Phosphorus and Compost on Potatoes

Compare compost with mineral P fertilizer as a means of supplying P to potato.


18 Feb 2003

2002 Annual Interpretive Summary

Phosphorus and Compost on Potatoes, 2002

The potato industry in southern Alberta continues to expand to meet the needs of newly established food processors. Soil testing laboratories and agronomists in Alberta are uncertain as to what phosphorus (P) recommendations should be used for potatoes. Petiole testing for P has only recently been used in the area. Standards for adequate levels of P in petioles have been used from the northwest U.S., but have not been adequately defined for the Southern Alberta region and its soils. The objectives of this project were to examine the effect of high rates of P fertilizer on yield and quality of potatoes, determine critical soil and tissue levels at which a response to P can be expected, and to compare compost with mineral P fertilizer as a means of supplying P to potatoes.

Results indicate that increased inputs of P gave increased levels of petiole P for both mineral fertilizer and compost. Using the petiole P standards from the northwest U.S., petiole samples collected in early July, late July, and mid-August usually fell within the sufficiency ranges. There were a few instances when the lower rates of fertilizer P resulted in petiole P levels that were below the suggested range. However, none of these deficiency levels were reflected as a significant effect on potato yield. The specific gravity of potatoes was not significantly affected by P treatments. However, tubers from two sites showed slightly lower specific gravity values on treatments where compost was added. The P in the compost was found to be immediately plant-available, even in early July. Compost had no negative impacts on plant or tuber disease, and was associated with a lower incidence of Rhizoctonia at one location in 2000. Results from this trial indicate that despite increases in petiole P, there were no discernible effects on yield. Petiole P standards from the northwest U.S. will require some modification for southern Alberta soils and conditions. AB-21F