Assessing planting opportunities in semiarid subtropical environments

Abstract

High rainfall variability in the subtropics makes rainfed crop production a risky enterprise. Planting opportunities are limited by the amount and timing of rainfall. Farmers face a decision of whether or not to plant when an opportunity occurs. This decision depends on the likely yield from different crops and cultivars, the probability of obtaining another planting opportunity, and the yield expectation from that later planting. In this paper, long-term climatic data for six locations in subtropical Australia were used to (i) compare criteria for identifying planting opportunities; and (ii) determine the frequency of occurrence of planting opportunities and the duration between opportunities. Although the occurrence of planting opportunities varied among months and locations depending on the criterion used, very few planting opportunities occur in these environments and the duration between opportunities is relatively long. The mean number of planting opportunities was never greater than one for any month at any location, and frequently (30–70% of years) no planting opportunities occurred in a given month. The highest probability of another planting opportunity occurring in the 30 days following an opportunity was 60%; in most cases the probability was much less. While the results are specific to the locations analyzed, the approach developed is generally applicable where quantifying the risk of planting opportunities is important to decisionmakers.