Nitrogen nutrition index and its relationship to N use efficiency in linseed

Plant-based diagnostic techniques such as the nitrogen nutrition index (NNI) are used to determine the level of crop N nutrition, but research, especially on linseed, is limited. The objectives of this study were to determine whether there is a relationship between the NNI of linseed and N use efficiency (NUE) and to use NNI as a diagnostic tool for predicting seed yield response to N fertilization. The relationship between NNI and NUE was investigated in a two year field study of three linseed cultivars (Livia, Lirina, Creola) under different N fertilization conditions (0, 40, and 80 kg ha−1). N fertilization affected N concentration in different plant parts. The NNI varied from 0.65 to 1.16 across years, growth stage, and cultivar and was affected by the fertilization level. Linseed NUE and its components (N uptake efficiency and N utilization efficiency) were also affected by the cultivar, N fertilization, growing season, and interactions among these variables. N utilization efficiency accounted for more of the variation of NUE than did N uptake efficiency in most cases, and a negative correlation was found between NUE and N utilization efficiency and also between seed yield and NNI. This study provides new information about the effect of N application on NNI and NUE in linseed. High yields of linseed are dependent on an adequate supply of N, which can be diagnosed using NNI.

Research highlights▶ N nutrition index (NNI) varied from 0.65 to 1.16. ▶ N use efficiency was negatively correlated with seed yield and NNI. ▶ Using of selection criteria to improve NUE might negatively affect seed yield. ▶ Selection of new cultivars for NUE should be based on multiple criteria.