134 EXPERIMENTS UPON LEGUMINOUS CROPS 



ground, instead of being impoverished, is actually enriched by 

 the residues left behind after the growth of some of these 

 crops. 



In the Geescroft field, which is no longer under experiment, 

 and where the land lies wetter than in any of the other 

 Rothamsted fields, trials with beans began in 1847 and were 

 continued with several years of failure until 1878, when they 

 were finally abandoned. Table XL VIII. shows a summary 

 of the crops obtained under the three conditions of no manure, 

 mineral manures only, and a complete manure containing 

 minerals and nitrogen ; the nitrogen was applied at first as 

 ammonium-salts, which, because of their ineffectiveness, were 

 afterwards replaced by nitrate of soda. 



It will be apparent from the table that the mineral 

 manures containing potash were the most effective factor in 

 promoting the growth of the beans, the addition of nitrogenous 

 manure producing little or no increase in the crop. The crop 

 shows a continual deterioration, but this is more apparent in 

 the failures of the plant than in the diminution of the crop 

 whenever a plant could be obtained ; the crops of 1874 and 

 1875, for example, being only exceeded a few times during 

 the whole course of the experiments, though it should be 

 observed that these crops followed three years during which 

 the land lay completely fallow. 



The difficulty of obtaining a plant which characterised the 

 later years of the experiment cannot, however, be wholly attri- 

 buted to what might be termed bean "sickness," for the tilth 

 of the land had deteriorated considerably through the repeated 

 growth of a shallow-rooted crop. The use of nitrate of soda 

 and other saHne manm-es had also a bad effect on the texture 

 of this soil, and from the combination of these causes it 

 acquired a close and unfavourable condition, with a compara- 

 tively impervious pan in the subsoil below. 



The whole evidence points, however, to the land becoming 

 gradually unsuited to the growth of beans, independently of 

 the deterioration of the tilth of the soil. 



