A simple agroclimatic index to delineate suitable growing areas for rainfed maize production in the Free State Province of South Africa

Abstract

The risk associated with climate and its variability over the Free State Province of South Africa is the major determining factor for agricultural productivity and has a major impact on food security in that region. In this study, suitability of planting a rainfed maize crop in the province was investigated using an agroclimatic index. The index is formulated from the combination of frost probability over the growing period, non-exceedence probability of onset of rains and agricultural drought index. The Poone AgroClimatic Suitability Index (PACSI) was introduced to integrate the major climate hazards affecting maize production in the Free State. The index was further used to delineate suitable areas across the Free State for planting a maize variety requiring 1420 growing degree days (heat units) to maturity. The resulting maps show areas of high maize production suitability over the Thabo Mofutsanyane district from mid-October to early November. Areas over Fezile Dabi and northern parts of the Lejweleputswa district also showed high suitability of maize especially from mid-November to the end of December. The western and southern Xhariep district is not suited for planting maize while other marginal dryland maize production areas include western Motheo, southwestern Lejweleputswa and most parts of the central and eastern Xhariep districts. Comparison of the index with maize yields and crop model outputs shows a good agreement in most stations and areas respectively and thus, PACSI can be used to delineate areas suitable for planting maize in the Free State Province of South Africa.