192 The Rothamsted Grass Experiments. 



pubescens, and Holcus lanatus being then the leading grasses. 

 After the supply of farmyard manure ceased, however, the 

 same grasses as without manure gradually became more 

 prominent on plot 2, whilst the Poa trivialis and Bromus 

 mollis had, in 1877, become insignificant in quantity. It 

 may be stated generally that, in the later years, there was 

 on plot 2, as compared with plot 3, a higher percentage and 

 a considerably larger quantity per acre of gramineous 

 herbage ; a considerably lower percentage and a smaller 

 amount per acre of leguminous herbage ; and a rather 

 lower percentage, but a somewhat larger actual amount, of 

 miscellaneous herbage. 



As the grasses increased, and the leguminous plants 

 diminished, under the farmyard manure, the herbage con- 

 tained a considerably lower and decreasing percentage of 

 nitrogen ; but there was a higher percentage of total mineral 

 matter. Of lime, magnesia, soda, and sulphuric acid there 

 was more, and of potash, phosphoric acid, chlorine, and 

 silica very much more, removed per acre from the farmyard 

 manured than from the continuously unmanured plot. There 

 was a greater or less available residue of all the mineral 

 constituents, and more especially of potash, phosphoric 

 acid, and silica, many years after the cessation of the appli- 

 cation of the manure. 



At what rate, and in what proportion, have the several 

 constituents of the farmyard manure, which were not 

 recovered during the years of the application, been recovered 

 since, and what prospect is there of their final total 

 recovery ? 



To answer this question there is on the one hand, a toler- 

 ably correct estimate of the amounts of nitrogen, and of the 

 several mineral constituents, removed in the crops during 

 the separate periods, but it is a more difficult matter to 

 arrive at the amount of the same constituents contained in 

 the 112 tons of farmyard manure applied per acre to the 

 plot during the eight years. The following figures, however, 



