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Thesis (MSc)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: New, more receptive surfaces can be generated in soils by a partial dissolution of existing, crystalline solids followed by re-precipitation as poorly crystalline colloids with a larger capacity to adsorb ionic and molecular contaminants. This priming process can be carried out by treating the soil with strong acid or base and then neutral ising it again. The aim of this study was to investigate the effectiveness of acid and base treatments in reducing inorganic contaminant availability in different soil types. The first study involved investigating the change in cation (cadmium[II], copper[II]) and anion (phosphate) sorption of four different soils before and after priming. Hydrochloric acid and KOH were used to adjust the pH of soils to below pH 2 or above pH 12 in the dissolution stage of the priming treatment. After neutralisation it was found that base priming resulted in an increase in metal cation adsorption in all the soils, most notably in the sesquioxidic (increase from 19.5 to 73.5 mmol Cd.kg-1 soil) and kaolinitic soils (from 16.9 to 38.3 mmol Cd.kg-1 soil), whereas acid priming decreased it or had little effect on cation sorption. However, acid priming increased anion sorption in all soil types, to a greater extent than base priming, most notably in the organic soil (from 6.3 to 14.7 mmol P04.kg-1 soil). This can be attributed to the differences in the nature of the precipitate (more aluminous or alumino-siliceous) depending on whether the dissolution was carried out in acid or basic conditions, and the final pH of the soil solution, as the hydroxyaluminium and hydroxyaluminosilicate precipitates which form are known to enhance pH-dependent sorption of metals. In the second study, the soil was suspended in Cd or Cu solutions and then the pH was adjusted to below 2 or above 12 using HCI or KOH. After 5 days of shaking the pH was adjusted to a neutral pH again. The availability of the Cd and Cu was determined at each of the stages in the treatment, and it was found that both the acid and base treatments were effective in removing Cu from solution, whereas only the base treatment was effective in removing Cd. Determinations were also carried out using H2S04 and Ca(OH)2 and it was found that they were equally effective. It can be proposed that this acid-base pair would be of most practical importance as the salt generated is gypsum which is generally considered benign, and can actually help to improve the soil structure. Activation of soils by acid or base conditioning could have some useful applications in decontaminating soils or decreasing the mobility of inorganic contaminants in soils. Primed soils could also be used as cheap absorbents for decontaminating water. / AFRIKAANSE OPSOMMING: DEKONT AMINERING VAN GROND DEUR AKTIVlERING MET SURE EN BASISE Nuwe, meer ontvanklike oppervlakke kan in gronde gegenereer word deur middel van gedeeltelike oplossing van bestaande, kristallyne vaste stowwe gevolg deur herpresipitasie as swak kristallyne kolloïede met 'n groter kapasiteit om ioniese en molekulêre kontaminante te adsorbeer. Hierdie behandelingsproses kan uitgevoer word deur die grond met sterk suur of basis te behandel en dit daarna te neutraliseer. Die doel van hierdie studie was om die effektiwiteit van suur- of basisbehandelings om anorganiese kontaminante te verminder, in verskillende grond tipes te ondersoek. Die eerste studie het die ondersoek na die verandering in katioon- (kadmium[II], koper[lI]) en anioon- sorpsie (fosfaat) van vier verskillende gronde voor en na suur of basis voorbehandeling behels. Soutsuur en KOH was gebruik om die pH van die gronde tot onder pH 2 of bo pH 12 aan te pas gedurende die oplosstadium van die behandelingsproses. Na neutralisasie is dit gevind dat basis voorbehandeling tot 'n toename in metaal katioonadsorpsie in al die gronde gelei het, en dit was veral waarneembaar in die seskwioksied (toename van 19.5 tot 73.5 mmol Cd.kg" grond) en kaolinitiese (van 16.9 tot 38.3 mmol Cd.kg-1 grond) gronde, terwyl suur voorbehandeling dit verlaag het of 'n klein effek op katioonsorpsie gehad het. Suur voorbehandeling, egter, het anioonsorpsie in al die gronde verhoog, tot 'n groter mate as basis voorbehandeling, veral in die organiese grond (van 6.3 tot 14.7 mmol fosfaat.kg' grond). Dit kan toegeskryf word aan die verskille in die aard van die neerslag wat meer alurninium- of alurniniumsilika-ryk kan wees afhangede of die oplossing uitgevoer was in suur of basis kondisies, en ook die finale pH van die grondoplossing omdat die hidroksi-aluminium en hidroksi-aluminiumsilikaat presipitate wat vorm bekend daarvoor is om pH-afhanklike sorpsie van metale te bevorder. In die tweede studie, was die grond in Cd- of Cu-oplossings gesuspendeer en die pH was aangepas tot onder 2 of bo 12 met HCI of KOH. Na vyf dae van skud was die pH weer aangepas tot by neutraal. Die beskikbaarheid van Cd en Cu was bepaal by elke stadium in die behandeling, en dit is gevind dat beide suur- en basisbehandeling meer effektief was in die verwydering van Cu uit oplossing, terwyl slegs die basisbehandeling effektief was in die verwydering van Cd. Bepalings was ook uitgevoer met die gebruik van H2S04 en Ca(OH)2 en dit is gevind dat dit net so doeltreffend was soos HCI en KOH. Dit kan voorgestel word dat hierdie suur-basis paar in die praktyk belangriker sal wees omdat die sout wat gegenereer word, nl. gips, as 'n gunstige sout beskou word. Aktivering van grond deur suur- of basis-kondisionering kan sekere bruikbare toepassings in die dekontaminering van gronde hê of dit kan gebruik word om die mobiliteit van anorganiese kontaminante te verlaag. Suur of basis voorbehandelde gronde kan ook gebruik word as goedkoop absorbante vir die dekontaminering van water.

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<p> Cover crops and crop residue play a multifunctional role in improving soil hydrological properties, soil water storage and water use efficiency (WUE). This study was conducted to better understand the role of crop residue and cover crop on soil properties and soil water dynamics. The study was conducted at the USDA-ARS North Central Agricultural Research Laboratory, located in Brookings, South Dakota. Two residue removal treatments that include low residue removal (LRR) and high residue removal (HRR) were established in 2000 with randomized complete block design under no-till corn (Zea mays L.) and soybean (Glycine max L.) rotation. In 2005, cover crop treatments which include cover crops (CC) and no cover crops (NCC) were integrated into the overall design. Soil samples were collected in 2014, 2015 and 2016. Data from this study showed that LRR treatment resulted in lower bulk density (BD) by 7 and 9% compared to HRR in 2015 and 2016, respectively, for 0-5 cm depth. Similarly, LRR treatment significantly reduced soil penetration resistance (SPR) by 25% in 0-5 cm depth compared with HRR treatment. In addition to this, LRR treatment significantly increased soil organic carbon (SOC) concentrations and total nitrogen (TN) by 22 and 17%, respectively, in 0-5 cm. Similarly, CC treatment resulted in lower BD and SPR by 7% and 23%, respectively, in 0-5 cm depth in 2015 compared with NCC treatment. The LRR significantly increased soil water infiltration by 66 and 22% compared to HRR in 2014 and 2015, respectively. Similarly, the CC treatment significantly increased infiltration by 82 and 22% compared to the NCC in 2014 and 2015, respectively. The significant impact of a crop residue was observed on soil water retention (SWR) in 2014 and 2015 for the 0-5 cm depth. The LRR and CC treatments increased the soil volumetric moisture content (VMC) and soil water storage (SWS) on the surface 0-5 cm depth. However, the trend was not always significant during the growing season. The CC treatment significantly impacted the soybean yield by 14% and WUE by 13% compared with NCC treatment. Some interaction of residue by cover crops was observed on BD, SPR, VMC, and SWS, which showed that the use of cover crops with LRR can be beneficial in improving the soil properties.</p>

<p> A field experiment was established during 2014 in Northeast Arkansas to evaluate the benefits of cover crop and tillage management for enhanced yield and soil quality. Cover crop management included cereal rye, wheat and crimson clover, and a winter fallow. Tillage management included tillage and no-tillage.</p><p> In the 2015 and 2016 seasons yield was not significantly changed by different tillage treatments. Cover crop out yielded no cover crop at the A-State site in the 2016 season. Organic matter and active carbon were significantly influenced by tillage treatments. Physical and biological properties were significantly increased with cover crops compared with no cover crops in the 2015 and 2016 seasons. Physical properties were also significantly improved with no-tillage as compared with tillage in the 2015 and 2016 season. Biological properties were significantly influenced by different tillage treatments in the 2015 season.</p>

Soil fertility management presents the organic farmer with assorted challenges. Organic farmers generally don't follow the typical nutrient prescription approach for fertilizing crops as their conventional counterparts do, having to respond to criteria established by the USDA National Organic Program (NOP). Instead they aim towards improving the organic matter and biological activity of soil. Often this is achieved through the use of composts, either made on farm or purchased. Yet, composting presents challenges to the farmer too, requiring considerable land base, specialized equipment, and attention to various parameters to ensure compost meets NOP standards. There are alternatives to composts that are less explored in our agricultural system; one of them is bokashi. Bokashi is produced by the fermentation of organic materials with a microbial inoculant. The concept of bokashi has East Asia origins, but has been adopted in farming communities throughout the world and is gaining recent attention in countries like the United States as a way to quickly and efficiently transform food and kitchen wastes into an effective soil fertilizer. Little is known about the characteristics and capabilities of bokashi as a soil fertility amendment. The goal of this project was to compare the use of bokashi made from food waste and Effective Microorganisms® inoculum to thermophilic compost and vermicompost as soil fertility amendments to grow spinach in greenhouse and field environments. The greenhouse experiment showed that bokashi (B) treatments had different fertility characteristics than thermophilic compost (TC), vermicompost (V) and control treatments, especially in terms of redox reactive nutrients NO3--N -, Mn, and Fe, which is attributed to the anaerobic process used in its production. B treatments were characterized by initial high concentrations of NH4+, Mn and Fe, while V treatments were characterized by high initial NO3--N - . However, by the conclusion of the experiment, NO3--N - concentrations were greatest in B treatments, and V treatments had concentrations similar to control levels. Aboveground plant height and biomass of spinach in V and B treatments was greater than the control. This experiment suggested that B had a comparable performance to V in terms of nutrient supply and spinach growth. The field trial showed similar effects of B applications on N speciation and Mn and Fe concentrations as observed in the greenhouse experiment. Spinach from B treatments had significantly greater foliar concentrations of N, K, Mn, and Zn, as well as a significantly greater marketable yield than all other treatments at the second cutting of spinach (p<0.05). The field trial indicated that EM bokashi made from food waste may be a suitable supplemental or alternative soil fertility amendment in organic vegetable production systems. In both greenhouse and field trials, the soil microbial community in B treatments had a carbon substrate utilization pattern unique from all other treatments on the basis of principal coordinate analysis. These data suggest that bokashi applications affect the functional diversity of the soil microbial community.

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A Dissertation Submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in partial fulfillment for the Degree of Master of Science in Engineering. Johannesburg, 1979. / Soil stabilization is the generic term for any process which has as its aim the upgrading or improvement of one or more soil properties. In South Africa, stabilization is usually effected using a combination of mechanical densification and the addition of a binder to the soil. Two waste materials, PFA (a power station waste) and phosphogypsum (a waste from the fertilizer industry) have been shown to be useful binders overseas. The purpose of this project was to investigate local samples of these waste materials to establish their potential as soil stabilizers. A limited amount of research into the use of these two materials has been carried out in South Africa. The results of these programmes are discussed. Generally, however, none of these programmes were comprehensive enough to reach categoric conclusions regarding either binder. The soils used in the investigation were taken from various locations in the Johannesburg Municipal area in which it is intended to construct surfaced roads for light traffic in the near future. The soils chosen cover a range of plasticity indices from 0 to 30, but unfortunately, were very similar mineralogically. The phosphogypsum used was supplied by Triomf Fertilizer (Pty) Limited. Two samples of PFA were used. One of them was supplied by Darling and Hodgson, Limited, who are extracting a "selected" ash from Grootvlei power station, and intend to make it commercially available at some stage. The other ash was obtained from Kelvin power station. Tests were done to establish both the short and long term effects of the binders on the soils. The short term effects were investigated by looking at changes in the plasticity and moisture density relationships for the soils immediately after the addition of the binders. The long term effects were investigated by looking at the changes in unconfined compressive strength of moulded soil samples with the addition of the binders. (Samples were moulded at 100% Mod AASHO density and optimum moisture content in a tapered cylindrical mould by static compaction). These effects were looked at from 3 different angles. i) the effect of binder composition (i.e. different ratios of PFA/lime and PFA/cement) ii) the effect of binder content iii) the effect of age on strength gain The results of the testing programme were not very encouraging. For the binder contents used, there were minimum short term effects for both binder types. The addition of phosphogypsum to the soils resulted in only very small strength increases. For the PFA binders, it appears that the lime content of many of the PFA/lime binders fell in a range where only short term reactions could be expected. However, even where sufficient lime was present to satisfy the initial lime demand of the soil, the PFA appeared to act mainly as a diluent to the lime. Similar conclusions apply to the PFA/cement binders. The general nature of PFA/lime stabilization was uncovered in this testing programme, but further tests will have conducted before conclusions regarding the quality of our local materials can be drawn.