The Soil of the Garden 73 



on page 60, to determine if it is ready for tillage. Repeat the 

 test at intervals of a few hours. Which becomes ready for tillage 

 first? which last? Make similar tests in the garden before 

 beginning the work of spading or of surface tillage after a rain. 



6. To test soils for acidity. Obtain a few strips of blue litmus 

 paper. Dig up some of the soil to be tested and place it in a pan. 

 Then insert three or four pieces of the litmus paper in the soil, 

 making sure that the soil particles are pressed firmly against the 

 paper. Examine one of the strips at intervals of several minutes, 

 or until one of them has turned red. The red color shows the 

 presence of acid. If at the end of half an hour the litmus paper 

 shows no change of color, the soil is free from acids. 



7. To solve a few of the gardener's problems in supplying com- 

 mercial fertilizer to the soil. Work on the following exercises 

 until you are sure that you could solve similar problems in your 

 own garden. 



A . A garden plot is 40 feet wide and 50 feet long. How many 

 pounds of general commercial fertilizer will the gardener need if 

 he desires to supply 5 pounds of the fertilizer to every 100 square 

 feet of the garden ? 



B. If a gardener wishes to make 100 pounds of the fertilizer 

 mentioned on page 67 , how many pounds of each of the ingredients 

 should be purchased? (The quantities given on the page just 

 referred to will make 2000 pounds of fertilizer.) What part of 

 2000 is 100? Therefore, what part of the total amount of each 

 ingredient given for the 2000 pounds is needed for 100 pounds? 



C. A gardener can obtain only (i) sodium nitrate, (2) acid 

 phosphate, and (3) potassium sulfate. He wishes to purchase 

 enough of each to make 100 pounds of a mixed fertilizer yielding 

 3^ per cent nitrogen, 8 per cent phosphoric acid, and 10 per cent 

 potash. Find the amount of each ingredient needed, as follows : 



(1) There should be enough sodium nitrate in the 100 pounds 

 to yield 3^ pounds of nitrogen. Sodium nitrate is 15 per cent 

 nitrogen; one pound has rtnr pounds of nitrogen; therefore, 

 it will require as many pounds of sodium nitrate as rtnr is con- 

 tained in 3^. What is this amount ? 



(2) Calculate the number of pounds of phosphoric acid required. 

 (Acid phosphate is about 14 per cent phosphoric acid.) How 

 many pounds of the acid phosphate are therefore needed to sup- 

 ply the amount of phosphoric acid required ? 



