京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第20769号 / 農博第2252号 / 新制||農||1054(附属図書館) / 学位論文||H29||N5089(農学部図書室) / 京都大学大学院農学研究科地域環境科学専攻 / (主査)教授 舟川 晋也, 教授 間藤 徹, 教授 縄田 栄治 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

Levees are a significant part of the United States flood protection infrastructure. It is estimated that over 100,000 miles of levees exist in the United States. Most of these levees were designed many years ago to protect farmland and rural areas. As growth continues in the United States, many of these levees are now protecting homes and other important structures. The American Society of Civil Engineers gave the levees in the United States a grade of D- in 2009. To bring flood protection up to modern standards there requires adequate methods of evaluating levees with respect to seepage, erosion, piping and slope instability. Transient seepage analyses provide an effective method of evaluating seepage through levees and its potentially destabilizing effects. Floods against levees usually last for days or weeks. In response to a flood, pore pressures within the levee will change from negative (suction) to positive as the phreatic surface progresses through the levee. These changes can be calculated by finite element transient seepage analyses. In order for the transient seepage analysis to be valid, appropriate soil properties and initial conditions must be used. The research investigation described here provides simple and practical methods for estimating the initial conditions and soil properties required for transient seepage analyses, and illustrates their use through a number of examples. / Ph. D.

Sendo a condutividade hidráulica do solo um parâmetro que traduz a facilidade com que a água se movimenta ao longo do perfil de solo, sua determinação, principalmente no campo, torna-se imprescindível, visto que o movimento da água no solo está diretamente relacionado à produção das culturas agrícolas. Com isso, a aplicação de um método confiável que quantifique a condutividade hidráulica versus umidade, a função ( ) q K , certamente contribuirá muito para uma correta avaliação dos resultados, principalmente tendo em conta a grande variabilidade dessa função devido à variabilidade natural das características do solo. Neste trabalho, testou-se o método do perfil instantâneo com o objetivo de avaliar a função ( ) q K com e sem a suposição de gradiente unitário e também o seu comportamento com relação aos os horizontes pedológicos do solo. A determinação da função foi feita usando tensiômetros com manômetros de mercúrio instalados às profundidades de 0,1; 0,2; 0,3; 0,4; 0,5; 0,6; 0,7; 0,8; 0,9; 1,0; 1,1 e 1,2 m e curvas de retenção determinadas para as mesmas profundidades, num Latossolo Vermelho Distrófico argissólico A moderado textura média, localizado no campo experimental da Escola Superior de Agricultura "Luiz de Queiroz", Universidade de São Paulo. A análise dos resultados foi feita pelo teste F de análise de variância, a fim de testar o paralelismo, a igualdade dos interceptos e a coincidência entre as retas lnK versus q, considerando e não considerando a suposição do gradiente unitário. Além disso, foram feitos também testes de similaridade da função ( ) q K de cada profundidade do solo pelo índice de concordância de Willmott (1981). Com base na análise dos resultados pode-se dizer que, com os procedimentos utilizados de delimitação da área para inundação e redistribuição da água, podem ser empregados modelos simples que consideram unitário o gradiente de potencial total e que, pela comparação feita entre as profundidades, a separação do perfil do solo em horizontes pedológicos parece seguir a separação em camadas com funções ( ) q K semelhantes, apenas a partir da profundidade 0,6 m. / The soil hydraulic conductivity is a parameter that quantifies the ability of the soil to conduct water along the soil profile. Hence its field determination is indispensable, since soil water movement is directly related to the field crop productions. Thus, the use of an adequate method that assesses the hydraulic conductivity as a function of soil-water content, the ( ) q K function, certainly will very contribute to a proper evaluation of results, mainly if it is considered the great variability of this function as a result of the natural variability of the soil characteristics. In this work, the instantaneous profile method was tested with the objective to evaluate a) the ( ) q K function taking and not taking into consideration the assumption of unit gradient and b) the behaviour of the ( ) q K function with respect to the pedological horizons of the soil. The determination of the function was made using mercury manometer tensiometers installed at the depths of 0.1; 0.2; 0.3; 0.4; 0.5; 0.6; 0.7; 0.8; 0.9; 1.0; 1.1 and 1.2 m and soil water retention curves determined for the same depths, in an Oxisol, located at experimental fields of Escola Superior de Agricultura Luiz de Queiroz, University de São Paulo, in Piracicaba (SP), Brasil (22 o 42’ 43,3’’ W and 47 o 37’ 10,4’’ S). The result analysis was made using an F-test in order to verify the paralelism, the intercept equality and the coincidence of the lnK versus q straight lines, taking and not taking account of the assumption of unit hydraulic gradient. Basides, similarity tests of the ( ) q K function were also made by the Willmott (1981) index. From the analysis of results, it could be concluded that, with the procedures used to delimit the experimental plots in this experiment to water the soil profile and to follow the water redistribuition, the unit gradient approches seem to be adequate to assess the field ( ) q K function and also that the pedological horizons seem to follow the layers of similar ( ) q K function, for depths greater than 0.6 m.

O conhecimento sobre o balanço de água no solo é essencial ao manejo do sistema solo-água- planta. Esta pesquisa objetivou estudar os componentes do balaço de água em Cambissolo cultivado com meloeiro irrigado por gotejamento, com e sem cobertura da superfície, em Baraúna-RN. Em área experimental de 20 m x 50 m cultivou-se melão Amarelo, variedade AF- 646, no espaçamento de 2,00 m x 0,35 m, num total de dez linhas de plantas de 50 m de extensão cada. A 1/3 e 2/3 da extensão de cada linha de plantas foram instalados quatro tensiômetros, um em cada uma das profundidades 0,1; 0,2; 0,3 e 0,4 m. A instalação foi feita adjacente à linha de irrigação (0,1 m da linha de plantas) entre duas plantas selecionadas, com os tensiômetros espaçados 0,1 m entre si. Em cinco linhas aleatórias fez-se a cobertura com folhas secas de bananeira (Musa sp.) ao longo da linha de gotejamento numa faixa de 0,5 m. Nas outras cinco manteve-se o cultivo sem cobertura. Assim, o experimento consistiu de dois tratamentos, com dez repetições, em quatro períodos fenológicos: inicial (7-22 DAS dias após a semeadura), vegetativo (22-40 DAS), frutificação (40-58 DAS) e maturação (58-70 DAS). As precipitações pluviais foram medidas com pluviômetro e as armazenagens de água estimadas pelo método do trapézio, a partir das leituras dos tensiômetros e das curvas de retenção. Para a determinação das densidades de fluxo de água no limite inferior do volume de controle de solo (0,3 m), foram considerados os tensiômetros nas profundidades 0,2; 0,3 e 0,4 m, sendo que o tensiômetro a 0,3 m foi utilizado para estimar o conteúdo de água no solo, com uso da curva de retenção de água para esta profundidade, e os outros dois para o cálculo do gradiente de potencial total. As densidades de fluxo foram calculadas pela equação de Darcy-Buckingham, com a condutividade hidráulica do solo determinada pelo método do perfil instantâneo. O deflúvio superficial foi desconsiderado e a evapotranspiração real da cultura foi calculada pela equação do balanço de massas. Concluiu-se que: a) à 0,2 m de profundidade a condutividade hidráulica do solo foi baixa; b) o manejo da irrigação com tensiômetros permitiu redução de 45% na lâmina de água em relação à usualmente praticada na região, sem afetar a produtividade da cultura; c) houve efeito positivo da cobertura do solo sobre a armazenagem de água, especialmente nos estádios inicial e vegetativo da cultura; d) o método do balanço de água no solo mostrou-se eficiente na estimativa da evapotranspiração real, em condições de cultivo de meloeiro irrigado; e) a aplicação de uma única lâmina diária de irrigação, mesmo em curto intervalo de tempo, apresenta risco de perda de água por drenagem interna, especialmente nas fases inicial e vegetativa do meloeiro; f) a variabilidade espacial da densidade de fluxo foi elevada quando houve ocorrência de precipitação pluvial; g) não houve efeito da cobertura do solo na evapotranspiração da cultura, nem sobre a produtividade e características pós-colheita dos frutos; h) a curva de coeficiente de cultivo apresenta grandes limitações quando utilizada para fornecer água para o meloeiro. / The knowledge about the soil water balance is essential to soil-water-plant system management. Thus, this research aimed to study the water balance components in an Inceptsol cropped with muskmelon under drip irrigation, with and without surface covering, in the county of Baraúna, Rio Grande do Norte State, Brazil (05º04\'48 S, 37º37\'00 W). In an experimental area of 20 m x 50 m grew up AF-646 muskmelon, spaced 2.00 m x 0.35 m, in a total of ten plants lines 50 m long each. At 1/3 and 2/3 of the length of each plant line, four tensiometers were installed, one in each depths of 0.1, 0.2, 0.3 and 0.4 m. The installation was made adjacent to the irrigation line (0.1 m from the plant line) between two selected plants 0.1 m apart. In five random lines, it was made a covering with dry leaves of banana (Musa sp.) along the drip line in the range of 0.5 m. In the other five there was no covering. Thus, the experiment consisted of two treatments whith ten repetitions in four phenological stages: initial (7-22 DAS - days after sowing), growing (22-40 DAS), fruiting (40-58 DAS) and maturing (58-70 DAS). Rainfall was measured with rain gauge and water storage estimated by trapezoidal method, from tensiometer readings and retention curves. To determine the soil water flux densities at the soil depth 0.3 m, tensiometers at depths 0.2, 0.3 and 0.4 m were considered; the tensiometer at 0.3 m was used to estimate the soil water content, from the soil water retention curve at this depth, and the other two to calculate the soil water total potential gradient. The flux densities were calculated by the Darcy-Buckingham equation, with the hydraulic conductivity being determined by the instantaneous profile method. There was no runoff and the crop actual evapotranspiration was calculated by the mass balance equation. It could be concluded that: a) at 0.2 m soil depth the hydraulic conductivity was low; b) controlled irrigation with tensiometers allowed a reduction of 45% in water application in relation to commonly used practice in the region, without crop productivity change; c) there was positive effect of soil covering on water storage, especially at the initial and vegetative stages; d) the method of soil water balance was efficient to estimate actual evapotranspiration, under irrigated muskmelon conditions; e) the application of a single irrigation depth daily, even in a short time period, presents risk of water to be lost by internal drainage, especially at initial and vegetative muskmelon stages; f) the spatial variability of soil water flux density was high when rainfall incidence occurred; g) there was no effect of covering on crop actual evapotranspiration, neither on yield and post-harvest fruits characteristics; h) the crop coefficient curve has severe limitations when used to provide water to the muskmelon.

Sendo a condutividade hidráulica do solo um parâmetro que traduz a facilidade com que a água se movimenta ao longo do perfil de solo, sua determinação, principalmente no campo, torna-se imprescindível, visto que o movimento da água no solo está diretamente relacionado à produção das culturas agrícolas. Com isso, a aplicação de um método confiável que quantifique a condutividade hidráulica versus umidade, a função ( ) q K , certamente contribuirá muito para uma correta avaliação dos resultados, principalmente tendo em conta a grande variabilidade dessa função devido à variabilidade natural das características do solo. Neste trabalho, testou-se o método do perfil instantâneo com o objetivo de avaliar a função ( ) q K com e sem a suposição de gradiente unitário e também o seu comportamento com relação aos os horizontes pedológicos do solo. A determinação da função foi feita usando tensiômetros com manômetros de mercúrio instalados às profundidades de 0,1; 0,2; 0,3; 0,4; 0,5; 0,6; 0,7; 0,8; 0,9; 1,0; 1,1 e 1,2 m e curvas de retenção determinadas para as mesmas profundidades, num Latossolo Vermelho Distrófico argissólico A moderado textura média, localizado no campo experimental da Escola Superior de Agricultura "Luiz de Queiroz", Universidade de São Paulo. A análise dos resultados foi feita pelo teste F de análise de variância, a fim de testar o paralelismo, a igualdade dos interceptos e a coincidência entre as retas lnK versus q, considerando e não considerando a suposição do gradiente unitário. Além disso, foram feitos também testes de similaridade da função ( ) q K de cada profundidade do solo pelo índice de concordância de Willmott (1981). Com base na análise dos resultados pode-se dizer que, com os procedimentos utilizados de delimitação da área para inundação e redistribuição da água, podem ser empregados modelos simples que consideram unitário o gradiente de potencial total e que, pela comparação feita entre as profundidades, a separação do perfil do solo em horizontes pedológicos parece seguir a separação em camadas com funções ( ) q K semelhantes, apenas a partir da profundidade 0,6 m. / The soil hydraulic conductivity is a parameter that quantifies the ability of the soil to conduct water along the soil profile. Hence its field determination is indispensable, since soil water movement is directly related to the field crop productions. Thus, the use of an adequate method that assesses the hydraulic conductivity as a function of soil-water content, the ( ) q K function, certainly will very contribute to a proper evaluation of results, mainly if it is considered the great variability of this function as a result of the natural variability of the soil characteristics. In this work, the instantaneous profile method was tested with the objective to evaluate a) the ( ) q K function taking and not taking into consideration the assumption of unit gradient and b) the behaviour of the ( ) q K function with respect to the pedological horizons of the soil. The determination of the function was made using mercury manometer tensiometers installed at the depths of 0.1; 0.2; 0.3; 0.4; 0.5; 0.6; 0.7; 0.8; 0.9; 1.0; 1.1 and 1.2 m and soil water retention curves determined for the same depths, in an Oxisol, located at experimental fields of Escola Superior de Agricultura Luiz de Queiroz, University de São Paulo, in Piracicaba (SP), Brasil (22 o 42’ 43,3’’ W and 47 o 37’ 10,4’’ S). The result analysis was made using an F-test in order to verify the paralelism, the intercept equality and the coincidence of the lnK versus q straight lines, taking and not taking account of the assumption of unit hydraulic gradient. Basides, similarity tests of the ( ) q K function were also made by the Willmott (1981) index. From the analysis of results, it could be concluded that, with the procedures used to delimit the experimental plots in this experiment to water the soil profile and to follow the water redistribuition, the unit gradient approches seem to be adequate to assess the field ( ) q K function and also that the pedological horizons seem to follow the layers of similar ( ) q K function, for depths greater than 0.6 m.

O conhecimento sobre o balanço de água no solo é essencial ao manejo do sistema solo-água- planta. Esta pesquisa objetivou estudar os componentes do balaço de água em Cambissolo cultivado com meloeiro irrigado por gotejamento, com e sem cobertura da superfície, em Baraúna-RN. Em área experimental de 20 m x 50 m cultivou-se melão Amarelo, variedade AF- 646, no espaçamento de 2,00 m x 0,35 m, num total de dez linhas de plantas de 50 m de extensão cada. A 1/3 e 2/3 da extensão de cada linha de plantas foram instalados quatro tensiômetros, um em cada uma das profundidades 0,1; 0,2; 0,3 e 0,4 m. A instalação foi feita adjacente à linha de irrigação (0,1 m da linha de plantas) entre duas plantas selecionadas, com os tensiômetros espaçados 0,1 m entre si. Em cinco linhas aleatórias fez-se a cobertura com folhas secas de bananeira (Musa sp.) ao longo da linha de gotejamento numa faixa de 0,5 m. Nas outras cinco manteve-se o cultivo sem cobertura. Assim, o experimento consistiu de dois tratamentos, com dez repetições, em quatro períodos fenológicos: inicial (7-22 DAS dias após a semeadura), vegetativo (22-40 DAS), frutificação (40-58 DAS) e maturação (58-70 DAS). As precipitações pluviais foram medidas com pluviômetro e as armazenagens de água estimadas pelo método do trapézio, a partir das leituras dos tensiômetros e das curvas de retenção. Para a determinação das densidades de fluxo de água no limite inferior do volume de controle de solo (0,3 m), foram considerados os tensiômetros nas profundidades 0,2; 0,3 e 0,4 m, sendo que o tensiômetro a 0,3 m foi utilizado para estimar o conteúdo de água no solo, com uso da curva de retenção de água para esta profundidade, e os outros dois para o cálculo do gradiente de potencial total. As densidades de fluxo foram calculadas pela equação de Darcy-Buckingham, com a condutividade hidráulica do solo determinada pelo método do perfil instantâneo. O deflúvio superficial foi desconsiderado e a evapotranspiração real da cultura foi calculada pela equação do balanço de massas. Concluiu-se que: a) à 0,2 m de profundidade a condutividade hidráulica do solo foi baixa; b) o manejo da irrigação com tensiômetros permitiu redução de 45% na lâmina de água em relação à usualmente praticada na região, sem afetar a produtividade da cultura; c) houve efeito positivo da cobertura do solo sobre a armazenagem de água, especialmente nos estádios inicial e vegetativo da cultura; d) o método do balanço de água no solo mostrou-se eficiente na estimativa da evapotranspiração real, em condições de cultivo de meloeiro irrigado; e) a aplicação de uma única lâmina diária de irrigação, mesmo em curto intervalo de tempo, apresenta risco de perda de água por drenagem interna, especialmente nas fases inicial e vegetativa do meloeiro; f) a variabilidade espacial da densidade de fluxo foi elevada quando houve ocorrência de precipitação pluvial; g) não houve efeito da cobertura do solo na evapotranspiração da cultura, nem sobre a produtividade e características pós-colheita dos frutos; h) a curva de coeficiente de cultivo apresenta grandes limitações quando utilizada para fornecer água para o meloeiro. / The knowledge about the soil water balance is essential to soil-water-plant system management. Thus, this research aimed to study the water balance components in an Inceptsol cropped with muskmelon under drip irrigation, with and without surface covering, in the county of Baraúna, Rio Grande do Norte State, Brazil (05º04\'48 S, 37º37\'00 W). In an experimental area of 20 m x 50 m grew up AF-646 muskmelon, spaced 2.00 m x 0.35 m, in a total of ten plants lines 50 m long each. At 1/3 and 2/3 of the length of each plant line, four tensiometers were installed, one in each depths of 0.1, 0.2, 0.3 and 0.4 m. The installation was made adjacent to the irrigation line (0.1 m from the plant line) between two selected plants 0.1 m apart. In five random lines, it was made a covering with dry leaves of banana (Musa sp.) along the drip line in the range of 0.5 m. In the other five there was no covering. Thus, the experiment consisted of two treatments whith ten repetitions in four phenological stages: initial (7-22 DAS - days after sowing), growing (22-40 DAS), fruiting (40-58 DAS) and maturing (58-70 DAS). Rainfall was measured with rain gauge and water storage estimated by trapezoidal method, from tensiometer readings and retention curves. To determine the soil water flux densities at the soil depth 0.3 m, tensiometers at depths 0.2, 0.3 and 0.4 m were considered; the tensiometer at 0.3 m was used to estimate the soil water content, from the soil water retention curve at this depth, and the other two to calculate the soil water total potential gradient. The flux densities were calculated by the Darcy-Buckingham equation, with the hydraulic conductivity being determined by the instantaneous profile method. There was no runoff and the crop actual evapotranspiration was calculated by the mass balance equation. It could be concluded that: a) at 0.2 m soil depth the hydraulic conductivity was low; b) controlled irrigation with tensiometers allowed a reduction of 45% in water application in relation to commonly used practice in the region, without crop productivity change; c) there was positive effect of soil covering on water storage, especially at the initial and vegetative stages; d) the method of soil water balance was efficient to estimate actual evapotranspiration, under irrigated muskmelon conditions; e) the application of a single irrigation depth daily, even in a short time period, presents risk of water to be lost by internal drainage, especially at initial and vegetative muskmelon stages; f) the spatial variability of soil water flux density was high when rainfall incidence occurred; g) there was no effect of covering on crop actual evapotranspiration, neither on yield and post-harvest fruits characteristics; h) the crop coefficient curve has severe limitations when used to provide water to the muskmelon.

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

Potatoes in the Eastern Shore of Virginia are traditionally planted between late February and early April and harvested between early June and late August. Potato prices are usually higher early into the harvest season and decrease slowly as the season progresses. Early planting dates are desirable for farmers, as it allows them to perceive higher prices for their product, but early planting is also associated with lower air temperature during the early season, which in turn can affect plant development, water and nutrient uptake, and overall yield. Additionally, variations in soil properties often affect nutrient and water availability for plants, as well as the distribution of soil-borne insect pests. Additionally, several techniques are available to map the variations of soil properties in commercial potato fields, but little effort has been made to relate this information to the potential presence of soil-borne pests. Hence, the objective of this project was to evaluate the effect of planting dates, nitrogen (N) rates, and irrigation regimes on potato production. Two comprehensive studies were conducted between February and July 2022 and 2023. The objective of the first study was to evaluate the effect of N rates, planting dates, and soil physicochemical properties in potato production and the presence of soil-borne pests. This study was established in a split-plot design with four replications, with planting dates on the main plot and N rates and time of application on the sub-plot. Late March planting resulted in the highest total tuber yield, while early planting produced significantly larger tubers. Early March planting reduced plant development and emergence, probably due to lower air and soil temperatures. There was no interaction between planting dates and N applications. Using N rates higher than 147 kg ha-1 resulted in no significant differences in total tuber yield. Regression analyses showed that the Normalized Differences Red Edge (NDRE) is an excellent predictor of N content in plant tissue and tuber yield. Moreover, Ca and H saturation percentages were linked to wireworm damage levels using classification algorithms. Similarly, K saturation percentage was identified as a potential predictor of nematode presence in this region. A second study was established with the objective of evaluating the effect of N rates and irrigation regimes on potato production. The study was established in a split-plot design with four replications, with the irrigation method on the main plot and total N rate on the subplot. Results from these experiments showed higher growth and tuber yield when combining overhead irrigation with crop evapotranspiration (ETc) estimation. Moreover, there were no significant differences when using N rates higher than 112 kg ha-1. Overall, results from these experiments suggest no changes in current N rate recommendations for this region. Additionally, these results suggest planting in late March and using irrigation regimes based on evapotranspiration with overhead irrigation systems. Future research should focus on adaptive fertilization based on growing degree days and refinement irrigation determination practices. / Master of Science in Life Sciences / In the Eastern Shore of Virginia, nearly 4,000 acres are annually dedicated to fresh white potato farming. The established planting window extends from early March to early April, aligned with peak market demands in late April. However, this traditional planting strategy exposes crops to varying temperatures, potentially affecting water and nutrient demands, as well as overall yield. A research project consisting of two studies was conducted with the objective of evaluating the effect of planting dates, nitrogen (N) rates, and irrigation regimes on potato production. The first study was conducted with the aim of optimizing yield and nutrient management by exploring the interplay between planting dates, N rates, and application timing. The second study evaluated overhead and subsurface drip irrigation systems with irrigation regimes determined either by crop evapotranspiration (ETc) or by soil moisture content through soil water sensors (SWS). Results demonstrated that early March planting resulted in delayed emergence and overall growth due to colder temperatures, while late March plantings produced the highest tuber yields. On the irrigation front, overhead irrigation integrated with ETc estimation consistently improved plant health and augmented yield. In addition, the Normalized Differences Red Edge (NDRE) index, obtained from multispectral drone imaging, produced a significant correlation with N content in plant tissue and with total tuber yields for both studies. This suggests its high potential as a yield prediction tool. Overall, results from these studies reinforce current N rate recommendations for Virginia. Furthermore, they not only refine regional potato cultivation practices but also suggest the need for research pivoting around adaptive fertilization based on growing degree days and the potential refinement of irrigation regimens.

Master of Science / Department of Biological & Agricultural Engineering / Ronaldo G. Maghirang / Particulate matter (PM) emissions from open beef cattle feedlots depend heavily on the level of water on the pen surface. Wet pen surfaces are able to keep PM emissions low, while dry surfaces have much higher rates of emission. Current research shows that 20-25% surface water content is a critical threshold for minimizing PM emissions from open cattle feedlots. The amount of water on the pen surface will also dictate the level of gaseous emissions, such as ammonia, nitrous oxide, and hydrogen sulfide. Traditional methods of measuring pen surface water are not sufficient within a dense cattle feedlot and cannot provide a continuous method of measurement unattended. The process of using infrared thermometry and meteorological variables to remotely sense surface water provides an inexpensive, ground level approach. Testing in laboratory, outdoor, and feedlot conditions was conducted to analyze the potential of using the thermal inertia remote sensing approach. This approach involved continuous measurement of weighted soil water content, surface temperature of the soil, air temperature, solar radiation, wind speed, and relative humidity. Controlled laboratory testing performed the best at predicting soil water content from the difference in soil surface and air temperature, with the coefficient of determination (R2) at 0.91 for a Smolan silt loam and 0.83 for dry feedlot soil. Outdoor testing achieved mixed results with R2 values only as high as 0.38 for 10-cm soil layer and 0.67 for 5-cm soil layer. Testing in a cattle feedlot with dry, loose manure layer proved to be imprecise, but was able to differentiate surface water levels varying from 4.1% to 9.1% wet basis.

Doctor of Philosophy / Department of Agronomy / Gerard J. Kluitenberg / The Parsons soil has a sharp increase in clay content from the upper teens in the A horizon to the mid fifties in the Bt horizon. The high clay content continues to the parent material resulting in 1.5 m of dense, slowly permeable subsoil over shale residuum. This project was designed to better understand soil-water management needs of this soil. The main objective was to determine a comprehensive hydrologic balance for the claypan soil. Specific objectives were a) to determine effect of tillage management on select water balance components including water storage and evaporation, b) to quantify relationship between soil water status and crop variables such as emergence and yield, and c) to verify balance findings with predictions from a mechanistic model, specifically HYDRUS 1-D. The study utilized three replicates of an ongoing project in Labette County, Kansas in which till and no-till plots had been maintained in a sorghum [Sorghum bicolor (L.) Moench] – soybean [Glycine max (L.) Merr.] rotation since 1995. Both crops are grown each year in a randomized complete block design. The sorghum plots were equipped with Time Domain Reflectometry (TDR) probes to measure A horizon water content and neutron access tubes for measurement of water throughout the profile. Precipitation, evaporation, and perched water depth were determined at the field scale. Drainage was estimated as negligible after performing hydraulic conductivity measurements on the clayey subsoil. Runoff was determined as the residual in this water balance. Cumulative differences in the hydrologic balances as a result of tillage management were found to be minimal over an entire growing season. However, tillage treatment differences were seen in early season evaporation, surface water content, and the resulting residual runoff values. The chisel-disk treatments had greater evaporation leading to reduced runoff when compared with no-till. There was interaction between tillage treatment and time for surface water content measurements. No effect of tillage treatment was found for whole-profile water content. Crop variables were unaffected by tillage other than the first days emergence, and first days tillering being greater for chisel-disk treatments. No correlation between stored water and crop variables could be found. All aspects of field measurement were well supported by the predictions of the HYDRUS 1-D model.