Food for greatest extent by far when the nitrogen was omitted from 

 1 the complete dressing. The mean of all of the experiments 



170 for all of the years gives the following results : The complete 

 dressing, consisting of phosphoric acid, potash and nitrogen 

 has given a gross profit of $18.59 P er acre a d per year. 

 When the potash was omitted from the complete dressing, 

 it has given a gross profit of $14.27, and if the phosphoric 

 acid was omitted, the yields fell to $12.20 per acre and per 

 annum, and if the nitrogen was omitted it fell to $3.88, 

 The results obtained from pot experiments have been fully 

 confirmed by the experiments in the open field; it is the nitro- 

 gen, without exception, that has been deficient, then phos- 

 phoric acid, then potash. Maximum yields have only been 

 obtainable when all necessary constituents of the complete 

 dressing, including nitrogen, were present. If maximum 

 yields are to be obtained the field must be fertilized with 

 nitrogen, phosphate and potash. Manures can only do their 

 work when a nitrogenous fertilizer is also applied in abund- 

 ance. 



It is quite possible, however, that the fields which 

 served for these experiments had had no dressing of barnyard 

 manure for several years, had received no green manuring, 

 and, perhaps in consequence of that, were becoming exceed- 

 ingly poor in nitrogen. Hence, the question is : 



How Far is Barnyard Manure Capable of Meeting 

 the Nitrogen Requirements of Crops? 



Still, information on this point must be derived from 

 experiments, in order to determine in-how-far the barnyard 

 manure at the disposal of the fanner suffices to feed the crop, 

 and what quantity and kind of chemical fertilizer must be 

 added in order to secure maximum yields. 



In order to determine this question, a field is divided 

 into plots, each plot to be similarly treated with barnyard 

 manure, in a sufficient quantity, and besides the dressings of 

 barnyard manure the plots receive in addition the following 

 plant-food in the form of commercial fertilizers: 

 Plot i. A complete dressing, consisting of phosphoric acid, 



potash and nitrogen. 



Plot 2. The like complete dressing, but without phosphoric 

 acid. 



