106 



THE EOTHAMSTED EXPERIMENTS. 



Effects of 

 nitrogen- 

 ous man- 

 ures upon 

 various 

 crops. 



Table 34 

 explained. 



Method of 

 calcula- 

 tion. 



Effects of Nitrogenous Manures in increasing the Produce 

 of various Crops. 



It is fully recognised 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 wow- 

 leguminous crops. It is to be borne in mind, too, 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-nitrogen- 

 ous substance starch. 



The influence of nitrogenous manures in increasing the 

 production of the non-nitrogenous constituents of our crops is 

 very strikingly illustrated by the results given in Table 34. 



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, when 

 each is 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 gives the estimated increased production of total car- 

 bohydrates, under the influence of the nitrogenous manures ; 

 and the last column the estimated gain of carbohydrates for 

 1 of nitrogen in manure. 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. 



The mode of calculating the amounts of carbon and of 

 carbohydrates is as follows : From the amount of dry sub- 

 stance in the crops, the amounts of mineral matter and of 

 nitrogenous substance are deducted ; and the remainder rep- 

 resents the amount of carbohydrates. The amount of carbon 

 in the nitrogenous substance is calculated, and then that in 

 the carbohydrates, 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, be only approximations, to the truth ; 

 but, accepted as such, they are useful, as conveying some 



