title: Fate of nitrate and bromide in an unsaturated zone of a sandy soil under citrus production.
abstract: Understanding water and nutrient transport through the soil profile is important for efficient irrigation and nutrient management to minimize excess nutrient leaching below the rootzone. We applied four rates of N (28, 56, 84, and 112 kg N ha(-1); equivalent to one-fourth of annual N rates being evaluated in this study for bearing citrus trees), and 80 kg Br- ha(-1) to a sandy Entisol with >25-yr-old citrus trees to (i) determine the temporal changes in NO3-N and Br- distribution down the soil profile (2.4 m), and (ii) evaluate the measured concentrations of NO3-N and Br- at various depths with those predicted by the Leaching Estimation and Chemistry Model (LEACHM). Nitrate N and Br concentrations approached the background levels by 42 and 214 d, respectively. Model-predicted volumetric water content and concentrations of NO3-N and Br- at various depths within the entire soil profile were very close to measured values. The LEACHM data showed that 21 to 36% of applied fertilizer N leached below the root zone, while tree uptake accounted for 40 to 53%. Results of this study enhance our understanding of N dynamics in these sandy soils, and provide better evaluation of N and irrigation management to improve uptake efficiency, reduce N losses, and minimize the risk of ground water nitrate contamination from soils highly vulnerable to nutrient leaching.
authors.affiliation: Center for Marine, Environmental Sciences, and Biotechnology Research, Savannah State University, GA 30404, USA. siva@savstate.edu
authors.forename: S
authors.initials: S
authors.lastname: Paramasivam
authors.forename: A K
authors.initials: AK
authors.lastname: Alva
authors.forename: A
authors.initials: A
authors.lastname: Fares
authors.forename: K S
authors.initials: KS
authors.lastname: Sajwan
mesh_terms: D000383:Agriculture; D001965:Bromides / Q000032:analysis*; D002957:Citrus; D007700:Kinetics; D008956:Models, Chemical; D009566:Nitrates / Q000032:analysis*; D018517:Plant Roots; D012822:Silicon Dioxide; D012989:Soil Pollutants / Q000032:analysis*; D014873:Water Pollutants / Q000032:analysis*; D014881:Water Supply
chemical_list: D001965:Bromides; D009566:Nitrates; D012989:Soil Pollutants; D014873:Water Pollutants; D012822:Silicon Dioxide