Rapid and accurate determination of soil nitrogen supply capacity by detecting nitrogen content plays an important role in guiding agricultural production activities. In this study, near-infrared hyperspectral imaging (NIR-HSI) combined with two spectral preprocessing algorithms, two characteristic wavelength selection algorithms and two machine learning algorithms were applied to determine the content of soil nitrogen. Two types of soils (laterite and loess, collected in 2020) and three types of nitrogen fertilizers, namely, ammonium bicarbonate (ammonium nitrogen, NH4-N), sodium nitrate (nitrate nitrogen, NO3-N) and urea (urea nitrogen, urea-N), were studied. The NIR characteristic peaks of three types of nitrogen were assigned and regression models were established. By comparing the model average performance indexes after 100 runs, the best model suitable for the detection of nitrogen in different types was obtained. For NH4-N, R2p= 0.92, RMSEP= 0.77% and RPD = 3.63; for NO3-N, R2p= 0.92, RMSEP= 0.74% and RPD = 4.17; for urea-N, R2p= 0.96, RMSEP= 0.57% and RPD = 5.24. It can therefore be concluded that HSI spectroscopy combined with multivariate models is suitable for the high-precision detection of various soil N in soils. This study provided a research basis for the development of precision agriculture in the future.
Danyang Wang,Bo Li,Jun Ma,Ju Wang,Haoyu Wang,Wenzhuo Li
Because traditional slow-release fertilizers cannot effectively retain soil heat and moisture, their ability to increase crop yields is limited. To solve this problem, novel sprayable liquid mulch films (lignin-starch-acrylate, LSA) were prepared with a slow-release urea function, created by emulsion polymerization between lignin (extracted from papermaking waste liquor), starch, and acrylate monomers. The introduction of lignin transformed the LSA emulsion into a pseudoplastic fluid with enhanced sprayability. The presence of lignin in LSA film increased the elongation at break and lowered the Young's modulus, resulting in a film that is more easily pierced by crop seedlings and preserves the heat and moisture of the soil after seedling piercing. Experimental results showed that at a mass ratio of lignin to acrylate monomers of 3/7, the LSA mulch film had good sprayability and film-forming properties, suitable mechanical properties, and the lowest urea release rate. This optimized LSA film exhibited better soil insulation and water retention performance than other slow-release fertilizers. The contents of available soil nitrogen, including NH 4 + -N and NO 3 − -N, in soil covered with LSA film were 44.82 and 45.49% higher than those in soil covered with urea, respectively, and the corresponding cabbage yields increased by 33.73%. The results of this study provide a new method for preparing agricultural materials with urea slow-release as well as soil moisture and heat preservation functions.
Microplastics are an emerging threat to soils, but little is known about their effects on soil nitrogen (N) and phosphorus (P) cycling. In this study, a three-month soil incubation experiment has been conducted to analyze the effects of polyethene (PE) and polypropylene (PP) microplastics in sizes of 0–1 mm and 1–5 mm on soil available phosphate, nitrate, and ammonium contents under different fertilization regimes. Soil phosphorus and nitrogen availability were continuously determined in-situ by ion-exchange membrane method during the incubation. Microplastic surface chemical composition and the specific surface area were analyzed by FTIR and BET, respectively. The 16s rRNA sequencing of soil bacterial communities as well as soil pH have been determined after the incubation. The results showed that the presence of microplastics could significantly (P < 0.05) decrease soil available phosphate content from 122.61 mg P L −1 to 63.43 mg P L −1 . The addition of PP microplastics could significantly increase soil available ammonium content from 0.94 mg N L −1 to 1.53 mg N L −1 . Since microplastics had undetectable specific surface area and limited effects on soil microorganisms, adsorption and microorganism alteration functions might not be the main drivers of microplastic effects on soil phosphorus and nitrogen.
危险品化学品经营许可证（带存储）