Leaching of N into ground water has become a major pollutant in several areas of the U.S. The potential for regulation of environmental plant producers is increasing, but limited information is available on cultural management. This factorial experiment tested a liquid and a slow release fertilizer source at 3 irrigation levels (100, 200 or 300 ml/20 cm pot/2 times/wk) for NH4+, NO3- and P found in leachate collected weekly for 12 weeks. Plant quality and fresh weight for all treatments was similar, but large variations occurred in NH4+, NO3- and P levels in leachate due to irrigation level. Increasing irrigation level from 100 to 300 ml twice weekly resulted mainly in linear increases of NO3- present in leachate, with levels as high as 159 mg/l observed near the end of the production cycle. NH4+ levels were most affected by irrigation and highest early in the experiment, but were generally lower than 1 mg/l. P levels ranged from 1.4 to 16.0 mg/l in leachate with responses to fertilizer source and irrigation mainly during the first 6 weeks.
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