For the successful reclamation of disturbed land, the reduction of initial erosion risk must be balanced with later vegetation establishment. A combination of erosion control and revegetation practices was researched using commercial (full-sized) equipment on a semi-desert grassland site in southern Arizona, USA. Two soils with different parent materials were used to add a 30 cm cap on sites at two elevations: 1646 and 1403 m asl. There were two surface roughness treatments: smooth and rough. Three straw mulch treatments were applied: no mulch, mulch incorporated into the surface soil, and mulch tackified onto the surface. Plots were planted with a 10 species native mix dominated by perennial grasses. After two growing seasons, the incorporated mulch treatment resulted in significantly more seeded grass aboveground biomass than the no mulch treatment while the no mulch treatment had more forb and volunteer biomass than the surface mulch treatment. There was significantly higher erosion on the rough surface treatment compared to the smooth surface. Increasing perennial grass biomass was correlated with reduced erosion while forb and volunteer biomass showed no relationship with erosion. The smooth surface with surface mulch best established perennial grasses, minimized weeds, and reduced erosion. This combination of practices both minimized erosion as well as maximized vegetation establishment. (C) 2016 The Authors. Published by Elsevier B.V.

The environmental fate of polycyclic aromatic hydrocarbons (PAH) is a significant issue, raising interest in bioremediation. However, the physio-chemical characteristics of PAHs and the physical, chemical, and biological properties of soils can drastically influence in the degradation. Moreover, PAHs are toxic and carcinogenic for humans and their rapid degradation is of great importance. The process of degradation of pollutants can be enhanced by manipulating abiotic factors. The effect of soil pH on degradation of PAHs with a view to manipulating soil pH to enhance the bioremediation of PAH’s was studied. The degradation rate of key model PAHs (Phenanthrene, Anthracene, Fluoranthene, and Pyrene) was monitored in J Arthur Brower’s topsoil modified to a range of pH between pH 4.0 and pH 9.0 at half pH intervals. Photo-catalytic oxidation of PAHs in the presence of a catalyst (TiO2) under UV light at two different wavelengths was studied. The degradation of PAHs during photo-catalytic oxidation was carried out at varying soil pH, whilst the degradation rate of each individual PAH was monitored using HPLC. It was observed that pH 6.5 was most suitable for the photo-degradation of all the PAHs, whilst in general acidic soil had greater photo-degradation rates than alkaline soil pH. Photo-degradation of PAHs at 375 nm exhibited greater degradation rates compared to 254 nm. Phenanthrene at both the wavelengths had greater degradation rate and pyrene has lower degradation rate of the four PAHs. Pure microbial cultures were isolated from road-side soil by shaken enrichment culture and characterized for their ability to grow on PAHs. Bacterial PAH degraders, isolated via enrichment were identified biochemically and by molecular techniques using PCR amplification and sequencing of 16S rDNA. Sequences were analyzed using BLAST (NCBI) and their percentage identity to known bacterial rDNA sequences in the GeneBank database (NCBI) was compared. The 6 bacterial strains were identified as Pseudomonas putida, Achromobacter xylosoxidans, Microbacterium sp., Alpha proteobacterium, Brevundimonas sp., Bradyrhizobium sp. Similarly, fungal PAH degraders were identified microscopically and with molecular techniques using PCR amplification and sequencing of 18S rDNA and identified as Aspergillus niger and Penicillium freii. Biodegradation of four PAHs with two and four aromatic rings were studied in soil with inoculation of the six identified bacteria and two identified fungi over a range of pH. It was observed that pH 7.5 was most suitable for the degradation of all the PAHs maintained in the dark. A degradation of 50% was observed in soil pH 7.5 within first three days which was a seventh of the time taken at pH 5.0 and pH 6.5 (21 days). Greater fungal populations were found at acidic soil pH and alkaline soil pH, in comparison with neutral pH 7.0. Pencillium sp. was found to be more prevalent at acidic pH whilst Aspergillus sp. was found to be more prevalent at pH 7.5-8.0. Bacterial populations were greater at pH 7.5 which was highly correlated with soil ATP levels. It was therefore evident that the greatest rates of degradation were associated with the greatest bacterial population. Soil enzyme activities in general were also greatest at pH 7.5. The converse effect of pH was found with fastest rate of photo-catalytic degradation at the optimal conditions were observed at acidic condition in soil pH 6.5 whilst, the results obtained during biodegradation at the optimal conditions exhibits fastest rate of degradation at alkaline conditions particularly at pH 7.5. Thus, manipulation of soil pH to 7.5 has significant potential to dramatically increase the degradation rate of PAHs.

Diss. (sammanfattning) Umeå : Sveriges lantbruksuniv. / Härtill 6 uppsatser.

Amending litter with aluminum sulfate (Al-S) has proven to be effective in reducing water-soluble P but there are concerns that it could result in soil pH reduction and increase levels of extractable soil Al if applied to acidic soils. A glasshouse study with soybean (Glycine max, L Merr) and cotton (Gossypium hirsutum L) as test crops was conducted to determine the impact of applying litter amended with Al-S at 0, 10 and 20% to an acidic sandy loam soil. These treatments were applied to meet N needs of a crop grown in soil with pH levels of 4.5, 5.0, 5.5 and 6.5. The experimental design was a randomized complete block. Application of BL + 20% Al-S to soil with initial pH of 4.5 or 5.0 significantly decreased the pH compared to BL. The decrease in soil pH with application of BL + 20% Al-S was attributed to high concentrations of geochemically labile Al which released hydrogen ions upon hydrolysis. Both BL and BL + 10% Al-S increased the initial soil pH and decreased extractable soil Al. Application of BL + 20% Al-S resulted in significant higher levels of extractable soil Al than BL and the differences were greater in the lower pH soils. Mehlich-3 extractable soil P, K, Mg, Ca, and Cu decreased with BL + 10 or 20% Al-S relative to BL. Soybean or cotton biomass from BL + 20% Al-S fertilization was significantly decreased relative to BL fertilized soils with initial pH of 4.5 or 5.0. Biomass with BL + 10% Al-S application were not statistically different from those fertilized with BL. Fertilizing cotton or soybean with BL + Al-S decreased tissue Al, N and P concentration. BL and BL + 10% Al-S showed the potential to increase soil pH and reduce extractable soil Al in acid soils but need further field evaluation.

Zinc deficient soils, or soils with low Zn bioavailability, are widespread, which exacerbates Zn deficiency in human as crops grown on these soils have low Zn content. Often crop yields are also compromised. Fertilizers based on soluble Zn salts often have limited efficacy in such soils. In this research, we evaluate the performance of polymer coated and bare ZnO nanoparticles (NPs) in an attempt to overcome limitations of soluble Zn salts in alkaline soils. We first synthesized 20-30 nm bare ZnO NPs with different surface chemistries to impart colloidal stability to the particles. Bare ZnO were treated in phosphate solution under certain conditions leading to the formation of a core made of ZnO NPs that is covered by a shell of amorphous Zn3(PO4)2 (core-shell NPs). This confers a negative charge to the particles over a wide pH range. The addition of nonionic (neutral dextran) and polyelectrolyte (negatively charged dextran sulfate (DEX(SO4)) during the synthesis resulted in the formation of DEX and DEX(SO4) ZnO NPs. Dextran has a minimal effect on the surface charge of ZnO but dextran sulfate confers a net negative charge. Bare and core-shell ZnO NPs were both electrostatically stabilized whereas DEX and DEX(SO4) ZnO NPs were sterically and electrosterically stabilized, respectively. We investigated the effect of treating seeds with ZnO NPs on the growth and accumulation of Zn in wheat (Triticum aestivum) seedlings in comparison to ZnSO4. All ZnO NPs stimulated seedling growth. Seedlings accumulated higher Zn concentrations when treated with ZnO NPs than with ZnSO4. Zinc sulfate was toxic even at the lower exposure concentrations, which was demonstrated by significantly lower germination success and seedling growth. In the second experiment, we investigated the effect of pH on the attachment and dissolution of ZnO NPs in soil, as compared to ZnSO4. Soil pH was adjusted to 6 and 8, then the soil was spiked with 100 mg Zn/kg soil in the form of ZnSO4, bare, DEX, DEX(SO4), and core-shell ZnO NPs. The results showed that DEX and core-shell ZnO NPs had significantly higher total Zn in soil solution compared to ZnSO4 at pH 8, with little dissolution. Dissolved Zn was similar among treatments except ZnSO4 at pH 6, indicating little dissolution of the ZnO NPs at either pH value. We also found that the engineered coatings dictate the behavior of the particles in simple aqueous systems, but their properties are altered in natural soil solutions because of the dominant effect of natural organic matter (NOM) on their surface chemistry. Based on the outcomes of the previous two experiments, we selected DEX and bare ZnO NPs to test the efficacy of ZnO NPs in delivering Zn to the grain of wheat under greenhouse conditions. We performed two independent studies where seeds were either treated with the NPs or grown in a soil spiked with Zn at pH 6 and 8 and spiked with Zn treatments (nano and ionic). We found that treating seeds with bare ZnO NPs significantly enhanced grain Zn concentrations as compared to the control, DEX-ZnO NPs, and ZnSO4. There were no differences in grain Zn concentration of plants treated with ionic or nano Zn treatments regardless of the soil pH. This work has elucidated important principles which will help carry forward efforts at developing effective ZnO NP-based fertilizers. It also suggests that treatment of seeds with ZnO NPs is more effective than amending soil or treating seeds with ZnSO4.

Thesis (M.Sc. Agric (Soil Science)) -- University of Limpopo, 2013 / Knowledge and management of soil pH, particularly soil acidity across spatially variable soils is important, although this is greatly ignored by farmers in the Limpopo Province of South Africa. The significance of understanding spatial variability of soil acidity is the implementation of best and site-specific management strategies because when soil acidity is poorly managed, toxicity and nutrient deficiency problems in the soil are inevitable. The objective of the study was to evaluate in-field spatial variability of soil pH, and compare the efficiency of managing soil pH through site-specific method vs. uniform lime application. The study was conducted in 3 site years (23o50’ S; 29 o40’ E and 23o59’ S and 28o52’ E) with site year I, and II adjacent to each other in the semi-arid regions of the Limpopo Province, South Africa. Soil samples were taken in four replicates within a 1 m radius from geo-referenced locations in 3 study sites to sampling depths of 0-20 cm on a regular grid of 30m using differential Global Positioning System (DGPS). Soils were analyzed for pH, and SMP buffer pH for lime recommendations. Lime requirement to achieve a soil pH of 6.5 for a 20 cm plough layer per hectare was calculated using CalciumCarbonateequivalent, efficiency factor (fineness factor), and neutralizing index of the liming materials. The spatial maps for SMP buffer pH and lime requirement maps were produced with surfer version 8.0 (Surfer Version 8, Golden Software, Golden, CO). The soil pH datasets from systematic unaligned randomly sampled soils on a 30-m grid were interpolated using inverse distance weighing (IDW) in Surfer software version 8.0 (Surfer Version 8, Golden Software, Golden, CO). Soil pH varied from strongly acidic to slightly acidic with minimum values of 4.22, 3.93, and 4.74 and maximum values of 6.11, 7.00, and 6.82 in site I, II, and II respectively. In Site I, II, and III, the areas of the field that had soil pH values of less than 6.0 were 99.43, 82.61, and 62.89% of the field. When lime was recommended for application using a conventional method of uniform lime application based on an average value derived from samples collected in the whole field, the results of the study showed a waste of lime in excess of lime recommended for individual grids. An excess amount of lime as high as 10, 30, and 7 tons/ha recommended on sites I, II and III respectively under uniform application. These recommendations were in excess on field areas that needed little or no lime applications. Again, the fields showed under applications of lime as much as 30, 35, and 13 tons/ha in site I, II, and III respectively for uniform liming applications. This under- and over recommendations of lime based on average soil pH values suggests that uniform soil acidity management strategy is not an appropriate strategy to be adopted in these fields. Again, in both of these sites as shown in the maps, the areas that required high amount of lime and those that require little or no lime are clearly defined, such that the fields can be divided into lime application zones. When a field is divided into lime application zones, management of soil acidity becomes easier because instead of applying variable rates of lime for every grid, lime rates are applied per zone. These zones could be areas in a field that require, (i) high rates of lime, (ii) low rates of lime, and (iii) areas that requires no lime at all. Agricultural fields that exhibit spatial variability of soil acidity must not be managed or treated as uniform when lime is applied in the field. Keywords: Lime requirement, Site specific management and Soil pH.

Agriculture is the principal land use throughout Europe and agricultural intensification has been implicated in large reductions in biodiversity, with the negative effects on birds particularly well documented. The lapwing (Vanellus vanellus) is one such species where changes in farming practices has reduced the suitability and quality of breeding habitat, leading to a drop in population size that has been so severe as to warrant its addition to the Red List of Birds of Conservation Concern in the UK. Lowland areas, where agricultural intensification has generally been most pronounced, have been worst affected, however, more recently declines in marginal upland areas, previously considered refuges for breeding wader populations, have been identified. An upland livestock farm in Stirlingshire that uses an in-bye system of fodder crop management and has unusually high densities of breeding lapwings provides a basis for this project to test causal hypotheses for the decline of upland lapwing populations and to identify potential conservation management solutions. Specifically this farm plants a forage brassica in an in-bye field for two consecutive years, followed by reseeding with grass and seven, out of sixteen, in-bye fields have undergone this regime at the study site since 1997. Fields that had undergone fodder crop management supported almost 60% more lapwings than comparable fields that had not previously been planted with the fodder crop. Lapwing density was highest in the year after the fodder crop was planted, once it had been grazed, which results in a high percentage of bare ground, likely to be attractive to nesting lapwings. Lapwing densities remained above that which occurred in fields that had not undergone fodder crop management for a further four years after the field had been returned to grass. The effect of management on lapwing food resources and nesting structure was tested through a field experiment; liming increased the abundance of Allolobophora chlorotica, an earthworm species that was associated with chick foraging location at the study site, suggesting that lapwings may benefit from liming conducted as part of fodder crop management. The relationship between lapwings and soil pH is further explored across 89 sites on mainland Scotland, using soil property data to improve the predictive power of habitat association models, something which has not previously been done for any farmland bird. Adding soil and topographical data to habitat models, based on established relationships between breeding lapwings and their habitat, improved model fit by almost 60%, indicating that soil properties influence the distribution of this species. The density of breeding lapwings was highest at higher altitude sites, but only when the soil was relatively less peaty and less acidic, providing further support for the hypothesis that agricultural liming benefits lapwings. In addition to assessing the conservation benefit of fodder crop management, the economic costs are also considered. Fodder crop management provides a source of livestock fodder in the autumn and winter during a period when forage demands outstrip grass growth, and ultimately improves the grazing quality of the grass that is replaced; this system currently operates outside of any agri-environment scheme (AES). However, at the study site, planting of the fodder crop and grass is delayed to avoid agriculture operations during the breeding season, which reduces yield and hence profitability. An initial estimate of £200 ha-1 is suggested as an incentive to encourage wider adoption of fodder crop management in a “lapwing friendly” manner, although further work is required to determine if this payment level is appropriate and the current method of AES implementation may limit the suitability of fodder crop management as an AES. The results indicate that agricultural liming could benefit breeding lapwings in pasture fields where soil pH falls below pH 5.2, by increasing earthworm abundance. Where soil pH is below pH 5.2, liming should provide a cost effective mechanism for farmers to improve grass yields. Regular soil testing and liming in response to low pH, within improved or semi-improved grassland fields, where management activities such as use of nitrogen fertiliser can contribute to soil acidification, should be advocated to farmers in marginal areas as a mechanism for improving grass productivity whilst potentially benefitting breeding lapwing and other species where earthworms contribute significantly to their diet.

Diss. (sammanfattning) Umeå : Sveriges lantbruksuniv., 2007. / Härtill 3 uppsatser.

Diss. (sammanfattning) Alnarp : Sveriges lantbruksuniversitet, 2006. / Härtill 4 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv. / Härtill 4 uppsatser.