Fig. 3From: Rapid diagnosis of nitrogen status in rice based on Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS)The photoacoustic intensity ratio of amide II to amide I. CO Control with no fertilization application, CF Conventional Fertilization, OF Optimized Fertilization. a The ratio of amide II to amide I in different treatments at four growth stages in the 2015 growth season, b the ratio of amide II to amide I in different treatments at mature stage in the 2015, 2016, 2017 and 2018 growth seasons. Bars are the standard error of the means. Different letters above the bars indicate a significant difference at P < 0.05 according to the Duncan testBack to article page