Improved estimation of nitrogen uptake in grasslands using the nitrogen dilution curve – reply to the letter to the editor by Lemaire and Gastal, 2016

ᅟ The critical nitrogen concentration (CNC) is a simple yet robust relationship that describes the changes in crop N during growth. In Reyes et al. (Agron Sustain Dev 35:1561–1570, 2015 ), we applied the concept of CNC to calculate N uptake across various cutting regimes. While it is well-established that decreasing cutting frequency changes growth rates, the parameters of the CNC equations may need to be adjusted based on the grass physiological age (i.e., vegetative versus reproductive stage). We do not question the validity of the CNC during vegetative growth; however, we recognize that there is research needed to test the effects of cutting date on composition and internal partitioning of N as it relates to the CNC. Moreover, we focus on the applicability of the CNC for use in process-based models for better understanding of the CNC for different crop ages and management considerations.