PRE-PLANT VERSUS IN-SEASON APPLICATION OF PHOSPHORUS FERTILIZER FOR RUSSET BURBANK POTATO GROWN IN CALCAREOUS SOIL

Potato (Solanum tuberosum L.) has active surface roots that may enable phosphorus (P) fertigation. Fertilizer trials were conducted in 2002–2004 with 0 or 224 kg P2O5 ha−1 applied as incorporated pre-plant broadcast, in-season fertigation, or split application (half pre-plant and half in-season). All of the P fertilization treatments increased petiole P concentration over the untreated control in all three years of the trial, but only the pre-plant application resulted in significant increases in US No. 1 and Total yields. Both the pre-plant and the split application resulted in significant increases in Marketable yield (US No. 1 & 2). These results show that P fertilizer should be applied and incorporated prior to planting. Fertigated P does enter into the plant, but the relative efficiency of this method of application for P is poor with regard to important yield and quality parameters and application as such should be limited to “rescue” situations.