Critical Nitrogen Dilution Curves for Nitrogen Management in Potato (Solanum tuberosum L.): A Minireview

Abstract

Potato (Solanum tuberosum L.) is one of the crops worldwide produced under different climatic and cropping systems conditions. With the multitude of cultivars and variable relative maturity, numerous studies have shown that nitrogen management in potatoes is a key to tuber yield and quality. Most potato growers tend to apply high amounts of nitrogen fertilizer while yield is not always consistent with the applied nitrogen fertilizer rates. Thus, potato cropping system specialists have been developing critical nitrogen dilution curves across different environments and for different potato cultivars with quite large variability in the equations. This review aims to inventory the developed critical nitrogen dilution curves for potatoes worldwide and analysis the discrepancies. A literature search was performed using online search engines for 6 months using keywords such as nitrogen dilution curve, critical nitrogen dilution curves of potatoes. Published results collection was done for the well-known peer reviewed journals. The critical N concentration (Nc) is defined as the minimum nitrogen concentration for achieving maximum aboveground biomass at any time during the crop growing season and it is represented by an allometric function, i.e. Nc = aW^−b where W is the total shoot biomass [Mg dry matter (DM) in ha ⁻¹], Nc is the total N concentration in shoot (g kg ⁻¹ DM), and a and b are estimated parameters. The parameter “a” of all monitored critical nitrogen dilution curves falls within the range [1.5, 7] of which 50% of the parameter “a” falls within the range of [5, 5.5] and the parameter “b” falls within the range [0.15, 0.60] with a large variation. The parameters “a” and “b” are impacted by the potato genotype, environment, and the management practices. Moreover, the estimation procedures of the parameters “a” and “b” were different and impacted the magnitude of these parameters. Based on some recent studies, we recommend the use of the Bayesian hierarchical method or the pooled Bayesian hierarchical method to develop a unique critical nitrogen dilution curve for potatoes that includes several genotypes, environment, and management practices for nitrogen fertilizer application rate optimization, system profitability and sustainability while reducing soil and water pollution by the nitrate leaching due to over fertilization and inappropriate split and timing of the nitrogen fertilizer application.