4 Cultivation on the banks of the Celtic fields
Brongers (1976, 71) was one of the first to point to the use of the banks for cultivation, considering “the rather high percentage (40%) of land otherwise not used”. After a period of lying fallow the soil in the banks should have recovered and could be used for agriculture.
The data of Gebhardt (1976) showing the highest phosphate values occurring in the banks and not in the fields, made Zimmermann (1976) argue for the possibility that the banks, in stead of the spaces in between, had been used for agriculture. The same holds true for the Celtic field of Zeijen (Spek et al. 2003). The analyses of Øster Lem Hede excavations in 2001 and 2007 have not yet been published. However, there is a list of analyses carried out by K. Dalsgaard (oral communication), concerning the 2001 excavation, pointing in the same direction.
Micromorphological research in the Celtic field of Zeijen has shown that regular soil tillage took place at the ridges, with an intensification in the top layers, which also show the highest phosphate values.
But when did this cultivation of the banks begin? Zimmermann (1976, 88) writes that the use of the banks for arable, wide and humic through long-lasting traditional cultivation could only have occurred in the last phase of the Celtic field. They were then probably used for cultivation of specific plants and prepared by necessary manuring, while the fields in between were used for extensive agriculture.
However, Behre (2000, 140) and followed by Spek et al. (2003) suggest another scenario. According to Spek et al. the start is with fields without banks, but probably some other kind of boundary in the Late Bronze Age and Early to Middle Iron Age. Zimmermann has proposed to call these early Celtic fields instead of pre-Celtic fields (Behre 2000). The development of the banks would have occurred in the last phase (Late Iron Age, Early Roman period), and it was mainly in these last phases that the banks were intensively cultivated. Behre (2000) is less specific concerning the dating of this cycle, he writes only of a later phase for the formation of the banks and for cultivation on them in a younger phase.