Critical phosphorus dilution curve and the phosphorus-nitrogen relationship in potato

Besides nitrogen (N), phosphorus (P) is the most limiting nutrient for potato growth and P acquisition and utilization is affected by the N supply. Estimating accurately the P nutrition status is critical from economic and environmental standpoints. Our objectives were to (i) compare a critical P (P-c) curve based on the biomass (DM) of the whole plant (vines + tubers) with those recently developed in Argentina (Zamuner et al., 2016, P-c = 3.92 x DM-0.30) and Colombia (Gomez et al., 2016, P-c = 5.23 x DM-0.19); (ii) analyze P dilution in vines and tubers, and to develop Pc curves for vines and tubers; and (iii) analyze the relationship between N and P concentrations in vine, tuber, and total biomass along with the changes in the N:P ratio with increasing biomass. Five P rates up to 240 kg P2O5 ha(-1) were applied to potatoes on soils located in four Canadian provinces from 2016 to 2018 for a total of 11 site-years. Vine, tuber, and total biomass, and N and P concentrations were measured weekly on five dates starting 50 days after planting, and tuber yield was measured at harvest. The Pc curve in total biomass (P-c = 3.57 x DM-0.38) was below that developed in Argentina and Colombia. The P and N concentrations of vine, tuber, and total biomass as well as the N:P ratio declined with increasing biomass. and Pc curves were developed for vines (P-c = 2.58 x DM-0.20) and tubers (P-c = 2.06 x DM-0.14). The P nutrition index (PNI) measured in vines or tubers with their respective P-c curves was significantly related to the PNI in total biomass, implying that P sufficiency before tuber initiation can be estimated by analyzing vines only. Indices to assess P sufficiency along with N and P imbalances in potato vine, tuber, or total biomass represent a promising alternative or a complement to the soil P tests traditionally used for fertilizer recommendations.

Automated summary

This study compared P nutrition status curves for potatoes from different countries, analyzed P dilution in vines and tubers, and found that the Pc curve for total biomass was slightly lower than those developed in Argentina and Colombia. The research also suggested that analyzing the P nutrition status of vines first can estimate P sufficiency before tuber initiation.