Nitrate-Nitrogen Leaching Following Urea Fertilization and Irrigation1
- J. W. Bauder and
- R. P. Schneider2
Wheat (Triticum aestivum) was grown in undisturbed columns of Gardena silt loam, a coarse-silty, mixed Pachic Udic Haploboroll, to evaluate NO3--N leaching from urea under irrigation. Optimum and excessive irrigation rates and 135 kg N/ha (as urea in single application vs. three increments applied during the growing period) were compared in factorial combination. Chloride was added to all columns for comparison with NO3--N. Leachate samples were collected throughout the study and analyzed for NO3--N, NH4+-N and Cl-. Columns were dismantled at crop maturity and sampled for residual NO3--N. Total N was determined in wheat at maturity.
Leaching fractions (LF) differed significantly between optimum and excessive irrigation but were not affected by applied urea. Cl- moved with the wetting front. Leaching patterns for NO3--N and Cl- were similar, but a slight lag in NO3--N was observed. Concentration of NO3--N in drainage water from all columns was initially similar (30 ppm NO3--N), but then decreased as leaching volume changed. Maximum NO3--N leaching occurred with split urea and excess irrigation. Minimum leaching occurred with optimum irrigation and split urea. Total NO3--N leachate load was directly correlated with leachate volume. Soil solution concentrations at crop maturity were as much as 170 µg NO3--N/ml. Residual NO3--N varied among treatments and revealed as many as three peaks in NO3--N concentration in the profile, indicating that N leaching occurred following each urea application. The results indicate marked NO3--N movement from urea under excessive irrigation.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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