Acta Agriculturae Zhejiangensis ›› 2025, Vol. 37 ›› Issue (5): 1159-1171.DOI: 10.3969/j.issn.1004-1524.20240379

• Biosystems Engineering • Previous Articles     Next Articles

Rapid detection of contents of different types of nitrogen in substrates using near-infrared spectrum and machine learning

WU Haolin1, WANG Shuzhen1, ZHU Zhujun1,2, HE Yong1,2,*()   

  1. 1. College of Horticultural Sciences, Zhejiang A&F University, Hangzhou 311300, China
    2. Key Laboratory of Quality and Safety Control for Subtropical Fruit and Vegetable, Ministry of Agriculture and Rural Affairs, Hangzhou, 311300, China
  • Received:2024-04-26 Online:2025-05-25 Published:2025-06-11

Abstract:

To establish near-infrared(NIR) models for determining ammonium nitrogen and nitrate nitrogen contents in common substrates(peat, vermiculite, and perlite), exogenous nitrate and ammonium nitrogen treatments were applied to the three substrates, and their NIR spectra were collected. Chemical methods were employed to measure ammonium nitrogen and nitrate nitrogen contents. Mathematical models for predicting ammonium nitrogen and nitrate nitrogen contents in the three substrates were constructed using partial least squares regression(PLSR) and support vector machine(SVM) model. The results demonstrated that for ammonium nitrogen content, the optimal spectral preprocessing method was first derivative+smoothing. For nitrate nitrogen content, the best preprocessing methods for peat, vermiculite, and perlite were multiplicative scatter correction(MSC)+smoothing, first derivative, and MSC+first derivative+smoothing, respectively. Both PLSR and SVM methods effectively established prediction models for substrate ammonium nitrogen and nitrate nitrogen contents. The SVM models exhibited higher coefficient of determination in prediction set( R p 2) and relative prediction deviation(RPD) values in the prediction set, along with lower root mean square error in prediction set(RMSEP) compared to PLSR models. For ammonium nitrogen content, the SVM models achieved R p 2 values of 0.983, 0.936, and 0.925 for peat, vermiculite, and perlite, respectively, with RMSEP values of 0.073, 0.528, and 0.540, and RPD values of 7.74, 4.50, and 4.80. For nitrate nitrogen content, the SVM models showed R p 2 values of 0.912, 0.956, and 0.921 for the respective substrates, with RMSEP values of 0.716, 0.933, and 0.976, and RPD values of 3.23, 3.75, and 3.30. The SVM models developed for peat, vermiculite, and perlite demonstrate reliability and can be effectively applied for analyzing ammonium nitrogen and nitrate nitrogen contents in these substrates.

Key words: substrate, nitrate nitrogen, ammonium nitrogen, near-infrared spectrum, machine learning

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