The driving mechanism of soil organic carbon biodegradability in the black soil region of Northeast China.

The biodegradability of soil organic carbon (BSOC), defined as soil mineralization C per unit of soil organic carbon (SOC), is considered to be an important indicator of SOC stability and is closely related to the global C cycle. However, the magnitude and driving mechanism of BSOC in farmland remain largely unexplored, especially at the regional scale. Here, we conducted regional scale sampling to investigate latitude distribution pattern of BSOC and the relative contributions of biotic (soil micro-food web) and abiotic (climate and soil) drivers to BSOC in the black soil region of Northeast China.

Effects of long-term no-tillage on the functional potential of microorganisms involved in the nitrogen, phosphorus and sulfur cycles of black soil.

Understanding the effects of different tillage practices on functional microbial abundance and composition in nitrogen (N), phosphorus (P) and sulfur (S) cycles are essential for the sustainable utilization of black soils. Based on an 8-year field experiment located in Changchun, Jilin Province, we analyzed the abundance and composition of N, P and S cycling microorganisms and their driving factors in different depths of black soil under no til-lage (NT) and conventional tillage (CT). Results showed that compared with CT, NT significantly increased soil water content (WC) and microbial biomass carbon (MBC) at soil depth of 0-20 cm.

[Research progress on soil aggregates and associated organic carbon in salinized soils].

Soil aggregate, as a basic component of soils, plays an important role in improving soil structure and enhancing soil organic carbon (SOC) sequestration. The special soil properties induced by salinization, such as high ion concentrations (mainly Na), shortage of organic material and bad condition of microbe, inhibit the formation and stability of soil aggregate. Therefore, it is important and meaningful to explore the dynamics of aggregate in salinized soils.

Ridge Tillage Improves Soil Properties, Sustains Diazotrophic Communities, and Enhances Extensively Cooperative Interactions Among Diazotrophs in a Clay Loam Soil.

Reduced tillage practices [such as ridge tillage (RT)] have been potential solutions to the weed pressures of long-term no tillage (NT) and the soil-intensive disturbances caused by conventional tillage [such as moldboard plow (MP) tillage]. Although soil diazotrophs are significantly important in global nitrogen (N) cycling and contribute to the pool of plant-available N in agroecosystems, little is currently known about the responses of diazotrophic communities to different long-term tillage practices. In the current study, we investigated the differences among the effects of NT, RT, and MP on soil properties, diazotrophic communities, and co-occurrence network patterns in bulk and rhizosphere soils under soybean grown in clay loam soil of Northeast China.

Straw-derived biochar mitigates CO emission through changes in soil pore structure in a wheat-rice rotation system.

To better understand the relationships between soil pore structure features and soil CO emission and soil organic carbon (SOC) sequestration following different straw return modes, undisturbed soil cores (0-5 cm and 5-10 cm) were collected from a rice-wheat rotation system under 4 straw return treatments as (1) no straw return (CK), (2) straw direct return (DR), (3) straw biochar return (BR); (4) straw-pig manure fermentation return (FR) for six years. Pore structure parameters including pore size distribution, porosity, connectivity, anisotropy and fractal dimension (FD) were determined using X-ray computer tomography. Soil CO flux and concentrations of SOC, readily oxidable carbon and nutrients were also measured.

Tillage-induced effects on SOC through changes in aggregate stability and soil pore structure.

Soil structure plays a key role in soil organic carbon (SOC) dynamics. To determine how soil structure and aggregate affects SOC, we collected undisturbed soil cores of 0-5 cm layer (Typic Hapludoll) at an experimental site in Northeast China. The site had been under continuous tillage treatments of conventional tillage (CT) and no tillage (NT) for 17 years.

Temporal Variation of Earthworm Impacts on Soil Organic Carbon under Different Tillage Systems.

Previous research has shown the varied effect of earthworms on soil carbon dynamics. We carried out a 180-day incubation experiment with earthworms and maize residue additions under conventional tillage (CT) and no tillage (NT) system conditions to quantify the earthworm effect in the black soil of northeastern China. Earthworms did not affect soil CO emissions, while residue addition significantly increased such emissions.

Decomposition of maize stover varies with maize type and stover management strategies: A microcosm study on a Black soil (Mollisol) in northeast China.

Crop residue decomposition has an important impact on soil organic carbon (SOC) sequestration and CO emission. Residue quality and management strategies are two important factors regulating decomposition process and SOC mineralization and greenhouse gas emission. In this study, a microcosm experiment in field condition was conducted on a silty loam (a Black soil) in Northeast China to investigate stover decomposition and soil CO emission characteristics as influenced by different crop cultivars and stover field incorporation methods.

Effect of tillage and crop residue on soil temperature following planting for a Black soil in Northeast China.

Crop residue return is imperative to maintain soil health and productivity but some farmers resist adopting conservation tillage systems with residue return fearing reduced soil temperature following planting and crop yield. Soil temperatures were measured at 10 cm depth for one month following planting from 2004 to 2007 in a field experiment in Northeast China. Tillage treatments included mouldboard plough (MP), no till (NT), and ridge till (RT) with maize (Zea mays L.

[Priming Effects of Soil Moisture on Soil Respiration Under Different Tillage Practices].

In the early stage of an incubation experiment, soil respiration has a sensitive response to different levels of soil moisture. To investigate the effects of soil moisture on soil respiration under different tillage practices, we designed an incubation trial using air-dried soil samples collected from tillage experiment station established on black soils in 2001. The tillage experiment consisted of no-tillage (NT), ridge tillage (RT), and conventional tillage (CT).

[Effects of corn and soybean straws returning on CO2 efflux at initial stage in black soil].

In this study, the CO2 emission characteristics and its relationships with C and N concentration in soil amended with different types of residues were studied by thermostatic incubation method to investigate the decomposition characteristics of different types of residues after adding to the soil and the effect of C, N concentration in residues on carbon sequestration. The results showed that during 61 days incubation, the CO2 efflux rates in the soils added with the different residues changed over time and exhibited an initial decrease, followed by a stable low plateau, and then an increase to a high plateau and finally followed by a decrease. The characteristics of CO2 emissions varied with residues, with the differences mainly occurring in the starting and duration of the high plateau CO2 emission period.

No tillage combined with crop rotation improves soil microbial community composition and metabolic activity.

Soil microbial community can vary with different agricultural managements, which in turn can affect soil quality. The objective of this work was to evaluate the effects of long-term tillage practice (no tillage (NT) and conventional tillage (CT)) and crop rotation (maize-soybean (MS) rotation and monoculture maize (MM)) on soil microbial community composition and metabolic capacity in different soil layers. Long-term NT increased the soil organic carbon (SOC) and total nitrogen (TN) mainly at the 0-5 cm depth which was accompanied with a greater microbial abundance.

[Effects of Different Residue Part Inputs of Corn Straws on CO2 Efflux and Microbial Biomass in Clay Loam and Sandy Loam Black Soils].

The decomposed rate of crop residues is a major determinant for carbon balance and nutrient cycling in agroecosystem. In this study, a constant temperature incubation study was conducted to evaluate CO2 emission and microbial biomass based on four different parts of corn straw (roots, lower stem, upper stem and leaves) and two soils with different textures (sandy loam and clay loam) from the black soil region. The relationships between soil CO2 emission, microbial biomass and the ratio of carbon (C) to nitrogen (N) and lignin of corn residues were analyzed by the linear regression.

[Impact of tillage practices on microbial biomass carbon in top layer of black soils].

A study was conducted on a long-term (13 years) tillage and rotation experiment on black soil in northeast China to determine the effects of tillage, time and soil depth on soil microbial biomass carbon (MBC). Tillage systems included no tillage (NT), ridge tillage (RT) and mould-board plough (MP). Soil sampling was done at 0-5, 5-10 and 10-20 cm depths in June, August and September, 2013, and April, 2014 in the corn phase of corn-soybean rotation plots.

Short-term effects of tillage practices on soil organic carbon turnover assessed by δ13C abundance in particle-size fractions of black soils from northeast China.

The combination of isotope trace technique and SOC fractionation allows a better understanding of SOC dynamics. A five-year tillage experiment consisting of no-tillage (NT) and mouldboard plough (MP) was used to study the changes in particle-size SOC fractions and corresponding δ (13)C natural abundance to assess SOC turnover in the 0-20 cm layer of black soils under tillage practices. Compared to the initial level, total SOC tended to be stratified but showed a slight increase in the entire plough layer under short-term NT.

[Assessment of humic and fulvic acids in black soils using near-infrared reflectance spectroscopy].

The organic carbon content and optical densities of humic acids in black soils of China were predicted and assessed using near infrared spectroscopy technique. The contents of humic acid (HA) and fulvic acid (FA) in 136 black soil samples in China were analyzed and the NIR spectra were collected using a VECTOR/22 (Fourier transform infrared spectroscopy). Partial least squares (PLS) regression with cross validation was used to develop prediction models with reference data and soil NIRS spectra, and the model was validated using an independent set of samples.

[Research methods of carbon sequestration by soil aggregates: a review].

To increase soil organic carbon content is critical for maintaining soil fertility and agricultural sustainable development and for mitigating increased greenhouse gases and the effects of global climate change. Soil aggregates are the main components of soil, and have significant effects on soil physical and chemical properties. The physical protection of soil organic carbon by soil aggregates is the important mechanism of soil carbon sequestration.

[Effects of tillage mode on black soil's penetration resistance and bulk density].

Taking an eight-year field experiment site in Dehui County of Jilin Province, Northeast China as test object, this paper studied the effects of different tillage modes (no tillage and ploughing in autumn) on the penetration resistance and bulk density of black soil. No tillage increased the soil penetration resistance, especially at the soil depth of 2.5-17.

[Prediction of soil organic carbon in different soil fractions of black soils in Northeast China using near-infrared reflectance spectroscopy].

The soil organic carbon (SOC) associated with different soil fractions varies in the composition and dynamics. The present work is aimed to evaluate the potential of near infrared spectroscopy (NIRS) to predict SOC content in different soil fractions of black soils. SOC contents of 136 black soil samples in China were analyzed and the NIR spectra were collected using a VECTOR/22 (Fourier transform infrared spectroscopy).

[Field sampling methods for earthworm: a review].

As a critical component of soil ecosystem, earthworm can improve soil structure and relates closely to soil nutrient cycling, playing an important role in promoting soil quality and productivity. However, there is lack of systematic study on the field sampling methods for earthworm, especially in China. This paper reviewed the operational processes of commonly used field sampling methods for earthworm, and discussed their corresponding merits, efficacy, and potential influence on research results.

[Near infrared spectroscopy in determining organic carbon and total nitrogen in black soil of Northeast China].

In this study, near infrared reflectance spectroscopy (NIRS) was used to determine the organic carbon (OC), total nitrogen (TN), and C/N ratio in black soil of Northeast China. Based on the 3699-12000 cm(-1) NIRS of 136 black soil samples collected in 2004-2005, and by using partial least square (PLS), the related quantitative models were established. Leave-one-out cross validation showed that the OC and TN were well predicted, with the values of coefficient of determination (R2) being 0.

[Characters of infiltration and preferential flow of black soil in Northeast China under different tillage patterns].

By using dye tracer and double-ring infiltrometer techniques, the characters of infiltration and preferential flow of black soil under no-tillage (NT) and fall moldboard plow (MP) were compared after six years continuous management. The results showed that the infiltration rate was higher under NT than under MP. When the infiltration reached steady, the infiltration rate and accumulative infiltration capacity under NT were 1.

[Distribution of water-stable aggregates and aggregate-associated C in black soil in Northeast China].

The study on the distribution characters of water-stable aggregates and aggregate-associated C in 32 pairs of virgin and cultivated black soils in Northeast China showed that in virgin soils, the amount of water-stable macroaggregates (>0.25 mm) and their associated C in 0-30 cm layer were higher than those of microaggreagtes (< 0.25 mm).

[Redistribution patterns of black soil in hillslope landform of Northeast China: a 137Cs study].

In the black soil region of Northeast China, soil and water loss is quite serious, but not fully investigated due to the lack of reliable methods. 137Cs technology is a good one to study the medium-and long term erosion and sedimentation rates and the spatial redistribution of soil. With this technology and the existing calibration models, this paper studied the redistribution patterns of black soil in a typical hillslope landform of Northeast China.

[Conservation tillage systems in North America and their significance for China].

Soil degradation through erosion and desertification reduces soil productivity, and is a serious problem in agricultural production of China. To avert our arable land from further degradation, soil management must be shifted from degrading tillage to conservation practices. Over viewing the technology used in the 20th century for controlling soil degradation from erosion, conservation tillage developed in the United States and adopted in South America and Africa is one of the most successful measures to overcome soil degradation problems.