Thesis (MScAgric (Soil Science))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Acidic soils are a major limitation to agriculture worldwide. The Highveld in South
Africa has many acidic soils and several coal burning power stations. These coal
burning power stations generate alkaline fly ash as a waste material and it can thus
serve as an ameliorant to the surrounding acidic soils.
A two year field trial was undertaken to compare fly ash and other calcium
ameliorants to alleviate the effects of subsoil acidity on maize root development. The
field trail was established on Beestepan Farm in Middelburg, Mpumalanga. It
consisted of 24 treatments, each done in triplicate, rendering a total of 72 plots.
The materials used were unweathered fly ash (CCE 10%), calcitic lime (CCE 77%)
and Calmasil (a calcium silicate slag, CCE 99%). Calmasil and lime were applied at
rates of 0-, 1-, 2-, and 4t/ha, while fly ash was applied at 0-, 7-, 14- and 28t/ha. These
treatments were applied to an acidic sandy loam soils in the presence or absence of
4t/ha gypsum.
Beans were harvested after the first season following the application of amendments
and maize was harvested in the second season. Yield, root length, leaf and soil
analysis was undertaken to evaluate the effectiveness of the different liming
materials. The effect of the treatments on fertility indicators such as pH, exchangeable
acidity, Ca and Mg was investigated.
Results indicated that all liming materials increased topsoil pH, soil nutrient and base
status and crop yield in both seasons. Calmasil was the superior liming material in all
respects.
Fly ash increased pH minimally but reduced exchangeable acidity by 12% and 24% in
the first and second seasons, respectively. Fly ash increased topsoil Ca levels from 74
to 102mg/kg and subsoil Ca from 61 to 114mg/kg. Topsoil Mg levels were increased
from 7.3 to 16mg/kg and subsoil Mg was increased from 9.4 to 13mg/kg. The
consequence of these increased nutrients was the subsequent increased foliar uptake
of Ca and Mg. The substantial increase in bean yield from 958 to 1724kg/ha and
maize yield from 5569 to 7553kg/ha following ash application compared well with
results obtained from lime and Calmasil application. This may partly be due to the
presence of additional plant nutrients such as P and K in the fly ash. Dissolution
behaviour of fly ash indicates that upon exposure to acidity the release of micronutrients like B, Co, Cu, Fe, Mo, Mn and Zn occurs, and preliminary data shows
that there is comparatively little concern regarding heavy metal accumulation in
crops.
The application of 4t/ha gypsum had no effect on pH and decreased subsoil acidity
only minimally however, subsoil Ca status and acid saturation levels were
considerably improved which would possibly account for the overall beneficial effect
on maize yield, increasing by an average of 1071kg/ha.
It was not possible to make any conclusions relating treatment application and maize
root length.
This field trial has confirmed that fly ash can be used as an efficient liming material
and that it compares well with traditional liming materials. / AFRIKAANSE OPSOMMING: Suurgronde is ‘n groot beperking tot landbou wêreldwyd. Die Suid Afrikaanse
Hoëveld het menigte suurgronde en verskeie steenkool-aangedrewe kragstasies.
Hiedie kragstasies produseer alkaliese vliegas as ‘n afvalproduk. Hierdie vliegas kan
dus dien as ‘n grondverbeteringsmiddel vir die aangrensende suurgronde.
‘n Tweejarige veldproef was onderneem om vliegas met ander kalsium-bevattende
grondverbetereringsmiddels te vergelyk om die effek van ondergrondse suurheid op
mielies op te hef. Hierdie veldproef was opgeset te Beestepan plaas in Middelburg,
Mpumalanga. Dit het bestaan uit 24 behandelings wat drie keer herhaal was en lewer
dus ‘n totaal van 72 persele.
Die kalkmateriale wat gebruik was, is onverweerde vliegas (KKE 10%), kalsitiese
kalk (KKE 77%) en Calmasil (‘n kalsium silikaat slak, KKE 99%). Calmasil en kalk
was toegedien teen 0-, 1-, 2-, en 4t/ha, en vliegas teen 0-, 7-, 14- en 28t/ha. Hierdie
behandelinge was toegedien tot ‘n suur leemsand met of sonder gips. Gips was
toegedien teen 4t/ha.
Een jaar nadat behandelinge toegedien was, is boontjies geoes en mieles was die
daaropvolgende jaar geoes. Opbrengs, wortel lengte blaar- en grondontledings was
uitgevoer om effektiwiteit te evalueer. Die effek van die behandelinge op indikatore
van grondvrugbaarheid soos pH, uitruilbare suurheid, Ca en Mg was ondersoek.
Resultate dui daarop dat alle kalkmateriale die grond se voedingstof- en basisstatus,
bogrond pH asook gewasopbreng verhoog het. Calmasil was die beste kalkmateriaal
in alle opsigte.
Vliegas het die pH minimaal verhoog, terwyl dit die uitruilbare suurheid verminder
het met 12% en 24% in die eerste en tweede jaar onderskeidelik. Vliegas het bogrond
Ca vlakke vanaf 74 tot 102mg/kg vermeer, sowel as ondergrond Ca vanaf 61 tot
114mg/kg. Bogrond Mg was vermeer vanaf 7.3 tot 16mg/kg, asook ondergrond Mg
vanaf 9.4 tot 13 mg/kg. Die gevolg van hierdie verhoogde voedingstowwe was die
toename van Ca en Mg in die blare van die gewasse.
Die beduidende toename in opbrengste van boontjies vanaf 958 tot 1724mg/kg en
mielies vanaf 5569 tot 7553kg/ha na die toediening van vliegas vergelyk goed met die
resultate van kalk en Calmasil. Dit is gedeeltelik toe te skryf aan die teenwoordigheid
van addisionele plantvoedingstowwe soos P en K in vliegas. Oplossingstudies van
vliegas dui op die teenwoordigheid van mikrovoedingstowwe soos B, Co, Cu, Fe, Mo, Mn en Zn. Aanvanklike data wys dat daar relatief min kommer oor swaarmetaal
akkumulasie in gewasse is.
Alhoewel 4t/ha gips geen effek op pH gehad het nie, en ondergondrondse suurheid
minimaal verminder het, het ondergrondse Ca en gevolglik suurversadiging heelwat
verbeter. Dit mag moontlik as verduideliking dien vir die oorhoofse voordelige effek
van gips op mielie opbrengste, wat verhoog het met ‘n gemiddelde 1071kg/ha.
Oorvleuende omstandighede het daartoe gelei dat geen konkrete afleidings gemaak
kon word oor die wortel lengte van die mielies nie.
Hierdie veldproef bevestig dat vliegas as ‘n effektiewe kalkmateriaal gebruik kan
word en goed vergelyk met tradisionele kalkmateriale.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/4119 |
| Date | 03 1900 |
| Creators | Awkes, Meryl Mandy |
| Contributors | Hoffman, J. E., Fey, M. V., University of Stellenbosch. Faculty of Agrisciences. Dept. of Soil Science. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | 174 p. : ill. |
| Rights | University of Stellenbosch |
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