24 THE PARK 



treatment of Plot 5 is now altered, but during the years the ammonium- 

 salts were applied the average yields per acre from these plots were : — 



Plot 17, single nitrate (18 years, 1858-1875), 33-9 * cwt. 

 „ 15, double „ (18 „ 1858-1875), 35-4 cwt. 



Plot 1, single ammonia (34 years, 1864-1897), 37*7 f cwt. 

 „ 5, double „ (34 „ 1864-1897),. 24-4+ cwt. 



It is very evident when a nitrogenous manure is used alone for grass, 

 nitrate of soda is far more effective than the ammonium salts ; e.g., on 

 l*lot 17 it has given an average crop of 34 cwt. against 26 cwt. produced 

 by double the quantity of nitrogen in ammonium-salts on Plot 5. 



Mineral Manures used alone. 



On three of the plots no nitrogenous manures have been applied since 

 the beginning of the experiments. On Plot 7 a complete mineral manure, 

 supplying phosphoric acid, potash, magnesia, and soda, is used ; Plot 8 

 has received the same application, but without potash, since 1861, while 

 Plot 4-1 receives superphosphate only. With the complete minerals 

 a fair crop is grown, avei'aging over 1^ ton of hay for the first cut alone. 

 The reason that the crop on this plot is maintained, although no nitrogen 

 is supplied in the manure, lies in the free growth of leguminous plants. 

 It will be seen that, taking the average over the whole period, the 

 leguminous plants form 25 per cent, of the herbage, and the proportion 

 has increased from year to year. 



The omission of potash on Plot 8 has caused a very striking difference 

 both in the crop and in the character of the herbage. The average crop 

 has been about one-third less over the whole period, and shows a pro- 

 gressive decline in fertility, until at the present time it is little more than 

 half that of Plot 7. The poor results on this plot, as compared with 

 Plot 7, must be put down to its poverty in leguminous herbage, the 

 development of which seems to depend on a free supply of potash. Of 

 late years the proportion of leguminous plants on this plot has amounted 

 to about one-half of that found on Plot 7, the grasses are also less, the 

 difference being made up by an increased amount of weed. 



Plot 4-1, which each year has received superphosphate only, now pre- 

 sents a very impoverished appearance, and is giving little more crop than 

 the unmanured plots. Indeed, the aspect of this plot, where the most 

 abundant grass is Quaking Grass, and where weeds, chiefly Hawkbit, 

 Burnet, and Plantain, are unusually prominent, would seem to indicate 

 that the land is more exhausted here than on the unmanured plot. 



Complete Manures — Nitrogen and Minerals. 



Among the plots which receive both nitrogenous and mineral manures,^ 

 Plot 9, with a complete mineral manure and ammonium-salts should be 

 compared with Plot 14, which is exactly similar except that the nitrogen 

 is applied in the form of nitrate of soda, and again with Plot 16, where 



* Over the whole period of 55 yrs. (1858-1912) Plot 17 gave an average of 33-7 cwt. per acre. 

 + „ ,, „ of 49 „ (1864-1912) „ 1 „ „ 33-6 „ 



% „ „ ,. of 42 „ (1856-1897) „ 5 „ „ 26-1 



