ON ACCUMULATION OF NITROGEN 



75 



It seemed probable in view of these results that three inch samples 

 might show more clearly any alteration in the mechanical composi- 

 tion which were in progress on the slag plots. Three inch samples 

 were accordingly carefully removed from Plots 16, 17 and C at 

 Horndon during August 1920 (two and a half years after the manures 

 were sown), and submitted to mechanical analysis. The results are 

 given in Table XXXIX. The differences between the figures for 

 Plots 16 and 17 are smaller than the experimental error. 



It would seem therefore that the effects of basic slag on the moisture 

 content of the soil which are described in the preceding section are 

 not due to any improvement in the mechanical structure of the soil 

 that can be disclosed by the ordinary methods of mechanical analysis. 

 This result must not of course be taken as indicating that the applica- 

 tion of basic phosphates to heavy clay pastures, and the consequent 

 development of the clover, does not affect the mechanical condition 

 of the soil, but simply that under the conditions of this particular 

 experiment the differences in the behaviour of Plots 16 and 17 at 

 Horndon with regard to moisture cannot be attributed to changes 

 in the mechanical condition of the soil on the respective plots. 



TABLE XXXIX. MECHANICAL ANALYSIS OF THE SOIL AT HORNDON 



TO A DEPTH OF 3 INCHES 



THE EFFECT OF PHOSPHATES ON THE ACCUMU- 

 LATION OF NITROGEN IN GRASS-LAND 



Field experiments at Rothamsted, and later at numerous other 

 places, have conclusively demonstrated that leguminous plants leave 

 the soil richer in nitrogen in spite of the fact that they are highly 

 nitrogenous themselves. Collins (4) has shown that the application of 

 phosphates, whether in the form of superphosphate or basic slag, on 



