Mineral Nutrients 145 



that there is no one ideal nutrient solution, since plants 

 vary considerably in their requirements. The solutions 

 given below have been much employed, and they are 

 among those that are generally satisfactory : 



1. PFEFFER'S SOLUTION 



Calcium nitrate 4 grains 



Potassium nitrate 1 gram 



Magnesium sulfate 1 gram 



Potassium dihydrogen phosphate 1 gram 



Potassium chloride 5 gram 



Ferric chloride trace 



Distilled water 3 to 7 liters 



2. CRONE'S SOLUTION 



Potassium nitrate 1.00 grams 



Iron phosphate 50 grams 



Calcium sulfate 25 grams 



Magnesium sulfate 25 grams 



Distilled water 2.0 liters 



The first solution has been more commonly employed. 

 For different plants it is particularly important to change 

 the ratio of calcium to magnesium. This is conveniently 

 done by reducing the amount of calcium nitrate and adding 

 to the potassium nitrate. The Crone solution is reported 

 satisfactory for cereals ; but it is more difficult to handle 

 on account of the relatively insoluble iron phosphate. 



Water cultures for most seed-plants are preferably 

 slightly acid at the outset, especially where the solution is 

 constituted as in number one. This solution becomes 

 alkaline in time. In the preparation of these solutions for 



