The Wohurn Pot-Culture Experiments, 1914. 315 



A fresh series of experiments will now be started with a 

 new supply of the soil. 



III. Expenmcnts oh the Acidity of Soil. 



Stacli'yard Field, Continuous Barley, 1914. 



The question of acidity in soils and the best way of 

 remedying this has of late aroused much interest. The use 

 of lime at Wohurn both in the field work and in pot-culture 

 exi)eriments has frequently been referred to, and it has been 

 shoAvn how the acidity caused by the prolonged use of sulphate 

 of ammonia on a soil naturally poor in lime can be entirely 

 corrected. At the same time, certain anomalies have appeared 

 during the progress of the field experiments, notably in the 

 case of plot 2bb (continuous wheat) where the application of 

 four tons of lime per acre (two tons per acre in December, 

 1897, and a repetition of tliis in January, 1905) has not as yet 

 produced such a good crop as that on plot 2b, where a single 

 application of two tons of lime per acre was made in December, 

 1897, and not repeated since. 



Seeing that in these field experiments lime had always 

 been applied in the caustic state, this seemed to indicate the 

 possibility of harm being done by the use of lime in the caustic 

 state to this extent. 



This deterioration, while occurring in the case of wheat, 

 was not, however, found with the barley crop, the repetition of 

 two tons of lime per acre having produced no harmful effect, 

 but, on the contrary, having yielded a much increased crop. 



It was accordingly resolved to carry out at the Pot-culture 

 Station further experiments on this point, and chiefly with a 

 view to seeing whether carbonate of lime in place of caustic 

 lime, and in what amounts, would be beneficial in correcting 

 the acidity of the soil. In the meantime, Dr. Hutchinson, of 

 the Rothamsted Experimental Station, had worked out a new 

 method for the estimation of the acidity of soils, and, having 

 been supplied with soil from several of the Woburn plots, he 

 calculated in them the amount of acidity in terms of carbonate 

 of lime, and kindly supplied the figures for use in these new 

 experiments. 



For the purposes of the experiments soil was taken from 

 the following continuous barley plots of Stackyard Field : — 



Plot 1. Un manured. 



„ 2a. Sulphate of ammonia alonu. 



,, 2VjVj. Sulpliate of ammonia with four tons of lime per acre. 



,, 5a. Mineral manures and sulphate of ammonia. 



,, 5b. As 5a, with four tons <if lime per aci'e. 



,, Haa. Mineral manures and sulphate of ammonia (double-dressing) 

 together witli four tons per acre of lime. 



