Abstract: Abstract：The Kjeldahl and combustion (Dumas) methods are the main methods used to determine total nitrogen (TKN andTCN) content in agriculture biomass. However, the results obtained using these methods differ because of differences in theirunderlying principles. Herein, we used these two methods to determine the total nitrogen content in 1 179 crop residues (ricestraw, wheat straw, corn stover, rape stalk, cotton stalk) from China, and systematically analyzed and compared in totalnitrogen content and their distributions in the collected crop residues by different types with these two methods. Sevencommon distributions (Normal, Lognormal, Gamma, Weibull, Exponential, Laplace, Lorentz) were used to determine the datadistribution types of TKN and TCN in different crop residues. The correlation between the two methods was explored usingordinary least squares regression (OLS), orthogonal regression (Orth), and least median square regression (LMS). Finally, theresearch reviewed the correlation between different biomass (food, flowers, grass, soil, crop, crop residues, sewage sludge andanimal manure, etc.) results of two methods for measuring nitrogen content. The results showed: The distributions of nitrogencontent were non-normal distributions in different crop residues. The total TKN and TCN contents were the same distributionsin rice straw, wheat straw, rape stalk and total crop residues which approximately followed Lognormal, Gamma, Lognormaland Lognormal respectively. The median method was recommended for data statistics, and results from low to high were:1) TKN: wheat straw (5.66 ± 1.07 g/kg), rape stalk (7.10 ± 1.87 g/kg), rice straw (8.20 ± 1.42 g/kg), corn stover (8.82 ±2.23 g/kg), cotton stalk (10.42 ± 1.45 g/kg); 2) TCN: wheat straw (6.17 ± 1.17 g/kg), rape stalk (8.50 ± 2.45 g/kg), rice straw(8.59 ± 1.45 g/kg), corn stover (10.10 ± 1.91 g/kg), cotton stalk (11.75 ± 1.48 g/kg). It was found that TKN was significantlylower than TCN in all types of crop residues (P < 0.05). TKN and TCN values were also significantly different among wheatstraw, cotton stalk and other crop residues (P < 0.05). Although the fitting efficiencies of OLS, Orth and LMS were the sameon the determination coefficient (R2) scale, the fitting results were different. LMS was recommended because it reduced theeffect of outliers compared with three methods, observed from kernel density – scatter plots. Five types of crop residues andthe total had different fitting result between TKN and TCN. The correlation between TKN and TCN for total crop residues wasquantified as the LMS equation. In addition, there was a gap of the linear relationships between TKN and TCN in differenttypes of biomass. The slope of plant biomass was generally lower than that of animal manure, whose potential reason wasdifferent forms and contents of nitrogen in different biomass (ammonium nitrogen, nitrate nitrogen, nitrite nitrogen,heterocyclic nitrogen, and nucleic acid nitrogen, etc.). The results may provide extensive and reliable data for reference fromlarge sample size, and methods support for the scientific utilization of nitrogen in crop residues.