Fate of Nitrate and Bromide in an Unsaturated Zone of a Sandy Soil under Citrus Production
2002
Paramacivam, Aru. (Aruṇakiri) | Alva, A. K. | Fares, A. | Sajwan, K. S.
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.
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