Phosphorus and Compost on Potatoes

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


10 Apr 2001


    In 1999 we conducted two experiments with rates of phosphorus on potatoes. One small plot experiment had nine rates of phosphorus, the other a field scale experiment with seven rates of phosphorus and four rates of compost. Phosphorus uptake as measured by tissue analysis was directly related to the amount of fertilizer or compost on the treatment. Tuber yield was increased only by the first rate of phosphorus. Phosphorus did increase tuber numbers and reduce the average tuber size.

    In 2000 three more field scale experiments were conducted. Two were on soils with 20-30 ppm phosphate phosphorus and the third on a soil with 57 ppm phosphate phosphorus. Five rates of phosphorus and three rates of compost were applied. Again only the lowest rate of phosphorus showed an increase in tuber yield. Petiole phosphorus levels respond to applications of fertilizer or compost. The size and specific gravity of tubers and occurrence of diseases on the crop and on the tubers were measured.

    In 2001 an additional set of field scale experiments will be conducted on subplots of about 0.5 acres each. Treatments will be replicated four times.
    • Five rates of phosphorus and three of compost will be applied;
    • fields will be selected with low or medium initial soil phosphorus;
    • yield will be determined from hand samples and from yield monitors;
    • tissue samples will be taken three times during the season and growth stage will be described and the influence of the treatments on yield, disease, specific gravity will be measured.