Determination of the hydraulic conductivity function of a highly compressible material based on tests with saturated samples

Abstract: An alternative procedure to determine the hydraulic conductivity function (k-function) based on relationships between saturated hydraulic conductivity and void ratio and between air-entry value and void ratio is proposed. The procedure was applied to determine the k-function of deinking by-products, a highly compressible industrial by-product that is used as alternative material in geoenvironmental applications. The validity of the procedure is verified by comparing the k-function of a compressible soil obtained based on the proposed procedure (using published experimental data) with experimentally determined unsaturated hydraulic conductivities for the same soil

Design of inclined covers with capillary barrier effect

Abstract: A design procedure is proposed to minimize water infiltration into landfills in optimizing the water diversion length of inclined covers with capillary barrier effect (CCBE). This design procedure aims at selecting materials and optimizing layer thickness. Selection among candidate materials is made based on their hydraulic conductivity functions and on a threshold infiltration rate imposed on the designer. The capillary break layer (CBL; bottom layer) is characterized by a weak capillarity, while the moisture retention layer (MRL; upper layer) is characterized by a stronger capillarity. The thickness of the CBL corresponds to the height where suction reaches its maximum value for a given infiltration rate. This height can be calculated using the Kisch (1959) model. The optimal thickness of the MRL is determined by applying an adaptation of the Ross (1990) model. The results obtained using the proposed design procedure were compared to those obtained from numerical simulations performed using a finite element unsaturated seepage software. The procedure was applied for two cover systems; one where deinking by-products (DBP) were used as MRL and sand as CBL and another where sand was used as MRL and gravel as CBL. Using this procedure, it has been shown that an infiltration control system composed of thin layers of sand over gravel is highly efficient in terms of diversion length and that its efficiency can be enhanced by placing a hydraulic barrier - such as a layer of DBP - above the MRL

Conditioning machine learning models to adjust lowbush blueberry crop management to the local agroecosystem

Agroecosystem conditions limit the productivity of lowbush blueberry. Our objectives were to investigate the effects on berry yield of agroecosystem and crop management variables, then to develop a recommendation system to adjust nutrient and soil management of lowbush blueberry to given local meteorological conditions. We collected 1504 observations from N-P-K fertilizer trials conducted in Quebec, Canada. The data set, that comprised soil, tissue, and meteorological data, was processed by Bayesian mixed models, machine learning, compositional data analysis, and Markov chains. Our investigative statistical models showed that meteorological indices had the greatest impact on yield. High mean temperature at flower bud opening and after fruit maturation, and total precipitation at flowering stage showed positive effects. Low mean temperature and low total precipitation before bud opening, at flowering, and by fruit maturity, as well as number of freezing days (<−5 °C) before flower bud opening, showed negative effects. Soil and tissue tests, and N-P-K fertilization showed smaller effects. Gaussian processes predicted yields from historical weather data, soil test, fertilizer dosage, and tissue test with a root-mean-square-error of 1447 kg ha−1. An in-house Markov chain algorithm optimized yields modelled by Gaussian processes from tissue test, soil test, and fertilizer dosage as conditioned to specified historical meteorological features, potentially increasing yield by a median factor of 1.5. Machine learning, compositional data analysis, and Markov chains allowed customizing nutrient management of lowbush blueberry at local scale

The Ionomics of Lettuce Infected by Xanthomonas campestris pv. vitians

Bacterial leaf spot (BLS) caused by Xanthomonas campestris pv. vitians (Xcv) places a major constraint on lettuce production worldwide. The most sustainable strategy known to date for controlling BLS is the use of resistant cultivars. The nutrient elemental signature (ionome) of ten lettuce cultivars with three levels of resistance was analyzed by inductively coupled plasma optical emission spectroscopy (ICP-OES) to determine which nutrient balances are linked to resistance to BLS, and to assess the effect of Xcv infection on the ionome. The elemental concentrations were preprocessed with isometric log-ratios to define nutrient balances. Using this approach, 4 out of 11 univariate nutrient balances were found to significantly influence the resistance of lettuce cultivars to BLS (P &lt; 0.05). These significant balances were the overall nutritional status balancing all measured nutrients with their complementary in the dry mass, as well as balances [Mn | Zn,Cu], [Zn | Cu], and [S,N | P]. Moreover, the infection of lettuce cultivars mostly affected the lettuce ionome on the [N,S | P] balance, where infection tended to lean the balance toward the N,S part relatively to P. This study shows that nutrient uptake in lettuce can be affected by BLS infection and that nutrient status influences resistance to BLS infection

Hydraulic and geotechnical aspects of capillary barrier design using a highly compressible recycled material

Low permeability covers, such as covers with capillary barrier effect (CCBE), constitute valid alternative for minimizing leachate production from municipal landfill facilities. The use of recycled materials as part of such cover has the advantages of reducing the amount of waste to bury and the amount of soil---a finite mineral resource---needed for its construction. Deinking by-products (DBP) is a paper recycling by-product whose void ratio varies considerably with suction. The challenge of this thesis is to predict the variation of hydraulic properties with suction of a highly compressible recycled material and, using those properties, incorporate this material for the design of a CCBE. The research program led to the design of an inclined CCBE field test at the Saint-Tite-des-Caps (Québec, Canada) landfill, using DBP as a material constituting a low permeability layer. Typical soils do not undergo significant capillary-induced pore shrinkage for suction values higher than air-entry value (AEV). However, this is not the case for highly compressible materials (HCM), such as expansive clays and DBP. A model capable of describing the suction-induced consolidation curve (void ratio function) and water retention curve (WRC) of HCM was developed and validated using published data for a Saskatchewan silty sand. This silty sand was selected for its large amount of available data. The WRC and the void ratio function obtained for the Saskatchewan silty sand were used to predict its hydraulic conductivity functions ( k -function). The proposed model is then applied to describe the WRC of DBP. Water content, suction and volumetric deformation data necessary to determine the WRC for DBP were obtained by applying an experimental technique developed for the determination of the WRCs of HCMs. The k -function was also obtained using Fredlund et al. [1994]'s k -function model. Results showed that volumetric water contents were underestimated if volume change was not taken into account, leading to inaccuracies in the WRCs (and in the models used to describe it) and, consequently, in the associated k -functions. It was shown that the Fredlund et al. (1994]'s k -function model can not be applied for all HCMs. An alternative procedure to determine the k -function based on relationships between saturated hydraulic conductivity and void ratio and between AEV and void ratio was also developed. The procedure was applied to determine the k -function of DBP. The validity of the procedure is verified by comparing the k -function of a compressible soil, a Saskatchewan silty sand, obtained based on the proposed procedure (using published experimental data) with experimentally determined unsaturated hydraulic conductivities for the same soil. A new design procedure based on the materials' k -function is proposed to minimize water infiltration into landfills in optimizing the water diversion length of inclined CCBEs. This design procedure was based on a conceptual, mathematical and numerical approach and aimed at selecting materials and optimizing layer thickness. Selection among candidate materials is made based on their k -functions and by a threshold infiltration rate imposed on the designer. Briefly, the capillary break layer (CBL; bottom layer) is characterized by a low capillary rise, while the moisture retention layer (MRL; upper layer) is characterized by a higher capillary rise. The thickness of the CBL corresponds to the height where suction reaches its maximum value for a given infiltration rate. This height can be computed using the Kisch [1959] model. The optimal thickness of the MRL is determined by applying an adaptation of the Ross [1990] model. The results obtained using the proposed design procedure were compared to those obtained from numerical simulations performed using a finite element unsaturated (or vadose zone) seepage software. The procedure was applied for two cover systems; one where DBP was used as MRL and sand as CBL and another where sand was used as MRL and gravel as CBL. Using this procedure, it has been shown that an infiltration control system composed of thin layers of sand over gravel is highly efficient in terms of diversion length and that its efficiency can be enhanced by placing a hydraulic barrier---such as a layer of DBP---above the MRL. The newly developed capillary barrier design procedure was applied for the design of the Saint-Tite-des-Caps experimental CCBE."--résumé abrégé par UMI

Biochemical fractionation of soil organic matter after incorporation of organic residues

<p>Description will come when the associated paper will be published.</p

Balancing guava nutrition with liming and fertilization

A resposta da goiabeira à calagem e à adubação pode ser monitorada por análises de tecido vegetal. O perfil nutricional é definido em relação a padrões de teores de nutrientes. No entanto, os teores de nutrientes-padrão são constantemente criticados por não considerarem as interações que ocorrem entre nutrientes e por gerarem tendências numéricas, decorrentes da redundância dos dados, da dependência de escala e da distribuição não normal. As técnicas de análise composicional de dados podem controlar esses dados tendenciosos, equilibrando os grupos de nutrientes, tais como os envolvidos na calagem e na adubação. A utilização das relações log isométricas (ilr) ortonormais, sequencialmente dispostas, evita tendências numéricas inerentes aos dados de composição. Os objetivos do trabalho foram relacionar o balanço de nutrientes dos tecidos vegetais com a produção de goiabeiras em pomares de 'Paluma' diferentemente corrigidos e adubados, e ajustar os atuais padrões de nutrientes com a faixa de equilíbrio das goiabeiras mais produtivas. Um experimento de calagem de sete anos e três, experimentos de três anos com doses de N, P2O5 e K2O, foram conduzidos em pomares de goiabeiras 'Paluma' em um Latossolo Vermelho-Amarelo. Os teores de N, P, K, Ca e Mg na planta foram monitorados anualmente. Selecionaram-se os balanços [N, P, K | Ca, Mg], [N, P | K], [N | P] e [Ca | Mg] para separar os efeitos da calagem (Ca-Mg) e dos fertilizantes (N-K) nos balanços de macronutrientes. Os balanços foram mais influenciados pela calagem do que pela fertilização. A produtividade das goiabeiras e seu balanço nutricional permitiram a definição de faixas de equilíbrio de nutrientes e sua validação com as faixas de concentrações críticas atualmente utilizadas no Brasil e combinadas em coordenadas ilr.Guava response to liming and fertilization can be monitored by tissue testing. Tissue nutrient signature is often diagnosed against nutrient concentration standards. However, this approach has been criticized for not considering nutrient interactions and to generate numerical biases as a result of data redundancy, scale dependency and non-normal distribution. Techniques of compositional data analysis can control those biases by balancing groups of nutrients, such as those involved in liming and fertilization. The sequentially arranged and orthonormal isometric log ratios (ilr) or balances avoid numerical bias inherent to compositional data. The objectives were to relate tissue nutrient balances with the production of Paluma guava orchards differentially limed and fertilized, and to adjust the current patterns of nutrient balance with the range of more productive guava trees. It was conducted one experiment of 7-yr of liming and three experiments of 3-yr with N, P and K trials in 'Paluma' orchards on an Oxisol. Plant N, P, K, Ca and Mg were monitored yearly. It was selected the [N, P, K | Ca, Mg], [N, P | K], [N | P] and [Ca | Mg] balances to set apart the effects of liming (Ca-Mg) and fertilizers (N-K) on macronutrient balances. Liming largely influenced nutrient balances of guava in the Oxisol while fertilization was less influential. The large range of guava yields and nutrient balances allowed defining balance ranges and comparing them with the critical ranges of nutrient concentration values currently used in Brazil and combined into ilr coordinates

Soil aggregation data from Tabi et al. (1990)

<p><strong>Note<br></strong>The description is yet incomplete.</p> <p><strong>Columns</strong><br>SOL: Pedologic class<br>SABLE: Sand proportion on mineral basis<br> LIMON: Silt proportion on mineral basis<br> ARGILE: Clay proportion on mineral basis<br> CO: Organic carbon proportion on dry basis<br>W1: 5.0-8.0 mm<br>W2: 2.0-5.0 mm<br>W3: 1.0-2.0mm<br>W4: < 1.0 mm</p> <p><strong>Reference</strong><br>Tabi M, Tardif L, Carrier D, Laflamme G, Rompré M. Inventaire des problèmes<br>de dégradation des sols agricoles du Québec. Rapport synthèse. Québec:<br>MAPAQ; 1990. url: http://huit.re/Welm8zYP</p