NITROGEN LEACHING FROM POTTED POINSETTIA WITH LEACHING FRACTIONS OF 0, 0.2, AND 0.4

Abstract

Single-pinched `V-14 Glory' poinsettias in 15-cm diameter pots of growing medium received 200 mg/L N constant liquid fertigation from Hoagland solution with N sources of 100% NO3-N and 60% NO3-N:40% NH4-N, P concentrations of 8 and 23 mg/L, and leaching fractions (LFs) of 0, 0.2 and 0.4. There were 26 irrigations during the 13 week study. The total fertigation solution and N applied ranged from 6.5 L and 1.3 g at 0 LF to 14 L and 2.8 g at 0.4 LF. Leachate N concentration ranged from 170 to 850 mg/L. The percentage of applied N in the leachate of 100% NO3-N plants was 57% at 0.2 LF and 76% at 0.4 LF. For 60% NO3-N plants, these losses were 49% at 0.2 LF and 67% at 0.4 LF. For 100% NO3-N plants, the percentage of the applied N found in shoot tissues was 26% for 0 LF, 20% for 0.2 LF, and 15% for 0.4 LF. For 60% NO3-N plants these percentages were 35% for 0 LF, 27% for 0.2 LF and 22% for 0.4 LF. Averaged for both 60% and 100% NO3-N plants, the N in the shoot was partitioned as follows: 43% in leaves, 39% in bracts, and 18% in stems.