48 Alfred J. Evxtrt : 



is often for convenience supplied in the form of the sulphate, 

 which is more soluble than the carbonate, not poii?onous like 

 the chloride, and less liable to contamination with injurious 

 impurities than the nitrate. Gypsum exercises, however, a 

 feeble action in freeino- potash in soils containing this substance 

 in an insoluble form, but it is much less active than quicklime. 

 It also neutralises alkalmo soil or alkaline irrigation water. 

 Thus— 



Neutral Alkaline soluble Neutral Soluble neutral 



soluble gypsuir. sodium carbonate air-slaked lime sodium sulphate 



CaSO^ aud Na.CO., form CaCOg and Na^SO^ 



No action of this kind took place, however, in the soil under 

 examination, and in both the clay and sandy soils the gypsum 

 reduced the yield below that for the unmanured plot. Gypsum 

 is, in fact, a substance which has crept into agricultural use as 

 a manure largely under false pretences. Even its action on 

 manure heaps in preventing the loss of ammonia is largely 

 exaggerated, and the «anae end is far better and more cheaply 

 attained by packing the manure tightly in walled enclosures or 

 in pits shielded from the weather. 



Plot 2 — Nitrate of Soda Siu-face 



(1201b. per acre) S inches 



16 inches 

 Average 



Plot 6 — Sulph. oi Ammonia Surface 

 (801h. per acre) 8 inches 



16 inches 

 Average 

 Both these manureis are highly soluble, 

 represent in the case of the nitrate of soda 0.148 gram per kilo- 

 gram of the superficial 2 inches, and in the case of the 

 ammonium sulphate 0.1 gram per kilogram, it is evident that 

 the movements of the added salts are not solely responsible 

 for the results, which are partly due to an indirect action, or 

 to the absorptive action of the crop. The latter probably ex- 

 plains the steady decrease in plot VI., which appears to be less 

 affected by rain than usual, and to show no increase in thje 

 Buperticial layer after drought. The j^lot II. shows the usual 

 movements of the soluble matter, though these are not very 



