BAELEY. 73 



It may be observed that, over the whole period of forty 

 years, the total produce (grain and straw together) was with- 

 out manure less than 1 ton per acre per annum, whilst with 

 the farmyard manure it was 2f tons, and in some years it 

 reached from 3| to 3f tons. 



To sum up in regard to the foregoing results : There was Summary 

 gradual exhaustion and reduction of produce without manure, withdwlq 

 and gradual accumulation and increase of produce with the and no 

 annual application of farmyard manure. But when the manwre - 

 application was stopped, although the effect of the residue 

 from the previous applications was very marked, it somewhat 

 rapidly diminished, notwithstanding that calculation showed 

 an enormous accumulation of nitrogen as well as other con- Accumu- 

 stituents. ^f°- 



Indeed, determinations of nitrogen in the surface-soil, after what be- 

 the twenty years' application of farmyard manure, showed it comes °f lt - 

 to be nearly twice as high as on the unmanured plot. 



How, then, is the reduction of produce to be accounted for? 

 The nitrogen of farmyard manure must obviously exist in 

 very different conditions. That due to the urine of the 

 animals will be the most rapidly available, that in the finely 

 comminuted matter in the feces will be much more slowly 

 available, and that in the litter still more slowly available. 

 Hence the small proportion that is at once effective, and the 

 very large amount that accumulates within the soil in a very 

 slowly available condition. 



But the evidence at command leads to the conclusion that 

 neither in the wheat-field nor in the barley-field does the 

 accumulation within the soil account for the whole of the 

 nitrogen supplied which is not recovered in the immediate 

 increase of crop. Some is doubtless lost as nitrates by drain- Loss of soil 

 age, and some probably by evolution as free nitrogen. The mtro 9 en - 

 fact of such losses is of considerable interest ; but it is some 

 consolation to believe that the loss will be proportionally 

 very much less in ordinary farm practice, where the amounts 

 of farmyard manure applied are much less, and where various 

 crops, with different root -ranges, and different periods of 

 accumulation, are grown. 



Results without Manure, and with Artificial Manures. 



We have next to consider — what is the character of the 

 exhaustion induced by the growth of the crop without man- 

 ure ? and to what constituent or constituents of farmyard 

 manure its effects are mainly to be attributed ? These points 

 will be illustrated by the results given in Tables 22 and 23 and% 2 e l- 

 (pp. 74 and 75), which show the effect of various mineral plained. 



