The Conveyor Belt Model for Fruit Bearing Vegetables: Application to Sweet Pepper Yield Oscillations

摘要

An absolute-sink-strength regulated crop growth model was developed to address the problem of sweet pepper synchronised yield oscillations (flushes). Yield oscillations in sweet pepper production are caused by crop physiology (fruit abortion at timesof heavy fruit load per plant) and result in periodic oversupply at the market level, as synchronisation occurs within, but also between glasshouses, due to weather conditions. Smart growers may not only aim to maximise production yields, but also to desynchronise their temporal yield pattern from that of the market, in order to target higher prices during low supply periods. The parameters that growers can change are those concerning pruning, harvesting at a green marketable stage, and climate control,whereas breeders may adjust physiological constants. The model consists of three ordinary differential equations and two partial differential equations, with fruit dry weight as second independent variable. Both the number of fruits per square meter andthe average ripeness of fruits with a particular weight are discretised into 40 weight classes. Sinks, from vegetative, fruit growth and maintenance draw on a common assimilate pool, eliminating the need for a relative-sink strength 'top-down' partitioning approach. The vegetative biomass is considered as two parts, for growing and non-growing biomass respectively. The model arrives at plausible output values for known biological variables and simulates assimilate-dependent abortion and thus fruit setexplicitly, although not yet fully validated. A bifurcation analysis is conducted to identify the regions in parameter space where either yield oscillations or a stable growth pattern occurs.