14 



BARN FIELD 



Series 







With 

 No Nitrogenous 



D 



Manure 



No Minerals. 



C 



With 

 Rape-cake. 



AC 



With 



Rape-cake A 



Ammonium Salts. 



jSuperphosphate. 



Superphosphate 

 and Potash, 



■ Superphosphate, Potash, 

 Niaj^nesia and Soda. 



Fi3. 4. — Manuel Wurzel. Effect of various Mineral Manures. Average 

 Produce of Roots per acre, 1876-1902. 



Effect of A rtific'ial Manures with Dung 



A comparison of Strip 2 with Strip 1 shows the effect of adding 

 superphosphate and sulphate of potash to the dung and nitrogenous 

 manures applied to Strip 1. A heavier crop and a healthier plant is 

 obtained, especially where a large amount of nitrogenous manure is used. 

 Since in the earlier experiments it was found that superphosphate had no 

 beneficial effect when used with dung we can put down the superiority of 

 Strip 2 over Strip 1 to the sulphate of potash which is now used. 



Effect of* Manures upon the Texture of the Soil 



On the strong Rothamsted soil several of the manures employed have 

 an injurious action upon the texture of the soil and often prevent a 

 satisfactory tilth being obtained in the spring, to the great injury of the 

 crop. This is particularly seen where no organic manure is used, both 

 dung and rape cake tend to keep the land in good condition. Of the 

 artificial manures nitrate of soda and sulphate of potash have the worst 

 effect upon the land, making it very sticky when wet, and hard and caked 

 when dry. Superphosphate on the contrary promotes a friable tilth. 



