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A YEAR IN AGRICULTURE 



of the soil is low. If the solution is yellowish, there is prac- 

 tically no nitrogen content. Compare the sample containing 

 only water with the one containing the caustic potash. Test 

 several samples of soil by this method, and record results as 

 follows : 



15. Pot cultures of community soils. In order to deter- 

 mine the limiting plant-food elements hi the soils of the 

 locality, the pot culture method is a practical one to use. 

 As many different systems of pots may be employed as there 

 are farmers represented by members of the class. For each 

 soil type to be studied secure ten "four-gallon earthen, jars. 

 Fill each jar with the same kind of soil, taken from the field 

 to be tested. Make sure that there is drainage from the bot- 

 tom of the jar. Treat the soil in each jar as follows: 



Jar No. 1 Nothing. 



" 2 Lime (hydrated), 12.5 grams. Well rotted barnyard 

 manure (a sufficient amount worked into the soil to 

 cover the surface about two or three inches). 

 " 3 Lime; nitrogen (dried blood, 15 grams). 

 " " 4 Lime; phosphorus (bone-meal, 6 grams). 



" 5 Lime; potassium (potassium sulphate, 3 grams). 

 " 6 Lime; nitrogen; phosphorus. 

 " " 7 Lime; nitrogen; potassium. 

 " " 8 Lime; phosphorus; potassium. 

 " " 9 Lime; nitrogen; phosphorus; potassium. 

 " " 10 Virgin soil, untreated. 



