Dr. Aziz Amoozegar - Phosphorus Mobility with a Fertilizer Enhancer and Soil Saturated Hydraulic Conductivity

Crop and Soil Sciences Seminar -Spring 2021 Wednesday, February 3 Dr. Aziz Amoozegar Professor of Environmental Soil Physics, Department of Crop and Soil Sciences Moderator: Ms. Sarah Jordan, Master of Soil Science Student Phosphorus Mobility with a Fertilizer Enhancer and Soil Saturated Hydraulic Conductivity ABSTRACT Phosphorus (P) is an essential element for all forms of life. In addition to being essential for life, in soil, water is the medium in which nutrients become available for plant uptake as well as being transported to groundwater and surface water resources. Two studies will be presented in this seminar. (1) Mobility of P through a clayey soil with and without AVAIL, a commercial fertilizer enhancer, was investigated using an innovative horizontal soil column under capillary flow system. (2) Four mathematical models for determining soil saturated hydraulic conductivity (Ksat) of the vadose zone were evaluated. In two experimental runs, air dried soil material, 0.25-mm and adjusted to pH 6, was packed in three side-by-side, 1.4 cm wide and 0.6 cm deep tracks. The tracks were connected to a sand box and water was imbibed into the soil via capillarity. While water was moving through the track, 5 μL of a solution containing 400 mmol/L P or P + AVAIL was applied at one point to each track. At the termination of water application, each track was sectioned and air-dried. Distribution of P at the surface of one sample from each track was analyzed using micro-X-ray fluorescence imaging at synchrotron facilities at Stanford University and Brookhaven National Lab. In the constant head well permeameter method, the rate of water flow rate from a cylindrical hole under a constant depth of water is used to calculate Ksat using a model. Since water flow from a cylindrical hole is three-dimensional, under an idealized condition, a saturated bulb of limited size is developed when steady-state is achieved. The surface area and volume of the idealized saturated bulb determined by four different models were compared. The results show that the Glover model, which is based only on saturated water flow around the hole, is superior to the three other models that consider both saturated and unsaturated water flow.