[Spectral characterization and N content prediction of soil with different particle size and moisture content].

The present work was focused on analyzing the influence of moisture content, particle size, light source incidence angle and observation height on a loamy mixed soil spectra Meanwhile, prediction models for N content with different moisture and particle sizes were obtained, and the influence of these properties on N prediction was studied. The future applicability of NIR spectroscopy as a technique able to make prediction on the spot was analyzed. Observation height 100 mm and light source angle 45 degrees were chosen to present a sharpest spectra. Moisture content and particle size were found to affect strongly the absorbance of the spectra, and an accurate N prediction was obtained when the particle sizes varied from 0. 5-1. 0, 1. 0-2.0 and 2-5 mm with r of 0. 82, 0. 81 and 0. 81, respectively. Poor N prediction was obtained when the soil kept its natural moisture with r of 0. 57 and SECV of 3. 06 compared with the performance when it was dry with r of 0. 81 and SECV of 2. 40.

Measurement and analysis of soil nitrogen and organic matter content using near-infrared spectroscopy techniques.

Near infrared reflectance (NIR) spectroscopy is as a rapid, convenient and simple nondestructive technique useful for quantifying several soil properties. This method was used to estimate nitrogen (N) and organic matter (OM) content in a soil of Zhejiang Province, Hangzhou County. A total of 125 soil samples were taken from the field. Ninety-five samples spectra were used during the calibration and cross validation stage. Thirty samples spectra were used to predict N and OM concentration. NIR spectra of these samples were correlated using partial least square regression. The regression coefficients between measured and predicted values of N and OM was 0.92 and 0.93, and SEP (standard error of prediction) were 3.28 and 0.06, respectively, which showed that NIR method had potential to accurately predict these constituents in this soil. The results showed that NIR spectroscopy could be a good tool for precision farming application.