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.

Thesis (MScAgric)--Stellenbosch University, 2012 / ENGLISH ABSTRACT: Biochar has been labelled to be a key factor in the global carbon mitigation act and has been described as the modern day equivalent (terra nova) to the terra preta dark earth soils of the Brazilian Amazon. Globally biochar has been evaluated as a means to improve soil fertility and to mitigate greenhouse gases (GHGs). Little research has however been published on the effects of biochar incorporation on soil physical properties. The objective of this study was to evaluate the effect of pine sawmill waste derived biochar (locally-produced via slow pyrolysis – 450°C) on selected soil physical properties, soil-water dynamics and crop production and- performance, when amended to a Kroonstad (Kd 1000 – Morgendal) soil form. This soil form is commonly found in the Western Cape area (South Africa) and can be classified as having low agricultural suitability for perennial- and annual crop species. Two pot trials were carried out in an atmospheric controlled greenhouse, where winter wheat and green beans respectively were planted, with five different application levels of biochar (0t/ha, 1t/ha, 10t/ha, 50t/ha and 200t/ha). Soil physical properties namely, water-stable aggregates, bulk density and water-retention capacity along with physiochemical characterisation of the sandy soil and biochar was determined. The water-use was monitored throughout the trials (evapotranspiration, volumetric water content and biomass water use efficiency, BWUE). The above- and below ground (specific leaf traits for the green bean and the root structural development for the winter wheat) biomass was collected and analysed at harvest. There was significantly higher volumetric water content measured for the 50t/ha and 200t/ha biochar treatments. This effect can be ascribed due to a change in the soil’s tortuosity and porosity where more meso- and micro-pores were present as the biochar rate increased. The same results were evident when a water-retention curve was established in vitro by means of the sandbox method. The bulk densities were only significantly lower for the 200t/ha biochar treatments. The wheat root systems differed greatly among the fertilised biochar treatments: the 50t/ha and 200t/ha treatments had a more complex fibrous root system (more extensive branching and thinner roots) than 0t/ha, 1t/ha and 10t/ha application levels. This is attributed to the increased water-holding capacity along with a reduction of N- and P availability with increasing addition of biochar. Several leaf traits were measured for the green bean crops; however the leaf nitrogen- and carbon content, chlorophyll content index (CCI) and carbon isotope fractionation yielded the most interesting findings. Concerning the fertilised biochar treatments, there was established that the 10t/ha treatments had the highest leaf nitrogen- and carbon content. The leaf chlorophyll content did not differ significantly between the fertilised biochar treatments; however a very interesting observation was evident regarding the measured leaf CCI for the unfertilised treatments. A decreasing trend and lower leaf CCI was measured as the biochar application levels increased. This effect was ascribed to be due to a decrease in N uptake by the plants as the biochar application increased, the C/N ratio also increased, and this leading to N immobilisation. The lowest leaf carbon isotope fractionation was measured for the 10t/ha fertilised treatments and is inversely correlated with BWUE and therefore endorses the conclusion that the 10t/ha biochar application had a positive effect on the long term water use efficiency for the green bean plants. Biochar promoted aggregation in the sand-rhizosphere interface for winter wheat, increased water-holding capacity and enhanced crop performance for green beans. The findings reported here provide new information on the effect of biochar on the structural development of sandy soil, combined with biochar- and root growth effects for winter wheat; along with detailed interpretations of specific leaf traits associated with crop production for commercial green beans. The addition of biochar at low application levels (approximately 1-10t/ha to 15 cm depth) increased the biomass yield and water use efficiency of the crop species. Besides long term carbon storage, biochar can have immediate positive effects on the physical properties of sand and plant growth. / AFRIKAANSE OPSOMMING: Biokoolstof word beskou as ‘n sleutel komponent rakende die wet op globale koolstofvermindering en is al beskryf as die moderne ekwivalent (terra nova) van die terra preta donker-aardgronde wat aangetref word in die Brasiliaanse Amasone. Wêreldwyd word biokoolstof tans geëvalueer met die doel om grondvrugbaarheid te verbeter asook kweekhuisgasse (KHG) se nadelige gevolge te verlig. Min navorsing was tot dus ver gedoen rakende die uitwerking met toediening van biokoolstof op grondfisiese-eienskappe. Die doel van hierdie studie was om die effek van biokoolstof, wat afkomstig is van denne-saagmeul-afval (plaaslik geproduseer is en d.m.v. stadige perolise - 450°C) te evalueer aangaande die volgende faktore: geselekteerde grondfisiese-eienskappe, grond-waterdinamika interaksie en die uitwerking op gewasproduksie; met toediening aan 'n Kroonstad (Kd 1000 - Morgendal) grondvorm. Hierdie grondvorm word as algemeen in die Wes-Kaap (Suid-Afrika) bestempel en kan geklassifiseer word as ‘n lae-geskiktheid landbougrond vir meerjarige- en eenjarige gewasse. Twee potproewe is uitgevoer onder beheerde atmosfeer in ‘n kweekhuis, waar winter koring en groenbone geplant is, met vyf verskillende behandelings van biokoolstof (0t/ha, 1t/ha, 10t/ha, 50t/ha en 200t/ha). Die volgende grondfisiese-eienskappe is ondersoek, naamlik water-stabiele aggregaat formasie, bulkdigtheid en waterhouvermoë, asook die fisiochemiese karakterisering van die sanderige grond en biokoolstof wat gebuik is. Waterverbruik is gedurende die proewe gekontroleer (evapotranspirasie, volumetriese waterinhoud en die biomassa se water verbruiksdoeltreffendheid, BWVD). Die bo- en ondergrondse biomassa, spesifiek die blaareienskappe van die groenboontjie en die strukturele ontwikkeling van die winter koring se wortels, is tydens die oes ondersoek en ontleed. Die volumetriese waterinhoud was betekenisvol, asook hoër vir die 50t/ha en 200t/ha behandelings. Hierdie effek word toegeskryf as gevolg van 'n verandering in die grond se kronkeligheid en porositeit; waar meer meso- en mikroporieë teenwoordig was soos die biokoolstof inhoud toegeneem het. Dieselfde resultate was verkry met die opstelling van ‘n water-retensie kurwe in vitro d.m.v. die Sandboks metode. Bulkdigtheid was slegs betekenisvol verskilled asook aansienlik laer vir die 200t/ha biokoolstof behandelings. Die koring se wortelstelsel het drasties verskil tussen die verskillende bemeste biokoolstof behandelings: die 50t/ha en 200t/ha behandelings het 'n meer komplekse en veselagtige wortelstelsel gevorm (hoër graad van vertakking en dunner wortels was aanwesig) as die 0t/ha, 1t/ha en 10t/ha behandelings. Die effek word toegeskryf aan die toenemende waterhouvermoë, tesame met 'n tekort aan N- en P-beskikbaarheid soos die biokoolstof toedieningshoeveelhede verhoog het. Verskeie blaareienskappe is gemeet vir die groenboon gewasse, maar die blaar stikstof- en koolstof-inhoud, chlorofil inhoud indeks (CII) en koolstof-isotoop fraksionering het die mees interessante bevindinge opgelewer. Die hoogste blaar stikstof-en koolstof-inhoud is gemeet vir die 10t/ha bemeste biokoolstof behandelings. Die blaar chlorofil inhoud het nie beduidend verskil tussen die bemeste biokoolstof behandelings nie, maar daar was egter 'n baie interessante waarneming vir die onbemeste biokoolstof behandelings. ‘n Tendens was aanwesig waar die CII afgeneem het soos die biokoolstof toedieningshoeveelheid ook afgeneem het vir die onbemeste behandelings. Die effek word toegeskryf as gevolg van 'n afname in N-opname deur die plant soos die biokoolstof toedieningshoeveelheid verhoog is en tot gevolg gehad het dat die C/N-verhouding ook toegeneem het, wat gelei het tot N-immobilisasie. Die laagste blaar koolstof-isotoop fraksionering was geassioseer met die 10t/ha bemeste biokoolstof behandelings en is omgekeerd gekorreleerd met BWVD en onderskryf dus die gevolgtrekking dat die 10t/ha biokoolstof behandeling 'n positiewe uitwerking het op die langtermyn waterverbruiksdoeltreffendheid vir groenboontjie plante. Biokoolstof het aggregasie bevorder binne die wortelsone, asook deurgans die waterhouvermoë verhoog en gewasproduksie verbeter. Hierdie bevindinge lewer nuwe inligting oor die effek van biokoolstof op die strukturele ontwikkeling van sanderige grond en die gekombineerde interaksie met biokoolstof toediening en hoe dit wortegroei beïnvloed van winter koring; asook 'n gedetailleerde interpretasie van spesifieke blaareienskappe wat verband hou met die produksie van gewasse vir kommersiële verbouing soos die groenboontjie. Die toediening van biokoolstof by die lae hoeveelhede (ongeveer 1-10t/ha tot op 15 cm diepte) het die opbrengs en waterverbruiksdoeltreffendheid van die gewasse verbeter. Behalwe vir die langtermyn koolstofvaslegging, kan biokoolstof toediening onmiddellike positiewe resultate teweeg bring aangaande die fisiese eienskappe van sandgronde en plantegroei.