6 



JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



to which the name colloid is given : nowadays chemists and physicists 

 attach great importance to colloids, and are pointing out their 

 significance in the soil. Perhaps the most striking property of the 

 decomposing organic matter is its power of securing a tilth and of 

 increasing the water-holding capacity of the soil. Thus, a soil rich 

 in organic matter can be more easily cultivated ; it keeps moist longer, 

 and it is liable to less drainage than soils poor in organic matter. All 

 these properties are well exhibited on the Rothamsted plots. On the 

 mangold field the plot annually receiving farm-yard manure gives 

 a better tilth, and therefore a better seed bed, than those that never 

 receive it. In a dry season this makes an enormous difference to 

 the young plant during June and July, though usually things right 

 themselves before the end of the season. On the Broadbalk field the 

 plots are all under-drained, so that we are able to observe the effect 

 on drainage. On the plots receiving no farm-yard manure the drains 

 run fairly frequently : on the plot annually receiving it the drain 

 runs very rarely. 



Number of Days when Drains ran. 





1903 



1904 



1905 



1906 



1907 



1908 



1909 



1910 



1911 



1912 



1913 



1914 



Average 

 of 12 

 Years 



Dunged plot 



2 



3 



None 



1 



None 



None 



I 



None 



None 



None 



None 



2 



0-7 



Unmanured 





























plot . 



27 



20 



11 



14 



10 



9 



10 



20 



20 



32 



9 



20 



17 



The effect of organic matter in building up a soil is strikingly shown 

 on one of the barley plots. This received farm-yard manure annually 

 for twenty years from 1852 to 1871, but nothing since. Alongside 

 is a plot that has received nothing during the whole period. The 

 effect of the farm-yard manure went on increasing during the first 

 thirteen years ; it then increased no more, but kept at its high level. 

 In 1872 the farm-yard manure was discontinued. The yield has 

 gradually fallen, but even after forty-six years it is still well above 

 the level of the unmanured plot. 



In farm practice the good effect of farm-yard manure is intensified ' 

 by another interesting property. It has a remarkable effect on 

 increasing the growth of clover. This was well shown last year on 

 the Little Hoos Field plots. Those which had received farm-yard 

 manure in the preceding year, and even two or three years before, 

 gave a much better crop than those which had only received artificials. 



Treatment. 



Dung for 

 Previous Crop. 



Artificials for 

 Previous Crop. 



No Manure for 

 Previous Crop. 



Yield of clover hay, cwts. per acre. 



65- 6 



419 



4 II 



When clover is good it makes the next crop also good, because it 

 enriches the soil in organic matter and in nitrogen taken from the 



