. Efficient use of nitrogen on crop land in the Northeast. Plants; Soils. Efficient Use of Nitrogen 19 8 HORIZON 20 o z I 10 a. 251â1âr - /v^:\ A / w â â¢w-\ _1 I I L_ C HORIZON n 1- 18 26 34 42 50. Figure 19. Six-year average of nitrate-N contents in soil solu- tions from plots that received 224 kg N/ha. Open circles are potatoes, closed circles are buckwheat. ( Rourke, Maine) year in which potatoes were grown. When buckwheat was grown, soil solution levels of NO3-N in the B horizon were similar to those with no N treatment. An early peak of NO3-N in the soil solution in the C horizon was
. Efficient use of nitrogen on crop land in the Northeast. Plants; Soils. Efficient Use of Nitrogen 19 8 HORIZON 20 o z I 10 a. 251â1âr - /v^:\ A / w â â¢w-\ _1 I I L_ C HORIZON n 1- 18 26 34 42 50. Figure 19. Six-year average of nitrate-N contents in soil solu- tions from plots that received 224 kg N/ha. Open circles are potatoes, closed circles are buckwheat. ( Rourke, Maine) year in which potatoes were grown. When buckwheat was grown, soil solution levels of NO3-N in the B horizon were similar to those with no N treatment. An early peak of NO3-N in the soil solution in the C horizon was found in mid-May with potatoes. The early level of NO3-N in the C horizon of the buck- wheat plots was half as high. Following the early peak concentration, the NO3-N in soil solution re- mained at or below 10 ppm in the C horizon until mid-November for potatoes and varied from 8 to 11 ppm from mid-June to freeze-up for buckwheat. Little change in the NO3-N content of the C horizon oc- curred relative to that of the control after the initial early season high. Table 9. Nitrogen removal in tubers ot Katahdin variety, Presque Isle, Maine. Rate of N 1973 1974 1975 1976 1977 1978 kg/ho_ 0 168 224 a* t a a a b b b b b b b b b b * Numbers followed by the same letter within columns ore not significantly different at Boyes .05 level, t Data not available. Data of Rourke, University of Maine, Orono. The level of NO3-N in the soil solution from the B horizon of soils receiving 224 kg N/ha when the plots were planted to potatoes is presented in Figure 19. Soil solution levels for the potato plots increased slowly from late April, when NO3-N in the soil solu- tion averaged 6 ppm, until mid-July, when the con- centration in the B horizon was 18 ppm. The soil solution level of NO3-N for potatoes remained between 14 and IS ppm from late June through freeze-up. In late July and early August, the soil solutio
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