Thesis (MScAgric)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: A new orange oil based soil ameliorant is available on the market. Apart from the orange oil, the other main constituents of the product are a nonionic surfactant and an anionic surfactant. Surfactants are used in the agricultural sector, amongst others, as a countermeasure for soil with poor infiltrability or with hydrophobic characteristics. Farmers who applied the orange oil based soil ameliorant to the soil observed a positive growth response by the crop. However, the main concern about surfactants is that it can cause the soil to disperse and thereby decrease the infiltration and saturated hydraulic conductivity thereof. The aim of this study was therefore to determine the effect which this product might have on the following selected soil physical properties: bulk density, aggregate stability, soil strength and unsaturated hydraulic conductivity. The product was applied on four farms on soils with different textures: Dublin Farm (22% clay), Wansbek (20% clay), Toitskraal (7% clay) and Two Rivers (3% clay). Field studies were repeated at Dublin Farm and Toitskraal to study the longevity effect of the product. Differences in bulk density were not attributed to the effect of the product, but to spatial variation. The aggregate stability at the 50 mm depth tended to decrease after application of the product at Dublin Farm trial 1, Toitskraal trial 1 and at Wansbek. At Dublin Farm trial 2 and Toitskraal trial 2 the application of the product tended to increase the aggregate stability. For Dublin Farm trial 2 and Wansbek the shear strength at the 50 mm depth tended to increase with increased application rates. The opposite was observed at Toitskraal and Two Rivers. The unsaturated hydraulic conductivity tended to be higher at the 0 mm depth for the treated soils at all of the trials except Toitskraal trial 2. From the aggregate stability results it is clear that the initial effect of the product was detrimental which can be attributed to the anionic surfactant. The long term effect can be attributed to the effect of the nonionic surfactant. The differences in shear strength can be attributed to aggregate stability (for Dublin Farm trial 2) and bulk density (for Two Rivers). There is however no explanation for the results found at Toitskraal and Wansbek. From the linear regression of bulk density against unsaturated hydraulic conductivity for Wansbek and Two Rivers it is clear that the application of the product definitely had an influence on the unsaturated hydraulic conductivity. For both farms, the correlation between bulk density and unsaturated hydraulic conductivity was better for the control than for the treated soils. To conclude with, the application of the product according to the recommended application rate, resulted in a slightly detrimental effect to the soil on the short term, but on the long term it tended to have a slightly positive effect on the soils. / AFRIKAANSE OPSOMMING: ‘n Nuwe grondverbeteringsproduk met lemoenolie as ‘n basis en ‘n nie-ioniese en ‘n anioniese benattingsmiddel as hoof bestandele, is op die mark. In die landbou sektor word benattingsmiddels onder andere gebruik as ‘n teenvoeter vir gronde met swak infiltrasie of hidrofobiese eienskappe. Die grootste voorbehoud omtrent die gebruik van benattingsmiddels is die moontlike afname in infiltrasie en versadigde hidroulieses geleivermoë as gevolg van klei dispergering. Positiewe reaksies van die gewasse is waargeneem deur boere wat van die produk gebruik maak. Die doel van die studie was dus om die moontlike effek van die bogenoemde grondverbeterings produk op die volgende geselekteerde grondfisiese eienskappe te bepaal: bulkdigtheid, aggregaatstabiliteit, grondsterkte en onversadigde hidrouliese geleivermoë. Die produk is toegedien op vier plase met verskillende grondteksture: Dublin Farm (22% klei), Toitskraal (7% klei), Wansbek (20% klei) and Two Rivers (3% klei). ‘n Ondersoek na die lewensduur van die produk is gedoen deur ‘n opvolg studie te doen by Dublin Farm en Toitskraal. Vir die bulkdigtheid resultate kon geen van die verskille toegeskryf word aan die effek van die produk nie. Die aggregaate stabiliteit by die 50 mm diepte van Dublin Farm proef 1, Toitskraal proef 1 en Wansbek, het geneig om laer te wees vir die behandelde gronde. Die aggregaatstabiliteit by die 50 mm diepte van Dublin Farm proef 2 en Toitskraal proef 2 het geneig om hoër te wees vir die behandelde gronde. Die skuifsterkte by die 50 mm diepte by Dublin Farm proef 2 en Wansbek, het geneig om toe te neem met ‘n toename in toedienings hoeveelheid, terwyl die teenoorgestelde tendens by Toitskraal en Two Rivers waargeneem is waar minder klei teenwoordig is in die grond. Die onversadigde hidroliese geleivermoë het geneig om hoër te wees by die 0 mm diepte van al die plase met die uitsondering van Toitskraal proef 2. Dit is duidelik vanaf die aggregaatstabiliteit resultate dat die aanvanklike effek van die produk nadelig is en dit kan toegeskryf word aan die effek van die anioniese benattingsmiddel. Die langtermyn effek kan toegeskryf word aan die nie-ioniese benatingsmiddel wat aggregaatstabiliteit kan verbeter. Die verskille in skuifsterkte kan toegeskryf word aan die verskille in aggregaatstabiliteit (vir Dublin Farm proef 2) en bulkdigtheid (vir Two Rivers). Daar is egter geen verklaring vir die verskille in skuifsterkte by Toitskraal en Wansbek nie. Die liniêre regressie van bulkdigtheid teenoor onversadigde hidroliese geleivermoë van Wansbek en Two Rivers dui aan dat die produk ‘n invloed het op die onversadigde hidroliese geleivermoë. Vir albei plase het die kontrole die beste liniêre verband tussen die twee grondeienskappe gehad, met ‘n swakker korrelasie vir gronde waar die lemoenolieproduk toegedien is. Dus kan die afleiding gemaak word dat op die korttermyn het die produk ‘n geringe negatiewe effek op die grond, maar op die langtermyn neig dit om ‘n positiewe effek te hê.

Thesis (MScAgric)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Soil amelioration and conditioning is desirable and in many cases essential, due to increasing food demand and the deterioration and exhaustion of soils. A new soil ameliorant, consisting of orange oil as a base and a mixture of surfactants, is on the global agricultural market. Use of this soil ameliorant by farmers has made an impact on crop production and plant growth on many farms. The effects of this soil ameliorant on selected soil properties as well as plant traits were evaluated by a field trial, a pot trial and a Water Characteristic Curve experiment. A field trial was performed in the Firgrove area near Somerset West, Western Cape (South Africa). It entailed the evaluation of the water content and lateral movement of water in a sandy soil after the application of the soil ameliorant. The field was already planted with Capsicum annuum crop at the initiation of the trial. The trial was performed in a drip irrigated field by taking soil water measurements using a Diviner 2000 probe over a nine week period. The trial showed significant increases in water content on the plots treated with the soil ameliorant. These increases are indicative of an increase in the lateral movement of the soil water, as the measurements were taken between two drippers. On average, the ameliorant treated soil had 17% higher water content than that of the control. A Water Characteristic Curve (WCC) experiment was conducted, which entailed establishing the WCC for a sandy soil treated with the soil ameliorant. The Sandbox apparatus, from Eijkelkamp Agrisearch Equipment, was used to perform the experiment and provides suction values of 0.1 to 10.1 KPa. The WCC showed that the ameliorant application increased water retention over all suctions, especially for the 10 l/ha ameliorant application. This substantiated the Field trial where water retention was increase in a sandy soil. A pot trial was performed in a greenhouse to evaluate the effect of the soil ameliorant on selected soil properties and certain plant traits. This experiment consisted of an ameliorant treatment and a control with a combination of four different Plant Available Water Depletion (PAWD) regimes namely, 10% depletion, 50% depletion, 80% depletion and 50%C depletion, where “C” refers to covered. The trial layout, with five single pot replicates per treatment combination, was according to a randomized block design. The surface covering of one of the 50% PAWDs was a plastic sheet which to prevent evaporation from the soil surface. The ameliorant treatment resulted in significant improvements in overall plant growth, total biomass production, especially dry root biomass. Leaf Area Index and plant height were also improved. The Biomass Water Use Efficiency was improved with the ameliorant application, especially for the 50%C PAWD illustrating the beneficial use of a mulch. Bulk density was decreased with application of the ameliorant but this difference was not statistically significant. Aggregate stability for the moist soils (10% and 50%C PAWD) was significantly improved with the ameliorant application. The application of this soil ameliorant made significant improvements in various facets of plant growth and certain soil physical properties. Especially water holding capacity in sandy soils and the overall improvement in plant growth. There is still much opportunity for research in this field and many questions remain, especially those pertaining to the mechanisms involved in the workings of a soil ameliorant containing a mixture of ingredients. / AFRIKAANSE OPSOMMING: Die bestuur van besproeingswater en die optimisasie van gewasproduksie is `n studieveld wat baie aandag verg, aangesien varswater bronne bedreig word. As gevolg van die stygende vraag na voedsel en die agteruitgang en uitputting van die grond, is grondverbetering en-kondisionering aanbeveelbaar en in sommige gevalle noodsaaklik. `n Nuwe grond verbeteraar, bestaande uit lemoen olie as `n basis en ‘n mengsel van benattingsmiddels, is beskikbaar op die wêreld landbou mark. Die gebruik van die grondverbeteraar deur boere het ‘n impak gemaak op gewasproduksie en plantegroei op baie plase. Die effek van die grondverbeteraar op geselekteerde grond-eienskappe sowel as plantkenmerke is geevalueer deur ‘n veld proef, ‘n pot proef en ‘n Water Karakeristieke Kurwe eksperiment. `n Veldproef is uitgevoer in die Firgrove omgewing naby Somerset Wes in die Wes-Kaap Provinsie, Suid Afrika. Die veldproef het die evaluasie van die grondwater inhoud en die laterale beweging van water in `n sanderige grond behels. Die gewas Capsicum annuum was alreeds in die veld aangeplant voor die begin van die proef. Die proef was uitgevoer in `n drup besproeide veld deur grondwater metings wat geneem is met `n Diviner 2000 peilstif oor `n periode van nege weke. Die proewe het `n beduidende verhoging in die groundwater-inhoud getoon waar die grond met die grondverbeteraar behandel is. Die verhogings was `n aanduiding van `n toename in die laterale vloei van grond water, aangesien die lesings tussen twee druppers geneem is. Die grond, wat met die grondverbeteraar behandel is, het gemiddeld 17% hoёr groundwater-inhoud gehad as die kontrole. `n Water Karakteristieke Kurwe (WKK) eksperiment is uitgevoer, wat bestaan het uit die opstel van die WKK vir `n sanderige grond behandel met die grondverbeteraar. Die “Sandbox” apparaat van Eijkelkamp, Agrisearch Equipment is gebruik wat negatiewe druk waardes van 0.1 tot 10.1 KPa toon. Die WKK het getoon dat die toediening van die grondverbeteraar die water retensie verhoog het oor al die drukke, veral in die 10 l/ha toediening. Dit staaf die resultate van die Veld eksperiment waar water retensie verhoog is in die sanderige grond. Die pot-eksperiment is uitgevoer in `n tonnel om die effek van die grondverbeteraar op geselekteerde grond eienskappe en verskeie plant eienskappe te evalueer. Die eksperiment het bestaan uit ‘n grondverbeteraar behandeling en ‘n kontrole met ‘n kombinasie van vier verskillende plantbeskikbare wateronttrekkings naamlik, 10%, 50%, 80% onttrekking, en ‘n 50%C onttrekking, waar “C” verwys na “covered”. Die proef uiteensetting, met vyf enkel pot herhalings per behandeling kombinasie was volgens ‘n ewekansig blok uitleg. Die oppervlakte dekking van 50%C plantbeskikbare waterottrekking was `n 60 μm plastiek-vel wat verdamping vanaf die grondoppervlak verhoed het. Die grondverbeteraar behandeling het `n beduidende verbetering in algehele plantgroei, totale biomassa produksie en spesifiek droё wortel biomassa getoon. Die blaararea indeks en planthoogte het ook `n verbetering getoon. Die biomassa-watergebruiksdoeltreffendheid het verbeter met die toediening van die grondverbeteraar, spesifiek vir die 50%C plantbeskikbarewaterottrekking wat die voordele van die gebruik van oppervlakdekking illustreer. Die brutodigtheid is verminder deur die toediening van die grondverbeteraar, maar die verskil was statisties nie wesenlik nie. Agregaat-stabiliteit vir die grond met `n hoёr vogregime (10% en 50%C plantbeskikbare waterottrekking) is wesenlik verbeter met die toediening van die grondverbeteraar. Die toediening van die grondverbeteraar het wesenlike verbeteringe in verskeie plantegroei- en grondfisiese-eienskappe getoon. Spesifiek laterale beweging in sanderige grond en die verbettering van algehele plantegroei. Daar is nog baie geleenthede vir navorsing in die veld en baie vrae bly onbeantwoord, veral in verband met die meganismes met bretrekking tot die werking van die grondverbeteraar wat uit `n mengsel van bestandele bestaan.

Abstract The chemical characteristics of spent wash, an effluent from the distillation of ethanol from molasses, can vary, depending on the initial feed stock and the operations of the factory. Spent wash from Australia contained large quantities of dissolved organic carbon (DOC), K, N and Cl with moderate to low concentrations of Ca, Mg, Na, and S, and small amounts of trace elements (Fe, Al, Mn, Cu, Zn). Spent wash from Thailand was obtained from whisky distillation and generally had similar chemical attributes to the spent wash from ethanol production, although the Zn concentration was much higher (399-974 mg Zn L-1). Large differences in EC and pH were found between Australian (pH: 4.08-4.49; EC: 40.4-42.2 dS m-1) and Thai spent wash (pH: 7.86-9.20; EC: 11.3-82.4 dS m-1). However, the high concentration of K in spent wash from both manufacturing processes indicates the unique chemical characteristic of wastewater produced from molasses-based distillation. While chemical characterisations of spent wash have shown its potential value as a fertilizer, its utility needs to be more practical than by direct application. This is due to its dilute nature, associated with the presence of organic carbon (OC) and nutrients in soluble form, thus making direct application susceptible to leaching losses of nutrients, especially in soils of low cation exchange capacity (CEC). It was hypothesized that capturing OC and nutrients on a high activity exchanger would overcome this problem. Since the charge on organic components in spent wash is important to the capturing process, pH manipulation is one of the major factors affecting the efficiency of this capture. The study of the influence of pH on development of charge on organic components in spent wash was undertaken using potentiometric titration. The potentiometric titration, and derived pH buffer curve, showed that the organic components in spent wash comprised a wide range of ionizable organic functional groups behaving like a mix of weak acids. While the inflection point (s) could not be obtained from the potentriometric titration, the absorbance of spent wash in the UV waveband (250 to 400 nm) confirmed the presence of phenolic groups in spent wash. The charge on organic components in spent wash was strongly pH dependent, and highest in the pH range of 4.0-5.0. The manipulation of pH and salt concentration (EC) was shown to have an effect on flocculation/dispersion and it is inferred that this was due to changes in the molecular arrangement of organic components in spent wash. A coiled configuration is suggested at acidic pH, whereas a linear flexible configuration and macromolecular structure tending to occur at neutral and alkaline pH respectively. Ca-saturated bentonite, originally sourced from Mantuan Downs, Central Queensland, was used in an investigation of the capture of OC and nutrients from Sarina spent wash at different pH values (4.5, 6.0, 8.0). This study demonstrated that manipulation of pH and electrolyte concentration had a small effect on adsorption of OC by the clay, probably the result of effects on the charge characteristics of both clay mineral surfaces and organic molecules and also on molecular sizes of the dissolved organic matter (DOM). The highest absorption of OC was only 28% for dewatered spent wash, suggesting Ca-saturated bentonite may not be a strong sorbent for DOM from a wastewater of high EC and which contains high concentration of DOC of the composition found in spent wash. The study of the adsorption of K by bentonite in a pure inorganic system (without DOM) indicated sufficiently high concentrations of K can compete with divalent Ca2+ for exchange sites on the clay surface. The adsorption of K in an organic system (the DOM component in spent wash) showed that DOM had a positive influence on adsorption of inorganic ions (e.g. K+). Characterisation of the spent wash/ clay mixture demonstrated its potential to be used as a soil ameliorant on the basis of the large quantity of OC and nutrients it contained (especially N and K). Wet and dry organic clays were produced and assessed as ameliorants in a glasshouse trial using forage oat (Avena sativa var. Coolobah) as test species. This pot study indicated a positive influence of application of either wet or dry organic clay on crop biomass at the high application rate (equivalent to 40 tonnes ha-1). The high proportional K recovery from this high application rate application suggests that organic clays can be used as K fertilizer. The crop nutrient uptake data also indicated its use as a source of S and Mn.