52 RESULTS WITH WHEAT 



manuring is of course practically limited to certain soils and 

 climates ; thin soils, with a gravel or chalk subsoil, cannot be 

 relied on to yield a profitable return from soluble manures. 



The number of accurate experiments are at present too few for 

 any exact statement as to the average return to be expected from 

 the use of sulphate of ammonia, the details of the experi- 

 ments we have already given show how greatly this return is 

 affected by the special characters both of the soil and season. 

 In the brief experiments at Rodmersham, we have an average 

 return of only 1-8 bushel from i cwt. of sulphate of ammonia. 

 At Holkham, the return is 3-8 bushels. Mr. F. J. Cooke also 

 gives 3 bushels as the general return obtained in three years' 

 experiments on several Norfolk farms having a thin soil, with 

 a sandy, gravelly, or chalky subsoil. At Rothamsted the 

 average return in 40 years is 5 bushels for i cwt. of sulphate 

 of ammonia. Mr. Cooke also names 5 bushels as the return 

 obtained during three years on Norfolk farms having a deep 

 loam as their soil. At Woburn we have during 20 years the 

 excellent return of 8 bushels of wheat for i cwt. of sulphate 

 of ammonia. This first-rate return we have already seen 

 is probably connected with the exceptional retention of nitrates 

 in the Woburn soil, a deep fine sand, which alloAvs any unused 

 nitrates of one season to remain available in the soil for the 

 next crop. A return of five bushels from i cwt. of sulphate 

 of ammonia is perhaps the nearest approach to an average 

 result which the figures before us seem to warrant. 



For the profitable growth of wheat by artificial manures it 

 is of course essential that the land shall be kept clean ; the 

 crop and not the weeds must make use of the plant food given 

 if a money profit is to be realised. 



While the superphosphate and kainite, which form part of 

 the artificial dressing, are best applied to the land and harrowed 

 in before drilling the seed, the sulphate of ammonia will 

 generally do best when given as a top-dressing in the spring. 

 When possible, large dressings should be applied early, in the 

 south of England in March, and a light harrow at once taken 

 across the land to help cover the manure. If the harrow is not 

 to be used, the fair intervals of showery weather should be 



