2:)0 



Solitblc JJiimiifi and r/oi/intirciutits 



pulled, ;is it seemed uimecessary to allow tlieiii to ripen. The crops 

 were dried, weighed, and the iiitroireii determined as before. The soil 

 in all the pots was thrown out and tlii)roii<jhly dried before replacing in 

 the pots and sowing with a fourth crop- mustard. 



iMustar<l was sown in all the pots in April, l!ll."), and was left till tlie 

 end of Aiay when it was ])ulled, dried an<l weighed. There was a fair 

 cro]) on all the soils e.xcejjt on the E.xtraeted Jiarpenden Field Soil, where 

 it failed entirely. The jjlaiits were cut wlien just flowering. 



T.Mti.io \'i. Wciijlils of fdinlh crop. Mustard. 



Soil 



Allotment Soil ... 

 Allotmrnl Soil K.xtracted 

 JiariM'iulcn Field Soil ... 

 Harpendeii Field Soil E.\tracted 



Table VII gives a summary of the croj) and nitrogen data for the 

 dilTerent soils. 



Table VII. Summary of rveighls of all four crops. 



Thus it will be seen that in five cases out of eight the plants obtained 

 more nitrogen from the extracted than from the untreated soils, in one 



