ASSESSING PLANTING OPPORTUNITIES IN SEMIARID SUBTROPICAL ENVIRONMENTS

High rainfall variability in the subtropics makes rainfed crop product ion a risky enterprise. Planting opportunities are limited by the amou nt and timing of rainfall. Farmers face a decision of whether or not t o plant when an opportunity occurs. This decision depends on the likel y yield from different crops and cultivars, the probability, of obtain ing another planting opportunity, and the yield expectation from that later planting. In this paper, long-term climatic data for six locatio ns in subtropical Australia were used to (i) compare criteria for iden tifying planting opportunities, and (ii) determine the frequency of oc currence of planting opportunities and the duration between opportunit ies. Although the occurrence of planting opportunities varied among mo nths and locations depending on the criterion used very few planting o pportunities occur in these environments and the duration between oppo rtunities is relatively long. The mean number of planting opportunitie s was never greater than one for any month at any location, and freque ntly (30-70% of years) no planting opportunities occurred in a given m onth. The highest probability of another planting opportunity occurrin g in the 30 days following an opportunity was 60%; in most cases the p robability was much less. While the results are specific to the locati ons analyzed, the approach developed is generally applicable where qua ntifying the risk of planting opportunities is important to decision-m akers.