40* N. H. AGR, EXPERIMENT STATION. [Bulletin 142 



amount of potash was believed to be unavailable or else so 

 slowly soluble as to be of little use in intensive farming. 



Several successive years of observations of the hay crop, on 

 old fields long unplowed and with no top-dressing of any sort, 

 made it evident that the grasses were making use of the soil- 

 potash, and the problem presented by these observations was the 

 determination of the rate of availability of the natural potash 

 compounds, and whether it was sufficiently rapid to produce 

 large crops without exhausting the soluble compounds. 



EXPERIMENTS OF 1905 AND 1906. 



In July, 1905, samples of soil were taken from different fields 

 on the College Farm and in the vicinity, and also samples of the 

 hay crop growing on these soils. The crop was cut from a meas- 

 ured square yard, dried, weighed and prepared for analysis. 

 The soil sample was obtained by making numerous borings with 

 an auger within the square yard . and mixing them together. 

 The samples were usually taken to the depth of eight inches, 

 but on the lowest fields six inches was sufficient to reach the line 

 of subsoil. 



Instead of determining the potash soluble in strong acid, as 

 in the early work, the soils were subjected to the usual treatment 

 of mineral analysis and the total amount of potash present de- 

 termined. On arranging the results in two groups, lowland soils 

 and upland soils, it was readily seen that there was a higher 

 average percentage of potash in the lowland group. Since this 

 group of soils contains more clay than the other group, it shows 

 that the clay is richer in potash than the other soil constituents. 



Tablk I. — Potash in Soils^ 1005. 



Lowland Group. Upland Group. 



1 2.28 II 2.07 



VI 2.47 III 2.32 



VII 2.78 IV 2.40 



VIII 3.22 V 2.07 



IX 3.16 XI 2.75 



X 3.56 XII 2.32 



XIII 3.48 XIV 2.19 



XV 8.56 XXI 2.05 



XVI 2.21 XXII 2.07 



XVII 3.19 XXIII 2.29 



XVIII 3.96 Average 2.25 



XIX 3.00 



XX 3.07 



XXIV 2.59 



XXVII 2.72 



Average 3.01 



• See footnote page 58. 



