Applications of fertilizers derived from non-renewable resources, along with improved land management practices have contributed greatly increased crop yields in the past 70 years. Biofertilizers and organic amendments, provide alternative sources of nutrients for increased plant yields and resistance against abiotic stress. The objective of this work was to evaluate the effectiveness of various biofertilizers and an organic amendment on improve plant health and/or crop yield. The first study focused on the organic amendment, glucoheptonate and found that applications of 800-1600 kg/ha can increase available water capacity in fine textured soils by up to 3%. The second study evaluated the effectiveness of dual-inoculating biofertilizers Mung beans (Vigna radiata (L.) Wilczek) with two, bradyrhizobium spp. and arbuscular mycorrhizal fungi. Dual inoculation significantly increased grain yield (+33%) compared to a synthetic N fertilizer application but did not significantly increase grain yield compared to the control (+22%). Dual inoculation may increase grain yields of mung beans compared to synthetic fertilizer regime but does not show evidence of improving N fixation. The final study was a greenhouse experiment focused on evaluating some mung bean cultivars to determine their susceptibility to salt stress while also evaluating the effect of inoculation in combating saline soils. Germination was significantly decreased at 6 dS/m in all cultivars by about 36% when compared to the control treatment (0 dS/m). Seed yields, pods per plant and seeds per plant, increased as salt concentration increased. No factors recorded where affected by inoculation. Overall, our research suggests that the use of biofertilizers and organic amendments can improve crop health, but other management and environmental considerations need to be accounted for when reporting effectiveness of such alternative soil amendments / Doctor of Philosophy / Applications of fertilizers derived from non-renewable resources, along with improved land management practices have contributed greatly to increased crop yields in the past 70 years. Biofertilizers and organic amendments, provide alternative sources of nutrients for increased plant yields and resistance against abiotic stress. The objective of this work was to evaluate the effectiveness of an organic amendment and various biofertilizers to improve plant health and/or crop yield. The first study focused on the organic amendment, glucoheptonate and found that applications of 800-1600 kg/ha can increase available water capacity in fine textured soils by up to 3%. The second study evaluated the effectiveness of dual-inoculating Mung beans (Vigna radiata (L.)Wilczek) with two biofertilizers, bradyrhizobium spp. and arbuscular mycorrhizal fungi. Dual inoculation significantly increased grain yield (+33%) compared to a synthetic N fertilizer application but did not significantly increase grain yield compared to the control (+22%). Dual inoculation may increase grain yields of mung bean compared to synthetic fertilizer regime but does not show evidence of improving N fixation. The final study was a greenhouse experiment focused on evaluating mung bean cultivars (4) to determine their susceptibility to salt stress while also evaluating the effect of inoculation in combating the effect of saline soils. Germination was significantly decreased by about 36% at a salinity of 6 dS/m across all cultivars compared to the control at 0 dS/m. Seed yields, pods per plant and seeds per plant, increased as salt concentration increased for some cultivars. No factors recorded were observed to be affected by inoculation. Overall, our research suggests that the use of biofertilizers and organic amendments can improve crop health, but other management and environmental considerations need to be accounted for when reporting effectiveness of such alternative soil amendments.

The Mekong River Basin (MRB) is famous for its rice farming and export and produces more than 20 million tons of rice per year. Rice production depends on climate, irrigation, soil fertility. However, this region is adversely impacted by several environmental concerns like nutrient deficiency from sediment and saltwater intrusion. The decrease in sediment deposition in the Mekong basin is caused by a number of factors. In China, Lao PDR, and Vietnam, the hydropower generation from dams has improved people's overall living standards, leading in more dams being built or planned in the future. However, dam construction work is adversely impacting the overall salinity condition in this region by reducing upstream flow. Upstream lower flows during the dry season contributes to the increased salinity in the lower Mekong Delta. In addition to these, multiple dams in the upper and middle region of the Mekong basin are trapping sediments and decreasing it in the lower zones. This study found that the reservoirs, built by China between 2008-2015, has reduced the sediment load at all five stations considered in the study. When a reservoir is removed from the model, the sediment load is increased which showed the substantial impact of reservoir construction on sediment load in this area. The landuse pattern is another factor for variability of the sediment yield in the study area. Forest area contributes to higher sediment production whereas agricultural area results in lower sediment yield. The GFDL RCP (4.5) and GFDL RCP (8.5) future climate change projection scenarios used in this study also demonstrated substantial variability in the precipitation pattern for the study region. GFDL RCP (4.5) scenario resulted in a lower sediment yield during the dry season. On contrary to that, GFDL RCP (8.5) showed higher sediment yield due to higher precipitation during the wet season. The severe salinity impact was observed in the Cai Nuoc, Nam Can, and Thanh Phu districts. In Ca Mau province, the observed salinity is highest among the provinces of the study area during dry season (February to May), about 12-14 PPT (parts per thousand) whereas the lowest level of salinity (less than 1 PPT) was observed in the Dong Thap and Vinh Long provinces. This salinity intrusion is adversely impacting the rice production in the study area. In the year 2000, rice production in the Ca Mau province was about 100-150 thousand tons. But salinity intrusion is drastically reducing the rice production in this area, about 10-30thousand tons per year during 2015-2017. Rice production is increasing in the upper deltaic part of the Mekong Delta region where preventive measures were taken. / Master of Science / The Mekong River Basin (MRB) is famous for its rice farming and export and produces more than 20 million tons of rice per year. The rice production is governed by rainfall, temperature, irrigation, soil fertility etc. However, this region is adversely impacted by multiple environmental concerns like nutrient deficiency, sediment concentration, and salinity. The decrease in sediment deposition in the Mekong basin is caused by several factors. In China, Lao PDR, and Vietnam, the hydropower sector has improved people's overall living standards. As a result, more reservoirs are being constructed or planned to be constructed in the future. But this dam construction work is adversely impacting the overall salinity condition in this region. Upstream flows rate during the dry season (February to May) contributes to the increased salinity condition in lower Mekong Delta. In addition to these, multiple dams in the upper portion of the Mekong basin are trapping sediments and decreasing it in the lower region. From the analysis performed in this study it was found that the reservoirs, built by China between 2008-2015, has reduced the sediment load at all five stations. When the reservoir is removed from the model, the sediment load is increased implying the substantial impact of reservoir construction on sediment load in this area. The landuse pattern is another dominating factor for variability of the sediment yield in the study area. Forest area contributes to higher sediment production whereas agricultural area results in lower sediment yield. Two future climate projection scenarios considered for this study are the GFDL RCP (4.5) and GFDL RCP (8.5). These two scenarios also demonstrated substantial variability in the precipitation pattern for the study region. The severe salinity impact was observed in the Cai Nuoc, Nam Can, and Thanh Phu districts. In Ca Mau province, the observed salinity is highest among the provinces of the study area during dry season (February to May), about 12-14 PPT ((parts per thousand) whereas the lowest level of salinity (less than 1 PPT) was observed in the Dong Thap and Vinh Long provinces. This salinity intrusion is adversely impacting the rice yield in the study area. In the year 2000, rice production in the Ca Mau province was about 100-150 thousand tons. But salinity intrusion is drastically reducing the rice production in this area, about 10-30thousand tons per year during 2015-2017. Rice production is increasing in the upper deltaic part of the Mekong Delta region where preventive measures were taken.

Rice production plays an important role in the economy of the Mekong River Delta (MRD), but rice production is endangered by sea-level rise and the associated increased incidence of salinity intrusion. This study examines the diffusion of salt-tolerant rice varieties (STRVs) in the MRD that were promoted through Consortium for Unfavorable Rice Environment (CURE) activities. Evidence is found of widespread adoption in salinity-prone areas, with CURE related varieties covering 47% of rice area in at least one of two growing seasons surveyed, but that adopting areas are highly clustered. Multivariate analysis reveals that location characteristics associated with high risk of salinity inundation, rather than individual characteristics associated with household risk preferences, explain the observed pattern of adoption in the MRD. In particular, CURE-related varieties are disproportionately likely to be adopted in non-irrigated areas and in irrigated areas that are not protected by salinity barrier gates. The results imply that CURE has effectively targeted unfavorable rice growing environments and that efforts to further diffuse STRVs need to both increase the area of suitability through further varietal adaptation and promote adoption in existing suitable areas by taking advantage of strong neighborhood externalities in household adoption decisions. In terms of varietal performance, inconclusive evidence is found of higher yields of CURE-related varieties in a low-salinity year. Further, any yield gains are more than off-set by lower market prices for CURE-related varieties. / Rice is a staple crop in the Vietnamese diet and one of Vietnam's leading exports. The Mekong River Delta (MRD) accounts for more than 90 percent of rice exports. However, rice production in the MRD is endangered by saltwater intrusion due to rising sea-levels. Farmers have adopted rice varieties that are tolerant to rice to reduce their production risk that were promoted through Consortium for Unfavorable Rice Environment (CURE) activities. This study examines the rates of adoption of these CURE-related varieties, the reasons farmers choose CURE-related varieties, and variety performance on farmers' fields. Results from a household-level survey show at 47% of fields in salinity-prone areas of the MRD grow a CURE-related variety in at least one of the areas two main rice-growing seasons. Farmers are particularly likely to adopt CURE-related varieties on fields that are not protected against salinity intrusion by gates. Adoption decisions are also highly correlated with neighbors’ decisions within villages. Finally, CURE- and non-CURE-related varieties yields are similar in a year with low levels of salinity intrusion. But revenues from CURE-related varieties are slightly lower due to their lower market price, suggesting CURE-related varieties are a relatively low-cost insurance policy for MRD rice farmers in salinity-prone areas against future salinity intrusion.

Joint-head grass (Arthraxon hispidus) is a widespread nonindigenous plant species in the eastern United States. It is observed forming large monodominant patches that impact native and managed grassland systems. With such little understanding of its foundational biology or ecological impacts, leaving land managers desperate for effective control measures to manage A. hispidus invasion. We conducted a series of complementary experiments on six populations of A. hispidus to better understand how environmental factors affect seed germination. Germination is a critical life stage that allows a species to disperse. Freshly harvested seeds germinated effectively within 14 days of imbibition in the dark at 23°C, exhibiting little to no dormancy or influence by light. A pH range of 5 - 10 resulted in ≥ 80% germination, suggesting that pH will not limit colonization in other portions of the United States. Arthaxon hispidus was tolerant to abiotic stressors such as salinity and osmotic potential. The concentration required to limit germination to 50% (LD50) in the populations tested surpassed soil salinity found in the contiguous United States and some tidal systems (Frederick, MD = 354; Lincoln, MO = 354; Williamsburg, VA = 298 mM NaCl). While drought adversely affects A. hispidus germination, the LD50 occurred in moderate to more severe osmotic potentials (Frederick, MD = -0.67; Lincoln, MO = -0.37; Williamsburg, VA = -0.25 MPa) making A. hispidus expansion more likely in wetter years and regions. Constant temperature treatments resulted in germination percentages across a range of temperatures (8 - 37°C), and A. hispidus is well distributed in several major temperature regimes found in the United States. Finally, emergence greatly decreased with burial depth. Emergence occurred at ≥ 43% at 1 - 2 cm, decreasing to 5% at 6 cm, and 0% at 8-cm depths. With adequate soil moisture, a broad range of germination temperatures, and a decreased emergence rate with depth, we believe A. hispidus is unlikely to develop a seed bank. These initial studies on A. hispidus' germination posit a broad range of environmental tolerances; although, it may be limited by other life stages. / Master of Science / Joint-head grass is a non-native invasive plant species commonly found in the eastern United States. It is observed growing in large patches that negatively affect the environment. These effects can include decreasing biodiversity or lowering forage availability which negatively can impact cattle production. To better understand the basic biology of joint-head grass, we decided to harvest seeds to study from several populations in the United States. We tested differences in the populations by examining the different environmental effects on joint-head grass germination. Germination is a critical life stage of invasive plants; therefore, we developed complementary experiments to test the effects of the environment on seed germination. We've determined that germination occurs effectively under the effect of several environmental stressors. Germination occurred under salty (NaCl) conditions which may allow it to establish in tidal systems where brackish water is present. We've also determined that germination occurs effectively ( ≥ 80%) at a pH range from 5 - 10. This will allow joint-head grass to germinate in more basic soils commonly found in the western part of the United States. Further, we tested the moisture requirements for germination to occur, and we've found that it is tolerant to moderate to more severe drought conditions. Joint-head grass is also capable of germinating across a range of temperatures (8-37°C). The United States has well-distributed rainfall and suitable temperatures in large portions of the country. We believe the climate of the United States is well-suited for joint-head grass establishment, and that it may spread more frequently in years with higher precipitation during the growing season. This species potentially poses a threat to both our natural and agricultural systems.

published_or_final_version / Civil Engineering / Master / Master of Philosophy

This study examines the effects of a low oxygen environment, in concert with fluctuating temperature and salinity conditions, on the nearshore depth distributions (0-1 m) and flood tide movements of juvenile chinook (Oncorhynchus tshawytscha) and chum (O. keta) salmon. Comparisons are made between an unpolluted and a sewage polluted estuarine intertidal flat in the Fraser River estuary, British Columbia, the polluted area being characterized by the regular occurrence of low dissolved oxygen levels. Results are based on 380 beach seine samples taken between April and June of 1984. In general, chum and chinook salmon of increasing length were captured in increasing depths, though this pattern was modified by seasonal changes in water temperature. Low dissolved oxygen conditions in deeper waters may have been responsible for the presence of larger, and often sluggishly swimming fish in higher oxygenated surface water layers or in shallow waters near the shore. In both areas, the risk of aerial predation was high. On a flood tide, the likelihood of capturing a chinook salmon was reduced as temperatures increased and oxygen levels decreased. A combination of avoidance behaviour and a regularity in the movement patterns of chinook onto the study area in the later stages of the flood tide may account for their rare occurrence in low oxygen concentrations (<6 mg/1) and high temperatures (>20 °C). Fish mortalities were most likely to occur on the ebb tide when fish were forced into waters of low oxygen content by the drainage patterns characteristic of the polluted study area. Though wide ranges in salinity were recorded on both tidal flats, this factor was not strongly correlated to Chinook distributions. However, significantly higher salinity levels in the unpolluted area may account for the greater numbers of chum salmon captured there. An understanding of the influence of estuarine water quality conditions on the distribution of juvenile salmonids may assist in the identification of significant sources of mortality in their early marine life. This knowledge is particularly important in the evaluation of water quality changes as caused by human activity. / Science, Faculty of / Zoology, Department of / Graduate

No description available.

Among ornamental plants, roses (Rosa L.) are considered the most economically important, being among the most popular garden shrubs, as well as the favorite cut flowers sold by florists. In the past roses have been classified as fairly salt-sensitive, however, recent nutrition studies suggest that they may actually tolerate moderate to relatively high salinities. The general objective of this research was to reassess the limits of tolerance to salinity of roses and the influence of the rootstock used, to determine the ameliorative properties of supplemental Ca2+ on the response to salt stress, and to establish the influence of Na+- and Cl--counter ions on the detrimental effects caused by these salinizing elements. The NaCl or NaCl-CaCl2-salinity tolerance limit for greenhouse roses, although greatly influenced by the rootstock, was between 12 and 15 mmol.L-1. Plants grafted on ?Manetti? sustained their productivity/quality characteristics for longer time periods, tolerated greater salinity concentrations, and accumulated less Cl- and Na+ in leaves of flowering shoots than those grafted on ?Natal Briar?, confirming the greater ability of the former rootstock to tolerate salt stress. Supplementing the saline solution with 0-10 mmol.L-1 Ca2+ (as CaSO4) did not alleviate the harmful effects caused by NaCl-salt stress (12 mmol.L-1) on the productivity and quality responses of roses. The detrimental effects caused by Na- and Cl-based salinity were greatly influenced by the composition of the salt mixtures (i.e. their counter ions). Sodium sulfate and CaCl2 were the least harmful salts; NaCl had intermediate effects, while NaNO3 and KCl were the most deleterious. Among the most distinguishable effects caused by the more toxic Na+ and Cl- counter ions were lower osmotic potential (piSS) and greater electrical conductivity (ECSS) of the salinized solutions, markedly increased uptake and/or transport of either Na+ or Cl- to the flowering shoot leaves, and altered uptake and/or transport of other mineral nutrients. Computations of the saline solutions? chemical speciation revealed that salts containing divalent ions had lower ionization and exhibited greater ion associations compared to monovalent ion salts, rendering a lower number in free ions/molecules in solution which caused greater SS and lower ECSS in those solutions.

Reverse electrodialysis (RED) is a technique that can capture electrical potential from mixing two water streams of different salt concentration through permselective ion exchange membranes. Effective design of ion exchange membranes through structure optimization is critical to increase the feasibility of salinity gradient power production by RED. In this work, we present the preparation of organic-inorganic nanocomposite cation exchange membranes containing sulfonated polymer, poly (2,6-dimethyl-1,4-phenylene oxide), and sulfonated silica (SiO2-SO3H). The effect of silica filler size at various loading concentrations on membrane structures, electrochemical properties, and the RED power performance is investigated. The membranes containing bigger-sized fillers (70 nm) at 0.5 wt% SiO2-SO3H exhibited a relatively favorable electrochemical characteristic for power performance: an area resistance of 0.85 Ω cm2, which is around 9.3% lower than the resistance of the membranes with smaller filler particles. The power performance of this nanocomposite cation exchange membrane in a RED stack showed 10% higher power output compared with the membranes containing small particle size and achieved the highest gross power density of 1.3 W m-2. Thus, further optimized combination of material properties and membrane structure is a viable option for the development of effective ion exchange membrane design, which could provide desirable electrochemical performance and greater power production by RED.

Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Concrete evidence of dryland salinity was observed in the Berg River catchment in the Western Cape Province of South Africa. Soil salinization is a global land degradation hazard that negatively affects the productivity of soils. Timely and accurate detection of soil salinity is crucial for soil salinity monitoring and mitigation. It would be restrictive in terms of costs to use traditional wet chemistry methods to detect and monitor soil salinity in the entire Berg River catchment. The goal of this study was to investigate less tedious, accurate and cost effective techniques for better monitoring. Firstly, hyperspectral remote sensing (HRS) techniques that can best predict electrical conductivity (EC) in the soil using individual bands, a unique normalized difference soil salinity index (NDSI), partial least squares regression (PLSR) and bagging PLSR were investigated. Spectral reflectance of dry soil samples was measured using an analytical spectral device FieldSpec spectrometer in a darkroom. Soil salinity predictive models were computed using a training dataset (n = 63). An independent validation dataset (n = 32) was used to validate the models. Also, field-based regression predictive models for EC, pH, soluble Ca, Mg, Na, Cl and SO4 were developed using soil samples (n = 23) collected in the Sandspruit catchment. These soil samples were not ground or sieved and the spectra were measured using the sun as a source of energy to emulate field conditions. Secondly, the value of NIR spectroscopy for the prediction of EC, pH, soluble Ca, Mg, Na, Cl, and SO4 was evaluated using 49 soil samples. Spectral reflectance of dry soil samples was measured using the Bruker multipurpose analyser spectrometer. “Leave one out” cross validation (LOOCV) was used to calibrate PLSR predictive models for EC, pH, soluble Ca, Mg, Na, Cl, and SO4. The models were validated using R2, root mean square error of cross validation (RMSECV), ratio of prediction to deviation (RPD) and the ratio of prediction to interquartile distance (RPIQ). Thirdly, owing to the suitability of land components to map soil properties, the value of digital elevation models (DEMs) to delineate accurate land components was investigated. Land components extracted from the second version of the 30-m advanced spaceborne thermal emission and reflection radiometer global DEM (ASTER GDEM2), the 90-m shuttle radar topography mission DEM (SRTM DEM), two versions of the 5-m Stellenbosch University DEMs (SUDEM L1 and L2) and a 5-m DEM (GEOEYE DEM) derived from GeoEye stereo-images were compared. Land components were delineated using the slope gradient and aspect derivatives of each DEM. The land components were visually inspected and quantitatively analysed using the slope gradient standard deviation measure and the mean slope gradient local variance ratio for accuracy. Fourthly, the spatial accuracy of hydrological parameters (streamlines and catchment boundaries) delineated from the 5-m resolution SUDEM (L1 and L2), the 30-m ASTER GDEM2 and the 90-m SRTM was evaluated. Reference catchment boundary and streamlines were generated from the 1.5-m GEOEYE DEM. Catchment boundaries and streamlines were extracted from the DEMs using the Arc Hydro module for ArcGIS. Visual inspection, correctness index, a new Euclidean distance index and figure of merit index were used to validate the results. Finally, the value of terrain attributes to model soil salinity based on the EC of the soil and groundwater was investigated. Soil salinity regression predictive models were developed using CurveExpert software. In addition, stepwise multiple linear regression soil salinity predictive models based on annual evapotranspiration, the aridity index and terrain attributes were developed using Statgraphics software. The models were validated using R2, standard error and correlation coefficients. The models were also independently validated using groundwater hydro-census data covering the Sandspruit catchment. This study found that good predictions of soil salinity based on bagging PLSR using first derivative reflectance (R2 = 0.85), PLSR using untransformed reflectance (R2 = 0.70), a unique NDSI (R2 = 0.65) and the untransformed individual band at 2257 nm (R2 = 0.60) predictive models were achieved. Furthermore, it was established that reliable predictions of EC, pH, soluble Ca, Mg, Na, Cl and SO4 in the field are possible using first derivative reflectance. The R2 for EC, pH, soluble Ca, Mg, Na, Cl and SO4 predictive models are 0.85, 0.50, 0.65, 0.84, 0.79, 0.81 and 0.58 respectively. Regarding NIR spectroscopy, validation R2 for all the PLSR predictive models ranged from 0.62 to 0.87. RPD values were greater than 1.5 for all the models and RMSECV ranged from 0.22 to 0.51. This study affirmed that NIR spectroscopy has the potential to be used as a quick, reliable and less expensive method for evaluating salt-affected soils. As regards hydrological parameters, the study concluded that valuable hydrological parameters can be derived from DEMs. A new Euclidean distance ratio was proved to be a reliable tool to compare raster data sets. Regarding land components, it was concluded that higher resolution DEMs are required for delineating meaningful land components. It seems probable that land components may improve salinity modelling using hydrological modelling and that they can be integrated with other data sets to map soil salinity more accurately at catchment level. In the case of terrain attributes, the study established that promising soil salinity predictions could be made based on slope, elevation, evapotranspiration and terrain wetness index (TWI). Stepwise multiple linear regressions soil salinity predictive model based on elevation, evapotranspiration and TWI yielded slightly more accurate prediction of soil salinity. Overall, the study showed that it is possible to enhance soil salinity monitoring using HRS, NIR spectroscopy, land components, hydrological parameters and terrain attributes. / AFRIKAANSE OPSOMMING: Konkrete bewyse van droëland sout is waargeneem in die Bergrivier opvanggebied in die Wes- Kaap van Suid-Afrika. Verbrakking van grond is 'n wêreldwye probleem wat ‘n negatiewe invloed op die produktiwiteit van grond kan hê. Tydige en akkurate herkenning van verandering in grond soutgehalte is ‘n noodsaaklike aksie vir voorkoming. Dit sou beperkend wees in terme van koste om konvensionele nat chemiese metodes te gebruik vir die opsporing en monitering daarvan in die hele Bergrivier opvanggebied. Die doel van hierdie studie was om ondersoek in te stel na minder tydsame, akkurate en koste-effektiewe tegnieke vir beter monitering. Eerstens, is hiperspektrale afstandswaarnemings (HRS) tegnieke wat die beste in staat is elektriese geleidingsvermoë (EG) in die grond te kan voorspel deur gebruik te maak van individuele bande, 'n unieke genormaliseerde grond soutindeks verskil (NDSI), parsiële kleinste kwadratiese regressie (PLSR) en afwyking in PLSR, is ondersoek. Spektrale reflektansie van droë grondmonsters is gemeet deur gebruik te maak van 'n spektrale analitiese toestel: FieldSpec spektrometer in 'n donkerkamer. Voorspellings modelle vir grond soutgehalte is bereken met behulp van 'n toets datastel (n = 63). 'n onafhanklike validasie datastel (n = 32) is gebruik om die modelle te evalueer. Daarbenewens is veld-gebaseerde regressie voorspellings modelle vir EG, pH oplosbare Ca, Mg, Na, Cl and SO4 ontwikkel deur gebruik te maak van grondmonsters (n = 23) versamel in the Sandpruit opvangsgebied. Hierdie grondmonsters is nie gemaal of gesif nie en die spectra is gemeet deur gebruik te maak van die son as ‘n bron van energie om veld toestande na te boots. Tweedens, is die waarde van NIR spektroskopie vir die voorspelling van die EG, pH, oplosbare Ca, Mg, Na, Cl, en SO4 met behulp van 49 grondmonsters geëvalueer. Spektrale reflektansie van droë grondmonsters is gemeet deur gebruik te maak van die Bruker NIR veeldoelige analiseerder . Kruisvalidering (LOOCV) is gebruik om PLSR voorspellings modelle vir EG, pH, oplosbare Ca, Mg, Na, Cl, en SO4 te kalibreer. Hierdie modelle is gevalideer: R2, wortel-gemiddelde-kwadraat fout kruisvalidering (RMSECV), verhouding van voorspellings afwyking (RPD) en die verhouding van die voorspelling se inter-kwartiel afstand (RPIQ). Derdens is land komponente gekarteer vanweë die nut daat van tov grondeienskappe, en die waarde van DEMs is ondersoek om akkurate land komponente af te baken. Land komponente uit die tweede weergawe van die 30 m gevorderde ruimte termiese emissie en refleksie radio globale DEM (ASTER GDEM2), die 90-m ruimtetuig radar topografie sending DEM (SRTM DEM), twee weergawes van die 5 m Universiteit van Stellenbosch DEMs (SUDEM L1 en L2) en 'n 5 m DEM (GEOEYE DEM) afgelei van GeoEye stereo-beelde, is vergelyk. Land komponente is afgebaken met behulp van helling, gradiënt en aspek afgeleides van elke DEM. Die land komponente is visueel geïnspekteer en kwantitatief ontleed met behulp van die helling gradiënt standaardafwyking te meet en die gemiddelde helling-gradiënt-plaaslike variansie verhouding vir akkuraatheid. Vierdens, is die ruimtelike akkuraatheid van hidrologiese parameters (stroomlyn en opvanggebied grense) geëvalueer soos afgelei vanaf die 5 m resolusie SUDEM (L1 en L2), die 30 m ASTER GDEM2 en die 90 m SRTM . Die verwysings opvanggebied grens en stroomlyn is gegenereer vanaf die 1,5-m GEOEYE DEM. Opvanggebied grense en stroomlyn uit die DEMs is bepaal deur gebruik te maak van die Arc Hydro module in ArcGIS. Visuele inspeksie, korrektheid indeks, 'n nuwe Euklidiese afstand indeks en die indikasie-van-meriete indeks is gebruik om die resultate te valideer. Laastens is die waarde van die terrein eienskappe om grond southalte te modeleer ondersoek, gebaseer op die EG van die grond en grondwater. Grond soutgehalte regressie voorspellings modelle is ontwikkel met behulp van CurveExpert sagteware. Verder, stapsgewyse meervoudige lineêre regressie grond soutgehalte voorspellings modelle gebaseer op jaarlikse evapotranspirasie, die dorheids indeks en terrein eienskappe is ontwikkel met behulp van Statgraphics sagteware. Die modelle is gevalideer deur gebruik te maak van R2, standaardfout en korrelasiekoëffisiënte. Die modelle is ook onafhanklik bekragtig deur die gebruik van grondwater hidro-sensus-data wat die Sandspruit opvanggebied insluit. Hierdie studie het bevind dat 'n goeie voorspelling van grond soutgehalte gebaseer op uitsak PLSR met behulp van eerste orde afgeleide reflektansie (R2 = 0,85), PLSR deur gebruik te maak van ongetransformeerde reflektansie (R2 = 0,70), 'n unieke NDSI (R2 = 0,65) en die ongetransformeerde individuele band op 2257 nm (R2 = 0,60) voorspellings modelle verkry is. Verder is vasgestel dat betroubare voorspellings van die EG, pH, oplosbare Ca, Mg, Na, Cl en SO4 in die veld moontlik is met behulp van eerste afgeleide reflektansie. Die R2 van EG, pH, oplosbare Ca, Mg, Na, Cl en SO4 is 0.85, 0.50, 0.65, 0.84, 0.79, 0.81 en 0.58 onderskeidelik. Ten opsigte van NIR spektroskopie het die validasie van R2 vir al die PLSR voorspellings modelle gewissel tussen 0,62-0,87. Die RPD waardes was groter as 1,5 vir al die modelle en RMSECV het gewissel tussen 0,22-0,51. Hierdie studie het bevestig dat NIR spektroskopie die potensiaal het om gebruik te word as 'n vinnige, betroubare en goedkoper metode vir die analise van soutgeaffekteerde gronde. T.o.v. hidrologiese parameters, het die studie tot die gevolgtrekking gekom dat waardevolle hidrologiese parameters afgelei kan word uit DEMs. 'n nuwe Euklidiese afstand verhouding is bevestig as 'n betroubare hulpmiddel om raster datastelle te vergelyk. Ten opsigte van grond komponente, is daar tot die gevolgtrekking gekom dat hoër resolusie DEMs nodig is vir die bepaling van sinvolle land komponente. Dit lyk waarskynlik dat die land komponent soutgehalte modellering hidrologiese modellering verbeter en dat hulle geïntegreer kan word met ander datastelle vir meer akkurate kaarte op opvangsgebied skaal. In die geval van die terrein eienskappe het, die studie vasgestel dat belowende grond soutgehalte voorspellings gemaak kan word gebaseer op helling, elevasie, evapotranspirasie en terrein natheid indeks (TWI). 'n stapsgewyse meervoudige lineêre regressie grond soutgehalte voorspellings model wat gebaseer is op elevasie, evapotranspirasie en TWI het effens meer akkurate voorspellings van die grond soutgehalte gelewer. In geheel gesien, het die studie getoon dat dit moontlik is om grond soutgehalte monitering te verbeter met behulp van HRS, NIR spektroskopie, land komponente, hidrologiese parameters en terrein eienskappe. / The Agricultural Research Council (ARC), Water Research Commission and the National Research Foundation for funding.