If you love history, then this is a must-read paper for you! It starts with a wonderful quote: “According to Tacitus, a Roman historian around AD 100, one of the significant differences between the Romans and the Germanic tribes was that the latter surprisingly did not try to heighten the fertility of their soil, just because they had such an abundance of arable land and were too lazy to care anyway.”
Times have changed and those lazy Germans learned a thing or two about managing their soils. Yet, over two thousand years ago, Roman farmers learned to improve their soils by spreading manure, green manuring, and applying mineral fertilizers and other materials. The idea to restore an exhausted field to new strength by adding some sort of fertilizer was widespread, and so was the understanding that this contributed to crop yields.
The paper includes a table that shows the ranking of different manures in Roman times, which is remarkably similar to what modern science suggests nowadays. Pigeon and other bird manures were rated highest, followed by human excrement! Green manuring was widespread, mainly through growing lupines, beans, or vetch in years when the land would have been left fallow, or in vineyards. Today we call that ‘cover cropping’. The most common type of mineral fertilizer appears to have been ash, but various kinds of sediments were applied too.
The expert ways of Roman farming led to a nutrition level of the working class population which was only met again as late as the mid-20th century. The average height of a male person in Roman times was 168 cm, whereas the mean height of an early modern male European was in the low 160 cm range. Reading this paper, I felt that many of the lessons learned long ago are still valid today. We should certainly not forget them in the current public debate about food security, nutrition, soil health, and the environment.
