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• 1. [Article] Relationships between degree of ponding and uniformity of soil moisture distribution under irrigation sprinklers

  Often low intake rate soils need special consideration when applying water during an irrigation. Surface flooding for extended periods may cause adverse crop growth conditions. Properly designed sprinkler ...

  Citation × Citation Citation Abstract Copy Title: Relationships between degree of ponding and uniformity of soil moisture distribution under irrigation sprinklers Author: Dehlinger, Charles Robert Often low intake rate soils need special consideration when applying water during an irrigation. Surface flooding for extended periods may cause adverse crop growth conditions. Properly designed sprinkler systems often eliminate irrigation problems, because the application rate and quantity of water applied can be readily controlled. Research workers who have studied sprinkler irrigation disagree on many things. Differences are found in the literature concerning the procedures used to determine sprinkler distribution uniformity and the optimum rate of application of water to the soil. Several authors suggest that moisture movement within the soil occurs after an irrigation. If trans location of moisture occurs, it may be possible to use sprinkler system design specifications that are less critical than those now in use. In order to determine the effect of sprinkler application rate on the resulting soil moisture distribution it is necessary to have criteria relating degree of ponding, crop cover, and slope of the land to the uniformity of soil moisture. Experimental plots were designed and prepared to study and relate these factors to each other. Sprinkler distribution measurements were made to be used in computing sprinkler uniformity. Using neutron equipment, soil moisture determinations were made before the irrigation, one day after irrigation, and three days after irrigation to determine the effect of the irrigation. Final analysis of the data from the experiment indicated that there was not an optimum degree of ponding. In fact, ponding, application rate, grade of plots, and crop cover did not appear to appreciably affect the distribution of soil moisture after an irrigation. Title: Relationships between degree of ponding and uniformity of soil moisture distribution under irrigation sprinklers Author: Dehlinger, Charles Robert Often low intake rate soils need special consideration when applying water during an irrigation. Surface flooding for extended periods may cause adverse crop growth conditions. Properly designed sprinkler systems often eliminate irrigation problems, because the application rate and quantity of water applied can be readily controlled. Research workers who have studied sprinkler irrigation disagree on many things. Differences are found in the literature concerning the procedures used to determine sprinkler distribution uniformity and the optimum rate of application of water to the soil. Several authors suggest that moisture movement within the soil occurs after an irrigation. If trans location of moisture occurs, it may be possible to use sprinkler system design specifications that are less critical than those now in use. In order to determine the effect of sprinkler application rate on the resulting soil moisture distribution it is necessary to have criteria relating degree of ponding, crop cover, and slope of the land to the uniformity of soil moisture. Experimental plots were designed and prepared to study and relate these factors to each other. Sprinkler distribution measurements were made to be used in computing sprinkler uniformity. Using neutron equipment, soil moisture determinations were made before the irrigation, one day after irrigation, and three days after irrigation to determine the effect of the irrigation. Final analysis of the data from the experiment indicated that there was not an optimum degree of ponding. In fact, ponding, application rate, grade of plots, and crop cover did not appear to appreciably affect the distribution of soil moisture after an irrigation. Close

• 2. [Article] Determination of irrigation frequencies and amounts by soil moisture sampling and gypsum electrical resistance blocks

  Citation × Citation Citation Abstract Copy Title: Determination of irrigation frequencies and amounts by soil moisture sampling and gypsum electrical resistance blocks Author: Abd El-Samie, Ahmed Gamal Title: Determination of irrigation frequencies and amounts by soil moisture sampling and gypsum electrical resistance blocks Author: Abd El-Samie, Ahmed Gamal Close

• 3. [Article] Influence of soil moisture on the movement of bromacil in soil

  In previous research, bromacil gave good performance when it was applied in early fall with fairly dry soil conditions and before the fall germinating weeds had started growth. On the other hand, if bromacil ...

  Citation × Citation Citation Abstract Copy Title: Influence of soil moisture on the movement of bromacil in soil Author: Ross, Claude Gray In previous research, bromacil gave good performance when it was applied in early fall with fairly dry soil conditions and before the fall germinating weeds had started growth. On the other hand, if bromacil was applied in late November, December, or January on nearly saturated soil with weeds that had grown for one or two months, weed control was quite noticeably reduced. Field and greenhouse studies were conducted at Corvallis, Oregon, to determine the influence of soil moisture and time of herbicide application on bromacil movement and performance. In one field trial, two or six acre-inches of water were applied by sprinkler irrigation at intervals following herbicide treatment. Intervals used were one day, two, four, or eight weeks following herbicide application on dry soil. Field bioassay with rape, wheat, oats, annual bluegrass, sugar beets, and winter field peas indicated that the performance of bromacil applied to dry soil was not affected by differences in irrigation levels or by the time interval between application and irrigation. Bioassay of core segments taken from the top six inches of soil showed no difference due to treatment and indicated that bromacil was not leached below three inches regardless of irrigation treatment. Of the bromacil found in the top three inches, approximately half of it was in the 0-1 inch segment. Difficulty in duplicating fall conditions appeared to have a definite effect on results of field studies. Extensive loss of soil moisture due to evaporation was probably the main factor causing deviation from the desired conditions. Another field trial included 0-, 1.5-, 3-, and 6-inch sprinkler irrigation rates on an annual bluegrass stand which had been treated with either pre- or post-emergence applications of bromacil. Irrigations were applied immediately after the post-emergence treatment. Both pre- and post-emergence applications of bromacil gave good control of annual bluegrass regardless of subsequent post-emergence irrigation. However, total precipitation during the first month was only 0.25 inches and where there was no irrigation, bromacil did not give adequate control. Greenhouse leaching studies with soil columns did not give satisfactory results. Consistent patterns of leaching throughout replications could not be accomplished. When bromacil movement was determined by the use of soil columns and subirrigation with 1.5 inches of water, there was no difference in movement whether it was applied to water-saturated or dry soil. A preliminary experiment with a shorter subirrigation period, however, resulted in less movement of the bromacil applied to dry soil. Bromacil movement in soil by subirrigation is not the same as leaching downward. Water moving through soil from subirrigation occurs through all except the very large pores; whereas in downward leaching, water primarily moves by gravity through the large pores once the small pores are filled. Title: Influence of soil moisture on the movement of bromacil in soil Author: Ross, Claude Gray In previous research, bromacil gave good performance when it was applied in early fall with fairly dry soil conditions and before the fall germinating weeds had started growth. On the other hand, if bromacil was applied in late November, December, or January on nearly saturated soil with weeds that had grown for one or two months, weed control was quite noticeably reduced. Field and greenhouse studies were conducted at Corvallis, Oregon, to determine the influence of soil moisture and time of herbicide application on bromacil movement and performance. In one field trial, two or six acre-inches of water were applied by sprinkler irrigation at intervals following herbicide treatment. Intervals used were one day, two, four, or eight weeks following herbicide application on dry soil. Field bioassay with rape, wheat, oats, annual bluegrass, sugar beets, and winter field peas indicated that the performance of bromacil applied to dry soil was not affected by differences in irrigation levels or by the time interval between application and irrigation. Bioassay of core segments taken from the top six inches of soil showed no difference due to treatment and indicated that bromacil was not leached below three inches regardless of irrigation treatment. Of the bromacil found in the top three inches, approximately half of it was in the 0-1 inch segment. Difficulty in duplicating fall conditions appeared to have a definite effect on results of field studies. Extensive loss of soil moisture due to evaporation was probably the main factor causing deviation from the desired conditions. Another field trial included 0-, 1.5-, 3-, and 6-inch sprinkler irrigation rates on an annual bluegrass stand which had been treated with either pre- or post-emergence applications of bromacil. Irrigations were applied immediately after the post-emergence treatment. Both pre- and post-emergence applications of bromacil gave good control of annual bluegrass regardless of subsequent post-emergence irrigation. However, total precipitation during the first month was only 0.25 inches and where there was no irrigation, bromacil did not give adequate control. Greenhouse leaching studies with soil columns did not give satisfactory results. Consistent patterns of leaching throughout replications could not be accomplished. When bromacil movement was determined by the use of soil columns and subirrigation with 1.5 inches of water, there was no difference in movement whether it was applied to water-saturated or dry soil. A preliminary experiment with a shorter subirrigation period, however, resulted in less movement of the bromacil applied to dry soil. Bromacil movement in soil by subirrigation is not the same as leaching downward. Water moving through soil from subirrigation occurs through all except the very large pores; whereas in downward leaching, water primarily moves by gravity through the large pores once the small pores are filled. Close

• 4. [Article] The control of moisture condensed from saturated air flowing through cooled porous media

  Citation × Citation Citation Abstract Copy Title: The control of moisture condensed from saturated air flowing through cooled porous media Author: Trent, Donald S. Title: The control of moisture condensed from saturated air flowing through cooled porous media Author: Trent, Donald S. Close

• 5. [Article] The effect of soil moisture tension on the transpiration rate of a young sunflower when irrigated by a condensation method

  Citation × Citation Citation Abstract Copy Title: The effect of soil moisture tension on the transpiration rate of a young sunflower when irrigated by a condensation method Author: Chen, Tsu-fang Title: The effect of soil moisture tension on the transpiration rate of a young sunflower when irrigated by a condensation method Author: Chen, Tsu-fang Close

• 6. [Article] SaydeChadiBioEcolEngMappingVariabilitySoil.pdf

  Citation × Citation Citation Abstract Copy Title: SaydeChadiBioEcolEngMappingVariabilitySoil.pdf Author: English, Marshall, Rodriguez-Sinobas, Leonor, van de Giesen, Nick, El Khoury, Laureine, Selker, John S., Benitez Buelga, Javier, Sayde, Chadi Title: SaydeChadiBioEcolEngMappingVariabilitySoil.pdf Author: English, Marshall, Rodriguez-Sinobas, Leonor, van de Giesen, Nick, El Khoury, Laureine, Selker, John S., Benitez Buelga, Javier, Sayde, Chadi Close

• 7. [Article] SaydeChadiBioEcolEngMappingVariabilitySoil_SupportingInformation.pdf

  Citation × Citation Citation Abstract Copy Title: SaydeChadiBioEcolEngMappingVariabilitySoil_SupportingInformation.pdf Author: English, Marshall, Rodriguez-Sinobas, Leonor, van de Giesen, Nick, El Khoury, Laureine, Selker, John S., Benitez Buelga, Javier, Sayde, Chadi Title: SaydeChadiBioEcolEngMappingVariabilitySoil_SupportingInformation.pdf Author: English, Marshall, Rodriguez-Sinobas, Leonor, van de Giesen, Nick, El Khoury, Laureine, Selker, John S., Benitez Buelga, Javier, Sayde, Chadi Close

• 8. [Article] Mapping variability of soil water content and flux across 1-1000 m scales using the Actively Heated Fiber Optic method

  This is the publisher’s final pdf. The published article is copyrighted by the American Geophysical Union and can be found at: http://agupubs.onlinelibrary.wiley.com/agu/journal/10.1002/%28ISSN%291944-...

  Citation × Citation Citation Abstract Copy Title: Mapping variability of soil water content and flux across 1-1000 m scales using the Actively Heated Fiber Optic method Author: English, Marshall, Rodriguez-Sinobas, Leonor, van de Giesen, Nick, El Khoury, Laureine, Selker, John S., Benitez Buelga, Javier, Sayde, Chadi This is the publisher’s final pdf. The published article is copyrighted by the American Geophysical Union and can be found at: http://agupubs.onlinelibrary.wiley.com/agu/journal/10.1002/%28ISSN%291944-7973/. Title: Mapping variability of soil water content and flux across 1-1000 m scales using the Actively Heated Fiber Optic method Author: English, Marshall, Rodriguez-Sinobas, Leonor, van de Giesen, Nick, El Khoury, Laureine, Selker, John S., Benitez Buelga, Javier, Sayde, Chadi This is the publisher’s final pdf. The published article is copyrighted by the American Geophysical Union and can be found at: http://agupubs.onlinelibrary.wiley.com/agu/journal/10.1002/%28ISSN%291944-7973/. Close

• 9. [Article] Leaf stress in corn, beans, and tomatoes under optimum soil moisture conditions

  Under adverse soil moisture conditions a critical water stress or water potential develops in the plant and productivity is reduced, or in extreme cases, terminated. Research to determine the soil moisture ...

  Citation × Citation Citation Abstract Copy Title: Leaf stress in corn, beans, and tomatoes under optimum soil moisture conditions Author: Nilsson, Colin Wayne Under adverse soil moisture conditions a critical water stress or water potential develops in the plant and productivity is reduced, or in extreme cases, terminated. Research to determine the soil moisture status for maximum production of specific crops has been conducted for decades. The results have done much to increase the productivity of the irrigable acreage. Yet, even with irrigation water available, under adverse atmospheric conditions water stress will still develop in the agronomic crops. The degree of stress that develops and the duration, however, is generally unknown. Limited research in controlled environments has been conducted, but actual plant water stress levels under field conditions have not been studied. The purpose of this research was to determine the levels of leaf water potential (water stress) that develop in specific horticultural crops under conditions of optimum soil moisture. Further studies were made to relate the leaf water potential to atmospheric parameters and leaf temperature. Three horticultural crops, sweet corn (Zea mays), tomatoes (Lycopersicon esculentum), and bush beans (Phaseolus vulgaris) were grown on a Cloquato silt loam soil under high soil moisture conditions and exposed to the natural atmospheric conditions common to the Willamette Valley of Oregon. A pressure chamber was used to monitor, in the field, the leaf water potential that developed during each of five days throughout the summer months. An infrared radiometer was utilized to monitor the temperatures of the leaves during the same periods. Sweet corn consistently developed the highest leaf water potential, reaching as high as 13.0 atmospheres. The tomatoes and beans developed leaf water potentials above 10.0 atmospheres. On all five days the corn plants developed leaf water potentials above the critical 8.0 to 9.0 atmospheres suction levels reported in the literature by other investigators. On four of the five days, the Ψl of the tomato and bean plants equalled or exceeded these critical levels although not to the same degree as the corn plants. The length of time that the leaf water potential remained above 8.0 atmospheres suction varied, but lasted up to 9 1/4 hours in the corn and up to 7 hours in the beans and tomatoes. During these periods photosynthesis formation, soluble nitrogenous and phosphorous compounds formation, RNA accumulation, carbohydrate synthesis, and cell growth are reportedly impaired, limiting productivity. Leaf temperature under these stress conditions followed closely the same general trends as ambient air temperature. High levels of leaf water potential did not necessarily cause the temperature of the leaf to rise significantly. Leaf temperatures exceeded ambient air temperature by a maximum of 3.8 °C, but were generally in close agreement with or below ambient air temperature. The results of this study indicated that many horticulture crops may be limited in productivity by fairly frequent periods of critical leaf water potential even though soil moisture levels are adequate. On none of the five days studies were made did the atmospheric conditions exceed those normally experienced in the Willamette Valley. The maximum air temperature was 32.5 °C and the maximum solar radiation level was 1.16 cal/cm²/min. Further investigation is required to determine the effects on yield, quantity and quality,of detrimental plant water potentials and to develop means of alleviating Ψl before it reaches detrimental levels. Further investigation could also lead to a new outlook in plant breeding. Title: Leaf stress in corn, beans, and tomatoes under optimum soil moisture conditions Author: Nilsson, Colin Wayne Under adverse soil moisture conditions a critical water stress or water potential develops in the plant and productivity is reduced, or in extreme cases, terminated. Research to determine the soil moisture status for maximum production of specific crops has been conducted for decades. The results have done much to increase the productivity of the irrigable acreage. Yet, even with irrigation water available, under adverse atmospheric conditions water stress will still develop in the agronomic crops. The degree of stress that develops and the duration, however, is generally unknown. Limited research in controlled environments has been conducted, but actual plant water stress levels under field conditions have not been studied. The purpose of this research was to determine the levels of leaf water potential (water stress) that develop in specific horticultural crops under conditions of optimum soil moisture. Further studies were made to relate the leaf water potential to atmospheric parameters and leaf temperature. Three horticultural crops, sweet corn (Zea mays), tomatoes (Lycopersicon esculentum), and bush beans (Phaseolus vulgaris) were grown on a Cloquato silt loam soil under high soil moisture conditions and exposed to the natural atmospheric conditions common to the Willamette Valley of Oregon. A pressure chamber was used to monitor, in the field, the leaf water potential that developed during each of five days throughout the summer months. An infrared radiometer was utilized to monitor the temperatures of the leaves during the same periods. Sweet corn consistently developed the highest leaf water potential, reaching as high as 13.0 atmospheres. The tomatoes and beans developed leaf water potentials above 10.0 atmospheres. On all five days the corn plants developed leaf water potentials above the critical 8.0 to 9.0 atmospheres suction levels reported in the literature by other investigators. On four of the five days, the Ψl of the tomato and bean plants equalled or exceeded these critical levels although not to the same degree as the corn plants. The length of time that the leaf water potential remained above 8.0 atmospheres suction varied, but lasted up to 9 1/4 hours in the corn and up to 7 hours in the beans and tomatoes. During these periods photosynthesis formation, soluble nitrogenous and phosphorous compounds formation, RNA accumulation, carbohydrate synthesis, and cell growth are reportedly impaired, limiting productivity. Leaf temperature under these stress conditions followed closely the same general trends as ambient air temperature. High levels of leaf water potential did not necessarily cause the temperature of the leaf to rise significantly. Leaf temperatures exceeded ambient air temperature by a maximum of 3.8 °C, but were generally in close agreement with or below ambient air temperature. The results of this study indicated that many horticulture crops may be limited in productivity by fairly frequent periods of critical leaf water potential even though soil moisture levels are adequate. On none of the five days studies were made did the atmospheric conditions exceed those normally experienced in the Willamette Valley. The maximum air temperature was 32.5 °C and the maximum solar radiation level was 1.16 cal/cm²/min. Further investigation is required to determine the effects on yield, quantity and quality,of detrimental plant water potentials and to develop means of alleviating Ψl before it reaches detrimental levels. Further investigation could also lead to a new outlook in plant breeding. Close

• 10. [Article] Variations of moisture retention properties and bulk densities of soils between and within soil-mapping units in central Oregon

  The objective of this study was to estimate the bulk densities and points on the moisture-tension curves and to determine their associated variances for some of the selected mapping units in Central Oregon. ...

  Citation × Citation Citation Abstract Copy Title: Variations of moisture retention properties and bulk densities of soils between and within soil-mapping units in central Oregon Author: Jibury, Falih Khidir The objective of this study was to estimate the bulk densities and points on the moisture-tension curves and to determine their associated variances for some of the selected mapping units in Central Oregon. These variances will produce informations concerning the precision of the mean and the optimum sampling schemes, for other similar soils. Disturbed and undisturbed samples taken from random locations have been analyzed separately for the 0.1-, 0.5-, 1.0-, 5-, 10- and 15-bar moisture percentages and bulk density for the two depths. From the bulk-density values, 0.1- and 15-bar percentages, the amount of moisture held between 0.1 and 15 bars was calculated. Variances among and within locations in a particular mapping unit were calculated also. According to the data which were obtained, it appears that Deschutes and Redmond soils practically, are very similar in their bulk density and moisture retention properties. Therefore, due to these similarities, it would be expected that the irrigation scheduling would be about the same for a specific crop. The variances among and within locations were of the same order of magnitude. Using these variances it was calculated that the optimum number of sites per location for bulk density and 15-bar percentage was 2, as used in this study. The limits about the mean for a mapping unit which would include different percentages of randomly selected locations within a mapping unit are presented in this thesis. It could be noticed that the mean for the mapping unit may be a rough estimate for a given location; therefore, the number of samples required to estimate the true mean of a location, within different percentages and 5 percent significance level are presented also. Title: Variations of moisture retention properties and bulk densities of soils between and within soil-mapping units in central Oregon Author: Jibury, Falih Khidir The objective of this study was to estimate the bulk densities and points on the moisture-tension curves and to determine their associated variances for some of the selected mapping units in Central Oregon. These variances will produce informations concerning the precision of the mean and the optimum sampling schemes, for other similar soils. Disturbed and undisturbed samples taken from random locations have been analyzed separately for the 0.1-, 0.5-, 1.0-, 5-, 10- and 15-bar moisture percentages and bulk density for the two depths. From the bulk-density values, 0.1- and 15-bar percentages, the amount of moisture held between 0.1 and 15 bars was calculated. Variances among and within locations in a particular mapping unit were calculated also. According to the data which were obtained, it appears that Deschutes and Redmond soils practically, are very similar in their bulk density and moisture retention properties. Therefore, due to these similarities, it would be expected that the irrigation scheduling would be about the same for a specific crop. The variances among and within locations were of the same order of magnitude. Using these variances it was calculated that the optimum number of sites per location for bulk density and 15-bar percentage was 2, as used in this study. The limits about the mean for a mapping unit which would include different percentages of randomly selected locations within a mapping unit are presented in this thesis. It could be noticed that the mean for the mapping unit may be a rough estimate for a given location; therefore, the number of samples required to estimate the true mean of a location, within different percentages and 5 percent significance level are presented also. Close