Soil Nitrogen Content Model Based on Near Infrared Spectroscopy and Effect of Biochar on Soil Spectra

Soil with biochar（labeled as ABS）and soil without biochar（labeled as CS）were collected and near-infrared spectra were obtained, two kinds of soil nitrogen content prediction models were established through pretreatment algorithm and partial least squares regression（PLS）, results showed that prediction models of CS and ABS pretreated with Baseline and Smoothing were the best, R² was 0.913 and 0.753 respectively, RMSEP was 0.093 and 0.753 respectively, near infrared spectroscopy could be used to model and predict nitrogen content of two kinds of soil．Then, effects of biochar on soil spectra and modeling were studied, results showed that addition of biochar would change content of soil components, making near-infrared spectroscopy and modeling different from ordinary soil, and joint modeling could reduce impact of differences and achieve better prediction results, joint modeling results showed that prediction effect after smoothing pretreatment was the best, R² was 0.907, RMSEP was 0.086．