X. Agricultural, botanical, and chemical results of experiments on the mixed herbage of permanent meadow, conducted for more than twenty years in succession on the same land.—Part I
In the experiments at Rothamsted with different manures, wheat has now been grown for 36 years in succession on the same land, barley for 28 years, and oats for nine years. Somewhat in like manner, but with some breaks, beans have been grown over a period of more than 30 years, clover for many years, and "root crops” (turnips, sugar-beet, or mangel-wurzel) also for more than 30 years. Each of these individual crops has exhibited certain distinctive characters under this unusual treatment. But, withal, those of the same natural family—wheat, barley, and oats, for example—have shown certain characters in common; those of the Leguminous family characters widely different; whilst the so-called root-crops, belonging to the Cruciferous and Chenopodiaceous families, have exhibited characteristics differing from those of either the Gramineæ or the Leguminosæ. Compared with the conditions of growth of any one of these individual crops grown separately, those of the mixed herbage of grass land are obviously extremely complicated. Thus, it comprises, besides numerous genera and species of the gramineous and leguminous families, representatives also of many other natural orders, and of some of great prominence and importance as regards their prevalence and distribution in vegetation generally. And if, under the influence of characteristically different manuring agents, as has been the case, there have been observed notable differences in the degree of luxuriance of growth, and in the character of development, even between closely allied plants when each is grown separately, and much greater differences between the representatives of different families when so separately grown, might we not expect very remarkable variations of result when different manures are applied to an already established mixed herbage of perhaps some 50 species growing together, representing nearly as many genera, and more than 20 natural orders? Such—far beyond what could have been anticipated-—has been the case in the experiments to be described. So complicated, indeed, have been the manifestations of the “ struggle ” that has been set up, that even after more than 20 years of laborious experiment, both in the field and in the laboratory, and following up both the botany and the chemistry of the subject, we can hardly claim to have yet done much more than reach the threshold of a very comprehensive enquiry. Still, we hope to establish some points of general interest, and possibly to indicate promising paths of future research.