The Healthy Soil 5 



food, and indirectly in the manufacture of starch. 

 It also encourages the production of finer plant tis- 

 sue, thus increasing the plant's resistance to disease. 

 The aim of the greenhouse man is to produce early 

 truck crops or cut flowers and this is directly con- 

 cerned with feeding. Because the four plant food 

 elements above mentioned are of extreme impor- 

 tance, their application cannot be indiscriminate. 

 The greenhouse man must know how much of them 

 to use in combination or separately. He must know 

 also which element will especially benefit the par- 

 ticular crop with which he deals. In his investiga- 

 tions with the fertilizer requirements of lettuce, 

 Stuart * reached the following conclusions : Potash 

 when used in any considerable amount either alone 

 or with nitrate of soda is unfavorable for growth 

 (fig. 1, D.). Acid phosphate alone, in combination 

 with nitrate of soda, or in combination with muriate 

 of potash, stimulates growth (fig. i. A, B, C). For 

 lettuce the use of chemical fertilizers proved slightly 

 superior to stable manure, while nitrate of soda was 

 found to be superior to dried blood. Wheeler and 

 AdamSjf in their work with radishes, found that an 

 application of partially composted horse manure at 

 the rate of 75 tons per acre gave better results than 

 any other combination of fertilizers used. Work- 

 ing with carnations. Darner + and his associates 



• Stuart W., Indiana Agr. Expt. Sta. Bui. 84, Vol. 10: 115-142, ^900. 



t Wheeler, H. J., and Adams, G. E., Rhode Island Agr. Expt. 

 Sta. Bui. 128: 183-194, 1908. 



i: Darner, H. B., et al., Illinois Agr. Expt. Sta. Bui. 176: 365- 

 386, 1914. 



