Abstract
The rapid determination of nitrogen, phosphorus, potassium and other major nutrient elements is an important technical guarantee in the quality control of chemical fertilizers. In this study, a small visible spectrometer and a small near-infrared spectrometer were used to collect spectrum information of 33 different common chemical fertilizers including compound fertilizers, blended fertilizers and controlled-release fertilizers. The 550~950 nm and 1050~1640 nm spectra with stable signals were intercepted as the analysis spectrum, and the competitive adaptive reweighted sampling algorithm (CARS) was used to select 161, 229, and 161 spectral characteristic wavelengths for the three nutrient contents of N, P2O5, and K2O respectively. The partial least squares (PLS) and extreme learning machine (ELM) models of N, P2O5, and K2O were established based on the 550~950 nm waveband, 1050~1640 nm waveband, full spectrum, and characteristic wavelength, respectively. The coefficient of determination (R2), root mean square error (RMSE), and residual predictive deviation (RPD) were used to evaluate the effect of the model. With the optimal prediction models, the values of Rp2 for N, P2O5, and K2O were 0.989, 0.963, 0.981, and for RPD were 9.71, 5.09, 7.29, respectively. The research results show that Vis/NIR spectroscopy can predict the content of nitrogen, phosphorus, and potassium nutrients in fertilizers, and the near-infrared band from 1050 nm to 1640 nm has a better prediction effect. The characteristic wavelength selection reduces the spectral variables by 9/10, and the performance of the model based on the characteristic wavelength is close to that of the full-spectrum model.
Highlights
In modern agriculture, chemical fertilizer is applied to provide necessary nutrients for crops to improve the quality and yield of crops
Compound fertilizer and blended fertilizer contain two or more kinds of nutrient elements, which have the advantages of high nutrient content, less subsidiary ingredients and good physical properties
The 33 kinds of fertilizers contained two or more effective nutrient elements of nitrogen, phosphorus, and potassium, which are reflected in the three equivalent detection indicators of N, P2 O5, and K2 O
Summary
Chemical fertilizer is applied to provide necessary nutrients for crops to improve the quality and yield of crops. Used chemical fertilizers mainly include compound fertilizer, controlled-release fertilizer, blended fertilizer, etc. Controlledrelease fertilizer can regulate the release of nutrient elements in chemical fertilizer for a long time. Compound fertilizer and blended fertilizer contain two or more kinds of nutrient elements, which have the advantages of high nutrient content, less subsidiary ingredients and good physical properties. Most of the compound fertilizers in actual use are inorganic compound fertilizers, which use phosphoric acid, ammonia, etc. As raw materials, and are produced through mechanical processing, drying, screening, and cooling. Different from fertilizers with a single nutrient element such as urea, compound fertilizers and blended fertilizers can simultaneously apply multiple nutrient elements to achieve Most of the compound fertilizers in actual use are inorganic compound fertilizers, which use phosphoric acid, ammonia, etc. as raw materials, and are produced through mechanical processing, drying, screening, and cooling.
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