Control of Topology of Water Fluxes in Arid Agriculture: Amalgamation of Subsurface Irrigation, Managed Aquifer Recharge and Engineered Soil Substrat

We present the results of field-, farm- observations and experiments, as well as mathematical modeling of optimal control of descending, ascending and lateral water fluxes (viz., evapotranspiration, infiltration, seepage from/to subsurface emitters/drains, losses/gains from/to a deeper confined aquifer commingled via a leaky layer with the irrigated one, and water uptake by roots)

Nitrogen mineralization of manure-amended soil: Effects of salinity and moisture content

Application of manure has been used to increase the nitrogen status of many arid and semi-arid agricultural soils, however, organic nitrogen contained in animal manures must be mineralized prior to utilization by crops. Nitrogen mineralization is, like other biological processes, affected by soil water status. This can be due to the direct influence of soil moisture and/or salt interactions on the nitrogen dynamics. It is critical to understand the interactive effects of salt and water on nitrogen in soils amended with organic fertilizer. Such knowledge may be used for improving and quantifying nitrogen use efficiency. Objectives of this study were (i) to examine the relative and interactive influences of soil osmotic and matric water potentials on nitrogen transformations in manure-amended and non-manured soils, (ii) to determine the extent of nitrogen mineralization over a range of soil water potentials, and (iii) to study the effect of manure addition on nitrogen dynamics in an agricultural desert soil. Gila fine sandy loam soil was treated by addition of varying amounts of distilled water, NaCl, and dairy manure and incubated at depth of 20 cm in 0.025 mm thickness Ziploc® bags. Ammonium nitrogen, nitrate nitrogen, gravimetric soil moisture content, and total soil water potential were measured weekly for 16 weeks. Our study showed a decrease in the amount of inorganic N released from both the non-manured and manure-amended soils at total soil water potentials of approximately -55 bars or less. Maximal amounts of inorganic-N were released at potentials of -23 to -3.5 bars. There was an accumulation in the amounts of NH₄-N released at potentials of -55 bars or less, presumably because of a reduction in net nitrification. The manure caused nitrogen immobilization especially during the early part of our study. Immobilization also occurred in non-manured soil, but this generally lasted only a few weeks. Immobilization was prolonged in soils with lower water potentials. Net N mineralization in the manure-amended soils was higher than in the non-manured soils when soil moisture content was at field capacity

Two Cases of Pneumatoceles in Mechanically Ventilated Infants

Pulmonary pneumatocele is a thin-walled, gas-filled space within the lung that usually occurs in association with bacterial pneumonia and is usually transient. The majority of pneumatoceles resolve spontaneously without active intervention, but in some cases they might lead to pneumothorax with subsequent hemodynamic instability. We report two cases presented to the pediatric intensive care unit at the Royal Hospital, Oman with pneumatoceles. The first was a 14-day-old baby who underwent surgical repair of total anomalous pulmonary venous connection (TAPVC) requiring extracorporeal membrane oxygenation (ECMO) support following surgery. He was initially on conventional mechanical ventilation. Seven days after the surgery, he started to develop bilateral pneumatoceles. The pneumatoceles were not regressing and they did not respond to three weeks of conservative management with high-frequency oscillation ventilation (HFOV). He failed four attempts of weaning from HFOV to conventional ventilation. Each time he was developing tachypnea and carbon dioxide retention. Percutaneous intercostal chest drain (ICD) insertion was needed to evacuate one large pneumatocele. Subsequently, he improved and we were able to wean and extubate him. The second case was a two-month-old male admitted with severe respiratory distress secondary to respiratory syncytial virus (RSV) pneumonitis. After intubation, he required a high conventional ventilation setting and within 24 hours he was on HFOV. Conservative management with HFOV was sufficient to treat the pneumatoceles and no further intervention was needed. Our cases demonstrate two different approaches in the management of pneumatoceles in mechanically ventilated children. Each approach was case dependent and could not be used interchangeably

Use of Soil-Structured Capillary Barrier can Mitigate the Impact of Saline-Irrigation Water on Marigold Grown Under Field Condition

Capillary barriers (CBs) as engineered porous composites is novel and promising technology for mitigating salinity and drought stress of plants. This study aimed to imitate a naturally formed CB structure recently discovered in the reservoir bed of Al-Khoud dam at the Governorate of Muscat in northern Oman and to test the impact of this unique CB on mitigating the salinity stress of marigold plants grown under an open field condition. A plot was constructed and divided into “structured” (engineered cascade CB design) and “unstructured” soils and planted with marigold (Tagetes erecta) plants that were subjected to four salinity treatments (control with ECi ≈ 0.6 dS m-1 ; 3 dS m-1; 6 dS m-1; and 9 dS m-1). Plant physiological, vegetative, and reproductive growth parameters were measured in each treatment. The results showed that the structured soil significantly saved irrigation water and reduce salts accumulation. Structured soil improved all vegetative and reproductive plant parameters measured and helped in reducing the effects of salinity stress on the growth and production of the marigold under arid-climate field conditions. The results also showed the capability of structured soil in water saving and improving water use efficiency. This study substantiates a novel method in mitigating salinity problem and in water saving in arid and semi-arid regions, in particular in Oman. Further studies are required to test the use of the engineered cascade CB design with different crops and with alternative (e.g. subsurface) irrigation methods

Moisture and temperature in a proppant-enveloped silt block of a recharge dam reservoir: Laboratory experiment and 1-D mathematical modelling

Mosaic 3-D cascade of parallelepiped-shaped silt blocks, which sandwich sand- lled cracks, has been discovered in the eld and tested in lab experiments. Controlled wetting-drying of these blocks, collected from a dam reservoir, mimics field ponding-desiccation conditions of the topsoil layer subject to caustic solar radiation, high temperature and wind, typical in the Batinah region of Oman. In 1-D analytical modelling of a transient Richards’ equation for vertical evaporation, the method of small perturbations is applied, assuming that the relative permeability is Avery-anov’s 3.5-power function of the moisture content and capillary pressure is a given (measured) function. A linearized advective dispersion equation is solved with respect to the second term in the series expansion of the moisture content as a function of spatial coordinates and time. For a single block of a nite thickness we solve a boundary value problem with a no- ow condition at the bottom and a constant moisture content at the surface. Preliminary comparisons with theta-, TDR- probes measuring the moisture content and temperature at several in-block points are made. Results corroborate that a 3-D heterogeneity of soil physical properties, in particular, horizontal and vertical capillary barriers emerging on the interfaces between silt and sand generate eco-niches with stored soil water compartments favourable for lush vegetation in desert conditions. Desiccation significantly increases the temperature in the blocks and re-wetting of the blocks reduces the daily average and peak temperatures, the latter by almost 15°C. This is important for planning irrigation in smartly designed soil substrates and sustainability of wild plants in the region where the top soil peak temperature in the study area exceeds 70°C in Summer but smartly structured soils maintain lash vegetation. Thee layer of dry top-blocks acts as a thermal insulator for the subjacent layers of wet blocks that may host the root zone of woody species.

Moisture and temperature in a proppant-enveloped silt block of a recharge dam reservoir: Laboratory experiment and 1-D mathematical modelling

Mosaic 3-D cascade of parallelepiped-shaped silt blocks, which sandwich sand- lled cracks, has been discovered in the eld and tested in lab experiments. Controlled wetting-drying of these blocks, collected from a dam reservoir, mimics field ponding-desiccation conditions of the topsoil layer subject to caustic solar radiation, high temperature and wind, typical in the Batinah region of Oman. In 1-D analytical modelling of a transient Richards’ equation for vertical evaporation, the method of small perturbations is applied, assuming that the relative permeability is Avery-anov’s 3.5-power function of the moisture content and capillary pressure is a given (measured) function. A linearized advective dispersion equation is solved with respect to the second term in the series expansion of the moisture content as a function of spatial coordinates and time. For a single block of a nite thickness we solve a boundary value problem with a no- ow condition at the bottom and a constant moisture content at the surface. Preliminary comparisons with theta-, TDR- probes measuring the moisture content and temperature at several in-block points are made. Results corroborate that a 3-D heterogeneity of soil physical properties, in particular, horizontal and vertical capillary barriers emerging on the interfaces between silt and sand generate eco-niches with stored soil water compartments favourable for lush vegetation in desert conditions. Desiccation significantly increases the temperature in the blocks and re-wetting of the blocks reduces the daily average and peak temperatures, the latter by almost 15°C. This is important for planning irrigation in smartly designed soil substrates and sustainability of wild plants in the region where the top soil peak temperature in the study area exceeds 70°C in Summer but smartly structured soils maintain lash vegetation. Thee layer of dry top-blocks acts as a thermal insulator for the subjacent layers of wet blocks that may host the root zone of woody species

Control of Topology of Water Fluxes in Arid Agriculture: Amalgamation of Subsurface Irrigation, Managed Aquifer Recharge and Engineered Soil Substrat

We present the results of field-, farm- observations and experiments, as well as mathematical modeling of optimal control of descending, ascending and lateral water fluxes (viz., evapotranspiration, infiltration, seepage from/to subsurface emitters/drains, losses/gains from/to a deeper confined aquifer commingled via a leaky layer with the irrigated one, and water uptake by roots)

Customized biochar for soil applications in arid land: Effect of feedstock type and pyrolysis temperature on soil microbial enumeration and respiration

Biochar is rapidly gaining worldwide interest as an agro-technology for increasing soil health and carbon storage. This study investigated the physicochemical characteristics and impact on soil microbes of biochar amendments from three feedstock sources: date palm leaves (D), mesquite plants (M) and sludge compost (S.C.); pyrolyzed at 450 ℃, 600 ℃ and 750 ℃. Scanning electron microscopy images showed an apparent pore size increase with increasing pyrolysis temperature. The increase in pyrolysis temperature decreased O-H and C-O bonds and increased the proportion of C-C bonds, as obtained from the Fourier transform infrared spectroscopy studies. Thermostability was highest at a pyrolysis temperature of 750 ℃, with distinct thermal decomposition profiles for each of the three feedstock materials used, as indicated by the dynamic thermal gravimetric analysis. The SC biochars showed the highest mineral content (45–66%) with significantly higher water-soluble and total concentrations of mineral elements. The SC samples also showed the presence of possible soil contaminants such as Pb and As, and its use as a soil amendment is not recommended, even though the SC at 450 ℃ was the only nonalkaline biochar in this study. The M feedstock produced biochar with the highest surface area (600 m2 g−1) and carbon content based on loss on ignition (94.98%); nevertheless, the M biochar reduced soil microbial enumeration and respiration. This reduction increased with increasing pyrolysis temperature. Therefore, the M biochar feedstocks are not recommended for improving soil health and may be tested in the future as a microbial inhibitor for soil-borne plant pathogens. Considering the physicochemical properties and the biochar impact on soil, D at 600 ℃ was the best biochar selected for further studies as a soil amendment. The large differences in biochar physicochemical properties and their effect on soil microbes observed in this study suggest that the feedstock type and pyrolysis temperatures must be considered during biochar amendment production for improving soil health in arid-land agroecosystems