Predicting Optimum Depth of Profile Modification by Deep Plowing for Improving Saline-Sodic Soils

A previously developed procedure for predicting the effect of mixed-salt solutions on soil hydraulic conductivity (HC) was used to predict the relative hydraulic conductivity (RHC) of separate soil horizons from saline-sodic soils, using a standard low-salt solution following a standard high-salt solution at a fixed exchangeable-sodium level. These values were then used to predict the RHC of mixtures of the same horizons simulating profiles modified to various depths by deep plowing. Weighting RHC values for individual horizons by the depth fraction of each horizon in the soil mixture provided RHC values of proper magnitude, except when large proportions of calcareous subsolum material were incorporated into the mixture. Results were improved by multiplying calculated RHC values for each soil mixture by the initial HC of the mixture. This corrected for the filling of conducting pores in more permeable horizons by smaller particles from less permeable horizons during the mixing process (analogous to particle dispersion and pore sealing during the leaching of saline-sodic soils). Soil constants determined for the mixed soils permit the prediction of the response of these soils to any other exchangeable sodium levels or soil solution concentrations of interest. Results were consistent with lysimeter and field plot observations on the same soils, including deep plowing trials

A 15-Year-Old Boy with Progressive Weakness after a Spider Bite

A 15-year-old boy presented to the emergency department at a referring facility with right lower extremity weakness and numbness. He reported being bitten in the right inguinal region by a spider similar in appearance to a brown recluse several hours prior to symptom onset. He first developed redness and pain at the site of the bite followed by stiffening, numbness, tingling, and weakness of the entire right lower extremity, intermittent right digital paresthesias, diffuse myalgias, headache, and abdominal pain. His initial examination was significant for an area of ecchymosis and erythema on his anterior right hip consistent with the location of the reported bite, inability to move his right lower extremity, slightly decreased right hand strength, decreased sensation to light touch over entire right lower extremity, and right patellar areflexia. The patient reported difficulty urinating, and a postvoid bladder ultrasound revealed a residual of approximately 1 L of urine. Initial evaluation, including a complete blood count with differential, basic metabolic panel, urinalysis, and magnetic resonance imaging (MRI) of the lumbar spine was normal

Conductividad hidráulica en un suelo aluvial en respuesta al porcentaje de sodio intercambiable Saturated hydraulic conductivity of an alluvial soil with different exchangeable sodium percentages

El efecto del porcentaje de sodio intercambiable (PSI) sobre la conductividad hidráulica de un suelo saturado, fue estudiado en condiciones de laboratorio a través de la determinación de las relaciones entre la conductividad hidráulica medida en un suelo normal y las medidas en suelos con diferentes PSI. Los resultados muestran una gran reducción de la conductividad hidráulica con el aumento de sodio en el suelo, llegando esta reducción a ser en las muestras más sodificadas de casi 100%, cuando comparadas con las muestras sin sodio, hecho probablemente acontecido debido al efecto dispersante del sodio sobre las partículas del suelo.<br>The effect of different exchangeable sodium percentages (ESP) on the saturated hydraulic conductivity of a soil was studied under laboratory conditions by determining the relationship between the hydraulic conductivity of a normal soil and that measured on soil with different ESP. The results show a great reduction in the saturated hydraulic conductivity with the increase of the exchangeable sodium percentage in the soil, this reduction being as great as 100% on the highly sodified samples when compared with those which did not receive sodium treatment. This fact is explained due to the dispersing effect of the exchangeable sodium on the soil particles