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

摘要

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.