CHAPTER IX. 



Agricultural Use of Cyanamid. 



Fertilizer Tests. — In the selection of the most economical 

 fertilizer it is necessary to consider, among other things, the 

 nature of the crop, the qualities desired in the plant grown, 

 the type of soil, the effect of long-continued use of the fer- 

 tilizer, the cost and the relative yields. Thus, the rice-plant 

 seems to be unable to assimilate nitrates easily, but readily 

 assimilates ammonium compounds.^ The quickly acting 

 forms of nitrogen usually produce rank, heavy growth 

 of the green parts of the plant, with little fiber, while 

 the slowly acting forms produce thinner leaves, and stems 

 with greater strength. For forcing purposes, the nitrates are 

 ideal ; for slow, steady growth, the organic forms of nitrogen, 

 Cyanamid, ammonium sulphate, etc., are to be preferred. Soil 

 conditions are often a determining factor. Thus, loose, open 

 soils in regions that receive a great deal of rain do not readily 

 retain nitrates. Soils of low lime content may become acid 

 by the addition of ammonium sulphate year after year: the 

 sulphate radical enters into combination with the lime of the 

 soil and carries away the calcium in the drainage waters.^ 

 Very acid soils are not economically fertilized with substances 

 like Cyanamid, ammonium sulphate and other materials requir- 

 ing nitrification, since nitrifying bacteria are notably deficient 

 in acid soils, especially acid sandy soils. Such soils should be 

 put into productive condition by proper judicious liming, some 

 time previous to the fertilization. On light, sandy soils where 

 heavy liming may damage the crop the yearly addition of a 

 small amount of lime as a part of the fertilizer is of great 

 assistance in overcoming the tendency towards acidity. The 

 relative yields per unit of money invested in the different fer- 

 tilizers is often the controlling factor in their selection, but 



1 Hawaiian Agr. Exp. Sta. Bulletin 24. 



2 A. D. Hall, Fertilizers and Manures, p. 62, 1909. 



