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THE INFLUENCE OF CONTACT TIME AND MINERAL TYPE ON THE EXTRACTABILITY AND AVAILABILITY TO PLANTS OF RADIOSTRONTIUM AND RADIOCALCIUM FROM SOILSJohnson, Gordon V. January 1965 (has links)
No description available.
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SOIL NITROGEN FORMS IN RELATION TO CROP RESPONSEYacoubi, Mohamed Abdouh, 1945- January 1974 (has links)
No description available.
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Plant uptake of iron, copper, and zinc from soils as influenced by source materialsGreene, Robert Edward, 1930- January 1960 (has links)
No description available.
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Soil conditions of the Jornada red loamy sand of southern New Mexico; as related to the degree of invasion by mesquite, Prosopis glandulosaValentine, Kenneth Alva, 1906- January 1941 (has links)
No description available.
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Tree growth and edaphic control in the south Rupununi Savannas, Guyana.Hutchinson, Ian January 1971 (has links)
No description available.
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The role of snow cover in the nutrient regime of oligotrophic, subarctic soils /Manuel, Patricia M. (Patricia Marie) January 1983 (has links)
No description available.
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Phosphorus sorption behaviour of some South African water treatment residues.Norris, Matthew. January 2009 (has links)
Water treatment residues (WTRs), which are by-products from the production of potable water, are chemically benign, inorganic materials which are suitable for disposal by land application. Their high phosphorus (P) sorption capacities have, however, generated some concern in an agronomic context where P is recognised as a growth limiting plant nutrient. The extent to which labile P pools are reduced or enhanced by WTR amendments is, therefore, a central issue with respect to their disposal by land application. Therefore, the aim of this study was, through the use of empirical adsorption isotherm equations and chemical fractionation of P within the residues, to investigate the chemical processes responsible for the retention and release of P from 15 South African WTRs. Chemical characterisation revealed considerable variation in residue properties relevant to P sorption-desorption processes. pH, exchangeable Ca and organic carbon content ranged from 4.77 to 8.37, 238 to 8 980 mg kg-1 and 0.50 to 11.6 %, respectively. Dithionate, oxalate and pyrophosphate extractable Al fractions ranged from 741 to 96 375, 1 980 to 82 947 and 130 to 37 200 mg kg-1, respectively. Dithionate, oxalate and pyrophosphate extractable Fe ranged from 441 to 15 288, 3 865 to 140 569 and 230 to 90 000 mg kg-1 respectively. Therefore mechanisms of retention were hypothesised to be residue specific, being dependent on the unique chemical properties of the sorbent. Elevated Ca and amorphous Al and Fe concentrations did, nevertheless, suggest that all residues had the capacity to adsorb high amounts of P and to retain this P in forms unavailable for plant uptake. These arguments were confirmed by the sorption study where labile P was, for all residues, found to constitute a small fraction of total applied P even at high application concentrations (128 mg P L-1). Sequential P fractionation revealed that most of the inherent P (which ranged from 1 149 to 1 727 mg P kg-1) and applied P were retained in highly resistant mineral phases or fixed within the organic component. Thus P replenishment capacities were restricted even though residual P concentrations were often within adequate ranges for plant growth. Phosphorus adsorption data was described by four empirical adsorption isotherm equations in an effort to determine possible mechanisms of retention. Sorption data was, for most of the WTRs, described by the Temkin isotherm while the Freundlich and linear models fitted data for two residues each. A key finding was that the distribution coefficient (Kd) tended to increase with the quantity of P adsorbed (S) as opposed to decrease or remain constant in accordance with model assumptions. Therefore, the models could not be used for mechanistic interpretation, even though they provided excellent descriptions of the data. The direct relationship between Kd and S suggested a mechanism of retention involving the activation of sorption sites. This notion was supported by the fractionation study which showed that P addition results in the transfer of an increasing quantity of organically bound P to resistant residual forms. Model affinity parameters were strongly correlated to dithionate and pyrophosphate extractable Al and Fe which suggested that P was adsorbed primarily through ligand exchange mechanisms. The mobility of P bound to organic fractions did indicate that P was retained through weaker forces of attraction such as monodentate ligand exchange, charge neutralisation or proton transfer. Evidence to support the notion that P is immobilised through the formation of Ca phosphates was lacking. Based on P fractionation data, it was suggested that strong chemisorption mechanisms and the diffusion of P into WTR micropores were largely responsible for the minimal quantity of P desorbed by disequilibria desorption processes. A greater quantity of P was desorbed in the presence of oxalate and citrate which suggested that plants may increase bio-available pools through the release of organic ligands. Phosphorus desorbed in the presence of these ligands did, however, decline with P addition which confirmed that the affinity of the WTR surface for P increases with P application. Therefore, it was concluded that the application of P to WTRs is an uneconomical process unless sorption sites are already saturated or immobilisation processes are inhibited. In light of these findings, it was suggested that the absence of plant P deficiencies under the field application of WTRs is due primarily to inhibited sorption. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.
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The effects of land use and management practices on soil microbial diversity as determined by PCR-DGGE and CLPP.Wallis, Patricia Dawn. January 2011 (has links)
The environmental impact of anthropogenic disturbances such as agriculture, on the
soil ecosystem, and particularly on soil microbial structural and functional diversity,
is of great importance to soil health, conservation and remediation. Therefore, this
study assessed the effects of various land use and management practices on both the
structural (genetic) and functional (catabolic) diversity of the soil bacterial and fungal
communities, at two long-term sites in KwaZulu-Natal. The first site is situated at
Baynesfield Estate, and the second at Mount Edgecombe Sugarcane Research
Institute. At site 1, the land uses investigated included soils under pre-harvest burnt
sugarcane (Saccharum officinarum, Linn.) (SC); maize (Zea mays, Linn.) under
conventional tillage (M); permanent kikuyu (Pennisetum clandestinum, Chiov)
pasture (KIK); pine (Pinus patula, Schiede) plantation (PF); and wattle (Acacia
mearnsii, De Wild) plantation (W), all fertilized; and undisturbed native grassland
(NAT) that had never been cultivated or fertilized. At site 2, a sugarcane (Saccharum
officinarum × S. spontaneum var. N27) pre-harvest burning and crop residue retention
trial was investigated. The treatments studied included conventional pre-harvest
burning of sugarcane with the tops removed (Bto), and green cane harvesting with
retention of crop residues on the soil surface as a trash blanket (T). Each of these
treatments was either fertilized (F) or unfertilized (Fo).
The polymerase chain reaction (PCR), followed by denaturing gradient gel
electrophoresis (DGGE) were used to determine the structural diversity, and
community level physiological profiling (CLPP) using BIOLOG plates, the catabolic
diversity. In addition, the soils were analysed with respect to selected
physicochemical variables, and the effects of these on the soil microbial communities
were determined. Replicate soil samples (0–5 cm) were randomly collected from three
independent locations within each land use and management, at both sites. Soil
suspensions for the CLPP analyses were prepared from fresh soil subsamples (within
24 h of collection) for the bacterial community analyses, and from 8-day-old soil
subsamples (incubated at 4°C to allow for spore germination) for the fungal
community analyses. BIOLOG EcoPlates™ were used for the bacterial CLPP study
and SF-N2 MicroPlates™ for the fungal analysis, the protocols being adapted and optimized for local conditions. This data was log [X+1]-transformed and analysed by
principal component analysis (PCA) and redundancy analysis (RDA). For PCRDGGE,
total genomic DNA was isolated directly from each soil subsample, and
purified using the MO BIO UltraClean™ soil DNA Isolation kit. Protocols were
developed and optimized, and fragments of 16S rDNA from soil bacterial
communities were PCR-amplified, using the universal bacterial primer pair
341fGC/534r. Different size 18S rDNA sequences were amplified from soil fungal
communities, using the universal fungus-specific primer pairs NS1/FR1GC and
FF390/FR1GC. Amplicons from both the bacterial and fungal communities were
fingerprinted by DGGE, and bands in the fungal DGGE gels were excised and
sequenced. The DGGE profiles were analysed by Bio-Rad Quantity One™ Image
analysis software, with respect to band number, position, and relative intensity.
Statistical analyses of this data then followed.
Soil properties [organic C; pH (KCl); exchangeable acidity; total cations (ECEC);
exchangeable K, Ca and Mg; and extractable P] were determined by PCA and were
shown to have affected the structural and catabolic diversity of the resident microbial
communities. At Baynesfield, canonical correspondence analysis (CCA) relating the
selected soil variables to bacterial community structural diversity, indicated that
ECEC, K, P and acidity were correlated with CCA1, accounting for 33.3% of the
variance, whereas Mg and organic C were correlated with CCA2 and accounted for
22.9% of the variance. In the fungal structural diversity study, pH was correlated with
CCA1, accounting for 43.8% of the variance, whereas P, ECEC and organic C were
correlated with CCA2, and accounted for 30.4% of the variance. The RDA of the
catabolic diversity data showed that the same soil variables affecting fungal structural
diversity (organic C, P, ECEC and pH) had influenced both the bacterial and fungal
catabolic diversity. In both the bacterial and fungal RDAs, organic C, P and ECEC
were aligned with RDA1, and pH with RDA2. However in the bacterial analysis,
RDA1 accounted for 46.0%, and RDA2 for 27.5% of the variance, whereas in the
fungal RDA, RDA1 accounted for only 21.7%, and RDA2 for only 15.0% of the
variance.
The higher extractable P and exchangeable K concentrations under SC and M, were
important in differentiating the structural diversity of these soil bacterial and fungal communities from those under the other land uses. High P concentrations under M
were also associated with bacterial catabolic diversity and to a lesser extent with that
of the soil fungal communities under M. Similarly, the higher organic C and
exchangeable Mg concentrations under KIK and NAT, possibly contributed to the
differentiation of these soil bacterial and fungal communities from those under the
other land uses, whereas under PF, the high exchangeable acidity and low pH were
possibly influencing factors. Under W, low concentrations of P and K were noted.
Other factors, such as the presence/absence and frequency of tillage and irrigation,
and the diversity of organic inputs due to the diversity of the above-ground plant
community, (in NAT, for example) were considered potentially important influences
on the nature and diversity of the various land use bacterial and fungal communities.
At Mount Edgecombe, CCA showed that organic C and Mg had a significant effect
on soil bacterial structural diversity. Organic C was closely correlated with CCA1,
accounting for 58.7% of the variance, whereas Mg was associated with CCA2, and
accounted for 41.3% of the variance. In the fungal structural diversity study, ECEC
and pH were strongly correlated with CCA1 and accounted for 49.1% of the variance,
while organic C was associated with CCA2, accounting for 29.6% of the variance. In
the functional diversity studies, RDA showed that both bacterial and fungal
community catabolic diversity was influenced by soil organic C, pH, and ECEC. In
the bacterial analysis, RDA1 was associated with organic C and pH, and accounted
for 43.1% of the variance, whereas ECEC was correlated with RDA2, accounting for
36.9% of the variance. In the fungal analysis, RDA1 was correlated with ECEC and
accounted for 47.1% of the variance, while RDA2 was associated with pH and
organic C, accounting for 35.8% of the variance. The retention of sugarcane harvest
residues on the soil surface in the trashed treatments caused an accumulation of
organic matter in the surface soil, which did not occur in the pre-harvest burnt
sugarcane. This difference in organic C content was a factor in differentiating both
bacterial and fungal communities between the trashed and the burnt treatments. Soil
acidification under long-term N fertilizer applications caused an increase in
exchangeable acidity and a loss of exchangeable Mg and Ca. Thus, as shown by CCA,
a considerably lower exchangeable Mg concentration under F compared to Fo plots
resulted, which was influential in differentiating the bacterial and fungal communities
under these two treatments. In the structural diversity study at Baynesfield, differences were found in bacterial
community species richness and diversity but not in evenness, whereas in the fungal
analysis, differences in community species richness, evenness and diversity were
shown. The soil bacterial and fungal communities associated with each land use were
clearly differentiated. Trends for bacterial and fungal diversity followed the same
order, namely: M < SC < KIK < NAT < PF < W. At Mount Edgecombe, no
significant difference (p > 0.05) in bacterial structural diversity was found with oneway
analysis of variance (ANOVA), but two-way ANOVA showed a slight
significant difference in bacterial community species richness (p = 0.05), as an effect
of fertilizer applications. A significant difference in fungal species richness (p = 0.02)
as a result of management effects was detected, with the highest values recorded for
the burnt/fertilized plots and the lowest for the burnt/unfertilized treatments. No
significant difference was shown in species evenness, or diversity (p > 0.05), in either
the bacterial or the fungal communities.
In the catabolic diversity study at site 1, the non-parametric Kruskal-Wallis ANOVA
showed that land use had not affected bacterial catabolic richness, evenness, or
diversity. In contrast, while fungal catabolic richness had not been affected by land
use, the soil fungal community catabolic evenness and diversity had. At site 2, the
land treatments had a significant effect on soil bacterial community catabolic richness
(p = 0.046), but not on evenness (p = 0.74) or diversity (p = 0.135). In the fungal
study, land management had no significant effect on the catabolic richness (p =
0.706), evenness (p = 0.536) or diversity (p = 0.826).
It was concluded, that the microbial communities under the different land use and
trash management regimes had been successfully differentiated, using the optimized
protocols for the PCR-DGGE of 16S rDNA (bacteria) and 18S rDNA (fungi).
Sequencing bands produced in the 18S rDNA DGGE, enabled some of the soil fungal
communities to be identified. CLPP of the soil microbial communities using BIOLOG
plates showed that, on the basis of C substrate utilization, the soil bacterial and fungal
communities’ catabolic profiles differed markedly. Thus, it was shown that the
different land use and management practices had indeed influenced the structural and
catabolic diversity of both the bacterial and fungal populations in the soil. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.
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The influence of soil organic matter on changes in leaf water potential of barley (Hordeum vulgare L.) during repeated cycles of moisture stress /Materechera, Simeon Albert. January 1985 (has links)
No description available.
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Concentration of soil nutrients beneath canopies of Acacia erioloba trees in a semi-arid savanna environment of the North-West province, South Africa / Romeo Nndamuleleni MurovhiMurovhi, Romeo Nndamuleleni January 2003 (has links)
Acacia erioloba (synonym: Acacia giraffae) commonly known as Mpatsaka (Sotho),
Mokala (Tswana), Kameeldoring (Afrikaans) and camel Thorn (English) is an indigenous
leguminous tree that is adapted and commonly found in semi-arid savanna environments of South Africa. Being a leguminous plant, Acacia erioloba can fix atmospheric nitrogen into the soil. The objective of this study was to quantify the concentration of plant nutrients in soils beneath the canopies of Acacia erioloba trees in three land-use practices viz: fallow, grazing and bare land. Three trees were randomly selected in each land-use practice and soil samples were collected from beneath and beyond the tree canopies at depths of 0-10 and 10-20 cm.
Consistently, soil analysis revealed that the concentration of nutrients (N, P, Ca, Mg, Zn
and Mn) and soil biological properties (organic carbon, particulate organic matter,
microbial biomass nitrogen and microbial biomass carbon) among the land-use practices
were in the order: fallow > grazing > bare. Differences in the concentration of soil
nutrients between the land-use practices seemed to be influenced by management within
the land-use practices. Nitrogen, phosphorus, potassium and zinc were significantly higher
(p<0.05) in land under grazing while calcium and magnesium, were significantly higher
(p<0.05) under fallow land. As expected, bare land had the lowest concentration of all the
nutrients studied. The presence of animals around Acacia erioloba trees contributed to
higher concentration of nutrients in land under grazing. The differences in the values of
biological properties were considered to be likely due to higher plant biomass on the
topsoil compared to the subsoil that increased the microbial activity. The improved
biological properties are thought to have improved the nutrient concentration through
processes such as mineralisation of nutrients from organic matter.
With the exception of phosphorus (P), potassium (K) and zinc (Zn), concentration of all
other nutrients (N, Ca, Mg and Mn) was not significantly different (p<0.05) in soil from
beneath the tree canopy and those from beyond the tree canopies in all land-use practices.
Topsoil (0-1 0 cm) had, significantly higher (p<0.05) concentration of all nutrients and
biological properties that were measured compared to the sub soil (10-20 cm). This was
attributed to the fact that much of the decomposition of soil organic matter takes place on
the surface layer of the soil where most of the organic materials are added. Nutrient
uptake from deep soil layers by roots of the trees may be another important mechanism
that could enrich surface soils beneath Acacia erioloba tree with nutrients.
The availability to a wheat crop of the nutrients found beneath the canopies of Acacia
erioloba was evaluated using a "Neubauer" seedling technique in a glasshouse. Wheat
seedlings were grown into PVC pots filled with soils collected from beneath and beyond
the tree canopies. The wheat that was grown in soils collected beneath Acacia erioloba
trees had significantly higher (p<O.OS) growth ~d nutrient uptake than that grown in soils
from beyond tree canopies. Plant height, dry matter yields and nutrient uptake by the
wheat seedlings were in the order fallow>grazing>bare land. The plant height were 20.9,
16.4 and 14.2 cm for fallow, grazing and bare, respectively. This was attributed to the high
accumulation of organic matter from different sources such as leaf litter, grass residues and animal wastes under fallow and grazing land. Fallow and grazing promotes large organic matter inputs and therefore create conditions that favour rapid decomposition of organic matter and mineralisation of nutrients.
Correlation coefficients between soil nutrients and nutrients in the tissues of wheat show
that there was a strong and significant relationship between the two. It was suggested from these results that Acacia erioloba trees has a potential to be used in agroforestry systems within the farming systems of the small-scale farmers in the semi-arid savanna ecosystem of the North-West Province. Such systems could include agrislviculture and
sylvopastoral. If Acacia erioloba trees are to be included in agroforestry systems, the
densities need to be increased. This would imply increasing their propagation. More
techniques of propagating the tree need to be researched. The nitrogen fixing potential of
Acacia erioloba needs to be thoroughly investigated. / Thesis (M.Sc (Agric.) North-West University, Mafikeng Campus, 2003
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