Alternative sources of nitrogen and phosphorus in potato fertilizer

Urea and diammonium phosphate were compared with ammonium nitrate and triple superphosphate, in all combinations, as sources of N and P in fertilizer on two soil types important in potato production in Ontario. Greenhouse experiments with these soils and a peat:vermiculite:sand mixture gave very varied root and shoot development which followed no constant pattern. The same combinations of fertilizer in the field gave no differences in emergence, appearance, or senescence, but there was one yield difference and minor, inconsistent differences in specific gravity and cooking quality.