36 



It will be seen that when nitrate of sodium, or ammonium salts, 

 were applied to land manured with superphosphate and sulphate of 

 potassium, the increase in the quantity of nitrogen in the roots by the 

 addition of these manures was practically the same as was obtained when 

 these cross-dressings were applied to land receiving farmyard manure ; 

 the 14 tons of farmyard manure had thus no depressing effect on the 

 action of the nitrate or ammonia. That the leaves, if taken into account, 

 would not alter this conclusion is shown by the fact that the proportion 

 of leaf is greatest in every case on the farmyard manure plot : the pro- 

 portion of nitrogen recovered in the crop would thus be more increased 

 on this plot than on the other, if the nitrogen in the leaf was taken into 

 account. Where rape-cake is used with the farmyard manure we do not 

 get so good a return in the roots as where the rape-cake is used without 

 dung ; with 2,0001b. oi rape-cake and 14 tons of farmyard manure we 

 apparently reach an amount of organic manure in excess of what can be 

 economically employed in an average season. 



Notwithstanding the excellent utilisation of the nitrogen of the 

 nitrate of sodium or ammonium salts when applied with dung to man- 

 gels, the increased weight of crop obtained from these cross-dressings is 

 by no means so great as when the same cross-dressings are applied 

 without farmyard manure. Thus the increase in root and leaf yielded by 

 the nitrate of sodium on the farmyard manure and superphosphate ^>lot 

 was 9 tons y cwt., and that yielded bv the ammonium salts 8 tons; 

 while, without farmyard manure, the iucrease from similar dressings 

 applied to land receiving superphosphate and sulphate of potassium was 

 respectively 14 tons 5 own. and 11 ions 19 cwt. Thi- considerable dif- 

 ference is due to the fact that nitrate of sodium or ammonium salts give 

 a smaller, but much more nitrogenous increase when applied to dunged 

 land than when applied to land receiving no other nitrogenous manure. 

 The fact is of considerable practical importance to the farmer, but it has 

 nothing to do with the question before us, which is: Does farmyard man- 

 ure interfere with the assimilation of nitrogen from other manures ? 

 That a smaller return is obtained in crop, per unit of nitrogen, as the 

 supply of nitrogenous manure is increased is a fact sufficiently familiar to 

 the agriculturist. 



Since 1895 some alterations have been made in the mangel field at 

 Rothamsted; 500 lb. of sulphate of potassium per acre are now applied 

 to plot 2; and since 1896, 450 lb. of basic slag have been applied to this 

 plot instead of superphosphate. The supply of ash constituents is thus 

 made far more complete, and opportunity is given for the heavier dress- 

 ings of nitrogenous manure to display their greatest effect. 



The mode of applying the manures has also been changed. In 



1896 and 1897 the basic slag, sulphate of potassium, and rape-cake were 

 broadcast towards the end of April, and ploughed in ; furrows were then 

 opened, the dung applied, and the land thrown into ridges. Seed was 

 drilled the first week in May. The nitrate of sodium and ammonium 

 salts were applied as a top-dressing in July, being distributed along each 

 side of the drills. In 1896 the top-dressing took place on July 7th, in 



1897 on July 20th. The lateness of the application in 1897 was due to 

 the drought in that season. When nitrogenous manures have been 



