SCIENTIFIC FARMING AT ROTHAMSTED. 93 



depth of from ten to fourteen feet furnishes good drainage for the 

 spaces between the drains. 



The nitrogen applied in the manures that is not taken up by the 

 crop or stored up in the soil, or lost in the waters discharged by the 

 tile-drains, may therefore be fully accounted for in the amount that 

 must be carried, under the conditions of the experiments, by the drain- 

 age-waters to the lower strata of the subsoil, without entering the 

 drains. The estimated losses of nitrogen by drainage, based on the 

 amounts detected in the waters discharged by the drains, may there- 

 fore with good reason be increased by the amount not accounted for 

 in the crop and in the accumulations of the soil. 



Practically, then, in the light of the Rothamsted experiments, we 

 may look upon the soil as the great source of the nitrogen of plants, as 

 the atmosphere can furnish but a small proportion of the needed sup- 

 ply, and this is more than counterbalanced by the losses from drainage. 



In connection with this imperfect outline of some of the leading 

 lines of investigation that have been so successfully prosecuted at 

 Rothamsted, it would be interesting to examine the data that indicate 

 the relations of nitrogen to other elements of plant-growth, as sup- 

 plied in manures and assimilated by crops when cultivated in suc- 

 cession or in rotation with other species ; but these, with other cognate 

 topics, must be omitted, as we can not at this time undertake anything 

 like an exhaustive discussion of the results of these valuable experi- 

 ments. 



The great importance of physiological researches and the compara- 

 tively subordinate influence of purely chemical methods in solving 

 the great problems of agricultural science, have been so fully illus- 

 trated in the experiments at Rothamsted that we must accept them 

 as the basis of a new departure in the development of a consistent 

 science of rural economy. In the light of these experiments the gen- 

 erally accepted theories of soil-exhaustion must be reconstructed, and 

 the action and relative value of manures must be investigated from a 

 new stand -point. 



The exhaustion of a soil can no longer be estimated by th constit- 

 uents removed in the crop, Wheat and oats, with other cereals, are 

 generally considered as exhausting crops, and a summer fallow is 

 looked upon as a means of increasing or restoring the fertility of 

 the soil ; but the grain -crops when grown by themselves, and the 

 summer fallow itself, are alike the occasion of a loss of fertilizing 

 materials, and in precisely the same way. In both cases there is a 

 long interval in which there are no living roots of plants in the soil 

 to take up the nutritive materials as they are transformed into the 

 soluble form, and they are lost by percolation to the lower strata of 

 the subsoil out of the reach of vegetation. 



Many of what are called restorative plants feed in the deeper layers 

 of the soil, and they may, by their scattered foliage and thick roots, 



