Continuous Growth of Wheat with Farmyard Manure. 49 



CONTINUOUS GROWTH OF WHEAT UPON THE 

 SAME LAND FOE FOETY YEAES WITH FAEM- 

 YAED MANUEE SUPPLIED EACH YEAE. 



When a plot of land which has grown wheat continuously 

 for forty years has every year received a dressing of farm- 

 yard manure, the lessons to be learnt from an examination of 

 the results cannot but commend themselves as eminently 

 deserving the attention of agriculturists. Plot 2 in the 

 experimental wheat-field at Eothamsted is such a plot, and for 

 the last forty years it has annually received ordinary farmyard 

 manure at the rate of 14 tons per acre. No attempt was 

 made to ascertain the exact composition of the manure 

 applied, for two reasons : (1) in the earlier years of the 

 experiments, the importance of knowing the exact amount 

 of the various ingredients applied to the soil was not well 

 understood; (2) later on, the uncertainty of the results 

 obtained in a very careful attempt to ascertain the exact 

 composition of some box-dung at Woburn made it apparent 

 that it would be preferable to trust to an estimate of the 

 composition based on numerous analyses of farmyard 

 manure. Table IX. gives the estimated amount of some of 

 the more important ingredients supplied to the soil of plot 2 

 annually in the 14 tons farmyard manure, as also the amount 

 of ingredients supplied in the artificial manure on plot 7, 

 which receives mixed minerals and 4001b. of ammonia- salts 

 per acre. 



TABLE IX. 



1501b. 7 years, 1852-8, lOOlb. each year since. 



