Excerpt from Results of Experiments at Rothamsted, on the Growth of Potatoes, for Twelve Years in Succession on the Same Land, Vol. 4: A Lecture Delivered July 27, 1888, at the Royal Agricultural College, Cirencester

But the great decline over the third four years, under all conditions of manuring, even where there was a full Supply of both nitrogen and mineral constituents, Shows that the seasons were then less favourable for luxuriant growth. Doubtless, too, with the mineral manures alone, the available supply of nitrogen within the soil, and with the nitro genous manures alone, the available supply of mineral constituents, had become deficient.

A point of considerable interest brought to View in the last column of the Table is, that there was, under every condition of manuring, a very much larger proportion of diseased tubers over the first four years when the Rock was grown, than afterwards with the Champion. The very bad result over the first four years was, however, doubtless in great measure due to the character Of the seasons also, which included some exceedingly wet and unfavourable ones. With the Champion, there was, upon the whole, a less proportion of diseased tubers over the third than over the second period of four years. It is true, that the later years were generally drier, ' and therefore less favourable, both for luxuriance of growth, and for the development of the disease. Nevertheless, it is of interest to Observe that the amount of disease was not enhanced by the continuous growth Of the crop on the same land, as is frequently assumed to be the case. It is further of interest to note that, with the highest manuring, and the most luxuriant growth, that is where ammonium salts or nitrate of soda, and the mixed mineral manures, were used together, there was, over the second four years, even with the Champion, a much higher proportion of diseased tubers than with any of the other manures though, over the third period, of drier seasons, the proportion was about as low as under the other conditions of manuring.

In the summary at the bottom of the Table is given the average produce over the total period of twelve years, under each Of the different conditions as to manuring. It will suffice to call special attention to the column Showing the total produce of tubers - good, small, and diseased - and to the last column, showing the average percentage of diseased tubers, under each condition of manuring.

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