UPON SOME PROPERTIES OF SOILS'. 69 



Royal Agricultural Society, there are two sets resembling each other in 

 every respect but one ; two are grown upon land kept entirely without 

 manure ; two are manured with minerals, and two are highly manured ; 

 the only difference between the two sets is, that upon one we have a 

 leguminous crop (beans or red clover) once in four years, while upon 

 the other we have a summer fallow. Thus, therefore, for a period not 

 much short of half a century no leguminous crop has been grown on 

 the latter portion of the experiments. Some years ago a few scattered 

 plants of yellow trefoil were seen amongst the barley on that portion 

 which had grown no leguminous crops. It would have injured the 

 barley if men had been sent in to pull them out, and it was considered 

 that as there would be a summer fallow in the following year the seed 

 would germinate and be destroyed ; at all events as we should have a 

 root crop before we took another barley crop, the fine tilth required for 

 the roots and the constant horse and hand hoeing would secure the 

 germination and destruction of every trefoil seed : such, however, was 

 not the case. Whether " an enemy " had sown the seed, or whatever 

 the cause, the trefoil came up thicker than ever, especially upon the 

 highly manured portions of the field, and it was found to be a very 

 serious and expensive undertaking to get rid of this little pest. It is 

 quite evident that when the land is kept free from leguminous 

 plant-growth, matters accumulate in the soil which are highly favourable 

 to these plants. This is seen both in the experiment just described 

 and in the top and bottom of our wheat field. It is tolerably certain 

 that the matter accumulated does not consist of ordinary manure 

 ingredients, because we cannot grow a leguminous crop continuously by 

 the use of them, as was seen in the bean field : important and interesting 

 investigations could be made on this subject. 



In the rotation experiments it was shown that after the first root 

 crop was removed from the unmanured land no further root crops 

 could be grown ; the plant even ceased to form a bulb. Upon the 

 same unmanured soil both barley and wheat have produced good crops, 

 and in all probability will continue to do so for a very long period of 

 time. The special property of the cereal crops to obtain their food and 

 to continue their growth on the same soil, when plants of other orders 

 fail to do so, appears to be a most important fact when we consider that 

 in some form or other these crops furnish the bulk of the food of the 

 whole world. I am disposed to think that if we could have in 

 succession the climate, that is, the temperature, rainfall, &c., suitable to 

 the various food crops of the world, rice, sugar-cane, maize, &c., they 

 would, if grown upon our wheat field, give results very similar to those 

 we obtain in the growth of wheat ; growing largely increased crops 

 when manured by the same manures, which now increase our wheat 

 crops, and growing continuously without any manure whatever. It has 

 sometimes been suggested that a piece of land which has received no 

 manure for fifty -five years and has grown an average crop of wheat 

 equal to, if not larger than the average crop of the world, must possess 

 some remarkable store of fertility ; I propose therefore to imagine what 



