Soil, Crop and Climate Sciences
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Browsing Soil, Crop and Climate Sciences by Subject "Agricultural conservation -- South Africa -- Eastern Free State"
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Item Open Access Influence of cropping sequence on wheat production under conservation agriculture in the Eastern Free State(University of the Free State, 2014-01) Visser, Magdalena Hendrika; Du Preez, C. C.; Barnard, A.English: Crop rotation is one of the pillars of conservation agriculture (CA). It has been adopted moderately in the summer rainfall area of South Africa, but the adoption of conservation tillage has been very slow. It has been observed that research information on crop rotation helped with the adoption of the CA concept in the Western Cape. Limited research has been done on crop rotation in the Eastern Free State. This study used the crop matrix trial design to evaluate the impact of different cropping sequences in a CA system on the growth, development, yield and quality of wheat as target crop. The profitability and production risk of the different crop rotations were also determined. Only preceding summer crop sequences had a significant (P≤0.1) influence on the yield parameters of the final wheat crop. For the final wheat crop three preceding sequences, namely sorghum × soybean, maize × sunflower and soybean × maize, led to a lower (P≤0.1) number of plants and ears, with a lower biomass and residue yield unit area. Although the poorest response was always recorded on the preceding sorghum × soybean sequence plots, it did not differ significantly from those of the other two crop sequences. The final wheat crop also had a significantly higher TKM and harvest index on preceding sorghum × soybean sequence plots. It was concluded that the lower number of plants on these plots could be attributed to lesser in-row competition for water and nutrients, which resulted in bigger and heavier wheat kernels with a higher TKM. The study confirmed previous research, namely that the final wheat crop planted on second season sunflower plots had a significantly (P≤0.1) higher number of ears m-2, with a better N(grain) use efficiency. That resulted in a significantly higher grain protein content. However, the yield of the final wheat crop did not differ between plantings on second season summer crop plots. Rotation with oats is often recommended to reduce Take-all, a soil-borne disease of wheat. It was found that the final wheat crop planted on second season oats plots had a significantly lower seedling number, with fewer ears and a lower grain yield per unit area. The wheat plants also had a lower (P≤0.1) precipitation use efficiency and grain nitrogen use efficiency, which led to a lower accumulation of grain protein. It was concluded that oats has a negative influence on wheat yield in a rotation system and that the crop should only be used as a break crop against Take-all. Thirty two of the 50 crop rotations had a total profit margin above the chosen target income of R1,000 ha-1. The soybean × maize × wheat rotation gave the highest total profit of R7,549.76 ha-1, while the sorghum × dry bean × wheat rotation realised the highest total loss of R1,903.93. Maize had a stable yield over two seasons, while the yield of the other four preceding summer crops posed a higher production risk under rainy conditions (pod shattering in dry bean and soybean crops), or potential bird damage situations (sunflower and sorghum). The crop matrix technique proved to be a reliable method to generate more information on cropping sequence in the same trial over a much shorter period. A multi-disciplinary approach in future cropping sequence research will help to provide producers with reliable information. If crop sequences can be proven to be effective at research level, clear guidelines and recommendations can be developed to help producers in implementing conservation tillage more successfully in the Eastern Free State.