U'OBURN EXPERIMENTS 47 



greater than the corresponding results at Rothamsted. To 

 what cause should we attribute the excellence of the Woburn 

 results ? 



\Yhen we come hereafter (p. 63) to consider the effect 

 produced on subsequent crops by the residue from a previous 

 dressing of ammoniacal manure, we shall find that while no 

 beneficial effect is perceived in the Rothamsted wheat field 

 from any residue remaining in the soil from a last year's 

 application of ammonia salts, a beneficial effect from such 

 residues is felt at Woburn, and sometimes to a surprising ex- 

 tent. The nitrates unused by the crop in one season at 

 Rothamsted are apparently afterwards lost, probably through 

 the drainpipes, or by absorption by the chalk subsoil, while at 

 Woburn the nitrates remain to a large extent in the soil and 

 serve for the nourishment of the next crop. Both ammonia 

 salts and nitrates are thus in the long run used with more 

 economy at Woburn than in the wheat field at Rothamsted. 

 The experiments on the influence of residual manures will be 

 described in detail by and by, the figures already given are 

 however sufficient to lead us to the view just expressed. 



If we consider the quantity of nitrogen usually present in 

 the grain and straw of wheat, we shall find that the 28 Ibs. of 

 ammonia contained in i cwt. of the best commercial sulphate 

 of ammonia cannot produce an increase of more than about 13 

 bushels of corn, with its equivalent of straw. The return at 

 Woburn occasionally reaches or exceeds this figure, and in 

 1894 considerably overpasses it. It is clear that in these 

 cases the result is not wholly due to a single application of 

 ammonia salts ; the return from the last application is, in 

 fact, increased by the remainder of the preceding application. 

 Two years of an abnormally great return can thus never 

 follo\v each other, and each splendid result is usually preceded 

 by a poor one. Of this fact the years 1893 an< ^ J ^94 afford 

 the most striking example. In the extreme drought of 1893 

 the produce of wheat on plot 5 at Woburn was only 13-1 

 bushels; in 1894 the produce on this plot was 54-4 bushels, a 

 crop which could only have been reached by the aid of the 

 unused residue of the manure applied in the preceding year. 



