Guideline for constructing nutrient balance in historical agricultural systemes (and its application to three case-studies in southern Spain)

The purpose of this paper is to provide interested researchers with a simple tool to evaluate the efficacy of different methods of fertility replenishment that have accompanied and made possible the contemporary agriculture. We propose a nutrient balance model created especially to be applied to the past. In the first part of this working paper each term in the balance is defined and specified the information the user must input into the model. The second part of this paper reports on the application of this methodology based on the balances of nutrients to the evolution of Andalusian agriculture since the mid 18th Century. The nutrient balances show the effects of agrarian growth in an environmentally limited context, offering reasonable doubt regarding the medium and long-term stability of certain forms of cultivation. The balances show that in the last decades of the 19th Century, productive intensification had reached its ceiling, with livestock numbers levelling off or clearly declining. The deficits of nutrients even began to exceed the fertilisation capacity of the available livestock. The intensification applied in unfertilised rotations and crops had to be sustained through the extraction of soil reserves.