CYCLIC IRRIGATION REDUCES CONTAINER LEACHATE NITRATE-NITROGEN CONCENTRATION

Two experiments were conducted to evaluate the effects of cyclic irrig ation on leachate NO3-N concentration, container leachate volume, tota l effluent volume, and growth of Ilex crenata Thunb. 'Compacta'. In Ex pt. 1, container leachate volume was reduced 34% when 13 mm of water w as applied in three cycles compared to continuous irrigation of 13 mm per unit time. Forty-nine percent less container leachate volume was c ollected from a continuous application of 8 mm than from that of 13 mm water. In Expt. 2, container leachate volume was reduced 71% when 6 m m was applied in a single application over 30 minutes compared to 13 m m applied continuously for 1 hour. Total effluent was reduced by 14% a nd 10% in Expts. 1 and 2, respectively, when 13-mm irrigation was appl ied in three cycles compared to one continuous irrigation. Container l eachate NO3-N concentrations from cyclic irrigation were generally les s than leachate NO3-N concentrations from continuous irrigation treatm ents. The percentage of applied N leached as NO3-N ranged from 46% whe n 13-mm irrigation was applied in three cycles to 63% when 13-mm irrig ation was applied in a single cycle. Leachate NO3-N concentration was reduced as irrigation volume was reduced from 13 to 6 mm in Expt. 2. P ercentage of applied N leached as NO3-N was 63%, 56%, and 47% when 13- mm irrigation was applied in one, two, and three cycles, respectively, compared to 19%, 16%, and 15% when 6-mm irrigation was applied in one , two, and three cycles, respectively. 'Compacta' holly shoot and root growth were minimally affected by cyclic irrigation or irrigation vol ume.