In order to meet the food requirements of an ever-growing population, agricultural production needs to increase. This is especially true for maize production in South Africa as it is the staple food for a large portion of the rural indigenous population. Climate variability is one of the major causes of volatility in agricultural production and causes uncertainty for maize production at the subsistence level. Small-scale farmers within the Modder River Catchment have a poor quantative understanding of seasonal rainfall and their relationship to their management strategies. In countries prone to high seasonal climatic variability, crop growth models such as APSIM can be used to assist farmers in making decisions regarding the suitability of different management strategies. This means that climate forecasts could be translated into crop production, while alternative management practices would be associated with different economic outcomes. The opportunity arose to aid these farmers by optimising rainfed maize production. Subsequently, the objective of this study was to produce an advisory for small-scale rainfed maize farmers in the Modder River Catchment.
Historical rainfall data (1950-1999) from selected rainfed maize production areas within the Modder River Catchment were used to calculate the seasonal rainfall totals for October to December (OND) and January to March (JFM). During dry seasons, the expected rainfall totals was less than 101.0 and 147.5 mm for OND and JFM, respectively. During wet seasons, the expected rainfall totals was more than 204.0 and 267.5 mm for OND and JFM, respectively. Recommended management practices were employed to validate APSIM using observed environmental and maize yield data for the 1980/81 to 2004/2005 seasons in the vicinity of Bloemfontein. Maize yields were simulated using two medium growth period cultivars (PAN 6479 and Pioneer 3237) under different planting dates, plant population densities, fertiliser applications and weeding frequencies. The model simulated PAN 6479 better than Pioneer 3237. For Pan 6479, the best set of management practices corresponded to a R2 of 0.66, D-index of 0.89, modelling efficiency of 0.59 and RMSEu/RMSE of 0.88. For Pioneer 3237, the modelling efficiency values under different management practices were negative. Stepwise linear regression was used to select those yield predictors that adhered to a partial R2 value greater than 0.0001 at a significance level of 0.15. In general itâs usually better to plant early (November) regardless of the seasonal rainfall scenarios. Advisories were set up to convey information regarding the best, second best and worst set of management practices under each seasonal rainfall scenario. These advisories also include the related field costs along with potential yields and economic benefits at the 25, 50 and 75% probability levels for each set of management practices. For example, during AN-AN rainfall conditions, the best set of management practices involved planting during 16-30 November and 1-15 November, weeding twice, 50 and 75 kg ha-1 N and using 21 000 and 18 000 plants ha-1 for PAN 6479 and Pioneer 3237, respectively. Farmers would spend R1 798 ha-1 on field costs when planting PAN 6479, while obtaining a yield of 2 854 kg ha-1 and making a profit of R1 972 ha-1 at the 50% probability level. For Pioneer 3237 the field costs would amount to R2 338 ha-1, while realising a yield of 4 232 kg ha-1 resulting in a profit of R3 253 ha-1 at the same probability level. The recommended management practices under various seasonal rainfall scenarios could assist small-scale rainfed maize farmers to increase their yields and maximise the associated profit. Unfortunately, site-specific calibration of APSIM is required against observed sets of climate, soil and yield data for which the associated management practices are known before these advisories can be used by extension officers to advise small-scale farmers within the Modder River catchment.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-08152012-150957 |
| Date | 15 August 2012 |
| Creators | Nape, Kholofelo Moses |
| Contributors | Dr GM Ceronio, Mr AS Steyn |
| Publisher | University of the Free State |
| Source Sets | South African National ETD Portal |
| Language | en-uk |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.uovs.ac.za//theses/available/etd-08152012-150957/restricted/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University Free State or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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