ABSTRACT
The plant species present in natural ecosystems are competing for resources, and the patterns of allocation of these resources between the different components are what defines the system. Resource-poor ecosystems tend also to be speciespoor, but often demonstrate high levels of specific adaptations to sub-optimal conditions or extremely high efficiencies of capture and utilization of scarce resources. By contrast, domesticated species and varieties are subject to radically different constraints. Effective cultivation and management maximizes ‘added value’ (the difference in the societal costs of the inputs and outputs) and allocates resources accordingly. If those societal costs equate (as they often do) to the difference between the simple monetary costs of production and the rewards of sale, then individual producers will tend to maximize production until demand is saturated. Such systems will tend towards increased inputs and towards the production of plant varieties which respond to such inputs. For example, in the period between 1900 and 1980, application of nitrogenous fertilizer to UK crops rose eightfold. Over the same period, average cereal yields doubled (Leach, 1976). The cultivars developed in the 1970s responded better to high available soil N than did earlier varieties, but the nitrogen efficiency of production (amount of grain produced per unit of added N) actually fell. Concerns over environmental pollution and a temporary local abundance of food in Western Europe has increased the perceived significance of input efficiency when compared with production efficiency, but an effective methodological basis for improving the efficiency of resource capture and allocation in cultivated plants does not yet exist.
