An incremental model for conversion of solar energy in agricultural systems

Abstract

Photosynthetic conversion of solar energy in agriculture leads to biomass storage of the intermittent solar irradiation. To explain and anticipate the data obtainable from prevailing soil-water-plant systems, an incremental model is devised in which various sectors present in the system are viewed as a series of discrete ‘compartments’ between which material and energy flow. Each compartment is to represent one of the main parameters encountered and their relations are assumed to be characterized by constant-coefficient linear differential equations. Presently, various coefficients that appear in the governing equations of a computerized version of this model are determined for alfalfa cultivation. The results indicate the balance and inter-relation of all the elements involved, and lead to the prediction of biomass energy yield per unit farm area, efficiency of photosynthetic conversion, and the cycling of the main nutrients. Furthermore, the changes that occur in the ecosystem parameters as a result of various operational schemes are predicted and it is shown that long-term soil pollution may occur as a consequence of soil contamination with excessive amounts of nutrients. One may thus regard the proposed model as a mathematical tool for determining the energy conversion capability of various agricultural systems, and obtain from it valuable guidance as to the choice of optimum farm management and type of crops suitable for any defined and specific purpose.