FERTILIZERS 135 



of phosphorous compounds: (1) soluble phosphoric acid, soluble 

 in water; (2) reverted phosphoric acid, soluble in weak acids; 

 (3) insoluble phosphoric acid, not soluble in water but soluble in 

 strong acids. In good fertilizers this should not exceed 1 per cent. 



Use of Fertilizers. It is somewhat difficult to give rules for the 

 use of fertilizers except in a general way. There are many sides 

 to this question, such as the condition of the soil, the kind of crop 

 desired, the nature of the climate, the composition of the fertilizers 

 that are available, and many other things along this line. 



Nitrogenous fertilizers, easily dissolved, had better be applied 

 to the soil after the plant has begun to grow. Such fertilizers stim- 

 ulate leaf and stem growth and are very beneficial to crops on soils 

 poor in decaying vegetable matter. Lettuce, beets, asparagus, 

 celery, turnips, cucumbers, melons, sweet corn, beans, peas, radishes, 

 carrots, wheat, rye, oats, barley, and meadow grass are all greatly 

 benefited by the use of nitrogenous fertilizers. The farmer may 

 find it advisable to use other fertilizing elements, but the combina- 

 tion should be such that nitrogen in general should be the dominant 

 element. 



Phosphatic fertilizers in general when in a soluble form should 

 be applied only a short time before the plant requires the food be- 

 cause of the tendency to change to insoluble forms. But mineral 

 phosphates and like products which decay slowly may be applied 

 a long time before they are needed by the plant. Phosphate 

 fertilizers are especially beneficial to corn, clovers, turnips, swedes, 

 sorghum, sugar cane, and the like. 



Potash Fertilizers. These should be applied some time before 

 they are required in order to secure their complete distribution. 

 The fall season is generally considered the best time for applying 

 a potash fertilizer on heavy soils. It is recommended for clovers, 

 potatoes, sweet potatoes, peas, beans, vetches, and flax. Sandy 

 soils are as a rule deficient in potash and are benefited by the ap- 

 plication of such a fertilizer. 



Field Tests. In order to determine what fertilizers are best 

 adapted to his needs the farmer should lay off ten testing plots 

 about twenty-one feet and four inches wide and one hundred and two 

 feet long, or any other convenient measurements which will make a 

 plot containing about one twentieth of an acre. If plenty of space 



