E. J. Russell and E. H. Richards 507 



In the 1915 potato experiments, samples Nos. 1 and 2 are close 

 together in crop producing power : No. 1 appears the better but the 

 difference is within the limit of error. On analysis it is poorer than 

 No. 2 in dry matter, total nitrogen and complex nitrogen compounds, 

 but it is distinctly richer in ammonia. No 3 is considerably poorer: 

 it contains less of everything especially ammonia. No. 4 is the poorest 

 of the lot, and it also comes out lowest on analysis. 



In the 1916 wheat experiments at Woking the same general relation- 

 ships come out, the total nitrogen and ammonia are both higher in 

 sample 1 than in sample 2 and the crop producing power is also higher — 

 more, indeed, than the figures indicate because through a misunder- 

 standing a furrow was run down the centre of the plot receiving sample 1, 

 so that the yield was depressed over that portion of the area : no allow- 

 ance has been made for this. 



The 1916 wheat experiments at Rothamsted on the whole fit in with 

 the others : No. 1 has by far the highest ammonia content and comes 

 out best in spite of the fact that its total nitrogen is lower than in 2 

 or 4. No. 2 follows close in crop producing power, its high total 

 nitrogen making up for its lower ammonia content : No. 3 is far behind 

 in crop producing power and in nitrogen and ammonia. The position 

 of No. 4 is not explained by the analyses : it was a loose heap stored 

 in the open with less crop producing power than the figures indicated. 



In the potato experiments also the manure stored in the open is 

 of less fertilising value than the figures indicate, and on the other hand, 

 the sheltered heap No. 1 has in comparison with the exposed heap No. 3 

 some value which the analysis does not show. 



Our general conclusion is that none of the analytical figures by them- 

 selves would indicate the crop producing value with absolute certainty, 

 but a consideration of the total nitrogen and of the ammonia together, 

 especially if the ammonia is weighted, gives a result which is in accord- 

 ance with the crop returns. Exceptions arise when sheltered heaps 

 are compared with exposed heaps ; the latter have less crop producing 

 value than the analysis indicates. 



Berry's investigations^ of manure heaps in the South- West of 

 Scotland and the Leeds experiments- both show a connection between 

 composition and crop producing power. The results are : 



1 West of Scot. Bull No. xiv. 1914. ^ Leeils Bull. No. 90, p. 9. 



