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 (Pâ¤0.1) influence on the
yield parameters of the final wheat crop. For the final wheat crop three preceding
sequences, namely sorghum à soybean, maize à sunflower and soybean à maize, led
to a lower (Pâ¤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 à 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 à 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 (Pâ¤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 (Pâ¤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 à maize à wheat rotation gave the highest total
profit of R7,549.76 ha-1, while the sorghum à dry bean à 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.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-08212014-144141 |
| Date | 21 August 2014 |
| Creators | Visser, Magdalena Hendrika |
| Contributors | Dr A Barnard, Prof CC du Preez |
| 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-08212014-144141/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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