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Evaluation of Irrigation-Nitrogen Management Practices for Celery using Continuous-Variable Irrigation¹

ABSTRACT

The interaction between N source and irrigation rate and the resultant effects on NO^-₃ leaching were characterized for celery, using a modified line-source sprinkler system which applied water across fertilizer plots at rates varying from replacement of evapotranspiration (ET) to 1.8 ET. Nitrogen, as (NH₄)₂SO₄ (AS), was applied at a rate of 300 kg/ha in split applications (AS₃₀₀); sulfur-coated urea (SCU) was applied alone at 300 kg N/ha (SCU₃₀₀), all preplant, or in a combination with 150 kg N/ha SCU preplant and 150 kg N/ha AS sidedressed (SCU₁₅₀AS₁₅₀). Plants with the AS₃₀₀ and SCU₃₀₀ treatments removed significantly less N at the lowest irrigation rate than those with the SCU₁₅₀AS₁₅₀ treatment, but this difference was not observed at high irrigation rates. All three N treatments produced large accumulations of NO^-₃ beneath the root zone which increased with increased leaching. Yields from the fertilized treatments were significantly higher at all irrigation levels than yields from unfertilized plots, but were not different from each other. Yields also did not vary substantially across the range of irrigation rates, indicating that deep percolation of water and NO^-₃ can be minimized through improved irrigation management without reducing celery yield.

¹ Contribution from the Department of Soil and Environmental Sciences, University of California, Riverside. Research support by the Office of Water Research and Technology, USDI, Project no. B-203-CAL, Water Resources Center Project UCAL-WRC-W-564, and California Water Resources Control Board Contract no. 9-029-500-0.

² Former Graduate Research Associate, now Assistant Professor of Agronomy, University of Idaho, Aberdeen, ID 83210; Assistant Professor of Soil Science; and Professor of Soil Physics.

Received for publication November 6, 1981. Accepted for publication September 30, 1982.