Verdoodt, A.Van Ranst, E.Van Averbeke, W.2025-04-142025-04-142003-12-040266-0032 (P)1475-2743 (E)https://: 10.1079/SUM2003216https://hdl.handle.net/20.500.14519/1595Hierarchical crop growth models can contribute significantly to land quality research because the yield gap between the estimated optimum and the actual crop production has been identified as a major land quality indicator. This study describes a three-level, hierarchical crop production model, simulating radiation-thermal, water-limited and natural production potentials of annual crops. Input requirements have been kept low to ensure its applicability to developing regions, which often have access only to limited data. The simplicity of this model also has disadvantages: inconsistencies have been reported when applying this model in semiarid regions, which are characterized by very irregular rainfall patterns. Revision of the water balance, which simulates the availability of water, was required. The modified model was validated using the experimental yields of maize and sun¯ower in Guquka, a semiarid region of South Africa. Yields were estimated very well, possible improvements to crop production were identified and implications for land-use planning highlighted. Yield gap analysis revealed that radiation, sunshine and temperature are favourable for crop production, but the heavy dependence on rainfall makes the region very vulnerable to drought, with devastating impact on yields. The generally low chemical soil fertility further reduces crop performance.372-380 PagesenAttribution-NonCommercial-ShareAlike 4.0 Internationalhttp://creativecommons.org/licenses/by-nc-sa/4.0/Yield gap analysisLand-use planningmaizeSun¯owerSemiarid regionSouth AfricaArticle