Critical dilution curves for phosphorus, potassium, and sulfur along with relationships to nitrogen for major crops

Abstract Background and Aims The concept of crop nutrient dilution with increasing shoot biomass as plant ages, initially developed for nitrogen (N), has been extended to other major nutrients such as phosphorus (P), potassium (K), and sulfur (S). Published critical dilution curves for P, K, and S are presented in this review paper along with a discussion on i) their stability across combinations of genotype, environment, and management (G × E × M); ii) the influence of N on P, K, and S critical dilution curves along with the implications for the relationships between nutrients; and iii) practical implications and future research perspectives. Results The study of P dilution is more advanced than that of K and S and the published critical P dilution curves suggest more stability across G × E × M situations for maize than for potatoes. Data, however, are lacking to refine the critical dilution curves for P, K, and S along with determining their universality or domain of applicability. The crop N status has been shown to affect the critical curves of P, K, and S. Conversely, N status appears to be similarly affected by K status, poorly by P status and unaffected by S status, though more data are necessary to confirm this. Conclusion Overall, the strong interaction between nutrients and the need to consider them when developing critical dilution curves is highlighted. Critical dilution curves of P, K, and S offer new opportunities for the efficient analysis of co-limitations and diagnosis of multi-element crop nutrition. The universality or domain of applicability of those critical dilution curves, their theoretical framework, and their practical field applications remain to be clarified.