NITROGEN GAINED OR LOST 



211 



amount of nitrogen for the land which we have no means 

 of calculating, but which we know is sufficient to benefit the 

 succeeding crops for at least three years. Table LXXIV. 

 shows the removal of nitrogen per acre per annum on the 

 plots growing beans and clover where the root crop is com- 

 pletely carted away. 



TABLE LXXIY. Nitrogen removed by Crops grown in rotation, Agdell 

 Field. Average of eight Courses, 1852-1883. Roots carted. 



On the plot receiving mineral but no nitrogenous manure 

 the removal of nitrogen is now nearly 40 Ib. per acre per 

 annum ; but if we exclude the clover or bean crop as providing 

 its own nitrogen, the loss is only a little over 23 Ib. per acre 

 per annum, some of which is undoubtedly replaced by the 

 nitrogen drawn from the atmosphere and left in the roots and 

 stubble of the clover. With the nitrogenous manuring for the 

 Swedes the annual removal of nitrogen amounts to nearly 64 Ib. 

 per acre per annum, or again excluding the amount contained 

 in the clover or beans, to about 41 Ib., of which the nitrogenous 

 manure used for the Swedes provides 35 Ib., reducing the net 

 loss to the soil to about 6 Ib. of nitrogen per acre per annum. 

 This is easily compensated for by the amount of nitrogen intro- 

 duced by the clover crop, and there is every indication that the 

 fertility of this plot, so far from falling off, has been increased 

 somewhat by each completed rotation. Hence we can con- 

 clude that fairly strong land, such as we are dealing with, 



