The application of geochemical analysis in archaeology provides a better understanding of ancient human activities. This paper presents the results of geochemical multi-element, LOI, MS, and geochronological analyses of a cultural layer at the Voorthuizen (The Netherlands) archaeological site. The study has revealed a difference in the geochemical composition of an occupational surface in the Iron Age settlement and an early Roman Time agricultural horizon. The former is enriched in Ba, Sr, Rb, Th, Cl, and Mg, while the latter displays elevated P, Pb, Ni, Mn, and V values. The study has provided a deeper insight into the agricultural techniques applied at the Voorthuizen site and on the so-called Celtic Fields, known as ancient field systems dating from the same period and widespread throughout north-west Europe. It seems that household waste was not used as a fertilizer at Voorthuizen, while the application of manure is characteristic of Celtic Fields. However, phosphorous values in the Voorthuizen agricultural horizon are comparable to those in the Celtic Fields, suggesting similar sources of P in both cases. Elevated Si and “mobile” Fe, Mn, V, Pb, As, and Sn, along with higher MS measurements, are indicative of the use of extra mineral matter for the fertilization of the Voorthuizen ancient arable field.