Did Soil Fertility Decline in Medieval English Farms? Evidence from Cuxham, Oxfordshire, 1320-1340

It has been suggested that during the century before the Black Death the fertility of the soil on English farms was declining, leading to decreased food production and increased mortality. We here estimate nutrient balances for a manorial demesne, to determine whether the nutrient status of the soil was declining. We calculate the losses of nitrogen, phosphorus and potassium in the produce during 1320-1340, using information from the demesne accounts. The main inputs of phosphorus and potassium would be from weathering of rock; these would probably have been enough to balance the losses of potassium but not of phosphorus. Potential inputs and non-produce losses of nitrogen are so large that we cannot say whether the demesne was in balance for nitrogen. The paper thus points to phosphorus as the key element likely to have led to falling soil fertility at this time.