Soil sustainability is a long-term goal. Although physical and chemical properties of soil
have been utilized extensively to evaluate soil quality, the application of biological
indicators is becoming more important. In order to assess soil quality, soil enzymes and
other biological parameters need to be considered.
In semi-arid Bethlehem, South Africa, samples were taken at a wheat (Triticum aestivum L.)
monoculture trial which was established in 1979 by the Agricultural Research Council-Small
Grain Institute. The treatments were: no-tillage (NT), stubble-mulch (SM), and conventional
tillage (CT); all paired with chemical weed control, the absence of burning residues, and 40
kg nitrogen ha-1 as limestone ammonium nitrate with single superphosphate as the
fertilizer sources. The study period lasted from October 2010 to October 2011 with eight
sampling times conducted over this year and two depths sampled (0-5 cm, 5-10 cm). Oat
(Avena sativa L.) was growing in the plots from the start of the study until December 2010
when it was harvested. A fallow period then lasted until the planting of wheat in August
2011 which was harvested after the end of the study period.
Potential enzyme activities were assayed for β-glucosidase, urease, acid- and alkalinephosphatase,
and dehydrogenase at all eight sampling times, along with soil texture, total
carbon, total nitrogen, Olsen-extractable phosphorus, and pH. Whole microbial community
profiling using BIOLOG EcoPlatesTM was employed at the first sampling time and
phospholipid fatty acid (PLFA) analysis for the first, third, and fifth sampling times.
It was found that NT and SM had higher values than CT across all enzymes except alkaline
phosphatase, which ranked NT higher than both SM and CT. BIOLOG EcoPlatesTM and PLFA
showed similar results across tillage treatments. Microbial biomass, estimated from both
potential dehydrogenase activities and PLFA values, was higher in NT and SM than in CT. Over the study period the values for all parameters varied but the average ranking of tillage
treatments stayed consistent. In comparing the two soil depths, soil quality was easily
shown to be higher in NT and SM in the 0-5 cm depth, but often in the 5-10 cm depth the
differences faded. Potential acid phosphatase activity was the only measured parameter
which was consistently higher in the 5-10 cm depth.
If the parameters can be used as an index of soil quality, then it can be accepted that NT
has higher quality than CT and often SM has higher quality than CT, but is not at the same
level as NT; it can then be recommended that in semi-arid South Africa, NT will enhance
soil quality under a monoculture cropping practice.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-05272013-113557 |
| Date | 27 May 2013 |
| Creators | Clayton, Hannah Gudrun |
| Contributors | Mr OHJ Rhode, Mrs E Kotzé, 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-05272013-113557/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. |
Page generated in 0.0054 seconds