80 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



potash in the soil, and of 2,503 lbs. and 4,778 lbs. per acre of- 

 total phosphoric acid, appears from these results to be immaterial 

 as a measure of present soil fertility, notwithstanding that the 

 degree of solubility of each constituent is largely increased on 

 the different plots according to the manure employed. As no 

 nitrogen has ever been applied to the plots of the mineral 

 series (1 to 40) there has been no strain on the natural resources 

 of the soil, and consequently the barley crops obtained have been 

 small. 



From the next group of plots, 1 A to 4 A, we get some valuable 

 information. To each of these portions of ground ammonium 

 salts have been added to the other manures. (See Table VII. [a].) 

 The total amount of potash is seen to range from 35,845 lbs. to 

 43,301 lbs. per acre ; of this quantity the soluble part ranges 

 from 50 lbs. to 1,029 lbs., showing that plot 3 A has 200 times 

 more available potash than plot 1 A, but, owing to the lack of 

 sufficient soluble phosphoric acid, the yield of barley is but 

 2 bushels per acre in excess of plot 1 A. The phosphoric acid 

 ranges in total amount from 2,452 lbs. to 4,602 lbs. per acre, 

 the soluble portion from 152 lbs. to 1,264 lbs. per acre. The 

 produce of barley grain and of barley straw is seen to be about 

 doubled from the previous series ; but in plot 1 A, receiving 

 ammonium salts alone, there is a starvation of the two mineral 

 constituents, potash and phosphoric acid, notwithstanding the 

 large amounts in the soil ; while in plot 3 A, receiving the nitrogen 

 and potash, but no phosphates, there is a starvation of phos- 

 phoric acid, with a consequent falling-off in the crop grown. 



Plot 7, which had received 14 tons of farmyard manure per 

 acre for thirty- eight years, amounting to the enormous quantity 

 of 532 tons of manurial material, but made up very largely of 

 organic matter and water, shows an accumulation in the soil of 

 33,374 lbs. of potash per acre, of which 669 lbs. only is soluble. 

 Phosphoric acid shows 3,669 lbs. per acre, of which 932 lbs. are 

 soluble. The returns of corn and straw on plot 7 show that 

 the accumulated residue of organic nitrogen in the soil enables 

 the crop to be maintained at a high standard, notwithstanding 

 that the amounts of potash and phosphoric acid in the top 

 9 inches of soil are lower than in the soils receiving artificial 

 manures. But doubtless the improved subsoil on the dunged 

 plot would have much to do with its increased produce. 



