Exploring the feasibility of near-infrared spectroscopy in analyzing the chemical and biochemical changes of chitin-amended soils

Authors: OMWANGE, KEN ABAMBA - Oak Ridge National Laboratory; CHEN, ANA - Michigan State University; Lu, Renfu; DAIEK, CARLY - Michigan State University; CELINI, JULIE - Michigan State University; LIU, YAN - Michigan State University

Submitted to: Journal of Agricultural Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/4/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Chemical pesticides, as one of the conventional pest control approaches, are widely used in agricultural production systems. However, increasing concerns about the negative effects of pesticides and stringent government regulations on their use call for new environmentally friendly pest control methods to replace these conventional chemical approaches. Biological methods such as bio-pesticides and biological control represent such an approach that would have minimal or no negative effects on humans and the environment. Chitin, which is available in many agricultural byproducts, can function as a plant disease vaccine to protect crops. However, the effects of chitin on the chemical and biochemical properties of soil are not well understood and under researched. Standard laboratory procedures require measuring the pH and DNA of soil samples for quantifying the structures and function of the microbial communities in the soil, which are tedious and time-consuming. This study was therefore aimed at using near-infrared (NIR) spectroscopy as a means for fast and nondestructive or noninvasive assessment of the chemical/biochemical properties of chitin-treated soil. Soil samples treated with different amounts of chitin were collected at 9 different days over a period of 122 days. Standard laboratory procedures were first used to measure the chemical/biochemical properties (i.e., pH, total DNA, and trpB DNA which analyzes potato pathogen streptomyces scabies) of the soil samples. NIR spectra were also acquired from the soil samples, followed with the development of prediction models for the measured chemical/biochemical properties. Results showed that addition of chitin to the soil modified the chemical/biochemical properties; the degree to which they changed, however, was dependent on the amount of the chitin added to the soil. NIR technique was able to achieve good predictions of pH, total DNA and trpB DNA, which suggests that the technique has potential for providing a fast and effective means for estimating the structures and functions of the soil’s microbial communities.

Technical Abstract: Chitin, a natural organic polymer, is added to soil to stimulate plant resistance against viruses, bacteria, and fungi. However, it is unclear how the chemical and biochemical properties of the soil would change after it has been treated with different levels of chitin. The current standard procedures for measuring the chemical and biochemical properties of soil are slow and tedious. This study was therefore aimed to use near-infrared (NIR) spectroscopy as a cost-effective means for fast measurement of the chemical/biochemical properties of chitin treated soil. pH, total DNA, chitinase activity, and a typical potato pathogen, Streptomyces scabies, were measured, using the standard laboratory procedures, for five groups of soils that were added with different amounts of chitin, i.e., control (0%), 0.2% fungus chitin, 2% fungus chitin, 0.2% Sigma chitin, and 2% Sigma chitin, at 9 different days over a period of 122 days. NIR reflectance spectra (900-1,650 nm) were acquired from the soil samples at each sampling time. Mathematical models based on partial least squares regression analysis were established for predicting the pH, total DNA, and trpB DNA targeting for the identification of Streptomyces scabies, after the spectra data have been subjected to three preprocessing methods, i.e., Kubelka-Munk, second derivative, and smoothed data. Laboratory analyses showed that adding fungus biomass (or chitin treatment) to the soil has modified its chemical/biochemical properties (i.e., pH, total DNA and tripB DNA); the degree to which they changed, however, depended on the amount of fungus biomass added to the soil. NIR technique was able to predict the three chemical/biochemical properties from the soil samples with the coefficients of determination of 0.915 for pH, 0.904 for total DNA and 0. 810 for trpB DNA. This study demonstrated that near-infrared spectroscopy technique coupled with partial least squares algorithms has great potential to estimate the biochemical properties of soils.