Inversion model of soil organic matter content in black soil by Vis-NIR spectroscopy using adaptive stacking

This extensive 10-year study conducted in Northern Kazakhstan investigates the intricate relationship between soil management techniques, crop rotations, and soil organic matter (SOM) content in Chernozem soils, an essential agricultural resource in the region. The experiments were established at the Karabalyk Agricultural Experimental Station, characterized by a arid continental climate. The study systematically examined the impact of two primary soil management techniques, conventional tillage (CT) and no-tillage (NT), in combination with various crop rotations. The crop rotations tested included grain-fallow rotations, fruit-exchange crop rotations, and an eight-field fruit-exchange crop rotation. The results provide valuable insights into the sustainable management of Chernozem soils in arid conditions, underscoring the role of crop rotation strategies in preserving SOM content. The findings reveal that among the crop rotations tested, the eight-field fruit-exchange crop rotation exhibited the most favorable outcomes for SOM preservation. This rotation helped maintain relatively stable SOM levels over the 10-year study period, contributing to soil health and fertility. In the context of the region's arid climate, the choice of soil management technique (CT or NT) had a limited impact on SOM content. The stability of SOM levels across diverse crop rotations and years highlights the dominant influence of crop management practices in this distinctive agricultural environment. This research serves as a valuable reference for tailored approaches to ensure soil health and organic matter preservation in the unique conditions of Northern Kazakhstan. It promotes the adoption of diversified crop rotations, with particular emphasis on the effectiveness of the eight-field fruit-exchange crop rotation, as a powerful strategy to mitigate organic matter loss, enhance soil quality, and optimize soil fertility in arid agricultural landscapes. The insights gained from this study are vital for sustainable land management in the region and underscore the importance of region-specific, holistic investigations to guide effective agricultural practices. The findings offer a solid foundation for the development of strategies that address soil health and safeguard the integrity of essential soil resources in these unique environments. The study conducted at the Karabalyk Agricultural Experimental Station in Northern Kazakhstan between 2011 and 2021 provides critical insights into the relationship between soil management techniques, crop rotations, and SOM content in Chernozem soils. The research suggests that diversified crop rotations, particularly the eight-field fruit-exchange crop rotation, represent a promising approach for mitigating organic matter loss and enhancing soil quality in arid regions.

In this study, it was aimed to determine the useful boron content of the soils of Kırıkhan-Kumlu region of Hatay province and its relationships with some physical and chemical properties. For this purpose, a total of 60 soil samples were taken from 0-20 and 20-40 cm depths and from 30 different points to represent the study area. The pH, total salt, composition, cation exchange capacity (CEC), lime, organic matter and useful boron contents of the soils were determined. According to the results of the research; pH contents of the soils were 7.95-8.43; total salt contents 0.009-0.115 %; clay contents 18.88-74.16 %; sand contents 7.12-59.84 %; silt contents 15.28-52.72 %; lime contents 0.47-26.59 %; organic matter contents 1.16-6.08 %; CEC contents 22.26-72.83 me/100 g and useful boron contents 0.10-1.25 mg/kg. In terms of useful boron content of Kırıkhan-Kumlu soils of Hatay province, it was determined that 50.00 % of them were very low, 40.00 % were low and 10.00 % were sufficient at 0-20 cm depth and 50.00 % of them were very low, 43.34 % were low and 6.66 % were sufficient at 20-40 cm depth. While a positive significant relationship was determined between useful boron and salt, clay, lime and CEC contents of soils, a negative significant relationship was determined between useful boron and sand content. Positive significant relationships were determined between salt and clay, lime and CEC contents of the soils, while negative significant relationships were determined between salt and pH and sand contents. Positive significant relationships were determined between clay and organic matter and CEC contents of the study area soils, while negative significant relationships were determined between clay and sand and silt contents. Significant negative relationships were determined between sand and organic matter and CEC contents of the soils. At the same time, while negative significant relationships were determined between silt and CEC and lime and organic matter contents of the soils, positive significant relationships were determined between organic matter and CEC. As a result, it was seen that the useful boron content of the soils in the study area was determined at low and very low levels above 92 % in all soils of the study area and it was seen that the useful boron content of the soils was insufficient and therefore boron fertilization should be done.

Black soil conservation has attracted increasing attention from researchers. However, few studies have addressed black soil degradation and conservation mechanisms in the black soil region of Northeast China. In this study, we investigated black soil in Bei’an City in Heilongjiang Province and conducted comparisons with soil in other locations with similar environmental conditions and agricultural production levels but different reclamation histories. We predicted and analyzed the changes in the organic matter and nitrogen contents of black soils after different numbers of years under reclamation by using a gray forecast model. In addition, we aimed to identify soil conservation practices that consider the physical, chemical, and microbial properties of soils in the black soil region of Northeast China for implementation in the long term. The results showed that human and natural factors, such as long-term unsustainable cultivation practices and soil erosion, have caused the structural degradation of black soil in Northeast China. The annual decreases in the organic matter and nitrogen contents of black soil in Bei’an City were determined as 0.17% and 0.18%, respectively, using the gray forecast model. Preliminarily explorations identified the potential mechanisms associated with the effects of soil conservation practices on the organic matter and nitrogen contents, and microbial dynamics in black soils. Finally, according to the current implementation of black soil conservation practices in the black soil region of Northeast China, the outlook for future soil conservation practices is reasonable. This study provides a theoretical reference to meet the aims of protection and utilization for black soil in Northeast China in the future.

Chernozem properties of Black Soils in the Baltic region of Germany as revealed by mass-spectrometric fingerprinting of organic matter

Black soil in northeast China is gradually degraded and soil organic matter (SOM) content decreases at a rate of 0.5% per year because of the long-term cultivation. SOM content can be obtained rapidly by visible and near-infrared (Vis–NIR) spectroscopy. It is critical to select appropriate preprocessing techniques for SOM content estimation through Vis–NIR spectroscopy. This study explored three categories of preprocessing techniques to improve the accuracy of SOM content estimation in black soil area, and a total of 496 ground samples were collected from the typical black soil area at 0–15 cm in Hai Lun City, Heilongjiang Province, northeast of China. Three categories of preprocessing include denoising, data transformation and dimensionality reduction. For denoising, Svitzky-Golay filter (SGF), wavelet packet transform (WPT), multiplicative scatter correction (MSC), and none (N) were applied to spectrum of ground samples. For data transformation, fractional derivatives were allowed to vary from 0 to 2 with an increment of 0.2 at each step. For dimensionality reduction, multidimensional scaling (MDS) and locally linear embedding (LLE) were introduced and compared with principal component analysis (PCA), which was commonly used for dimensionality reduction of soil spectrum. After spectral pretreatments, a total of 132 partial least squares regression (PLSR) models were constructed for SOM content estimation. Results showed that SGF performed better than the other three denoising methods. Low-order derivatives can accentuate spectral features of soil for SOM content estimation; as the order increases from 0.8, the spectrum were more susceptible to spectral noise interferences. In most cases, 0.2–0.8 order derivatives exhibited the best estimation performance. Furthermore, PCA yielded the optimal predictability, the mean residual predictive deviation (RPD) and maximum RPD of the models using PCA were 1.79 and 2.60, respectively. The application of appropriate preprocessing techniques could improve the efficiency and accuracy of SOM content estimation, which is important for the protection of ecological and agricultural environment in black soil area.

We studied the effects of urease/nitrification inhibitor combinations on urea hydrolysis and nitrification, aiming to screen out the effective inhibitor combinations for black soil and cinnamon soil in Northeast China. Urease inhibitor, N-butyl thiophosphate-triamine (NBPT), and its combination with nitrification inhibitor dicyandiamide (DCD), 3, 4-dimethylpyrazole phosphate (DMPP), 2-chloro-6 (trichloromethyl)-pyridine (CP), 2-amino-4-chloro-6-methylpyrimidine (AM) and 3-methylpyrazole (MP) were added to urea separately. Samples were collected 15 times in each of all the treatments during 125 days. We examined the changes of urea nitrogen, ammo-nium, nitrate, and nitrification inhibition rate in the two soils. Our results showed the hydrolysis of urea in black soil and cinnamon soil was about 7 d, and the addition of NBPT with or without diffe-rent nitrification inhibitors slowed down the hydrolysis to 21 d at least. Compared with the treatment with common urea, inhibitor addition significantly increased soil NH4+-N, decreased soil NO3--N, and maintained the high NH4+-N content in soil for a longer time. In black soil, application with nitrification inhibitor inhibited soil nitrification significantly and lasted for more than 125 d. DMPP and CP combined with NBPT increased the NH4+-N content in black soil by 1.6-1.8 times, while the nitrification inhibition rate was 47.9% and 24.1% at 125 d, respectively. In the cinnamon soil, the application of nitrification inhibitor could prolong the duration of ammonium oxidation from 80 d to 110 d. DCD and DMPP combined with NBPT increased the NH4+-N content in cinnamon soil by 2.1-3.4 times, while the nitrification inhibition rates at 125 d were 25.3% and 23.2%, respectively. Therefore, NBPT+DMPP combination with urea was recommended for utilization in black soil, followed by NBPT+CP. In cinnamon soil, NBPT+DCD combination with urea was recommended, followed by NBPT+DMPP.

Selenium (Se) is an essential trace element within human beings that hold with crucial biological functions. Investigating the complex origin of soil Se is of great importance to scientifically approach the land use of Se-rich land use, and the respective promotion of regional economic development. In this study, 160 soil samples from 10 profiles in farmland and woodland were collected in Hailun city, which is a typical black soil region in Northeast China, in order to characterize the distribution and speciation of Se in the black soil, and to identify the origin of soil Se. The total selenium content in the soil ranges from 0.045 to 0.444μgg-1, with an average selenium content in black soil (0.318μgg-1) of three times greater than that found in the yellow-brown soil (0.114μgg-1). The land-use type has a significant influence on the distribution of selenium in the black soil. Moreover, Se and heavy metals have a significant (positive or negative) correlation, in which TOC plays an important role. The black soil presents a consistent REE distribution pattern with underlying yellow-brown soil indicating black soil originates from yellow-brown soil. REE geostatistical analysis suggests that the soil Se partly originates from shale weathering and enriches in black soil. Moreover, elemental geochemical analysis and XRD results show that the paleoclimate change from humid and warm to dry and cold is favorable for organic matter accumulation, resulting in less leaching and enhanced adsorption of selenium into the black soil.

Woody peat addition increases soil organic matter but its mineralization is affected by soil clay in the four degenerated erodible soils

Long-term degradation of black soil has led to reductions in soil fertility and ecological service functions, which have seriously threatened national food security and regional ecological security. This study is motivated by the UN’s Sustainable Development Goal (SDG) 2—Zero Hunger, specifically, SDG 2.4 Sustainable Food Production Systems. The aim was to monitor the soil organic matter (SOM) content of black soil and its dynamics via hyperspectral remote sensing inversion. This is of great significance to the effective utilization and sustainable development of black soil resources. Taking the typical black soil area of Northeast China as an example, the hyperspectral data of ground features were compared with SOM contents measured in soil samples to correlate SOM with spectral features. Based on their quantitative relationship, a dynamic fitness inertia weighted particle swarm optimization (DPSO) algorithm is proposed, which balances the global and local search abilities of a particle swarm optimization algorithm. The DPSO algorithm is applied to the parameter adjustment of an artificial neural network (BPNN), which is used instead of a traditional error back propagation algorithm, to build a DPSO-BPNN model. Then a global optimal analytical expression of hyperspectral inversion is obtained to improve the generalization ability and stability of the remote sensing quantitative inversion model. The results show that DPSO-BPNN model is more stable and accurate than existing models, such as multiple stepwise regression, partial least squares, and BP neural network models (adjust complex coefficient of determination = 0.89, root mean square error = 1.58, relative recent deviation = 2.93). The results of DPSO-BPNN inversion are basically consistent with the trend in SOM contents measured during surface geochemical exploration. As such, this study provides a basis for hyperspectral remote sensing inversion and monitoring of the SOM contents in black soil.

Globally, heavy metal (HM) soil pollution is becoming an increasingly serious concern. Heavy metals in soils pose significant environmental and health risks due to their persistence, toxicity, and potential for bioaccumulation. These metals often originate from anthropogenic activities such as industrial emissions, agricultural practices, and improper waste disposal. Once introduced into the soil, they can bind to soil particles, making them difficult to remove, while potentially entering the food chain through plant uptake or water contamination. Rapid access to reliable data on HM viscosity in soils is necessary to efficiently monitor remediated soils. Visible and near-infrared reflectance spectroscopy (350–2500 nm) is an economical and zero-pollution method that can evaluate multiple HM concentrations in soil simultaneously. Black soil is a valuable agricultural resource that helps guarantee food security worldwide and can serve as a soil carbon reservoir, but its protection faces several challenges. Due to long-term high-intensity development and utilization and the severe over-exploitation of groundwater, the arable land in China’s black soil area has been degraded. Using hyperspectral inversion of heavy metal content in soil can reduce the destructive sample collection and chemical pollution of soil, better protect black land resources, and steadily restore and improve the basic fertility of black land. Focusing on the black area region of Jilin Province, this study explored the correlation between three HMs, namely copper, zinc, and cadmium, and organic substances, clay minerals, and ferromanganese oxides through an in-depth analysis of soil samples using soil reflectance spectrometry. The spectra were transformed using first-and second-order derivatives, multiple scattering corrections, autoscales, and Savitzky–Golay smoothing. The successive projection algorithm was used to screen characteristic bands (Table S1) to establish the link between HM content in soil and soil spectra. By employing the support vector machine (SVM), random forest (RF), and partial least squares (PLS) models, feature band-based soil HM inversion modeling was established. Moreover, the optimal combinations of spectral transforms and inversion models were also examined. The findings indicate that the RF model (R2 > 0.8, RPIQ > 0) outperformed the SVM and PLS models in anticipating the three soil HMs, thus demonstrating superior accuracy. Understanding the behavior of heavy metals in soils and developing effective management strategies are essential for ensuring sustainable land use and protecting public health. This study contributes to the development of large-scale monitoring systems for the HM content of soil and assessments of HM contamination.

Potential role of organic matter in the transmission of antibiotic resistance genes in black soils

Effect of organic matter on phosphorus adsorption and desorption in a black soil from Northeast China

Plant growth depends on fertility and nutrient status of the soil. Presence of optimum range of these nutrients is inevitable for the growth survival of the flora. The present study was conducted during June 2021- June 2022 to know the chemical properties of black and red soils of the Pakhal wild life sanctuary, Telangana, India. Soil variables like PH, EC, organic matter, N, P, and K were assessed to know soil fertility. The study revealed the PH of the soil samples was 7.2 and it was on slightly alkaline. The values of EC observed in the present study were 0.10 and 0.75 dS /m respectively for black and red soils. Soil organic carbon analyzed was 0.61 for the black soil and it was 0.51 for red soil. The amount of available nitrogen was 213 and 226 kg/ha respectively for black and red soils. The phosphorus content of black soil is 32.61 kg/ha and for red soil it was 16.29 kg/ha. Potassium was reported to be 396 kg/ha and 517 kg/ha respectively for black and red soils. The study revealed that the soil is favorable for the growth of the plants.

<p>Soil organic carbon management is a key element in solving such urgent global-scale challenges as overcoming degradation of soils and mitigating climate change. Organic fertilizers application has a significant potential for sequestering C in soils, but their efficiency depends on decomposition characteristics. Firstly, it noted the dependence of resynthesis of humic compounds in a soil on a quality of organic inputs, secondly - a need for zonal approach to fertilizers production based on amphiphile properties of macromolecules.</p><p>The present study was conducted in long-term field experiment on black soil in Forrest-Steppe zone of Ukraine. The technology of production of organo-mineral fertilizers (OMFs) was based on the regulated processing of livestock waste with mineral components to stabilize it with hydrophobic bonds. OMFs in amorphous and granular form were compared in case of broadcast and band method of incorporation. The dose of OMF input was equivalent 350 C kg ha<sup>-1</sup> and 80 N, 80 P, 80 K kg ha<sup>-1</sup>. Organic carbon content in soil was determined by Turin method. Different organic matter fractions were isolated: humic acids (HA), fulvic acids (FA), and humin.</p><p>The soil C accumulation rates in OMF treatment was by 15 % higher than in manure treatment and up to 70 % higher than in chemical fertilizer treatment, respectively. The soil C accumulation was strongly influenced by the form of OMF and method of their application. The highest TOC level was found over band application of amorphous OMF, accumulating 6.2 t C ha<sup>–1</sup> yr<sup>–1 </sup>in 0-20 cm soil layer. Lower efficiency of broadcast incorporation OMFs could be explained by more intensive mineralization due to higher aeration. Taking into account the effect of OMFs on C stock an advantage of amorphous form versus granulated OMF with similar composition was proven. Black soil on control plot (without fertilization) had almost equal ratio between HA, FA and humin in humus composition. The content of humic compound increased in all treatments. Applying OMF significantly increased HA content in black soil compared to applying mineral fertilizer. OMFs application promoted the increase of the degree of condensation of organic matter. The highest HA/FA was found under the effect of broadcast incorporation OMF. That means that low molecular weight compounds were rapidly degraded while more resistant to mineralization HA were formed in soil. There was no significant difference in humus composition between amorphous and granulated OMF.</p>

As an important grain production area in China, the Northeast Black Soil Region has experienced many problems, such as soil degradation, fertility decline, and grain yield reduction, in recent years. Optimizing fertilizer management is an important measure to maintain and enhance soil fertility. However, improper fertilizer application could aggravate nutrient losses and greenhouse gas N2O emissions, thus leading to soil degradation and environmental pollution. The objectives of the present study were to investigate the response of N2O emission from black soil to long-term application of organic and chemical fertilizers and the key controlling factors. Soil samples （0-20 cm） were collected from a total of nine treatments, including organic fertilizer as the primary treatment （M0- no organic fertilizer； M1- low organic fertilizer； M2- high organic fertilizer） and chemical fertilizer as the secondary treatment （CK- no fertilizer； N- chemical nitrogen fertilizer； NPK- chemical nitrogen, phosphorus, and potassium fertilizer）, in a long-term experiment （32 years） on the black soil of Gongzhuling, Jilin Province. The soil samples were incubated at 25℃ with 65% field water holding capacity for 21 days, and N2O emission and soil physico-chemical biological properties were determined. The results showed that long-term application of organic and chemical fertilizers notably increased N2O emissions from black soil. Compared to those from the M0CK treatment [（0.25±0.01） mg·kg-1, in terms of N, the same as below], the cumulative N2O emissions from the only organic fertilizer treatment significantly increased by 361%-456% [（1.17±0.02） mg·kg-1 and （1.41±0.02） mg·kg-1 for the M1CK and M2CK treatments, respectively]. Furthermore, the N2O emissions strongly increased with increasing organic fertilizer application amounts. Cumulative N2O emissions were significantly higher in the chemical fertilizer treatments by 96%-236% [（0.49±0.01） mg·kg-1 and （0.84±0.03） mg·kg-1 for the M0N and M0NPK treatments, respectively] compared to those in the M0CK treatments. Moreover, the increased N2O emissions due to fertilizers application were significantly larger in the M0NPK relative to M0N treatments. The positive effects of chemical fertilizer application on N2O emission decreased under organic fertilizer amendments （M1 and M2）, indicating that organic fertilizer application alleviated increased N2O emission because of chemical fertilization. The application of organic fertilizers significantly increased bulk soil, aggregate organic carbon （SOC）, total nitrogen （TN）, and soil microbial carbon and nitrogen contents. The application of organic combined with chemical fertilizers further increased SOC and TN contents in bulk soil and aggregates. Pearson correlation and path model analyses showed that the N2O emission was positively correlated with soil carbon and nitrogen fractions and microbial carbon and nitrogen contents among organic and chemical fertilizer treatments. Long-term application of organic and chemical fertilizers strongly regulated N2O emissions via affecting the distribution of carbon and nitrogen contents in soil fractions and changing microbial biomass and substrate availability. In conclusion, the application of organic fertilizers could significantly facilitate N2O emission by increasing the available soil carbon and nitrogen pools as well as microbial carbon and nitrogen contents. The application of organic fertilizers mitigated the positive effects of chemical fertilizers on N2O emissions. Appropriate amounts of organic fertilizers should be used when applying chemical fertilizers, in order to balance the comprehensive effects of fertility improvement with nitrogen loss and greenhouse gas emissions.