21 



This shows that while in the dry seasons (in the dry climate 

 of Woburn, be it remarked) nitrate of soda was better than 

 ammonia salts by about 2^ bushels of corn and 2f cwt. of 

 straw per acre, ammonia salts gave a better return in the wet 

 seasons by about 4f bushels of corn and f cwt. of straw ' 

 per acre. 



Depending upon the absorptive power of the soil and the 

 rate of nitrification, are the two practical questions What is 

 the right time to use sulphate of ammonia, with reference 

 both to season of the year and stage of growth of crops? 

 and Is there any valuable residue left* after the first crop 

 has been taken from the land ? 



TIME OF YEAR TO APPLY SULPHATE. 



With regard to the former of these points, fuller know- 

 ledge has altered the ideas originally held. When it was 

 first discovered that most soils could firmly hold ammonia 

 applied to them, so that it was no longer liable to be washed 

 away, it was concluded that sulphate of ammonia might 

 safely be applied to the land in the autumn, especially in 

 the case of an autumn sown crop, such as wheat. The 

 extreme rapidity with which much of the nitrogen of 

 sulphate of ammonia may be nitrified was not at the time 

 recognized; and it was, therefore, considered an advantage 

 to apply it to the land some time before the period of active 

 growth in spring. Accordingly, in the Rothamsted wheat 

 experiments the ammonia salts were for many years applied 

 in autumn. In the course of investigations, however, 

 as to the composition of the drainage water from land 

 manured in various ways, it was observed that large quanti- 

 ties of nitrates and nitrites, chiefly of lime, \vere washed 

 away during the winter from land receiving ammonia salts 

 (equal weights of sulphate and muriate of ammonia) ; and, 

 further, that the amount of nitrates and nitrites was greatest 

 where the largest dressings of ammonia salts were employed. 

 Later experiments proved that the serious loss of nitrates 

 began after the application of the ammonia salts. 



Table IX. shows the proportion of nitrates in the 

 drainage water from various plots of the Rothamsted wheat 

 experiments on the different occasions when the drains ran 

 during the year 1881-2.* 



In the season of the experiment the drains did not run 

 after March 7 until harvest was over, so that there was no 

 loss by drainage during the growth of the crop. But when 

 drainage took place later in the year, loss of nitrate occurred 

 even from the plots receiving no nitrogenous manures 

 (Columns I. and II.). This nitrate would be produced by 

 the nitrification of the nitrogenous matter of the roots and 



* Lawes and Gilbert, " Journal of the Royal Agricultural Society of 

 England." Vol. XIX., S. S. 



