6 
CONTENTS. 
Section II. — The Broadbalk wheat soils — Continued. Page. 
General comparison of the quantity of total nitrogen per acre in the 
Rothamsted soils and subsoils with the quantity annually available or 
utilized when none is supplied in manure 89 
Broadbalk field 89 
Grassland... 91 
Root-crop soils 92 
Rotation land ... 92 
Rain and drainage (Barn field) 92 
Continuous wheat growing in relation to economy of nitrogen _ 94 
Mineral elements of fertility _ . 96 
Phosphoric acid 98 
General discussion and statement of analytical results on 
Broadbalk soils and subsoils of 1893 .... 98 
Probable limit denoting phosphoric-acid deficiency in soils. . .. 102 
Brief examination of the results obtained for individual plats _ _ 104 
Phosphoric acid in drainage waters . . . .... 110 
General conclusions as to phosphoric acid 111 
Potash.... 112 
General discussion and statement of analytical results on 
Broadbalk soils and subsoils of 1893 ... ... 112 
Brief examination of the results obtained in the case of individual 
plats 117 
Potash in drainage waters 122 
General conclusions as to potash 123 
Section III.— The Broadbalk wheat soils (continued) 125 
Comparison of the results of analyses of the various samples drawn, 
respectively, in 1865, 1881 , and 1893 125 
Total nitrogen and organic carbon 125 
Nitrogen as nitrates ( ' ■ nitric '* nitrogen ) _ 130 
Chlorin 133 
Phosphoric acid _ _ 135 
Potash 138 
Section IV.— The Hoos field barley soils _ 141 
Brief history _ 141 
Total nitrogen . . 142 
Carbon, and ratio of carbon to nitrogen 148 
Nitrogen as nitrates (" nitric" nitrogen) 149 
Chlorin 151 
Phosphoric acid and potash . _ 152 
Phosphoric acid _ 152 
Potash 153 
Section V.— Hoos field leguminous and wheat-fallow soils 155 
Investigations showing the effect of various leguminous crops on the 
nitrogen contents of the soil .. 155 
Section VI. — Barn field root-crop soils 164 
Section VII.— Agdell field experimental rotation soils 169 
Section VIII.— Humus and its nitrogen contents 177 
Conclusion. 180 
