1905.] Function of Silica in the Nutrition of Cereals. 457 



examination of the records indicated at once that the appearances noticed 

 were not accidental, hut had persisted from year to year. 



2. Field Experiments at Botlwmstcd with Soluble Silicates. 



At Eothamsted sodium silicate has been applied as a manure to certain 

 of the experimental plots over long periods of time, and shows regular and 

 well-marked effects. 



On the permanent grass plots in the Park, which is cut for hay every 

 year, there are two plots receiving similar heavy applications of ammonium 

 salts, phosphates, and potassium, sodium, and magnesium sulphates. One 

 of these, which receives sodium silicate also, yields a crop exceeding by 

 about 10 per cent, the crop of the parallel plot without sodium silicate, 

 taking an average over the last 42 years. It is possible, however, that the 

 weakly-held sodium base has some part in this action, by neutralising 

 the acidity produced in the soil by the continued use of ammonium salts. 

 This difficulty of interpretation does not, however, apply to the barley plots. 



In Hoos field, on which barley has grown every year since 1852, one 

 series of plots receives sodium nitrate with various combinations of mineral 

 manures, so as to provide plots receiving (1) nitrogen alone ; (2) nitrogen 

 and phosphoric acid without potash ; (3) nitrogen and potash without 

 phosphoric acid ; and (4) a complete manure. 



Since 1864 one-half of each of these plots has been cross-dressed with 

 sodium silicate ; hence the effect of the silicate is seen in conjunction with 

 each of the elements of a complete manure. The average results obtained 

 are set out in Table II. 



Table II. 



Plot. 





Manures per acre. 



Average over 41 Years, 1864 — 1904. 



Sodium 

 nitrate. 



Super- 

 phos- 

 phate. 



Potas- 

 sium 

 sulphate. 



Sodium 

 sulphate. 



Grain. 



Magne- 



Straw. 



sium 

 sulphate. Without 

 silicate. 



i 



With 

 silicate. 



Without 

 silicate. 



With 

 silicate. 





lb. 



cwt. 



lb. 



lb. 



lb. Bushels. 



Bushels. 



cwt. 



cwt. 



1 



275 









— 27 3 



33 -8 



16 -2 



19-8 



2 



275 



3 5 







— 1 42 -2 



43 -5 



24 -6 



25 -8 



3 



275 





200 



100 



100 1 28 -6 



36 -4 



17 -9 



21 -7 



4 



275 



3 -5 



200 



100 



100 41 -2 



44-5 



25 3 



27 6 



In this case only a normal amount of nitrogen is supplied in the form 

 of sodium nitrate, a neutral salt, so that there is no acid to be neutralised 



2 L 2 



