248 



Sol able II limns uiiil rruilucticcness 



whole is made slightly acid with HC'I to jiroiiiote fjocculation and allow 

 of easy filtration and washing. The acid is then removed, the soil dried 

 and passed through a 3 mm. sieve. 



The soils used were: (I) Allotment soil, a medium garden soil; 

 ("2) Harpenden Field Soil (Arable), a typical loam. The treatment 

 was found to reduce the nitrogen very considerably. 



Table I. 



Total Nitrogen in Untreated Allotment Soil, per cent. -315 



„ „ in E.\tracted „ „ „ -178 



,, ,, roinovcd, per cent. ... ... ... •I'il 



Percentage reduction ... ... ... ... ... 43-6 



Total Nitrogen in Untreated Field Soil, per cent. ... -186 



in E.xtractcd „ „ „ ... -lOfl 



„ ,, removed, per cent. ... ... ... -077 



Percentage reduction ... 41-2 



Vegetation oxperimcnts were made with the four soils (Untreated 

 Allotment, E.xtractcd Allotment, l^ntreated Field Soil, and E.xtracted 

 Field Soil respectively). 



Each pot had a capacity of 10 kilos.; 5 kilos, sharp sand were put 

 at the bottom, and above this 5 kilos, of the soil under investigation, 

 mixed with 1.5 per cent, of sharp sand. Each set consisted of 5 pots: 

 thus there were 20 pots in all. Chalk was added to replace carbonates 

 removed by the acid treatment and 1 gram KH2PO4 in solution was 

 added to each pot. Thus the soils were as follows: 



Table II. 



Fine Earth 

 Sand 



Chalk ... 

 KHjPO, ... 



Untreated 

 Allotment 



5000 grams 

 750 „ 



1 gram 



E.xtracted 



Allotment 



Untreated 

 Harpenden 



5000 grams 

 750 „ 

 21 „ 

 1 gram 



5000 grams 

 750 „ 



1 gram 



Extracted 

 Harpenden 



5000 grams 

 750 „ 

 47-5 „ 

 1 gram 



Wheat was sown on March 1 1th, 1914, and the pots were kept in the 

 glass-house till April 7th when the number of plants was reduced to 

 five per pot and all the pots were removed to the open. The plants 

 in all cases made slow growth ; those in the untreated soils tillered 

 better, but later in the growing period were caught up, and passed by 

 those in the treated soils. Subsequent growth was quite satisfactory, 

 and in August, when the crops were cut, the weights were: 



