224 NATUEE AND PROPERTIES OP SOILS 



from Haberlandt^ show the need of careful temperature con- 

 trol in the propagation of plants: 



Table XL VI 



GERMINATION TEMPERATURES 



Crop 



Minimum 



Optimum 



Mazimum 



Wheat 



Maize 



Pumpkin 



40° F 



49 



52 



84° F 



93 



93 



108° P 



115 



115 



Table XLVII 

 growth tempeeatures 



Ceop 



Minimum 



Optimum 



Maximum 



Wheat 



Maize 



Pumpkin 



32-40° F 



40-51 



51-60 



77- 78° F 

 88- 98 

 98-111 



88- 98 



98-111 



111-122 



Other desirable biological activities, especially those due to 

 bacteria, are impeded if not brought entirely to a standstill by 

 a temperature of 32° P. Such changes as decomposition of 

 organic matter, the production of ammonia from nitrogenous 

 organic matter, the formation of nitrate nitrogen from am- 

 monia and the jSxation of atmospheric nitrogen depend on 

 heat conditions which, fortunately, are optimum for the de- 

 velopment of higher plants. 



Desirable chemical reactions in the soil are much retarded 

 by low temperatures, heat greatly accelerating such phe- 

 nomena. This is especially noticeable in the tropics where 

 weathering is much more rapid and intense than in temperate 

 regions. Much of the hydration, ox-idation, carbonation and 

 solution in a temperate climate occurs in the summer when 

 high temperature lends its aid to such desirable reactions. 



^Haberlandt, F., Die Oh even und JJnteren Temperaturgrense fur die 

 Keinmng der Wichtigeren LandwirthschaftUcJien Sdmereien; Landw. 

 Versuehs. Stat, Band 17, Seite 104-106, 1874. 



