ON THE GROWTH OF LEGUMINOUS CROPS. 9 



EFFECTS OF NITROGENOUS MANURES IN INCREASING THE 

 PRODUCE OF VARIOUS CROPS. 



I need not remind you that, under the conditions in which the 

 crops are grown in ordinary agriculture, nitrogenous manures have 

 very marked effects in increasing the amounts of produce of Wheat, of 

 Barley, of Turnips, of Mangels, and of Potatoes ; that is, of the 

 comparatively low-in-nitrogen ft0ft-Leguminous crops. For detailed 

 evidence on the point, I may refer you to my former lectures relating 

 to these various crops. But I may recall to mind the fact that in the 

 case of Wheat and Barley the increased produce consists characteristically 

 of the non-nitrogenous substances starch and cellulose, in that of the 

 Root-crops of the non-nitrogenous substance sugar, and in that of 

 Potatoes of the non-nitrogenous substance starch. 



Table V. (p. 10), illustrates very strikingly the influence of 

 nitrogenous manures in increasing the production of the non-nitrogenous 

 constituents of our crops. 



The first column of figures shows, the estimated amounts of carbon, 

 per acre per annum, in the total produce of Wheat and of Barley, 

 in the roots of Sugar-Beet and Mangel- Wurzel, in the tubers of 

 Potatoes, and in the total produce of Beans ; in each case when 

 grown by a complex mineral manure without nitrogen, and also 

 with the same mineral manures with nitrogenous manure in addition. 

 The second column shows the estimated gain of carbon ; that is, the 

 increased amount of it assimilated under the influence of the nitrogenous 

 manures. The third column shows the estimated increased produc- 

 tion of total carbohydrates, under the influence of the nitrogenous 

 manures ; and the last column the estimated gain of carbohydrates for 

 1 of nitrogen in manure. 



The mode of calculating the amounts of carbon and of carbohydrates 

 is as follows. From the amount of dry substance in the crops, the 

 amounts of mineral matter and of nitrogenous substance are deducted; 

 and the remainder represents the amount of carbohydrates. The 

 amount of carbon in the nitrogenous substance is calculated ; and then 

 that in the carbohydrate, on the assumption that, in the Wheat, 

 Barley, and Beans, starch and cellulose are the main products ; in the 

 Sugar-Beet and Mangel- Wurzel, cane-sugar, pectine, and cellulose ; and 

 in the Potatoes, starch and cellulose. Such estimates can, obviously, 

 only be approximations to the truth ; but, accepted as such, they are 

 useful, as conveying some definite impression, of the influence of 

 nitrogenous manures on carbon-assimilation, and on carbohydrate- 

 formation. 



As Table V. shows, the calculations are based on the average 

 produce, by the different manures, of Wheat over 20 years, of Barley 

 over 20 years, of Sugar-Beet over 3 years, of Mangel- Wurzel over 8 

 years, of Potatoes over 10 years, and of Beans over 8 years. 



It is thus seen that, independently of the underground growth, the 

 Wheat was estimated to assimilate 988 Ibs. of carbon per acre per 



B 



