612 INFLUENCE OF SOIL AND CULTURE ON THE 



§ 14. Influence of sail and culture on the nutritive value of agricultural 



produce. 



I have on several former occasions, (pages 500 to 528), directed your 

 attention to the remarkable influence which soil, culture, and climate 

 have upon the chemical composition of the different corn and green crops 

 usually raised for food. Every such change of composition alters also 

 the nutritive value of any given crop. If the wheat or barley be richer 

 in gluten, it will build up more muscle — if it abound more in starch, a 

 smaller weight of it will supply the carbon of respiration — if it be richer 

 in fatty matter, it will round off' the edges of the bones, and fill, up the in- 

 equalities in an animal's body more quickly with fat. Such differences 

 as these I have already shown you do really exist among samples of the 

 same kind of grain grown upon soils either of different quality, or of tke 

 same quality when differ^tly cultivated or manured. 



But this different culture or manuring affects the relative proportions 

 of the several kinds of inorganic matter also— the phosphates and other 

 saline substances— which are known to exist necessarily in all vegetable 

 productions. In illustration of this, I would direct your attention to the 

 following analyses — made in my laboratory by Mr. Fromberg — of the 

 ash of two samples of the same kind of turnip (red topped yellow) 

 raised by Lord Blantyre, on the same field, the one with guano alone, 

 the other with farm-yard dung alone. The quantity of ash left by the 

 two varieties of turnip was 0*68 and 0-7 per cent, respectively, and this 

 ash was composed as follows : — 



Composition of the ash of turnips raised loith guano ^ and with farm-yard dung. 



GUANO. DtJNG. 



Chloride of Potassium 

 Sulphate of Potash 

 Carbonate of Potash . 

 Phosphate of Potash . 



Lime . 



Magnesia 



Alumina 



Carbonate of Lime 



Alumina 



Oxide of Manganese . 

 SiUca 



97-95 99-16 9908 99*02 



The most striking difference between the two varieties of ash is in the 

 proportion of phosphates they respectively contain. The ash of the 

 guano turnips contained from 25 to 30 per cent, of phosphates, that of 

 the dung turnips only from 9 to 11 per cent. This could not fail to 

 make an important difference in their relative values for the feeding of 

 stock whose bones are growing, and which require, therefore, a larger 

 supply of phosphates in their food. 



The phosphates of lime and magnesia form, as we know, one of the 

 valuable constituents of guano, but we could scarcely have inferred that 

 this manure would have caused so much larger a proportion of these 

 phosphates to enter into the constituents of the turnips raised with them. 



