MANUAL OF AGEICULTURE. 



269 



like considerations. But previously to observing in detail some 

 of the ordinary rotations, it will here be expedient to notice 

 succinctly the leading characteristics of our principal cultivated 

 plants, the soils to which they are naturally best adapted, and the 

 elements which they demand in greatest quantity from the soil. 

 Wheat is the most important of our cereal crops, as it possesses 

 the proximate constituents in the proportion best suited for man's 

 nutrition in temperate climates ; it is therefore the staple bread- 

 corn of the northern temperate zone. Its range of cultivation 

 is wide, extending between the tropics and the isothermal line 

 denoting the descent of the mean annual temperature to 56°. 

 Also, it is cultivated in a great variety of soils ; clayey loams 

 suit it best ; and its returns are more profitable from the stronger 

 than a light class of soils. The average composition of the grain 

 is indicated by the figures following : — 



Water, 15-00 



Nitrogenous compounds, 

 Oleaginous and respiratory do., 

 Woody fibre, . . . . 

 ^sn, . • . • • 



12-00 

 68-50 



2-75 

 1-75 



And the average of several analyses of the ash or mineral 



matter gives the following results 



Grain. 



27-72 



8-05 



2-81 



10-03 



•67 



"49-81 



-24 



1-17 



Straw. 



12-44 

 •16 

 6-7 

 3-82 

 1-3 

 3-07 

 5-82 



65-38 

 109 



Chaff. 

 9-14 

 1-79 

 1-88 

 1-27 

 •37 

 4-31 



81-22 



Potash, 



Soda, ..... 

 Lime, . . * . . 

 Magnesia, .... 



Iron, ..... 

 Phosphoric acid, 

 Sulphuric acid, 



Silica, ..... 

 Chloride of sodium, 



Barley has even a wider range of cultivation than wheat, 

 maturing in almost every climate in the world. Unlike the 

 wheat plant, whose roots penetrate deeply in the soil and sub- 

 soil, those of barley ramify in the looser material nearer the sur- 

 face, sending few down into the subsoil, but developing increased 

 numbers of fibrils and hairs, so that its absorbent powers are 

 very great. 



It matures much quicker than the other grain plants; a period 



of from seven to eight weeks between seed time and harvest often 



sulliccs. It is best suited with light free soils. The analysis of 



the grain is as follows : — 



Water, . . . . , 



Nitrogenous compounds, . 



OK-aginous and respiratory compounds, , 



Woody libro, . . . ' , 



iv.sii, . • • • • 



100-0 



