HORTICULTURAL SOILS. 



79 



TABLE VII. (b) Eothamsted Experiments. 



On the Growth of Barley for 38 years. Amount of Potash and Phosphoric 

 Acid in the Soil, and the quantity soluble. Also produce per acre. 



Plots 



Potash 



Soluble in 

 1 per cent. 



Citric 



Acid 



Phosphoric 

 Acid 



Soluble in 

 1 per cent. 



Citric 



Acid 



Produce 

 Grain 



per acre 

 Straw 





Quantities per 



acre, first 9 inches of 



soil. 







lbs. 



lbs. 



lbs. 



lbs. 



Bushels 



Cwts. 



1, U 



36,604 



91 



2,503 



139 



i ci 



Q3 



2,0 



37,918 



165 



4,601 



1,170 



21f 



10f 



3, 0 



42,848 



925 



3,059 



253 



18 



n 



4, 0 



43,429 



859 



4,778 



1,360 



22§ 



nf 



1, A 



35,845 



50 



2,452 



152 



29 



16 



2, A 



36,376 



57 



4,373 



1,073 



42f 



231 



3, A 



39,637 



1,029 



2,579 



205 



31f 



18 



4, A 



43,301 



753 



4,602 



1,264 



43§ 



251 



7-2 



33,374 



669 



3,669 



932 



481 



29 



The results show at a glance the comparative exhaustion or 

 accumulation of both potash and phosphoric acid. It will be 

 seen that plot 1 O, to which no manure of any kind had been 

 added for thirty-eight years, contained 36,604 lbs. of potash per 

 acre, of which only 91 lbs. was soluble, or available to plants. 

 Of phosphoric acid there was 2,503 lbs., of which only 139 lbs. 

 was soluble. With this small quantity of available plant-food 

 per acre it is not surprising that an average produce of 16J 

 bushels of barley grain, and 9| cwts. of straw only was obtained. 

 In fact, the wonder is that the land continued to grow corn 

 at all. 



The three other plots of the O series show from 37,918 lbs. to 

 43,429 lbs. of potash per acre, of which there is a range in the 

 solubility of from 165 lbs. to 925 lbs. per acre. The amount of 

 phosphoric acid ranges from 3,059 lbs. to 4,778 lbs. per acre, 

 and the soluble portion from 253 lbs. to 1,360 lbs. per acre; 

 the two plots (2 O and 4 O) receiving the phosphate manure 

 each year show from five to six times more available phos- 

 phoric acid than plot 3 O, which had never received phosphate 

 as manure. 



The difference between 36,604 lbs. and 43,429 lbs, of total 



