Designing improved plant types for the semiarid tropics: agronomists’ viewpoints

Abstract

The unpredictable and serious water constraint to erop produetion in the semiarid tropics poses a eonsiderable challenge to the design of improved plant types. In this paper, simulation models of the eontrasting crops, sorghum, maize and kenaf, and long-term climatie data were used to assess the value, in terms of both yie1d and risk, of different plant designs at a semiarid site in northern Australia.

The impact of three erop improvement strategies, modified phenology, improved yield potential and enhaneed drought resistance, on erop production was quantified. There was no clear yield advantage of the modified traits in all years, and the choice of plant type would depend on attitude to risk. Using a mean-standard deviation space, risk-efficient cultivars were selected as dominating other cultivars either by their higher mean yield or lower standard deviation.

Relative to our standard eultivars and site, simulated earlier maturity tended to improve yield in the lower yielding years and increased yield stability, in sorghum and maize, but not in kenaf. In all species, higher yield potential was advantageous, both in terms of yield and risk, despite the severe water limitation. However, there were species differenees in the value of improved designs based on drought resistanee traits.