CHAPTER IV. 



CROPS. 



The dry matter, nitrogen, and ash constituents, in average crops. Cereal 

 Crops. Characteristic composition Mode of feeding Most suitable 

 manuring. Meadow Hay. Characteristic composition Demand for 

 ash constituents Influence of manures on quantity and quality 

 Pastures especially adapted for obtaining nitrogen from the atmo- 

 sphere. Leguminous Crops Characteristic composition Special 

 source of nitrogen Clover-sickness. Root Crops. Characteristic 

 composition Differences in the nutrition of turnips, mangels, and 

 potatos. Forest Growth. Large production of dry matter for small 

 consumption of ash constituents and nitrogen. Adaptation of 

 Manures to Crops. The feeding power of each crop must be taken 

 into account. Economic distribution of manure in a rotation The 

 practical value of manures only known by experiments on each farm. 

 Influence of Climate and Season. Effect of excess or deficiency of 

 water and heat Influence of preceding Winter. Crop Residues. 

 Their action Differences between different crops. Weeds. Their 

 beneficial and injurious actions. 



To understand the chemistry of crops we must first 

 inquire as to their composition. The following table gives 

 the average composition of ordinary farm crops, and of 

 the annual produce of three descriptions of forest. The 

 quantities of carbon, hydrogen, and oxygen present are 

 omitted, also some of the smaller ash constituents. By 

 "pure ash 3 ' is understood the ash minus sand, charcoal, 

 and carbonic acid. 



The composition of grain is tolerably constant ; but the 

 composition of straw, leaves, roots, and tubers, will vary 

 very considerably according to the character of the soil, 

 the manuring, and the season. The composition of 



