LEACHATE ELECTRICAL-CONDUCTIVITY AND GROWTH OF POTTED POINSETTIA WITH LEACHING FRACTIONS OF 0 TO 0.4

Poinsettias (Euphorbia pulcherrima Willd. ex Klotzsch 'V-14 Glory') were grown in a greenhouse for 70 days in 1.3 liters of medium (13 cm deep in 15-cm pots) with a leaching fraction (LF) of almost-equal-to 0, 0.1, 0.2, or 0.4. Plants were fertigated with 300 mg N/liter from 20N-4.4P-16.6K. The electrical conductivity (EC) of the fertigation solution was 2.1 dS.m-1. The leachate EC increased from 2 dS.m-1 initially to plateaus of almost-equal-to 6, 9, and 15 dS.m-1 for LFs of 0.4, 0.2, and 0.1, respectively. Poinsettia height, shoot fresh and dry mass, and leaf and bract areas were not significantly different among the LF treatments. Leachate pH decreased from 6.1 initially to 5.1 at the end, but there was no significant difference among the LF treatments. The EC of a saturated medium extract (EC(e)) was between 17% and 48% higher in the lower third of the medium than in the middle third. The difference was greater with a lower LF. The EC(e) was 8.9, 7.3, 5.2, and 3.4 dS.m-1 in the lower third of the pot for a LF of 0, 0.1, 0.2, and 0.4, respectively. Under conditions of this study, container poinsettias required no leaching.