553
II. Units for determining commercial value of manures and
cash prices of manures 554, 555
III. Manurial value of nitrogen and potash in different
substances 556
IV. Comparative manurial value of different forms of
nitrogen and potash 557
V. Lawes' and Gilbert's tables for calculating unexhausted
value of manures 559

CHAPTER XXVI.--THE ROTHAMSTED EXPERIMENTS.

Nature of experiments on crops and manures 561
Soil of Rothamsted 561
Table I. List of Rothamsted field experiments 562
Wheat experiments--
Unmanured plots 562
Wheat grown continuously on same land (unmanured) 562
Table II. Results of first eight years 562
Table III. Results of subsequent forty years 562
Table IV. Wheat grown continuously with farmyard
manure (14 tons per annum) 564

Table V. Wheat grown continuously with artificial
manures 565
Table VI. Experiments on the growth of barley, forty years,
1852-91 566
Table VII. Experiments on the growth of oats, 1869-78 567
Table VIII. Experiments on root crops--Swedish turnips 568, 569
Table IX. Experiments on mangel-wurzel 568, 569
Table X. Experiments with different manures on permanent
meadow-land, thirty-six years, 1856-91 570
Table XI. Experiments on the growth of potatoes--average for
five seasons, 1876-80 571
Table XII. Experiments on growth of potatoes (continued)--
average for twelve seasons, 1881-92 572

* * * * *

INDEX 573

PART I.

HISTORICAL INTRODUCTION

MANURES AND THE PRINCIPLES OF MANURING.

HISTORICAL INTRODUCTION.

Agric