Improving Phosphorus Management on Irrigated Potato

Rapid expansion of the processing potato industry in Manitoba has generated a need for information regarding fertilizer management strategies for irrigated potato. The second year of a 3-year study was conducted in 2004 to determine the impact of phosphorus (P) fertilizer rate on potato tuber yield and quality, and the effectiveness of petiole P concentration in assessing P status of potato (cv. Russet Burbank).

A field experiment was conducted at one location near Carberry in 2004 to assess the effect of four P rates (0, 30, 60, and 90 lb P₂O₅/A as broadcast/incorporated monoammonium phosphate) on tuber yield and quality, petiole P status, and post-harvest soil P status. Spring soil test P levels at the experimental site ranged from 20 to 29 lb NaHCO3-extractable P/A across replicates, and would have resulted in a recommendation for P fertilizer. Preliminary analysis indicated that P fertilizer rate did not have a statistically significant effect on total tuber yield, which averaged 306 cwt/A, or on tuber size distribution. Phosphorus fertilizer rate had no effect on main grade or bonus tuber yield, but did affect marketable yield. Contrast analysis revealed a significantly (p=0.005) lower marketable yield with the application of 30 lb P₂O₅/A compared to other treatments. However, the reason for this effect is unclear. Studies continue in 2005. MB-19F