O entendimento dos processos hídricos do solo, tais como infiltração, drenagem, e disponibilidade de água para as plantas, necessita do conhecimento da relação entre o conteúdo de água no solo e o potencial matricial, representado pela curva de retenção de água no solo (CRA). No entanto, a determinação da CRA demanda tempo e possui um custo relativo alto. Uma alternativa é sua determinação através de modelos que estimam a CRA a partir de alguns atributos de fácil determinação, chamados funções de pedotransferência (FPT). A finalidade desse trabalho foi quantificar os efeitos da mudança do uso do solo sobre os atributos físicos e hídricos no Sudeste do Estado do Pará. Utilizou-se o banco de dados do Projeto Serviços ecossistêmicos e sustentabilidade das paisagens agrosilvipastoris da Amazônia Oriental, para obter dados de textura (areia, silte e argila), densidade do solo (Ds), carbono orgânico (CO), pH, capacidade de troca de cátions (CTC) e, as vezes, as CRA. Primeiramente, foram avaliadas 16 FPT existentes na literatura; 8 FPT paramétricas, que estimam os parâmetros empíricos do modelo de van Genuchten e 8 FPT pontuais, que estimam a umidade em potenciais específicos de água no solo. Posteriormente, buscando maior capacidade preditiva das FPT, através da técnica de regressão múltipla, desenvolveu-se uma FPT utilizando os atributos do solo mensurados no projeto. As melhores FPT foram utilizadas para estimar os parâmetros do modelo de van Genuchten nos sítios onde não havia CRA medida. Através desta extrapolação, avaliou-se o efeito da mudança de uso do solo sobre a distribuição dos tamanhos de poros, utilizando-se análise de componentes principais (ACP). Dentre as FPT testadas, as que apresentaram melhor resultado foram as FPT propostas por Tomasella et al. (2000), no entanto, a avaliação de desempenho realizada mostrou resultados não satisfatórios. Por outro lado, os resultados apresentados pela FPT desenvolvida neste trabalho alcançaram boa capacidade preditiva dos parâmetros empíricos do modelo de van Genuchten (1980). A ACP possibilitou identificar uma grande variabilidade entre os atributos medidos e estimados dos solos. Devido a esta variabilidade, não foram detectadas diferenças marcantes nos atributos dos solos em função do uso. Para isso, faz-se necessário estudos complementares, aumentando a escala e/ou classes de solo. / The understanding of soil water attributes, such as infiltration, drainage, solute movement and water availability for plants, needs the knowledge of the relationship between water content and soil matric potential, represented by the soil water retention curve (SWRC). However, the determination of the SWRC demands considerable time and has a relatively high cost. An alternative is to model its determination using pedotransfer functions (PTF) that calculate the SWRC parameters using easily obtainable soil attributes. The aim of this study was to use PTF to quantify the effects of changing land use on soil hydro-physical attributes at three locations in southern Pará. The database obtained in the project \"Ecosystem services and sustainable agroforestry landscapes in Eastern Amazonia\" was used in order to obtain soil texture data (sand, silt and clay), bulk density (Bd), organic carbon (OC), pH, cation exchange capacity (CEC) and the SWRC. First, 16 PTF found in the literature were evaluated (8 estimating the empirical parameters of the van Genuchten (1980) model and 8 to estimate soil moisture at specific matric potentials). Later, aiming at a greater predictive ability, a PTF was developed using the technique of multiple regression and the soil attributes determined in the project. The best PTF were used to estimate the model parameters of van Genuchten (1980) at the locations where there was no SWRC data. These results were used to determine the changes in pore distribution due to land use using principal component analysis (PCA). These changes were also associated with changes in content of OC and Bd using multivariate analysis. Of the FPT found in the literature the one that showed the best performance was the FPT developed by Tomasella et al. (2000), however, the evaluation performed showed poor results when the data was extrapolated to the locations where no SWRC were determined. The results presented by the FPT developed in this work showed a better efficiency in determining the SWRC in the locations that did not have this information. The PCA analysis performed on this data identified a large variability among the measured and estimated soil attributes. Because of this variability, there were no marked differences in soil attributes depending on land use. For this, more detailed studies are necessary at a increasing scale and/or at the soil class level.

Irrigated agriculture is the primary consumer of limited worldwide freshwater resources. Drought, growing world populations, and environmental demands compete with irrigation for freshwater resources"”threatening sustainable global food, fuel, and fiber production. This escalating global crisis demands that agriculture produce more food using less water. Traditional irrigation management has used technology to apply uniform irrigation rates across landscapes"”ignoring natural environmental variation. This provides inherent inefficiencies of over- or under- irrigation within individual fields. Variable-rate irrigation (VRI) is modern technology that employs global positioning systems and geographic information systems to match irrigation to spatially variable crop water demands within a field. Although commercially available, VRI lacks scientifically validated decision support systems to determine spatially and temporally variable crop water demand. The purpose of this research is to explore spatial and temporal variations in crop water demand to inform growers utilizing VRI. This research consists of four seasons of winter wheat (Triticum aestivum L.) production on a commercial farm in Idaho that employs a VRI system. In Chapter 1, the spatial variation of crop water productivity (CWP, the grain produced per unit of water consumed), is characterized for two seasons (2016-2017) and we propose a unique conceptual strategy for VRI management targeted at CWP. Observed CWP ranged from 4.1-21 kg ha-1 mm-1 with distinct spatial variation that, when considered together with grain yield, were shown to be useful for VRI management. During the 2017 growing season, VRI zones conserved 25% of irrigation compared to traditional uniform irrigation management. In the second chapter the spatial variation of soil water holding capacity (SWHC) was measured at 90 sampling points throughout the field. Then, during the 2016-2017 growing seasons, the spatial and temporal variation of soil moisture were modelled to characterize crop stress and its influence on grain yield. Soil within the field showed large spatial variation of SWHC, ranging from 147-369 mm. Under uniform irrigation in 2016, the natural variation of TAW created 21 day variation in the onset of crop stress throughout the field and under VRI in 2017 the onset of crop stress spanned 56 d. Surprisingly the variations in TAW did not statistically influence yield in 2016, and in 2017 the rate of irrigation predicted yield and TAW again did not statistically predict yield. This suggests that other environmental variables should be included when delineating irrigation zones and rates for VRI.

Irrigation needs to be applied to soils in relatively humid regions such as western Kentucky to supply water for crop uptake to optimize and stabilize yields. Characterization of soil and crop variability at the field scale is needed to apply site specific management and to optimize water application. The objective of this work is to propose a characterization and modeling of soil and crop processes to improve irrigation management. Through an analysis of spatial and temporal behavior of soil and crop variables the variability in the field was identified. Integrative analysis of soil, crop, proximal and remote sensing data was utilized. A set of direct and indirect measurements that included soil texture, electrical conductivity (EC), soil chemical properties (pH, organic matter, N, P, K, Ca, Mg and Zn), NDVI, topographic variables, were measured in a silty loam soil near Princeton, Kentucky. Maps of measured properties were developed using kriging, and cokriging. Different approaches and two cluster methods (FANNY and CLARA) with selected variables were applied to identify management zones. Optimal scenarios were achieved with dividing the entire field into 2 or 3 areas. Spatial variability in the field is strongly influenced by topography and clay content. Using Root Zone Water Quality Model 2.0 (RZWQM), soil water tension was modeled and predicted at different zones based on the previous delineated zones. Soil water tension was measured at three depths (20, 40 and 60 cm) during different seasons (20016 and 2017) under wheat and corn. Temporal variations in soil water were driven mainly by precipitation but the behavior is different among management zones. The zone with higher clay content tends to dry out faster between rainfall events and reveals higher fluctuations in water tension even at greater depth. The other zones are more stable at the lower depth and share more similarities in their cyclic patterns. The model predictions were satisfactory in the surface layer but the accuracy decreased in deeper layers. A study of clay mineralogy was performed to explore field spatial differences based on the map classification. kaolinite, vermiculite, HIV and smectite are among the identified minerals. The clayey area presents higher quantity of some of the clay minerals. All these results show the ability to identify and characterize the field spatial variability, combining easily obtainable data under realistic farm conditions. This information can be utilized to manage resources more effectively through site specific application.

Orientador: José Eduardo Corá / Resumo: Sistemas como a integração lavoura-pecuária-floresta (ILPF) têm ganhado destaque e importância econômica na agricultura brasileira, devido a estes intensificarem o uso da terra na produção de alimentos e energia, além de melhorarem as propriedades físicas, químicas e biológicas do solo. Complexidade de manejo e efeitos competitivos têm sido observados entre componentes em sistemas integrados, o que pode vir a prejudicar sua sustentabilidade a longo prazo. Objetivou-se monitorar a umidade do solo e a produtividade do componente agrícola, em dois sistemas ILPF, os quais diferiram apenas pela espécie do componente florestal (clone Urograndis I144 e Corymbia citriodora), no norte do estado de São Paulo (21º13’56” S, 48º17’19” O), em um Latossolo Vermelho distrófico, com valores de 310 g kg-1, 20 g kg-1 e 670 g kg-1 de argila, silte e areia, respectivamente, na camada 0 0,20 m. Em 2017 (quarto ano), utilizou-se tensiômetros, instalados a 0,20 m de profundidade, equidistantes a 3 metros, na área entre renques, para melhor compreender o processo de umidade do solo dentro destes sistemas e foram avaliadas as produtividades do milho segunda safra, cultivado nos anos agrícolas de 2014 a 2019 e da soja, cultivada nas safras 2017/2018 e 2018/2019. Influência negativa foi observada na umidade do solo e na produtividade das culturas agrícolas em função da proximidade das árvores, locais onde a produtividade do milho decaiu a partir do segundo ano de cultivo e a produtividade da soja foi me... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Systems such as crop-livestock-forest integration (ICLF) have gained prominence and economic importance in Brazilian agriculture, as they intensify land use in food and energy production, as well as improve the physical, chemical and biological properties of the soil. Management complexity and competitive effects have been observed between components in integrated systems, which may undermine their long-term sustainability. The objective was to monitor soil moisture and agricultural component productivity in two ICLF systems, which differed only by forest component species (clone Urograndis I144 and Corymbia citriodora) in northern São Paulo State (21º13'56” S, 48º17'19” O), in a dystrophic Red Latosol, with values of 310 g kg-1, 20 g kg-1 and 670 g kg-1 of clay, silt and sand, respectively, in layer 0 0.20 m In 2017 (fourth year), tensiometers installed at a depth of 0.20 m, equidistant at 3 meters in the area between rigs, were used to better understand the soil moisture process within these systems and the yields of second crop maize cultivated in the years 2014 to 2019 and soybean, cultivated in the 2017/2018 and 2018/2019 crops. Negative influence was observed on soil moisture and crop yield due to the proximity of trees, where corn yields declined from the second year of cultivation and soybean yield was lower in both ICLF systems. Greater distance between forest component rows and greater seeding distance of the crop compared to trees should be adopted in order to make... (Complete abstract click electronic access below) / Mestre

Efficient use of irrigation and nutrients are becoming increasingly important in commercial orchards in the Hawkesbury area. Proper irrigation scheduling practices can help in the better use of irrigation water and reduce environmental impacts. Field experiments were conducted during February 1999 to June 2000 to understand soil-water use, and to evaluate farmer’s irrigation practice under an alley cropping system consisting of turf and stone fruits. The study was carried out at Atlas Farm, 3.5 km from the University of Western Sydney, Hawkesbury campus. The experimental site is a floodplain of the Hawkesbury River. The river flows within 1 km of the farm boundaries. The study was conducted under the farmer’s existing irrigation water and nutrient management practices. The main aims of the thesis were to study the movement and redistribution of soil-water and soil-moisture dynamics in the turf and stone fruit alley cropping system and to understand deep percolation losses and nitrogen leaching using the water balance approach. The study indicated that drainage occurred mainly after heavy rainfall and when there was rainfall for a few consecutive days. Thus irrigation application should be delayed if there is a likelihood of rain in a few consecutive days to prevent loss of water due to deep drainage. Furthermore, the study showed irrigation scheduling was essential to reduce nitrate leaching in the field; that irrigation depths should be varied according to the stage of crop growth, and the proper timing of irrigation application could help reduce deep percolation and runoff losses. / Master of Science (Hons) (Agriculture)

The knowledge of the dynamics of soil water is essential in agricultural, hydrological and environmental engineering as it controls plant growth, key hydrological processes, and the contamination of surface and subsurface water. Nearby remote sensing can be used for characterizing non-destructively the hydrogeophysical properties of the subsurface. In that respect, ground penetrating radar (GPR) constitutes a promising high resolution characterization tool. However, notwithstanding considerable research has been devoted to GPR, its use for assessing quantitatively the subsurface properties is constrained by the lack of appropriate GPR systems and signal analysis methods. In this study, a new integrated approach is developed to identify from GPR measurements the soil water content and hydraulic properties governing water transfer in the subsurface. It is based on hydrodynamic and electromagnetic inverse modeling. Research on GPR has focused on GPR design, forward modeling of GPR signal, and electromagnetic inversion to estimate simultaneously the depth dependent dielectric constant and electric conductivity of the shallow subsurface, which are correlated to water content and water quality. The method relies on an ultrawide band stepped frequency continuous wave radar combined with an off-ground monostatic TEM horn antenna. This radar configuration offers possibilities for real time mapping and allows for a more realistic forward modeling of the radar-antenna-subsurface system. Forward modeling is based on the exact solution of Maxwell's equations for a stratified medium. The forward model consists in elementary linear components which are linked in series and parallel. The GPR approach is validated for simple laboratory and outdoor conditions. GPR signal inversion enables the monitoring of the soil water dynamics, which can be subsequently inverted for estimating the soil hydraulic properties. A specifically designed hydrodynamic inverse modeling procedure which requires only water content data as input is further developed and validated to obtain the soil hydraulic properties under laboratory conditions.

<p>Many geotechnical engineering problems involve combining two or more independent physical processes as a coupled solution of seepage, volume change and shear strength. For any physical process being modeled, it is desirous to be able to compute any of the volume-mass soil properties. When the volume-mass soil properties are combined with the stress state of the soil, the result is a volume-mass constitutive relationship. Three volume-mass constitutive relationships (i.e., void ratio, water content and degree of saturation) are generally viewed as being the most fundamental; however, only two of the relations are independent. The unsaturated soil properties associated with seepage, volume change and shear strength problems are also related to the volume-mass soil properties. While the unsaturated soil properties are often estimated as simply being a function of the soil-water characteristic curve, it is more accurate to define the properties in a more rigorous manner in terms of the volume-mass soil properties. The advancement of computing capabilities means that it is quite easy to formulate constitutive relations for shear strength and permeability, for example, in terms of all volume-mass properties of the unsaturated soil.</p><p>The objectives of this dissertation include: i) the development of volume-mass constitutive models for unsaturated soils; ii) the further study and verification of the volume-mass constitutive behavior of unsaturated soils; and iii) the development of techniques for visualization of volume-mass constitutive surfaces for unsaturated soils. To achieve these objectives, the present research study was conducted from both theoretical and experimental bases.</p><p>The theoretical program commenced with a comprehensive literature review of the volume-mass constitutive relationships for unsaturated soils. A new, more rigorous volume-mass constitutive model was then proposed. Appropriate terminology was introduced for the development of the model, followed by an outline of the assumptions used and the mathematical derivation. The proposed model requires conventionally obtainable soil properties for its calibration. The model is capable of predicting both the void ratio and water content constitutive relationships for various unsaturated soils, taking into account elastic and plastic volume changes. Various stress paths can be simulated and hysteresis associated with the soil-water characteristic curve can be taken into account. </p><p>Two closed-form equations for the volume-mass constitutive relationships were derived. A computer software program was written based on the theory of the proposed volume-mass constitutive model. Techniques for the visualization of the volume-mass constitutive surfaces were then presented. An experimental program was conducted in the laboratory. The experimental program involved the verification of a new testing apparatus. Several soils were selected for testing purposes and appropriate testing procedures were established (i.e., soil specimens were initially slurry). The testing stress paths followed in the experimental program were different from most research programs conducted in the past and reported in the research literature. Conclusions regarding the compressibility, stress path dependency, and hysteretic nature of the soil-water characteristic curve of an unsaturated soil were presented.</p><p>A considerable number of test results (i.e., from both the experimental program and the research literature) were used in the verification of the new volume-mass constitutive model. This model has proven to be effective in predicting both collapse and expansion of a soil. The volume-mass constitutive model appears to predict behaviour in a satisfactory manner for a wide range of soils; however, the predictions appear to be superior for certain soils. In all cases the volume-mass predictions of the model appear to be satisfactory for geotechnical engineering practice.

<p>Many geotechnical engineering problems involve combining two or more independent physical processes as a coupled solution of seepage, volume change and shear strength. For any physical process being modeled, it is desirous to be able to compute any of the volume-mass soil properties. When the volume-mass soil properties are combined with the stress state of the soil, the result is a volume-mass constitutive relationship. Three volume-mass constitutive relationships (i.e., void ratio, water content and degree of saturation) are generally viewed as being the most fundamental; however, only two of the relations are independent. The unsaturated soil properties associated with seepage, volume change and shear strength problems are also related to the volume-mass soil properties. While the unsaturated soil properties are often estimated as simply being a function of the soil-water characteristic curve, it is more accurate to define the properties in a more rigorous manner in terms of the volume-mass soil properties. The advancement of computing capabilities means that it is quite easy to formulate constitutive relations for shear strength and permeability, for example, in terms of all volume-mass properties of the unsaturated soil.</p><p>The objectives of this dissertation include: i) the development of volume-mass constitutive models for unsaturated soils; ii) the further study and verification of the volume-mass constitutive behavior of unsaturated soils; and iii) the development of techniques for visualization of volume-mass constitutive surfaces for unsaturated soils. To achieve these objectives, the present research study was conducted from both theoretical and experimental bases.</p><p>The theoretical program commenced with a comprehensive literature review of the volume-mass constitutive relationships for unsaturated soils. A new, more rigorous volume-mass constitutive model was then proposed. Appropriate terminology was introduced for the development of the model, followed by an outline of the assumptions used and the mathematical derivation. The proposed model requires conventionally obtainable soil properties for its calibration. The model is capable of predicting both the void ratio and water content constitutive relationships for various unsaturated soils, taking into account elastic and plastic volume changes. Various stress paths can be simulated and hysteresis associated with the soil-water characteristic curve can be taken into account. </p><p>Two closed-form equations for the volume-mass constitutive relationships were derived. A computer software program was written based on the theory of the proposed volume-mass constitutive model. Techniques for the visualization of the volume-mass constitutive surfaces were then presented. An experimental program was conducted in the laboratory. The experimental program involved the verification of a new testing apparatus. Several soils were selected for testing purposes and appropriate testing procedures were established (i.e., soil specimens were initially slurry). The testing stress paths followed in the experimental program were different from most research programs conducted in the past and reported in the research literature. Conclusions regarding the compressibility, stress path dependency, and hysteretic nature of the soil-water characteristic curve of an unsaturated soil were presented.</p><p>A considerable number of test results (i.e., from both the experimental program and the research literature) were used in the verification of the new volume-mass constitutive model. This model has proven to be effective in predicting both collapse and expansion of a soil. The volume-mass constitutive model appears to predict behaviour in a satisfactory manner for a wide range of soils; however, the predictions appear to be superior for certain soils. In all cases the volume-mass predictions of the model appear to be satisfactory for geotechnical engineering practice.

Precision management of cotton production can increase profitability by decreasing inputs. The overall objective of this project is to improve cotton production by minimizing seeding rates while still maximizing yields and lint quality in water-limited soils. The research for this study was conducted at the Texas AgriLife Research IMPACT Center located in the Brazos River floodplain. In 2008 and 2009, 27 measurement locations were selected in production-sized center-pivot irrigated fields and planted in cotton variety Deltapine 164 roundup ready flex / bollgard II. Sites were selected based on soil apparent electrical conductivity (ECa) values, in a low, medium, and high ECa zones. Three seeding rates (74,100; 98,800; and 123,500 seeds ha-1) were established in each of the three ECa zones with three replications. In 2009, an additional seeding rate was added at 49,400 seeds ha-1. At each measurement location, soil texture, soil moisture (weekly), lint quantity and quality (High Volume Instrument) were measured. An additional replication for each ECa zone and seeding rate was selected for lint quantity and quality (HVI) measurements. Results indicated that cotton lint yield increased as ECa values, clay content, and water holding capacity of the soil increased. The seeding rates did not consistently affect cotton lint yield or quality. Seeding rates of 74,100 and 49,400 seeds ha-1 in a low and medium ECa zone for IMPACT-08 and -09 yielded more lint (300 kg ha-1), respectively. HVI lint quality parameters, such as, micronaire, fiber length, strength, uniformity, and elongation were significantly better in ECa zone 3. While the seeding rates did not affect the amount of soil water used throughout the season, lint yield variations between ECa zones can be explained by the rate at which soil water was used. Lower rates at which soil water was used within ECa zone 3 resulted in higher lint yields when compared to ECa zones 1 and 2, which used soil water faster and at greater depths. The findings suggest that irrigation applied to the low ECa zone was not sufficient to meet the plants demand, while in a high ECa zone, irrigation could have been reduced, resulting in cost savings through reduced inputs.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2009. / Härtill 4 uppsatser.