for Tioenty Years in succession on the same Land. 155 
an excess of straw, by the nitrato, as compared with the ammonia- 
salts. The explanation of the difference of effect with the two 
crops would seem to be, that whilst for the wheat the nitrate was 
not sown until the spring, the ammonia-salts had been sown in the 
previous autumn, and were subject to a considerable loss by drain- 
age during several extremely wet periods of the winter, when 
there was no growth, and before the nitrate was sown. It will 
be remembered that a similar result was obtained with wheat 
after the wet winter of 1868-9 ; and also in other years, as referred 
to in the foot-note at p. 146. 
Finally, it will be observed that the results obtained in the 
experimental fields are in the main in accord with the reports of 
the crops of the country at large, in showing a considerably 
deficient wheat-crop, and a barley-crop above the average both 
in quantity and quality, though the twentieth in succession on 
the same land. 
Comparison of the Produce of Barley in the least, and in the most, 
productive Season of the Tioenty. 
The foregoing records of the characters of the seasons, and of 
the produce of barley in each individual year of the twenty, with 
the comments made upon them, very forcibly illustrate the 
diversity between one season and another, and how very varied 
is the final result, dependent on the mutual adaptations of heat, 
moisture, and stage of growth of the crops. In no two years has 
one and the same manure yielded precisely the same result both 
as to the quantity and the quality of its produce. Nor have 
the seasons which have been more or less favourable than the 
average for one description of manure, been equally favourable or 
unfavourable for other descriptions. 
Referring to the previous discussion, and to the materials 
brought together in the Appendix-Tables (pp. 163 — 185), for 
any more detailed consideration of the subject, it must suffice 
here, by way of illustration and summary, to call special attention 
to the produce yielded by the same description and quantity of 
manure in the least, and in the most, productive season of the 
twenty. 
Table XXII. (p. 156) shows, side by side, the quantity and 
quality of the produce obtained in 1854, which was upon the 
whole the most, and in 1856, which was upon the whole the 
least, productive of the twenty seasons ; also the difference 
between the two. For the purposes of this illustration, the same 
selection of plots has been made as in the foregoing consideration 
of the produce of each individual season. It is true that one or 
other of the descriptions of manure specified may have given more 
com, or a higher weight per bushel, or more straw, in some other 
