Conselho Nacional de Desenvolvimento Científico e Tecnológico / Starting from the assumption that changes in land use can provide changes in physical and chemical properties, influencing its quality, the study aimed to verify whether the introduction of Pinus taeda L., on soil under native grassland conditions, can degrade physical and chemical quality of Haplumbrept soil in different rotations. The study was conducted in the region of Campos de Cima da Serra - RS, Brazil, where there are large forested areas with pine trees. To this, were selected two study areas, one in the first (RT1) and another in the second rotation (RT2), with 13 years of age. For each stand, was assessed a combined area of grassland adjacent (control). In each area, five trenches were opened and collected soil samples at depths from 0.0 to 0.05, from 0.05 to 0.20, 0.20 to 0.40 and 0.40-0.60 m. Changes in physical properties were analyzed using the following parameters: particle size, particle density, bulk density, porosity, macro and micro porosity, hydraulic conductivity of saturated soil, soil air permeability and size distribution of water stable aggregates. The chemical determinations were: calcium, magnesium, phosphorus, potassium, pH, pHSMP, exchangeable aluminum, total nitrogen and total organic carbon. At RT1 was a change in the macro and microporosity, influencing the behavior of hydraulic conductivity and air permeability at 6 and 10 kPa. At RT2, the effect of pine in the macro, microporosity and hence hydraulic conductivity, occurred only in the surface layer (0.0 to 0.05 m) due to the management adopted in the area. Considering the two study areas, there was a reduction of the aggregate stability in the layer from 0.05 to 0.20 m. However, in the same layer, the RT2 presented an increase in stability of aggregates of smaller size classes, reflecting the management type. The chemical properties were altered mainly in the surface layers, with reductions of exchangeable bases (Ca and Mg) and elevation of P saturation. The pine has also promoted increased levels of Al and decrease in pH, increasing soil acidity and reducing thereby the quality of Haplumbrept soil. In RT1, the content of C and N were reduced in the surface layer, but in RT2, levels of C and N were similar to natural field, inferring in the long run, the ability to restore the levels of C in soil. / Partindo-se do pressuposto de que mudanças no uso do solo podem proporcionar alterações nas propriedades físicas e químicas, influenciando a sua qualidade, o objetivo do estudo foi verificar se a introdução da espécie Pinus taeda L., em solo sob campo natural, pode degradar física e quimicamente a qualidade do Cambissolo Húmico, em diferentes rotações. O estudo foi conduzido na região dos Campos de Cima da Serra RS, Brasil, onde ocorrem grandes áreas florestadas com pínus. Para isso, foram escolhidas duas áreas de estudo, uma em primeira (RT1) e a outra em segunda rotação (RT2), com 13 anos de idade. Para cada povoamento, foi avaliada conjuntamente uma área de campo natural adjacente (testemunha). Em cada área, foram abertas 5 trincheiras e coletadas amostras de solo nas profundidades 0,0-0,05; 0,05-0,20; 0,20-0,40 e 0,40-0,60 m. As alterações nas propriedades físicas foram analisadas através das seguintes determinações: granulometria, densidade de partículas, densidade do solo, porosidade total, macro e microporosidade, condutividade hidráulica do solo saturado, permeabilidade do solo ao ar, e distribuição do tamanho de agregados estáveis em água. As determinações químicas realizadas foram: cálcio, magnésio, fósforo, potássio, pH em água, pHSMP, alumínio trocável, nitrogênio total e carbono orgânico total. Na RT1 houve alteração na macro e microporosidade, influenciando o comportamento da condutividade hidráulica e permeabilidade ao ar a 6 e 10kPa. Na RT2, o efeito do pínus na macro, microporosidade e, consequentemente, na condutividade hidráulica, ocorreu somente na camada superficial (0,0 a 0,05 m), devido ao manejo adotado na área. Considerando as duas áreas de estudo, houve redução da estabilidade dos agregados na camada de 0,05 a 0,20 m. No entanto, na mesma camada, a RT2 apresentou elevação na estabilidade de agregados de classes de tamanho menores, refletindo o manejo adotado. As propriedades químicas foram alteradas principalmente nas camadas superficiais, apresentando reduções das bases trocáveis (Ca e Mg) e elevações dos teores de P trocável. O pínus também promoveu o aumento nos teores de Al e a diminuição do pH, elevando a acidez do solo e reduzindo, dessa forma, a qualidade do Cambissolo Húmico. Na RT1, os teores de C e N foram reduzidos na camada superficial, porém, na RT2, os níveis de C e N apresentaram-se similares ao campo natural, inferindo, em longo prazo, a capacidade de restauração dos níveis de C no solo.

Biochar has been heralded a mechanism for carbon sequestration and an ideal amendment for improving soil quality. Melaleuca quinquenervia is an aggressive and wide-spread invasive species in Florida. The purpose of this research was to convert M. quinquenervia biomass into biochar and measure how application at two rates (2% or 5% wt/wt) impacts soil quality, plant growth, and microbial gas flux in a greenhouse experiment using Phaseolus vulgaris L. and local soil. Plant growth was measured using height, biomass weight, specific leaf area, and root-shoot ratio. Soil quality was evaluated according to nutrient content and water holding capacity. Microbial respiration, as carbon dioxide (CO2), was measured using gas chromatography. Biochar addition at 5% significantly reduced available soil nutrients, while 2% biochar application increased almost all nutrients. Plant biomass was highest in the control group, p2 flux decreased significantly in both biochar groups, but reductions were not long term.

The submitted diploma thesis aims to extend the use of thermogravimetry for the analysis of organic C and total N contents in soils. The advantages of thermogravimetry in comparison to conventional analytical methods are that it is a versatile technique that provides fast analysis, does not require sample pretreatment and chemicals– and can be used for the analysis of various soil types. The research work performed so far showed correlations between thermogravimetric data and some soil properties. In the past, intact soils exposed to 76% relative humidity (RH) were analyzed by thermogravimetry for these purposes. However, this humidity is problematic to achieve and maintain for most thermogravimeters. Recent work has shown that correlations can be observed in agricultural land exposed to lower RH. Therefore, it can be assumed that a correlation between TG data exists in soils exposed to any RH. TG could then be used to analyze soil properties under any known RH conditions. The aim of this work was to verify this hypothesis and try to incorporate knowledge of RH into the relationships between TG and soil properties. For this reason, intact soils exposed to the relative humidity of 30, 55, and 76% were analyzed in this work. It was demonstrated the dependence between organic C content and mass loss between 320 and 330°C as well as total nitrogen content and mass loss between 410 and 420°C independently of relative humidity. Based on that knowledge, we have derived equations enabling determination of the content of organic C and total N for RH ranging 43% - 76% using mass losses and knowledge of RH. Nevertheless, due to the low number of tested RH, the equations are still only preliminary and need to be improved by analyzing soil samples at a larger number of RH.

Thesis (M.Sc. Agriculture (Soil Science)) -- University of Limpopo, 2022 / Soil health support crop production and answer to its sustainability and renewability. This study involved the use of under explored legumes in South Africa, Limpopo under maizelegume intercropping systems as a strategy to mitigate soil quality deterioration. The study was conducted at University of Limpopo (Syferkuil) and University of Venda (UNIVEN) Experimental farms during 2020/2021. A split plot experiment, with the main factor comprised of water regimes (irrigation and rainfed) and second main factor included cropping systems (Intercropping and monocropping). Five treatments comprised of 3 monocrops (Maize, Chickpea, and Mungbean) and 2 intercrops (maize-chickpea and maize-mungbean) replicated three times. Data collected from the soil before planting and after maturity were pH, Electrical conductivity (EC), particle size, bulk density, aggregate stability, organic matter (OM), organic carbon (OC), phosphorus (P), ammonium (NH4-N), nitrate (NO3—N), soil active carbon (SAC), and potentially mineralizable nitrogen (PMN). Plant parameters collected during vegetative and flowering stage included plant height, chlorophyll content, plant vigour, and leaf area index. All data was subjected to descriptive statistics and analysis of variance using GenStat software. Significant effect (p<0.05) was observed between treatments on soil pH (KCl), OM, organic carbon (OC), and ammonium (NH4) at Syferkuil Farm. Also, interaction between water regimes and cropping systems affected NH4 and pH (KCl). Cropping systems had significant effect (p<0.01) on pH (H2O), OM, OC, P, NH4, and NO3 at UNIVEN. Interaction between water regimes and cropping systems affected (p<0.01) pH (H2O), P but no significant effect was observed on OC, NH4, and NO3. Cropping systems and interaction at both locations did not affect particle size, bulk density, aggregate stability, EC, SAC, and PMN. Pure stands of maize and legumes had greater plant height, plant vigour, and chlorophyll content whereas intercrops had greater LAI. The results at both locations revealed that legume intercropping systems improved soil health variables without posing negative feedbacks and hence can be used to boost soil functioning. Keywords: Soil health, maize-legume intercropping, soil quality / National Research Foundation (NRF)

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Cellulosic biomass-to-bioenergy systems can provide environmental and economic benefits to modern societies, reducing the dependence on fossil-fuels and greenhouse gas emissions while simultaneously improving rural economies. Corn (Zea mays L.) stover and wheat straw (Triticum aestivum L.) residues have particular promise given these crops are widely grown and their cellulosic fractions present a captured resource as a co-product of grain production. Annual systems also offer the ability to change crops rapidly in response to changing market demands. However, concerns exist about residue removal effects on soil health, greenhouse gases emissions and subsequent crop productivity. The carbon footprint and the crop yield productivity and soil health responses resulting from the removal of crop residues has been studied extensively over the last 20 years, but this research has been largely conducted in the Corn Belt. To investigate the impact of crop residue removal in the Mid-Atlantic USA, combinations of corn stover (0, 3.33, 6.66, 10 and 20 Mg ha-1) and wheat straw (0, 1.0, 2.0, and 3.0 Mgha-1) were soil applied in a corn-wheat/soybean (Glycine max L. Merr.) rotation in Virginia's Coastal Plain. Corn stover (0, 3.33, 6.66, 10 and 20 Mg ha-1) was applied in a continuous corn cropping system in the Ridge/Valley province. For each system, residues were applied following grain harvest over two production cycles. Each experiment was conducted as a randomized complete design with four replications. The highest rates of stover retention resulted in greater greenhouse gas emissions in year 1, but not year 2 of these studies and did not affect overall global warming potentials. Stover application also increased soil carbon but had little effect on other measures of soil quality. Stover K levels were greater with high rates of stover retention. Overall, these studies indicate little effect of residue removal or retention (above typical residue production rates) on subsequent crop production, greenhouse gas emissions, or soil health measures in the short term. This study is one of the first to assess residue removal in the Mid-Atlantic USA and is the first study to investigate the impacts that managing more than one crop residue in a multi-crop system. Longer-term research of this type may be warranted both to determine the consequences of residue management and to start building a regionally-specific body of knowledge about these practices. / Ph. D. / Over the last decade, strategic economic and environmental concerns have increased interest in the use of crop residues as sustainable, renewable sources for bioenergy and bio-products. Most of the work investigating the sustainability of residue removal has occurred in the US Corn Belt, where corn stover and wheat straw (the part of the plant that is not grain) supplies are abundant. Although the research data from the Corn Belt provide guarded optimism about residue harvest systems in the Midwest, it is not suitable to extrapolate these results to the South because of differences in soils, climate, and cropping systems. Cooler, humid conditions can sustain higher levels of soil organic matter, lessening but not eliminating concerns about stover removal. Current research from the Midwest region suggests routine stover harvest – within limits – can be sustainable. The development of new bioenergy and bioproduct industries in the Southeast region is leading to a growing expectation that regional cropping systems will supply the millions of tons of biomass needed for these new businesses. However, few data are available regarding sustainable crop residue harvest from the Southeast. Sustainable levels of residue removal may be quite low given regional soil and climatic conditions, and the effects of residue removal on soil health parameters and greenhouse gas emissions remain to be defined. The purpose of this project was to determine the amount of corn stover and wheat straw can sustainably be harvested from Virginia’s grain-based cropping systems without reducing plant productivity or soil quality or increasing GHG emissions. This research generated regionally relevant information on the impacts of crop residue removal to help determine whether harvesting wheat straw and corn stover can be a sustainable practice for the region’s cropping systems. In a first stage, short term impacts of residue removal on soil quality and greenhouse gases were measured in Blacksburg and New Kent, VA, over the period 2015-2017.

Thesis (MSc (Microbiology))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The relationship between various land management practices, soil properties and the soil microbial communities are complex and little is known about the effect of these interactions on plant productivity in agricultural systems. Although it would be advantageous to have a single organism or property that can be used as a measure of soil health, it may not be possible. Soil organisms which include both the microorganisms as well as soil fauna are subjected to the effect of their immediate environment. This microenvironment in turn is determined by the soil properties as well as above ground flora and their interactions. Most soil indicators interact with each other, and these interactions can modify or influence the soil properties. The complexities of the interactions between critical soil indicator values often preclude its practical use by land managers and policy makers. However, soil microbial communities (e.g. diversity and structural stability) may serve as a relative indicator of soil quality. These communities are sensitive to land management practices and changes in the microenvironment. The objective of this study was to gain an understanding of the complex relationships by investigating the effect of conventional, integrated and organic apple production systems on the physical, chemical and biological (particularly soil microbial diversity) properties of the soil. Automated Ribosomal Intergenic spacer analysis (ARISA) was used to characterise fungal (F-ARISA) and bacterial (B-ARISA) communities from soil samples obtained from an experimental apple orchard in Elgin, Grabouw. The intergenic spacer (ITS) region from the fungal rRNA operon was amplified using ITS4 and fluorescently FAM (6- carboxylfluorescein) labelled ITS5 primers. Similarly, the 16S-23S intergenic spacer region from the bacterial rRNA operon was amplified using ITSR and FAM-labelled ITSF primers. The sensitivity of the technique allowed us to discriminate between the soil microbial communities of the different treatments. From our results we observed significant increase (p < 0.05) in the fungal community diversity between the February and April samples, while the bacterial community diversity was consistent (p > 0.05). Also, treatments with mulch showed a significantly higher microbial diversity than the other treatments at a 5 % significance level. Fungal communities showed significant correlation with the potassium concentration in the soil, while bacterial communities depicted a significant correlation with the soil phosphorous concentration. Based on the results we concluded that different management practices have a significant effect on the soil microbial communities and that these communities are particularly sensitive to small changes in the environment. However, there is still a need to determine what the composition of the soil microbial communities are to be able to correlate our observations with soil health. / AFRIKAANSE OPSOMMING: Die verhouding tussen verskillende landboubestuurspraktyke, grondeienskappe en die mikrobiese gemeenskappe in grond is kompleks en weinig is bekend oor die uitwerking van hierdie interaksies op die produktiwiteit van landboustelsels. Alhoewel dit voordelig sou wees om ‘n enkele organisme of eienskap te kan hê wat die gesondheid van grond kan meet, sal dit dalk nie moontlik wees nie. Grondorganismes wat die mikroörganismes sowel as die grondfauna insluit, is onderworpe aan die invloed van hulle onmiddelike omgewings. Hierdie mikro-omgewings op hulle beurt word weer beïnvloed deur die grondeienskappe sowel as die die oppervlak flora en hulle wisselwerkinge. Meeste van die grondaanwysers toon ook wisselwerkinge met mekaar, en hierdie wisselwerkinge kan die grondeienskappe beïnvloed or selfs verander. Die kompleksiteit van die wisselwerkinge tussen kritiese grond aanwysers is meestal die rede waarom dit nie deur grondbestuurders en beleidsmakers gebruik word nie. Dit is ongeag die feit dat grond mikrobiese gemeenskappe (bv. diversiteit en stukturele stabiliteit) mag dien as ‘n relatiewe aanwyser van grondkwaliteit. Hierdie gemeenskappe is sensitief vir bestuurspraktyke en veranderinge in die mikro-omgewing. Die doel van die studie was om die ingewikkelde verhoudings in die grondgemeenskappe te bestudeer en die uitwerking van konventionele, geïntegreerde en organiese appel produksie sisteme op die fisiese, chemiese en biologiese eienskappe (veral die grond mikrobiologiese diversiteit) te bepaal. Geoutomatiseerde Ribosomale Intergeniese Spasie Analise (ARISA) is gebruik om die fungus (F-ARISA) en bakteriese (B-ARISA) gemeenskappe van grondmonsters wat vanaf ‘n proef appelboord in Elgin (Grabouw) verkry is, te bepaal. Die intergeenspasie (ITS) area van die fungus rDNA operon is vermeerder deur die ITS4 en fluoresserende FAM (6-karboxylfluorescein) gemerkte ITS5 inleiers te gebruik. Soortgelyk is die 16S-23S intergeenspasie area van die bakteriese rDNA operon vermeerder deur ITSR en FAM-gemerkte ITSF inleiers te gebruik. Die sensitiwiteit van die tegniek laat ons toe om te onderskei tussen die grond mikrobiese gemeenskappe vanaf verskillende grondbehandelings. Vanuit die resultate kon ons aflei dat daar ‘n toename (p < 0.05) in die fungus gemeenskap diversiteit vanaf Februarie to April was terwyl die bakteriese gemeenskap ‘n konstante diversteit getoon het (p > 0.05). Behandelings met grondbedekking het ook ‘n beduidend hoër mikrobiese diversiteit getoon as ander behandelings. Fungus gemeenskappe het beduidende korrelasies getoon met kalium konsentrasies in die grond, terwyl bakteriese gemeenskappe ‘n beduidende korrelasie getoon het met grond fosfor konsentrasies. Gebaseer op die resultate kon ons aflei dat verskillende bestuurspraktyke ‘n uitwerking kan hê op die grond mikrobiese gemeenskappe en dat hierdie gemeenskappe sensitief is vir klein veranderinge in die omgewing. Dit sal egter nog nodig wees om die spesifieke samestelling van die grond mikrobiese gemeenskappe te bepaal voor ons hierdie waarnemings kan korreleer met grondgesondheid.

Os ecossistemas naturais e agropecuários dependem fundamentalmente do solo como recurso básico para sua funcionalidade. Neste contexto, a qualidade do solo tem tido uma crescente importância global. Os objetivos deste estudo consistiram em propor modificações metodológicas e/ou instrumentais visando determinações mais acuradas dos indicadores da qualidade física do solo mediante o desenvolvimento de (i) um sistema eletro-mecânico que permite a obtenção de amostras indeformadas de solos sem aplicação de golpes; (ii) um penetrômetro estático automatizado, de baixo custo e portátil, para medidas de resistência à penetração (RP) e resistência tênsil (RT) sob regime de velocidade constante de 1,55 mm s-1; (iii) um consolidômetro, de baixo custo e de maior portabilidade, para determinações da curva de compressão do solo, da RP e da RT utilizando propulsão pneumática e (iv) melhorias instrumentais em um permeâmetro de carga constante de ar pela redução de oscilações durante a medição do gradiente de pressão bem como a otimização da seleção de diferentes níveis de vazão mássica de ar. Os resultados obtidos mostraram que (i) o sistema eletromecânico garantiu a preservação da estrutura do solo em amostras coletadas comparado com a amostragem por golpes, principalmente no solo mais argiloso; (ii) a RP e a RT puderam ser determinadas com elevada acurácia à velocidade constante de 1,55 mm s-1; (iii) a curva de compressão do solo foi sensível às diferenças entre os tratamentos (linha e entrelinha da cultura) e a utilização de propulsão pneumática não influenciou os resultados da RP e da RT e (iv) a instrumentação utilizada no permeâmetro de carga constante de ar permitiu realizar determinações da permeabilidade do solo ao ar tanto em campo quanto em laboratório com rapidez e elevada acurácia. / Natural and agricultural ecosystems rely fundamentally on soil as a basic resource for their functionality. In this context, soil quality has had a growing global importance. The objectives of this study were based on proposing methodological and/or instrumental modifications aiming to obtain more accurate determinations of soil physical quality indicators by developing: (i) an electro-mechanical system that allows the extraction of undisturbed soil samples without mechanical impact (no-hammering); (ii) a low cost and portable static automatic penetrometer, for measuring soil penetration resistance (PR) and tensile strength (TS) at a constant speed of 1.55 mm s-1; (iii) a low cost and portable consolidometer, for determination of soil compression curve, PR and TS using pneumatic propulsion and (iv) instrumental improvements to a constant head air permeameter by reducing the oscillation during measuring the pressure head gradient and the optimization of the selection of different levels of air mass flow. The results showed that (i) the electro-mechanical system ensured the preservation of soil structure in undisturbed samples in comparison to samples extracted by hammering procedures, especially in clayey soil; (ii) PR and TS could be determined with high accuracy at the constant speed of 1.55 mm s-1; (iii) the soil compression curve was sensitive to differences between treatments (crop row and inter-row) and the use of pneumatic propulsion did not influence the results of PR and TS, and (iv) the instrumentation used in the constant head air permeameter allowed determination of soil air permeability either on the field or in the laboratory with high speed and accuracy.