24 BROADBALK FIELD 



mineral manure containing potash. The result is seen in the way 

 leguminous plants have gradually invaded the plot until they now 

 predominate as they do on Plot 7, where mineral manures have been 

 used throughout. The southern half of Plot 5 has also been manured 

 with minerals instead of ammonium-salts since 1898, and the gradual 

 invasion of leguminous plants may now be seen in progress. The 

 northern half of Plot 5 has been unmanured since 1898, when the 

 ammonium-salts were discontinued. 



On Plot 15 nitrate of soda was applied up to 1875, when a change to 

 a complete mineral manure was made, with the same result of the incoming 

 of the leguminous plants. 



The southern halves of Plots 1 to 4-2, 7 to 11-2, 13 and 16 were 

 dressed with ground quick-lime at the rate of 2000 lb. per acre in 

 January 1903, and changes in the herbage resulting therefrom are now in 

 progress. 



Plot 18, which, up to 1905, was in an impoverished condition, has since 

 been receiving a complete manure except for the omission of any phosphoric 

 acid. 



Use of Dung 



Three plots were selected in 1905 to illustrate the effects of dung applied 

 occasionally, either alone or in combination with artificial manures, as 

 follows : — 



Plot 19. 14 tons Dung 1905, and every fourth year. 

 Unmanured intervening years. 



Plot 20. 14 tons Dung 1905, and every fourth year. 

 1 J cwt. Nitrate of Soda \ t^ * 4- 



200 lb. Superphosphate r 

 100 lb. Sulphate of Potash J y^^^' 



Plot 13. 14 tons Dung 1905, and every fourth year. 



6 cwt. Fish Guano 1907, and every fourth year. 



BROADBALK FIELD— WHEAT 



The experiments on the continuous growth of wheat were begun in the 

 Broadbalk field in 1843, but for the first eight years the manuring was of 

 a varied description, so that only three of the plots have received the same 

 treatment during the whole period of sixty years. The plots as seen to-day 

 began in 1852, since which time the few changes in manuring have been 

 matters of detail and not of principle. 



The chief difficulty experienced in growing wheat continuously is that 

 of keeping the land clean ; not only does the crop occupy the ground for 

 the greater part of the year, and so leave little opportunity for cleaning 

 operations, but the weeds whose habit of growth is favoured by the crop 

 tend to accumulate from year to year. Thus in spite of repeated hand- 

 hoeings, some weeds, like the " Black Benf"* grass, Alopecurus agrestis^ are 

 kept under with the greatest difficulty. 



