Soluble Constituents in Alluvial Soil. 47 



Plot 9 —Quicklime Surface 



(Two tons per acre) 8 inches 



16 inches 

 Average 



Plots 2, 3, 5, 7, 8 Surface 



(Bulked Average) 8 inches 



16 inches 

 Average 



In all the plots, the fallen dejecta membra of the crop tend to 

 raise the percentage of humus in the surface layers. The air- 

 slaked lime produced a pronounced fall in the pereentace of 

 humus, which, however, increased at a depth of 8 inches with 

 the quicklime, and to a) slight extent also in the unmanured 

 plots. At 18 inches, the humus decreased in all cases, though 

 only to a slight extent, except where air-slaked lime was 

 applied. It must be remembered that the quicklime plot 

 produced the heaviest crop, so that the increase in the percent- 

 age of humus is, to a slight extent, due to the greater devel<ip- 

 ment of the root system, and not entirely to the lessened 

 oxidation. The air-slaked, lime produced less crop, and caused 

 a great waste of humus. The averages for the other manured 

 plots show that, as compared with the unmanured plot, the 

 rate of oxidation of the humus was increased disproportionately 

 to its heightened production by the manured crop. 



"VVater-Soluble Constituents (continued). 



May 18 Sept. 25 Dee. 20 

 Plot 4— Gypsum Surface 1.12 0.36 0.54 



(One ton per acre) 8 inches 0.73 0.72 0.72 

 16 inches 0.59 1.11 0.91 

 Average 0.81 0.73 0.72 

 The gypsum is comparatively readily soluble, and comes 

 readily away in the filtrate. It is easily washed downwards by 

 rain, a very large part being lost during the rainy season, but is 

 drawn to a certain extent up to the surface again in dry weather. 

 The manurial value of this substance is commonly gi-eatly exag- 

 gerated. It has but little of the favourable mechanical action of 

 lime, it does not favour nitrification, and is a poor and expen- 

 sive way of adding calcium to the soil. The unduly high 

 manurial value attached to it may possibly arise from the fact 

 that, when plants are grown in nutrient solutions, the calcium 



