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Economic benefits of varying maize production strategies
under various seasonal rainfall scenarios
in the Modder River catchment, South Africa
K.M. Nape 1,2 and A.S. Steyn 1
1. Department Soil, Crop and Climate Sciences, University of the Free State, South Africa,
dr.bean@webmail.co.za
2. Agricultural Research Council – Institute for Soil, Climate and Water, South Africa
ABSTRACT
The Modder River catchment is characterised by high rainfall variability which leads to a mismatch between water
demand by crops and water supply by rainfall. It is understood that farmers aim to employ a farming system that
maximizes production and minimizes risk whilst making a profit. Reducing the risk associated with rainfall
variability could have significant impacts on crop production. The main objective of this study was therefore to
investigate the economic benefits of different maize production strategies using a crop model against the backdrop
of various seasonal rainfall scenarios.
Seasonal rainfall totals were calculated from 1950-1999 for selected quaternary catchments within the Modder
River catchment for two 3-month periods (October, November, December and January, February, March)
comprising the maize growing season. Each 3-month period were subsequently categorized as above-normal (AN),
near-normal (NN) or below-normal (BN). A crop model (APSIM) was used to simulate maize yields under various
management strategies (i.e. choice of cultivar, plant density, planting dates, fertilizer application and weeding
frequency) for all the seasons. The simulated maize yields were analysed in order to determine the economic
benefit of applying different management decisions.
During above-normal rainfall seasons (AN-AN) the best practices involved a plant density of 21 000 plants/ha, a
fertiliser application of 50 kg/ha N and weeding twice for a crop planted during 16-30 November. This would lead
to a 50% probability of obtaining a profit of R2 319/ha. During dry seasons (BN-BN) the most productive
combination included a plant density of 12 000 plants/ha, fertiliser application of 35 kg/ha N and weeding twice for
a crop planted during 1-15 November. This would lead to a 50% probability of obtaining a mere profit of R497/ha.
The results indicate that management strategies guided by seasonal rainfall forecasts could aid in achieving
sustainable rainfed maize production.
KEYWORDS: maize production strategies, seasonal rainfall scenarios; crop model
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