fertilizer on the 

 seed in the other hill. 

 Jar No. 3 Same as Jar No. 2, only apply the fertilizer in the soil on the 



side of the hills. 

 Jar No. 4 Apply one ounce of rock phosphate on the seed in one hill 



and the same amount of mixed fertilizer in the other hill. 

 Jar No. 5 Apply muriate of potash broadcast at the rate of 200 pounds 

 per acre. Mix the fertilizer well into the soil. Plant 4 

 kernels of corn. (One acre equals 43,560 sq. ft.) 

 Label jars properly, and place in the greenhouse. W^ater. 

 (Students may work in groups of five on this exercise.) 

 Questions. (a) When corn is planted in hills 3 feet 8 inches each way, 

 how much mixed fertilizer should be applied per hill when 100 pounds are 

 applied per acre? 



(6) What precaution should be observed in applying fertilizers in the 

 hill or drill? 



To Determine Why Barnyard Water is Colored. Procedure. Every 

 farm boy has observed the peculiar color of barnyard water and has detected 

 strong ammonia odors in the horse stable. The one condition is closely related 

 to the other in this way: the nitrogen of an animal body is excreted through 

 the urine. The principal nitrogenous substance in urine is urea. Urea is 

 acted upon by fermenting organisms producing ammonium carbonate which, 





