SCIENTIFIC FARMING AT ROTHAMSTED. 91 



and that the soil, under certain conditions, may suffer a loss of nitro- 

 gen in this form. 



Of the rain falling upon the drain-gauges, the unmanured soil of 

 which, it will he remembered, is in a natural state of consolidation and 

 kept free from vegetation, for a period of ten years, about forty-four 

 per cent has appeared as drainage-water, and about fifty-six per cent 

 has been evaporated. Approximately, two thirds of the evaporation 

 takes place during the summer months, and one third during the win- 

 ter months. 



The annual loss of nitrogen in the drainage-water has been, upon 

 the average, at the rate of 437 pounds per acre. This represents, 

 approximately, the loss involved under the conditions of a bare sum- 

 mer fallow. 



When the roots of growing plants are distributed through the soil, 

 they take up the nitrogen as it becomes soluble in the process of nitri- 

 fication, and the loss by drainage is to that extent diminished. 



The drainage from the unmanured wheat-plots contained nitrogen 

 at the rate of only from 1256 to 18*62 pounds per acre each year, and 

 during two seasons of excessive drainage, when every running from 

 the drains was analyzed, " it was estimated that from fifteen to seven- 

 teen pounds of nitrogen were lost per acre, per annum, by drainage 

 from plots which had received no nitrogenous manure for many years," 

 and the average for thirty years was from ten to twelve pounds per 

 acre. During its period of active growth, the crop appropriated the 

 nitrogen of the soil, so that there was little or none lost by drainage, 

 and nearly the entire loss took place after harvest, and during the 

 winter and spring months. 



The nitrogen lost by drainage on land receiving no nitrogenous 

 manure is therefore considerably more than can reasonably be esti- 

 mated in the supply from atmospheric sources. 



When nitrogenous manures were applied, the loss of nitrogen by 

 drainage was materially increased, and on the average for more than 

 thirty years, and under the most favorable conditions of growth, less 

 than one third of the nitrogen applied as manure was recovered in the 

 increase of the crops, and much less than this when there was a de- 

 ficiency of potash or phosphoric acid in the soil. 



In connection with these facts, relating to the amounts of nitrogen 

 removed in the crops and lost by drainage, and the inadequate supplies 

 of available atmospheric nitrogen for the purposes of plant-growth, it 

 becomes a matter of particular interest to trace the influence of this 

 system of continuous cropping, without nitrogenous manures, upon 

 the nitrogen contained in the soil itself. 



The nitrogen in the soil of the unmanured wheat-plots has grad- 

 ually diminished, and Dr. Gilbert says, " So far as we are able to form 

 a judgment on the point, the diminution is approximately equal to the 

 nitrogen taken out in the crops, and the amount estimated to be re- 



