Orientador: José Frederico Centurion / Banca: Elias Nascentes Borges / Banca: Itamar Andrioli / Resumo: A estimativa da curva de resistência do solo à penetração (CRP), a partir de variáveis de fácil obtenção, como o conteúdo de água (Ug), representa uma medida muito útil não só para a quantificação do estado de compactação, mas também para facilitar a interpretação da resistência do solo à penetração (RP), obtida em diferentes condições de campo. O objetivo foi estimar a CRP em solos de diferentes granulometrias e densidades, a partir de dados obtidos com o penetrômetro de impacto. O experimento foi realizado em laboratório, na Faculdade de Ciências Agrárias e Veterinárias (UNESP), Jaboticabal, SP. Foram utilizadas quatro classes de solos: Neossolo Quartzarênico, Argissolo Vermelho-Amarelo, Latossolo Vermelho Distrófico e Latossolo Vermelho Acriférrico, os quais foram amostrados na camada de 0-0,20 m. Colunas de PVC foram preenchidas de forma a se obter diferentes condições de densidade: solo não compactado e compactado. O Ug, inicialmente elevado até o ponto de saturação, foi monitorado diariamente através de um medidor eletrônico composto pelo Profile Probe PR2 acoplado ao Moisture Meter HH2. A RP foi mensurada através de um penetrômetro de impacto adaptado para vaso. Os pares de dados entre a RP e o Ug foram ajustados e as CRP submetidas ao teste de significância. A relação entre a RP e o Ug foi descrita pelo modelo exponencial decrescente, representado pela seguinte equação: RP = a+be Ug/c em que: RP representa a resistência do solo à penetração (MPa); Ug o conteúdo gravimétrico de água (kg kg-1) e a, b e c são os parâmetros da equação. Foram obtidos coeficientes de determinação que variaram de 0,57 a 0,96. / Abstract: The estimate of soil resistance to penetration curve (RPC) from easy attainment variables, like the water content (Wc), represents a very useful measure not only in the evaluation of soil compaction, but also to simplify the interpretation of the soil resistance to penetration (SR) obtained in different field conditions. The objective was to estimate the RPC in soils of different textures and bulk densities, from data obtained with the impact penetrometer. The experiment was carried out in Faculdade de Ciências Agrárias e Veterinárias (UNESP), Jaboticabal, SP, and four classes of soil were used: Entissol, Alfissol, Oxisol medium texture and clayey Oxisol, which were collected at 0-0.20 m soil depth. The PVC columns filled in manner to obtain a condition of non compacted and compacted soil. The Wc, initially elevated to the saturation point, was daily monitored through an electronic measurer composed by Profile Probe (PR2) connected to a Moisture Meter HH2. The SR was measured by an impact penetrometer adapted to the vase. The pairs of data between SR and Wc were adjusted and the RPC submitted to the significance test. The equation that best described the relationship between the SR and Wc was the exponentially decreasing, as follows: SR = a+be Wc/c where SR is the soil resistance to penetration (MPa), Wc soil water content (kg kg-1) and a, b and c are the parameters of the equation. There was a significant relation between soil resistance to penetration and water content and the equations fit the data with coefficients of determination ranging from 0.57 to 0.96. / Mestre

A pesquisa teve como objetivo integrar o método GPR (Ground Penetrating Radar) com a sísmica de refração, visando o mapeamento do N.A. e a estimativa do teor de umidade em uma área de estudos hidrogeológicos no campus da USP, assim como analisar a acurácia da medida dos dois métodos. Foram realizados ensaios geofísicos, granulométricos, de teor de umidade, do grau de saturação, do monitoramento do N.A. e acompanhamento dos índices pluviométricos em três períodos com variações sazonais no decorrer de um ano denominados período chuvoso (janeiro/2004); período intermediário (abril/2004) e período seco (setembro/2004). O mapeamento do N.A. com GPR foi feito com geometria multi-offset, com as antenas de freqüências centrais 50 MHz, 100 MHz e 200 MHz, sendo que as antenas de 100 MHz e 200 MHz foram as que caracterizaram o N.A., refletindo sua variação sazonal e mantendo a tendência prof. N.A. janeiro < prof. N.A. abril < prof. N.A. setembro. O emprego da sísmica de refração gerou maiores erros e ambigüidades na inversão dos dados. Neste estudo, a sísmica de refração não foi sensível às variações sazonais e, embora os resultados tenham se aproximado das observações diretas, não permitiram mapear a flutuação do N.A. entre os diferentes períodos. A estimativa do teor de umidade volumétrico pelo GPR foi obtida com duas metodologias diferentes que utilizaram a onda direta no solo. Foram empregadas antenas de 50 MHz, 100 MHz e 200 MHz nos diferentes períodos. Observou-se uma variação da umidade entre os períodos, sendo o teor de umidade de janeiro > abril > setembro. A antena de 200 MHz foi a que possibilitara uma melhor acurácia na estimativa do teor de umidade volumétrico. / The present study had as objective to integrate GPR (Ground Penetrating Radar) method to seismic refraction, focusing on water table mapping and on the estimate of water content in an area of hydrogeological studies at USP\'s campus, as well as analysing the measuring accuracy of both methods. Several assays were accomplished, such as geophysical, granulometric, of water content, saturation degree, water table monitoring assays and also accompaniment of pluviometric indexes in the study periods with seasonal variations, along a year, denominated rainy period (january/2004), intermediaty period (april/2004), and dry period (september/2004). Water table mapping by GPR was made with multi-offset geometry, with 50 MHz, 100 MHz and 200 MHz central frequency antennas, seeing that 100 MHz and 200 MHz antennas were those ones, which characterized the water table, reflecting its seasonal variation and maintaining the depth of the water tablejanuary < depthapril < depthseptember tendency. The use of seismic refraction generated larger mistakes and ambiguities in the data inversion. In this study, seismic refraction was not sensitive to seasonal variations and, although the results have approached to direct observations, they did not allow mapping the water table fluctuation among the different periods. The estimate of volumetric water content by GPR was obtained with two different methodologies that have used the direct ground wave. Fifty MHz, 100 MHz and 200 MHz antennas were used in the different periods. A moisture variation was observed among these periods, being the water content of January > April > September. Two hundred MHz antenna was the one that had facilitated a better accuracy in the estimate of moisture content.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The knowledge of soil moisture is quite important because it indicates soil hydric conditions and it can help on saving water and electric energy, given that monitoring of soil moisture allows controlled and timely applications of water pointing out how much and when to irrigate, according to the crop water requirements. Therefore, soil moisture should be determined before the irrigation and will serve as a parameter for the amount of water to be applied by the system. There are any methods used for determination of soil water content, in this way, the present study aimed to compare the results of soil moisture obtained by different methods for expeditious determination of the water content of the soil in different textural classes. The study was conducted in the Laboratório de Hidráulica Agrícola da Universidade Federal de Santa Maria . Four methods were tested (standard method, M0; electric oven method, M1, microwave oven method, M2; weighing method, M3) with three soil samples (S1, S2, S3) and three repetitions for each. The linear regression was made between the standard method and alternative methods, for obtaining the correlation coefficient (r), the linear coefficient and the slope, the Wilmott concordance index (Iw) and Performance Index (Id). From the results obtained can be stated that the electric oven method and the microwave oven method have excellent performance when compared to the standard method. The method of weighing presented a performance good and very good. In addition, it was concluded that the 20 minutes period for the electric oven method was efficient signifying a time reduction for the moisture content determination. For the microwave oven method the 5 minute drying period was sufficient and did not differ statistically from the standard method. The method of weighing was also reliable in determining soil moisture. Therefore, it is possible to use alternative methods to determine the soil moisture. / O conhecimento da umidade do solo é de fundamental importância, pois indica em que condições hídricas encontra-se o mesmo, podendo auxiliar na redução dos gastos com água e energia elétrica, haja vista que o monitoramento da umidade do solo possibilita aplicações controladas e pontuais de água, respondendo o quanto e quando irrigar em função das necessidades hídricas das culturas. Assim sendo, para a realização da irrigação, a umidade do solo deve ser determinada anteriormente e servirá de parâmetro para a quantidade de água a ser aplicada pelo sistema. Inúmeros são os métodos utilizados para a determinação do conteúdo de água no solo, dessa maneira, o presente trabalho objetivou comparar os resultados de umidade do solo obtidos pelos diferentes métodos expeditos para determinação do conteúdo de água no solo em diferentes classes texturais. O estudo foi desenvolvido no Laboratório de Hidráulica Agrícola da Universidade Federal de Santa Maria. Foram testados quatro métodos (método padrão de estufa, M0; método do forno elétrico, M1, método do forno de micro-ondas, M2; método das pesagens, M3), com três amostras de solo (S1, S2, S3) e três repetições para cada. Foi feita a regressão linear entre os métodos alternativos e o método padrão de estufa, com a finalidade de se obter o coeficiente de correlação (r), o coeficiente linear e o coeficiente angular, o índice de concordância de Wilmott (Iw) e o índice de desempenho (Id). Através dos resultados obtidos pode-se afirmar que o método do forno elétrico e o método do forno de micro-ondas apresentaram desempenho ótimo quando comparados ao método padrão. O método das pesagens apresentou desempenho bom e muito bom. Também concluiu-se que o tempo de 20 minutos para o método do forno elétrico foi eficiente, significando redução no tempo para determinação da umidade. Para o método do forno de micro-ondas o tempo de 5 minutos de secagem foi suficiente, não diferindo estatisticamente do método padrão. O método das pesagens também se mostrou confiável na determinação da umidade do solo. Portanto, existe a possibilidade de usar os métodos alternativos para a determinação da umidade do solo.

La gestion de l’irrigation et de la fertilisation dans les systèmes de production hors sol est particulièrement cruciale afin de limiter tous risques d’asphyxie racinaire, de lessivage d’éléments minéraux, voire de développement de pathogènes liés à une irrigation excédentaire, ou, à l’inverse, de réhumectation délicate et de stress hydrique de la plante dans des conditions limitantes en eau. Ayant pour finalité d’améliorer l’efficience de l’eau pour les plantes cultivées sur substrats, les travaux développés dans cette thèse ont visé à analyser l’évolution des propriétés hydrauliques de différents substrats au cours de laculture, en se focalisant tout particulièrement sur les effets combinés du développement racinaire et de la gestion de l’irrigation.Des essais culturaux ont été menés sur tourbe, fibres de coco, fibres de bois et écorce, prenant pour plante modèle utilisée le rosier Knock Out®. Des mesures de biomassesracinaires et aériennes, ainsi que celles des propriétés de rétention en eau et en air, de conductivité hydraulique, de diffusivité des gaz et de mouillabilité ont été effectuées surchaque substrat soumis à des régimes d’irrigation différents (variant d’un optimum hydrique à des conditions de stress hydrique). Les résultats montrent d'importantes modifications aufil du temps, principalement en raison de l'histoire hydrique. Cela conduit à des modifications(1) de la distribution et de la taille des pores, traduite par une réduction de leur tortuositéqui génère une augmentation de la diffusion gazeuse dans le milieu, ainsi que (2) unediminution de / Precise irrigation management of substrates is of vital importance in horticultural soilless systems to avoid root asphyxia, nutrient leaching, and plant disease in case of excessive watering; as well as, nutrient and water deficiency, and then plant physiological stress in the driest conditions. The study presented here aimed to improve water efficiency for plants grown in pots or containers, focusing on the evolution of hydraulic properties of substratesdue to root development and irrigation strategies during plant growth. Crop trials were performed on peat, coir, wood fiber and pine bark, using the rose Radrazz Rosa x hybrida as plant model.Shoot and roots biomasses, air and water retention properties, hydraulic conductivity, relative gas diffusivity and wettability were measured on each substrate, managed with different irrigation strategies (from an optimal water content to hydric stress conditions). Results showed significant changes over time, mainly due to the hydric history. This led to changes (1) in pore distribution and size, and then a decrease in pore tortuosity generating an increase in relative gas diffusivity in the substrates, and (2) a decrease in substrates’ wettability according to the intensity of drying. Although they were with weaker amplitude to those resulting of the hydric history, filling of macroporosity by the root system led to limit substrates’ consolidation due to drying/wetting cycles, and moreoverto amplify pore connectivity and then relative gas diffusivity and to limit degradation inwettability.

Le travail de recherche présenté dans ce mémoire de thèse s'inscrit dans le cadre d'un projet de développement d'un outil radar pour la cartographie de la teneur en eau des sols agricoles et se consacre plus particulièrement à la conception de deux prototypes d'antennes radar large bande. Deux prototypes d'antennes ont ainsi été conçus de manière numérique sur la base d'un code de simulation électromagnétique en trois dimensions basé sur la méthode des différences finies dans le domaine temporel (FDTD) pour la résolution des équations de Maxwell. Les prototypes ont été conçus avec comme ligne directrice un encombrement minimum (format A4) et une largeur de bande maximum sur la gamme 100 MHz - 1 GHz (dans l'air). Afin d'étudier apriori le comportement de ces prototypes en présence de sols, une étude numérique a été réalisée en représentant les sols par des demi-espaces infinis. Cette étude numérique se base sur l'évolution du coefficient de réflexion des prototypes dans le domaine fréquentiel (s11). Pour s'approcher au mieux des conditions de terrain, l'effet d'un contact non idéal entre l'antenne et le sol (représentée par une élévation de l'antenne) ainsi que celui de la rugosité du sol (représenté par des surfaces en tôle ondulée et en boîtes d'oeufs) ont été investigués. Sur la base de cette étude numérique, deux prototypes d'antennes (une antenne de type bow-tie et une de type dipôle elliptique) ont été fabriqués et testés en laboratoire et sur le terrain. Les premiers tests en laboratoire ont permis : (i) de vérifier la bonne cohérence entre mesure de s11 en milieu contrôlé et simulation FDTD précise de l'antenne (i.e. prenant en compte tous ses éléments constitutifs), (ii) une calibration en champ lointain et en champ proche de l'antenne permettant l'utilisation d'un modèle analytique pour simuler le s11 de l'antenne en présence d'un sol, (iii) une première estimation de la permittivité diélectrique d'un sol simple (sable) par les deux types de modélisation (FDTD et analytique). Enfin, les prototypes d'antennes ont été testés sur le terrain afin de vérifier leur comportement lors de mesures in situ. Ces tests montrent un fort impact (bruit) des câbles coaxiaux utilisés lors des mesures (notamment à haute fréquence), ainsi qu'une bonne sensibilité du dispositif aux contrastes de permittivité diélectrique. / The research work submitted in this PhD dissertation is part of research project which aims to develop a new tool for mapping the soil water content in agricultural context with ground penetrating radar technology. The scope of this particular work is the development of two prototypes of wideband radar antennae. Hence, two prototypes of antennae have been numerically designed based on a 3D finite-difference in time-domain (FDTD) electromagnetic solver of Maxwell's equations. The guiding principles that have been followed during the design are mainly a small size antenna (A4 format) and achieving the wider bandwidth possible in the frequency range 100 MHz - 1 GHz (in the air). In order to study the behavior of our prototypes when put in presence of soils, we conducted a numerical study representing the soils by half-spaces. This numerical study was based on the analysis of the antennae reflection coefficient in the frequency domain (or return loss coefficient s11). To be as close as possible to field conditions, the effect of a non ideal contact between the antenna and the soil (represented by a small elevation of the antenna) as well as the effect of soil surface rugosity (represented by corrugated iron-like and eggbox-like surface) have been investigated. Based on this numerical study, two prototypes of antennae (one bow-tie-like and on elliptical dipole) have been physically built and tested in both lab and field conditions. The test in lab condition enabled us to: (i) check the similarity between measured s11 in a controlled environment and corresponding FDTD simulation of the antenna including all antenna parts, (ii) calibrate the antenna in both far field and near field conditions which enabled the use of an analytical model to simulated the antenna s11 in presence of soil, (iii) estimate the dielectric permittivity of a sand sample using both FDTD and analytical simulations. Finally, the prototypes were tested in field condition in order to verify their behavior for in situ measurements. These tests show that using unshielded coaxial cable has a very important impact on the data (noise) and that the prototypes demonstrate a good sensitivity to dielectric permittivity contrasts.

Les sols sont définis comme étant caillouteux à partir d’une proportion supérieure à 35 % d’éléments grossiers. Les sols caillouteux - dont certains supportent des zones de grandes cultures - couvrent environ 30% de la superficie de l’Europe occidentale. Outre le fait qu’ils sont plus contraignants pour la production agricole car les opérations culturales y sont plus délicates, les sols caillouteux sont souvent des sols peu épais ; ils contribuent ainsi de façon significative à la recharge des nappes mais sont a priori très sensibles au lessivage hivernal du nitrate et des produits phytosanitaires. Malgré leur grande étendue géographique et leurs propriétés spécifiques, les sols caillouteux ont été peu étudiés. Devant ce déficit de connaissances et devant les problèmes spécifiques posés par les sols caillouteux (variabilité de la phase caillouteuse, échanges entre la phase caillouteuse et la fraction fine des sols), tant en termes de production végétale qu’en termes de protection de l’environnement, ce projet de thèse a eu pour objectifs de : i) déterminer la réserve utile des éléments grossiers de sols caillouteux d’origine sédimentaire ; ii) d’évaluer qualitativement et quantitativement la pierrosité de sols caillouteux à l’échelle parcellaire ; et iii) d’estimer la réserve utile effective de sols caillouteux et leur fonctionnement hydrique sur de grands territoires agricoles. Grâce à des analyses au laboratoire, nous avons montré que les cailloux étaient saturés en eau à -100 hPa et que les teneurs en eau à la capacité au champ et au point de flétrissement pouvaient s’exprimer simplement en fonction de la masse volumique, ce qui a permis de définir des fonctions de pédotransfert robustes et opérationnelles pour le calcul de l’humidité utile des éléments grossiers. Grâce à l’analyse du bruit du signal de la résistivité électrique, mesurée in situ par prospections géophysiques, il a été possible d’évaluer leur pierrosité volumique à l’échelle d’une parcelle. Enfin, à l’échelle régionale, nous avons montré que la non-prise en compte du volume de la phase caillouteuse et/ou de ses propriétés conduisait à des sous-estimations de 20 % de la réserve utile, ce qui avait pour conséquence une surestimation du déficit hydrique de 20 mm par an en moyenne, avec une grande variabilité spatiale. Ces travaux permettront, à terme, une meilleure gestion spatialisée des agrosystèmes, aux échelles locales et régionales. En effet, les nouvelles propriétés hydriques calculées permettront d’améliorer la compréhension du fonctionnement environnemental spatialisé des sols afin de mieux estimer certains risques (lessivage de nitrate, émissions de gaz à effet de serre par les sols, etc.). / Stony soils are soils containing a proportion of rock fragments larger than 35%. These soils - including intensive agricultural areas - cover about 30% of the surface of Western Europe. Stony soils are not only more stringent for agricultural production because the farming operations are usually more difficult, but also they are often thin; they then significantly contribute to the groundwater recharge, but are they are very sensitive to winter leaching of nitrate and pesticides. Despite their geographical spread and their specific properties, the stony soils have not been largely studied whereas they present specific scientific problems (variability of phase stony, exchanges between the stony phase and the fine fraction of soil). In that context, this thesis aimed at: i) determining the available water content of rock fragments from rock fragments of sedimentary origin; ii) assessing qualitatively and quantitatively the stoniness of stony soils at field scale; and iii) estimating the effective available water content of stony soils and their hydric functioning for large agricultural areas. From laboratory experiments, we demonstrated that rock fragments were saturated for a water potential of -100 hPa and that their water content at field capacity and at permanent wilting point could be easily estimated from their bulk density, which enable to define robust and operational pedotransfer functions for the estimation of the available water content of rock fragments. Thanks to the analysis of the signal noise of the electrical resistivity, measured in situ by geophysical prospectings, it was possible to assess the stoniness of stony soils at the plot scale. Finally, at the regional scale, we demonstrated that the available water content could be underestimated of about 20 % when the volume and/or properties of rock fragments were not taken into account, which induced overestimations of the hydric deficit of about 20 mm as a mean, with high spatial variability. This work will ultimately be used for a better spatial management of agricultural soils, at local and regional scales. Indeed, the new hydric properties will help in improving our knowledge of the environmental spatial soil functioning in order to better estimate some risks (nitrate leaching, greenhouse gas emissions from soils).

One can use unlicensed and often very inexpensive radios for unconventional communication (underwater- and underground) links. However, one can go further, and use these radios as sensors rather than communication links. Such communication links and sensors can have important application in hydroscience. While the attenuation of RF signals is high in these mediums, by using the wireless sensor network (WSN) paradigm of multi-hop and retransmission, reliable networks can be formed underwater and underground. One no longer needs to think of RF modules as only a source of data transmission. This revelation lends itself to thinking of these modules as inexpensive RF wave generators at prescribed unlicensed frequencies. Analyzing the received signal strength indicator (RSSI) of a link over time, one can infer changes in the medium from the changes in RSSI. In this thesis, I develop a simple mathematical model to relate changes in RSSI to changes in the medium. Additionally, five experimentally validated examples demonstrate the possibility of non-traditional uses for RF modules. Demonstrated sensor possibilities include soil moisture estimation, leaf wetness measurement, and vegetation water content estimation. This thesis served to validate the use of inexpensive unlicensed RF modules as more than just communication links through air, but as links in unconventional media, and more importantly as measurement instruments.

Cette recherche s’inscrit dans le cadre de la surveillance structurale des enceintes de confinement des centrales nucléaires qu’EDF exploite. L’objectif est de déterminer comment la connaissance de la teneur en eau du béton de ces ouvrages pourrait améliorer les prédictions de leur comportement mécanique, qui sont régulièrement réalisées dans le cadre de la démonstration de sûreté des installations.Dans un premier temps, nous avons étudié comment les incertitudes de mesure d’auscultation se propageaient dans les modèles pour quantifier l’information apportée par la mesure de teneur en eau. Nous avons également considéré les effets de ces incertitudes sur les extrapolations en fin de vie de l’ouvrage. Dans un second temps, nous avons proposé un modèle de surveillance des déformations différées comprenant la teneur en eau comme variable explicative et fondé sur une dépendance linéaire avec les déformations. Cette approche a été validée grâce aux données issues de la maquette VeRCoRs.Nous avons voulu ensuite estimer plus précisément l’exigence métrologique pour qualifier les chaines de mesure in situ de teneur en eau des bétons. Pour cela, nous avons utilisé la méthode de Monte Carlo pour simuler la propagation des incertitudes de mesures, en comparant les performances du modèle que nous proposions avec celles d’une approche d’ingénierie plus classique. / This research takes place within the framework of the structural monitoring of nuclear power plant containments that EDF operates. Our goal is to determine how the knowledge of the concrete water content these structures could improve the predictions of their mechanical behavior, which are periodically undertaken as part of the safety case for the facilities.As a first step, we have studied monitoring data uncertainties propagation through the models, in order to quantify the information brought by the water content measurement. We have also addressed the effects of these uncertainties on the extrapolations to the end of the structure lifetime. In a second phase, we have proposed a delayed deformation monitoring model including water content as an explanatory variable and based on a linear dependence with strains. This approach has been validated with data from the VeRCoRs mock up.Then, we sought to estimate more accurately the metrological requirement to qualify in-situ measurement systems for concrete water content. To do this, we used the Monte Carlo method to simulate the propagation of measurement uncertainties, by comparing the performances of the model that we proposed with those of a more conventional engineering approach.

Improved soil water conservation has become an important subject in semi-arid areas due to low and erratic rainfall which is often combined with higher temperatures to provide unsuitable conditions for successful crop productivity. Dryland agriculture remains vulnerable to yield losses in these areas. This calls for implementation of conservation agricultural practices that would improve dryland maize productivity. An on-station field trial was started in 2007 at Zeekoegat experimental farm (24 kilometers north of Pretoria), to establish the effect of different conservation agriculture practices on soil and plant properties. The experimental lay-out was a split-plot randomized complete block design, replicated three times, with each replicate split into two tillage systems (whole plots) and then each whole plot (reduced tillage (RT) and conventional tillage (CT)) was subdivided into 12 treatments (two fertilizer levels x 6 cropping patterns). The present study explored the impacts of different tillage practices, cropping patterns and fertilization levels on soil water content, soil temperature and dryland maize productivity during the 2010/11 and 2011/12 growing seasons. To improve the quality of soil water content (SWC) data, the effect of correction for concretions on soil bulk density and the relationship between volumetric soil water content (SWC) vs neutron water meter (NWM) count ratios was also investigated. Corrections for concretions on soil bulk density did not improve NWM calibrations in this study. In all seasons, significantly higher mean SWC was found under RT treatment than in CT at all depths except at 0-300 mm. For example, during the 2010/11 growing season, SWC under RT was 1.32 % and 1.10 % higher than CT for the 300 – 1350 mm and 0 – 1350 mm soil profiles, respectively. The mean weekly SWC was consistently higher for RT throughout both the growing seasons. Significantly higher SWC was also found under monoculture at all soil depths (except at 0-300 mm during 2011/12) compared to treatments under intercropping. For example, during 2010/11, at 0-300mm, SWC under maize monoculture was 1.72 % higher than under intercropping. The maximum and minimum soil temperatures were significantly higher at 100 and 400 mm soil depths under CT than under RT during 2010/11. During 2011/12, significantly higher minimum soil temperatures at 100 mm depth and lower temperature differences (maximum – minimum soil temperatures) at 400 mm depth were observed under intercropping. Despite the higher SWC and reduced soil temperature under RT, the maize seeds emergence rate was lower and plant stand was reduced. This is attributed to other factors associated with RT systems such as increased soil penetration resistance which often leads to poor root development. The lower soil temperatures under RT were generally within the range that would not be expected to inhibit growth and uptake of nutrients. Slower growth under RT resulted in lower biomass and grain yield. Plants that received high fertilizer rates grew more vigorously than plants under lower fertilizer levels when water was not a limiting factor, but produced lower grain yield due to water shortage in March, especially in 2011/12. The harvest index was therefore lower for treatments that received high fertilizer levels. Maize biomass under monoculture x low fertilizer level was significantly lower compared to other fertilizer x cropping pattern treatments. Maize plant growth under intercropping was improved throughout the seasons, which led to significantly higher grain yield than under maize monoculture. It is therefore recommended that farmers in dryland areas take the advantage of intercropping maize with legumes to obtain higher maize productivity. Further research should focus on investigating the possibility of roots restrictions occurring under RT conditions and under various environmental and soil conditions. / Dissertation (MScAgric)--University of Pretoria, 2014. / lk2014 / Plant Production and Soil Science / MScAgric / Unrestricted

Drywall board-based structures, a competent and cost-effective method of providing flexible partitioning assemblies in commercial and residential houses, are now widely used as walls or ceilings. However, the gypsum-based drywall that has been used in construction is not water-resistant and can create problems such as mold growth and structural defects. The aim of this study is 1) to develop a new sandwich panel with better physical and mechanical properties using locally sourced materials 2) to investigate the long-term hygrothermal performance of the new sandwich panel through using a numerical simulation. The sandwich panel is composed of two different thicknesses of kraft-paper honeycomb core bonded to two cementitious panels with silicone-based adhesive. The experimental results show that the sandwich panel with a thicker core has lower thermal conductivity and higher flexural strength compared to the gypsum-based drywall. The heat and moisture performance of two wall structures were performed using the WUFI Pro simulation program. The results of the modeling analysis present that wall assembly with gypsum-based drywall has higher water content than multilayer sandwich panel. In addition, the multilayer sandwich panel shows a 4.6% lower annual heat flow compared to the reference wall.