Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2008. / Härtill 6 uppsatser.

Thesis (MSc)--Stellenbosch University, 2005. / ENGLISH ABSTRACT: The agricultural sector in South Africa relies heavily on the use of pesticides to protect crops against pest organisms. Pesticides can affect non-target organisms such as the meso- and macrofauna in the soil detrimentally. Since these organisms play an important role in the processes of mineralization and decomposition in the soil and contribute to soil fertility, it is important that they are protected. A large amount of published literature exists on the biological importance of soil meso- and macrofauna and the effects that various agricultural practices have on them. The main aim of this study was to investigate the influence of agricultural practices on the abundance and diversity of meso- and macrofauna in different vineyard soils. A comparative study was conducted of an organically managed, conventionally managed and an uncultivated control soil. A secondary aim was to determine the effect of these agricultural management practices on the biological activity of these animals. Soil samples were taken, from which mesofauna (Collembola and Acari) were extracted with a modified Tullgren extractor, identified and counted. Earthworms were extracted from the soil using hand sorting methods. Soil parameters such as pH, water holding capacity, organic matter content, soil texture and soil respiration were determined. Bait lamina and litter-bags were also used to help determine the biological activity within the soil. The mesofauna diversity was quantified using the Shannon Weiner diversity index, as well as a diversity index described by Cancela da Fonseca and Sarkar (1996). Differences in abundance of both the meso-and macrofauna were statistically measured using ANOVA's. Biological activity results were also interpreted using ANOV A's. Results indicate that the abundance of the meso fauna was the highest at the organically treated vineyard soil and lowest in the conventionally managed soil where pesticide application took place. The earthworms also showed the same trend as the mesofauna, but were much more influenced by seasonal changes. Biological activity, according to the bait lamina and the litter-bag results, was higher in both the conventionally and organically managed soils than in the control, but no statistical significant differences were found between the two experimental soils. The soil respiration (C02-flux), also indicating biological activity, was highest in the organically treated soil and lowest in the conventionally treated soil. The different sampling techniques used gave variable results and although the organically managed soil proved to have higher abundances of both meso- and macrofauna, the biological activity did not show the same trends. In conclusion the data did not give enough evidence as to whether organic management practices were more beneficial than conventional management practices for the maintenance of soil biodiversity. / AFRIKAANSE OPSOMMING: Die Suid Afrikaanse Landbousektor steun hewig op die gebruik van verskillende chemiese pestisiede om oeste teen pes organismes te beskerm. Pestisiede kon ook verskeie ander nie-teikenorganismes soos die meso- en makrofauna in die grond negatief affekteer. Hierdie organismes behoort beskerm te word omdat hulle 'n belangrike rol speel in grondprosesse soos mineralisering, en die afbreek van organiese materiaal. Hierdie organismes dra ook by tot die vrugbaarheid van die grond. Daar is heelwat gepubliseerde literatuur beskikbaar wat verband hou met die biologiese belangrikheid van grond meso- en makrofauna en die effekte wat verskeie landbou behandelings op hulle het. Die primêre doel van hierdie studie was om vas te stel watter invloed konvensionele landboupraktyke op die hoeveelheid en diversiteit van meso- en makrofauna in verskillende wingerdgronde het. 'n Vergelykende studie is gedoen om wingerdgronde wat konvensioneel en organies behandel is sowel as 'n onbehandelde kontrolegrond met natuurlike plantegroei met mekaar te vergelyk. 'n Sekondêre doel van hierdie studie was ook om die effek van die verskillende boerderymetodes op die biologiese akitiwiteit in die grond te ondersoek. Grondmonsters is geneem, waaruit die meso fauna (Collembola en Acari) deur middel van 'n aangepaste Tullgren ekstraktor ge-ekstraheer, geïdentifiseer en getel. Die erdwurms is deur middel van handsorteringsmetodes versamel. Die volgende grond parameters is gemeet: pH, waterhouvermoë, organiese materiaal inhoud, grondtekstuur en grondrespirasie. "Bait lamina" en "litter bags" is ook gebruik om biologiese aktiwiteit in die grond te bepaal. Die diversiteit van mesofauna is bepaal met die Shannon Weiner diversiteitsindeks, as ook 'n diversiteitsindeks wat deur Cancela da Fonseca en Sarkar (1996) ontwikkel is. Die resultate van beide die meso- en makrofauna hoeveelhede in die verskillende wingerdgronde is met mekaar vergelyk deur van ANOV A's gebruik te maak. Die resultate van die biologiese aktiwiteit is ook deur middel van ANOVO's statisties met mekaar vergelyk. Die resultate het aangetoon dat die hoeveelheid mesofauna die hoogste in die organies behandelde grond en die laagste in konvensionele grond was. Die erdwurms het dieselfde patroon as die mesofauna getoon, maar is baie meer deur seisoenale faktore geaffekteer, bv. reënval. Volgens die resultate van die "bait lamina" en die "litter bags" was die biologiese aktiwiteit in die grond hoër in beide die eksperimentele grond as in die kontrolegrond. Die grondrespirasie (C02-puIs) was hoër in die kontrolegrond as in die ander eksperimentele gronde. Daar was groot variasie tussen die resultate wat met die verskillende tegnieke verkry is en alhoewel die organiese perseel hoër hoeveelhede van beide meso- en makrofauna gehad het, het die biologiese aktiwiteit nie dieselfde tendens gewys nie. Vanuit die data wat verkry is kon daar dus nie met sekerheid afgelei word dat organiese boerderymetodes beter vir die biodiversiteit van gronde,soos hier gemeet, is as konvensionele boerderymetodes nie.

It was found that Azotobacter vinelandii grown in a dialyzed soil medium did not fix nitrogen and had a much lower rate of respiration than when grown in Burk's nitrogen-free medium. When para-hydroxybenzoic acid served as the added oxidizable organic carbon source in dialyzed soil medium, the azotobacter grown in it were found to be unable to fix nitrogen. On the other hand, A. vinelandii fixed nitrogen when grown in soil supplemented with glucose. It was concluded that natural conditions in the soil are not conducive to nitrogen fixation by A. vinelandii.

Thesis (MTech (Horticulture))--Cape Peninsula University of Technology, 2013. / This study evaluated the effects of supplementary phosphorus, copper and zinc alone and in conjunction with arbuscular mycorrhiza on Artemisia afra grown in a simulated soil medium. The treatments consisted two groups. Group A had no mycorrhizal inoculation and 1) no supplementary fertilization, 2) supplementary zinc application, 3) supplementary copper 4) supplementary phosphorus 5) supplementary zinc and copper, 6) supplementary zinc and phosphorus, 7) supplementary copper and phosphorus, 8) supplementary zinc, copper, and phosphorus. Group B had mycorrhizal inoculation in combination with 9) no supplementary fertilization, 10) supplementary zinc application, 11) supplementary copper 12) supplementary phosphorus 13) supplementary zinc and copper, 14) supplementary zinc and phosphorus, 15) supplementary copper and phosphorus, 16) supplementary zinc, copper, and phosphorus. There was also a pilot study into the pH range most suitable for the cultivation of A. afra in a hydroponic system, which was used to refine the mycorrhizal investigation, as pH has influences with regards to nutrient uptake of plants.

This study is aimed on teaching of soil biology at secondary schools. Available biology textbooks are assessed and their content on soil biology is evaluated. Part of the thesis constitutes of a survey among teachers of biology. It is focused on contemporary teaching approaches, availability of materials and the requirements of teachers to teach soil biology at individual schools. In conclusion, I propose an educational project focusing on the importance of soil.

Carbon accumulation in soils constitutes a significant sink for carbon. How the climate change with increasing temperatures will affect the soil carbon storage represents uncertainty of the predictions in the climate change ecosystem feedback mechanisms. In this study the temperature impact on the decomposition of the large carbon pools in peatlands was investigated. Peat cores from different microtopographic units in a boreal oligotrophic minerogenic mire in northern Sweden were collected from in three depths (5-10, 10-15 and 15-20 centimeters below the surface). The samples were incubated at four temperatures: 4, 9, 14 and 19°C and the heterotrophic respiration (CO2- production) was measured hourly or 37 days. Unexpectedly, basal respiration did not show any correlation with temperature. However, the exponential increase in respiration (µ) was correlated with temperature: i.e.  giving Q10 values between 2 (SE +/- 0.36) and 5 (SE +/-1.05). Soil depth or vegetation covers did not affect temperature response (Q10) of µ. The substrate induced respiration (SIR) did not occour but for a few of the samples. The conclusion from this study is that degradation of peat seams not be affected by a temperature increase. The addition of glucose, nitrogen and phosphorus increased with increasing temperature with a Q10 value as expected.

The effects of increasing periods under sugarcane monoculture (managed by preharvest burning) on soil organic matter content and related soil properties were investigated in the 0 to 10 cm layer of a sandy coastal Ochric Cambisol (Glenrosa soils) and a red Rhodic Ferralsol (Hutton soil) from the sugar belt of KwaZulu-Natal. The organic C content at both sites under undisturbed vegetation is about 48 g C kg-I. This declined exponentially with increasing years under sugarcane. For the Glenrosa site, organic C reached a new equilibrium level of about 20 g kg-I while at the Hutton soil the equivalent value was 41 g kg-I. The higher organic matter content maintained at the Hutton site was attributed mainly to clay protection of organic matter since the clay content of the Hutton soil was 61 % compared to the 18 % for the Glenrosa soil. The loss of soil organic matter under sugarcane resulted in a concomitant decline in soil microbial biomass C, microbial quotient, basal respiration, aggregate stability, arylsulphatase and acid phosphatase activity. The activities of arylsulphatase and acid phosphatase like those for concentrations of microbial biomass and organic C, were higher for the Hutton than Glenrosa soils. At the Glenrosa site, the natural OBC abundance in soils was used to calculate the loss offorest-derived, native soil C and the concomitant input of sugarcane-derived C. Sugarcane-derived C increased over time until it accounted for about 61 % of organic C in the surface 10 cm in soils that had been under sugarcane for greater than 50 years. The effects of agricultural land use (including burnt sugarcane) on organic matter content and related soil properties were compared with those under undisturbed native grassland in KwaZulu-Natal. Two separate farms situated on Oxisols were used and both contained fields with continuous long-term (>20 years) cropping histories. At site 1, soil organic C content in the surface 10 cm followed the order permanent kikuyu pasture> annual ryegrass pasture> native grassland> preharvest burnt sugarcane > maize under conventional tillage (CT). At site 2, organic C in the surface 20 cm decreased in the general order kikuyu pasture> native grassland > annual ryegrass pasture> maize under zero tillage (ZT) ~ maize (CT). Organic C, microbial biomass C, microbial quotient, basal respiration and aggregate stability were substantially greater in the surface 5 cm under maize ZT than maize CT. In the undisturbed sites (eg native grassland and kikuyu pasture) the metabolic quotient increased with depth. By contrast under maize CT and sugarcane there was no significant stratification of organic C, yet there was a sharp decrease in metabolic quotient with depth. Aggregate stability was high under both native grassland and kikuyu pasture and it remained high to 40 cm depth under the deep-rooted kikuyu pasture. Although soil organic C was similar under maize CT and sugarcane, values for microbial biomass C, microbial quotient, basal respiration and aggregate stability were lower, and those for metabolic quotient and bulk density were higher, under sugarcane. This was attributed to the fallow nature of the soil in the interrows of sugarcane fields. It was concluded that the loss of soil organic matter, microbial activity and aggregate stability is potentially problematic under maize CT and sugarcane and measures to improve organic matter status should be considered. For sugarcane, this could include green cane harvesting and the use of green manure crops in rotation. / Thesis (M.Sc.)- University of Natal, Pietermaritzburg, 2002.

This study examined the influence of different management practices under sugarcane production on soil chemical, biological and physical properties on a long-term (59yr) field experiment in KwaZulu-Natal. These management practices included conventional post-harvest burning of crop residues, with the tops either left on the soil surface or with tops removed, and green cane harvesting with the retention of crop residues on the soil surface as a trash blanket. Each of these treatments were either fertilized or did not receive fertilizer. The data collected was used to evaluate the effect of crop residue management on soil quality under sugarcane production. Soil organic matter content increased from 39 g C kg¯¹ soil, under conventional burning to 55 g C kg¯¹ soil in the surface 10 cm under green cane harvesting where crop residues are returned to the soil. It also resulted in greater recycling of nutrients and increases in exchangeable K and Ca and extractable P. Fertilizer application resulted in a build-up of soil nutrients in combination with trash retention. Fertilizer application induced increases in exchangeable P and also some accumulation in soil organic P. Exchangeable and non-exchangeable K concentrations were also higher in fertilized than non-fertilized treatments. However, nitrogen fertilizer application and, to a lesser degree, organic matter mineralization, resulted in soil acidification to a depth of 30 cm. Acidification in the fertilized treatments resulted in a concomitant increase in exchangeable acidity and exchangeable Al, due to the increase in H⁺ ions and solubilized Al species on exchange sites. Base cations moved into soil solution and were leaching to lower soil layers. The decrease in soil pH resulted in the surface charge conferred on the variable charge surfaces on soil colloids becoming less negative and as a result there was a decrease in ECEC. Acidification in fertilized treatment not only increased exchangeable Al but also the buffering reserve of non-exchangeable al; both that complexed with soil organic matter (CuCl₂- extractable) and that present as hydroxy - Al associated with mineral colloids (ammonium acetate - extractable). The increased organic matter content under trash retention resulted in an increase in ECEC. This enabled the soil to retain greater amounts of Ca²⁺, Mg²⁺ and K⁺ which were returned to the soil in the trash. Both residue retention and fertilizer application had a positive effect on the microbial biomass C and N and the microbial quotient increased from 0.39% to 0.86% as organic C increased from 39 g C kg¯¹ soil under burnt treatments to 55 g C kg¯¹ soil under trashed, fertilized treatments. This increase was associated with increased concentrations of labile organic material (K₂S0₄₋extractable) present as well as increased amounts of nutrients being cycled through the plant-soil system. The light fraction organic matter also increased with increasing returns of organic residues. However, the large active microbial biomass under the trashed, fertilized treatment resulted in an increased turnover rate of this fraction and consequently resulted in lower LF dry matter, C and N than in the unfertilized treatment. Aggregate stability increased with increasing amounts of organic material returned due to trash retention. Nevertheless, fertilized treatments induced a lower aggregate stability than unfertilized ones, despite the tendancy for the latter to have higher organic C and microbial biomass values. This was attributed to an increase in the proportion of exchangeable cations present in monovalent form (due to application of fertilizer K and leaching of Ca and Mg) favouring dispersion and a decline in aggregate stability. Green cane harvesting resulted in an increase in microbial activity (basal respiration, FDA hydrolytic activity, arginine ammonification rate and dehydrogenase activity) and in the activity of specific soil enzymes involved in turnover of C, N, P and S to a depth of 30 cm. Increased activities of these enzymes reflect a higher rate of turnover of C, N, P and S. The metabolic quotient decreased with increasing residue return, indicating a more metabolically efficient microbial community. Fertilizer application resulted in a variable effect on enzyme activity. Long-term fertilizer application resulted in an increase in invertase and acid phosphatase, a decrease in L-histidase and arylsulphatase and had little effect on protease and alkaline phosphatase. These variable effects were explained in terms of an interaction between fertilizer - induced increases in Corg and soil nutrient status and fertilizer - induced soil acidification. The size and activity of the soil microbial biomass was studied in the plant row and in the inter-row of a sugarcane field under burning or green cane harvesting. Soils were sampled to 30 cm depth in (i) the centre of the plant row, (ii) 30 cm out from the row centre and (iii) 60 cm out from the row centre (i.e. the middle of the inter-row area). Under burning, the only substantial input of organic matter to the soil was from root turnover in the row area where the root biomass was concentrated. As a consequence, the size (microbial biomass C) and activity (basal respiration of the soil microbial community were concentrated in the row. However, under green cane harvesting there was a large input of organic matter in the inter-row area in the form of the trash blanket itself and through turnover of crop roots that were concentrated in the surface 10 cm of the soil below the blanket. As a result, soil microbial activity was considerably higher in the interrow area under green cane harvesting than under burning. Phospholipids are essential membrane components of microorganisms and a good correlation was found between the total PLFA's extracted from soils and the microbial biomass C, indicating that phospholipids are an accurate measurement of living biomass. Mutivariate statistical analysis (PCA) was used to separate different PLFA profiles under burning versus trash retention and under different land uses (sugarcane, maize, annual and perennial pasture and undisturbed veld). Soil organic matter content contributed the greatest variance in the data along the first axis. That is increasing soil organic matter return not only increased the size of the microbial biomass, but also affected the composition of the microbial community. There was a shift in the different sub-fractions under different management practices. MUFA's are general biomarkers of Gram negative bacteria and were found to be a sensitive indicator of higher substrate availability (i.e they increased under green cane harvesting). Fungal biomarkers indicated an increased fungal biomass associated with surface application of residues. Soil physical conditions were considered to be a contributing factor to the shift in microbial community structure. Increased organic matter content improved soil physical conditions and preferentially stimulated the growth of aerobic microorganisms. In addition to this, the proportion of SATFA (gram positive bacteria) was found to increase in response to burning. This increase was attributed to the survival mechanisms of these microorganisms (i.e. endospore formation). It was found that the conversion from burning to trash management changes the composition of the soil microbial community. The effect of management practices on soil functional diversity was also evaluated using two methods (i.e. Biolog plates and substrate induced respiration (SIR)). Biolog plates are a selective technique that stimulate growth of a small proportion of the soil microbial community whereas the SIR technique measures the activity of the metabolically active microbial community in situ. As a result the SIR method separated treatments more effectively than Biolog plates (i.e. annually tilled treatments, permanent grassland sites and fertilized and unfertilized treatments). The quantity and the quality of organic C supply influenced the catabolic diversity. Conversion from burning to green cane harvesting greatly increased catabolic evenness and richness and therefore presumably also tended to increase the resilience of the soil to stress and disturbance particularly in relation to decomposition functions. It was concluded that conversion from preharvest burning to green cane harvesting results in an increase in soil organic matter content, an improvement in soil structure and soil nutrient status, an increase in the size, activity, taxonomic and functional diversity of the soil microbial community. The practice should therefore be promoted to the South African sugar industry. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 2003.

Lic.-avh. (sammanfattning) Uppsala : Sveriges lantbruksuniv. / Härtill 2 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2006. / Härtill 5 uppsatser.