Modelling the application of chemicals in box potato stores

Abstract

Chemicals are applied in crop stores for the control of diseases and, in the case of potatoes, sprouting. Non-uniform deposition of chemicals on crop surfaces can lead to excessive chemical residues in parts of the store and impaired efficacy in those parts of the store where deposition is low. With the aim of improving the efficiency of chemical applications, this paper presents a transient three-dimensional model consisting of the mass, momentum and energy equations which were solved to predict the air flows, temperature and moisture changes of the air and crops and the movements and deposits of small airborne particles of chemical in box potato stores. The crop was treated as a porous medium and the interaction between the air flow and crop was described by the Ergun equation. The movements of three sizes of chemical particles were predicted and the results validated against measurements of deposits of CIPC (a common potato sprout suppressant) in a 3-tonne experimental store. The predictions showed good agreement with the measured trends in the spatial variation of deposits. Measured deposits varied between 16.3 and 176.0 mg CIPC per kg of potatoes while predicted values varied between 13.1 and 140.3 mg CIPC per kg of potatoes. The largest difference between measured and predicted deposit was 37.2%.