A CLOVER-SICK FIELD. 159 



througli this, the upper parts are soon covered with a 

 corky coating, and only the fine root-fibres ramifying 

 tlirough the subsoil convey food to the plant. 



Now, if we look at the experiments made by Messrs. 

 Lawes and Gilbert to render a clover-sick field pro- 

 ductive again for clover, we see, at once, that all the 

 means employed were well adapted to enrich the upper- 

 most layers of their field with nutritive substances for 

 wheat and barley ; but that the clover plant could derive 

 benefit from this manuring only in the first stage of 

 developement, while the condition of the lower layers 

 remained unaltered, just as if the field had received 

 no nutriment of any kind. 



The manures applied by Messrs. Lawes and Gilbert 

 were superphosphate of lime (300 lbs. of bone-earth and 

 225 lbs. of sulphuric acid per acre); sulphate of potash 

 (500 lbs.); sulphate of potash and superphosphate, mixed 

 all^aline salts (500 lbs. of sulpliate of potash, 225 lbs. 

 of sulphate of soda, 100 lbs. of sulphate of magnesia) ; 

 mixed alkalis with superphosphate ; further, salts of 

 ammonia alone, and the same salts with superphosphate 

 or mixed alkalis; farm-j^ard manure (15 tons), together 

 with lime, or with lime and superphosphate, or with lime 

 and alkahs in the most varied proportions ; then soot ; 

 soot with lime ; soot witli lime, alkalis, and superphos- 

 phate. Xone of these manures had the sliglitest efiect ; 

 the clover-sick field continued just as unproductive for 

 clover as before. 



The reason wliy these manures were inoperative is 

 not difficult to find. Messrs. Lawes and Gilbert, in their 

 report, leave us, indeed, in the dark as to the nature 

 and condition of the soil upon which their experiments 

 were made ; but from some incidental observations in 

 previous papers, we know that the fields at Eothamstead 



