3^6 How LONG DOES LiME LAST IN THE SOIL ? [SEPT., 



surface is sufficient to bury things about one inch in every 

 fifteen years. Cinders, stones, and Biuy other substances on the 

 surface of grass land are buried just as readily as lin::e or chalk, 

 as may be seen by the fact that stones are never found lying 

 on old grass land, however stony the neighbouring arable land 

 may be. But on arable land, as the Rothamsted analyses show, 

 there is no tendency for the lime to sink in the soil. Although 

 it is certainly more than sixty-five years since the chalking there 

 was done (probably, indeed, most of it took place more than a 

 hundred years ago), yet the chalk still remains wholly in the 

 top nine inches of the soil. Thus, while we know that lime 

 sinks in the soil of grass land from purely mechanical reasons, in 

 arable land it does not sink, but is subject to a steady wastage 

 by solution in the rain water percolating through the soil. 



The Rothamsted plots further enable one to answer another 

 important question, the effect of the various manures usually 

 applied to land upon the rate at which the carbonate of lime 

 is washed out. Briefly the results of the investigation are as 

 follows : — 



(1) Superphosphate, sulphate of potash, kainit, and kindred 

 manures do not increase the loss to any appreciable extent. 



(2) Farmyard manure and probably all organic manures 

 diminish the loss of carbonate of lime. 



(3) Nitrate of soda also diminishes the loss. 



(4) Sulphate of ammonia increases the loss, removing about 

 half its own weight of lime or nearly its own weight of chalk. 



The effect of sulphate of ammonia in removing lime from the . 

 soil has always been understood; the ammonium salts to a large 

 extent behave like free acids, and have to be neutralized by car- 

 bonate of lime in the soil. Whenever the carbonate of lime 

 becomes deficient then the continued use of ammonium salts 

 actually gives rise to an acid reaction in the soil and may cause 

 almost complete sterility, as in the case of .some of the plots on 

 the Royal Agricultural Society's farm at Woburn. In that soil 

 there was at the outset of the experiments only a trace of car- 

 bonate of lime, and the continued use of ammonium salts for 

 thirty years has made the soil so acid that barley will no longer 

 grow and wheat is seriously affected. A dressing of lime, how- 

 ever, restores the soil to its normal condition. At Rothamsted 



