Average annual rates of 243.2 kg/ha N and 31.5 kg/ha P were applied as high rates of fertilization. Eighty‐six kg/ha of N and 12.2 kg/ha of P were applied as moderate rates of fertilization. Ammonium nitrate was used as the N source while 46% superphosphate was the P source. The soil was an association of Lima and Kendaia silt loam. (Glossoboric Hapludolf and Aeric Haplaquent fine loamy, mixed, mesic.) Effluent from drains was measured and analyzed for inorganic N and orthophosphate. Concentrations of NO 3 calculated as N in drainage water ranged from 51.1 ppm to 3.0 ppm. The higher concentrations were associated with high fertilization. During two, 3‐week test periods, NO 3 calculated as N delivered from the tile drains in kilos per hectare per week ranged from .225 to 2.75. Ammonium concentrations seemed to be only slightly related to fertilization, ranging consistently between .02 to .03 ppm. Weekly outputs of NH 4 nitrogen calculated as N were less than .00258 kilos/ha. Orthophosphate concentrations calculated as P ranged from .004 to .01 ppm with a weekly output range of .00016 to .00088 kilos/ha. Nitrogen was applied as ammonium nitrate. Phosphorus was applied as 46% superphosphate.
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Zwerman et al. (1972) studied this question.