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    农业生态环境-有机碳与农业废弃物还田合辑Agro-ecosystem & Environment—SOC

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    Variation in spectral characteristics of dissolved organic matter derived from rape straw of plants grown in Se-amended soil
    JIA Wei, ZHAO Xiao-hu, ZHAO Yuan-yuan, XU Jia-yang, MING Jia-jia, CAI Miao-miao, HU Cheng-xiao
    2020, 19 (7): 1876-1884.   DOI: 10.1016/S2095-3119(19)62867-4
    Abstract102)      PDF in ScienceDirect      
    Straw return is an effective management practice.  It not only utilizes agricultural waste but also introduces dissolved organic matter (DOM) into the soil.  Selenium (Se) is an essential trace element in the human diet and contributes to the popularity of Se-enriched agricultural products in the Chinese market.  Moreover, there are still some Se-enriched agricultural products that have yet to be utilized.  This study investigated whether Se addition in soil caused component changes in the DOM extracted from rape straw.  DOM extracted from rape straw grown in soil with four Se levels (0, 0.1, 0.5 and 1.0 mg Se kg–1 soil) was characterized by UV-Visible spectroscopy, fluorescence spectroscopy and FTIR spectroscopy.  The UV-visible spectra revealed that 0.1 mg Se kg–1 soil reduced the molecular weight of DOM and caused the presence of more irreplaceable aromatic structures in the substituent groups of the DOM, while 0.5 and 1.0 mg Se kg–1 soil only reduced the DOM molecular weight.  Fluorescence spectroscopy indicated that Se improved the humification degree but reduced the aromaticity of DOM.  FTIR spectra proved that Se altered the contents of carboxylic acids, amino acids, alcohols and aromatic heterocycles in DOM, which were maximized in the 0.5 and 1.0 mg Se kg–1 treatment groups.  We concluded that Se application could change the composition of DOM extracted from rape straw, potentially impacting the nutrient bioavailability in soil.  This study provides basic data on Se-enriched rape straw utilization for eco-agriculture.
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    Phosphorus fertilization alters complexity of paddy soil dissolved organic matter
    ZHANG Zhi-jian, WANG Xian-zhe, LIANG Lu-yi, HUANG En, TAO Xing-hua
    2020, 19 (9): 2301-2312.   DOI: 10.1016/S2095-3119(20)63215-4
    Abstract94)      PDF in ScienceDirect      
    The structural complexity of soil dissolved organic matter (DOM) may reflect soil biogeochemical processes due to its spectral characteristics.  However, the features of DOM structural complexity in paddy soil amended with long-term chemical P fertilization are still unclear, which may limit understanding of nutrient-related soil C cycle.  We collected soil samples from field experiments receiving application of 0, 30, 60, and 90 kg P ha–1 yr–1 to assess the effect of exogenous P on the complexity of soil DOM structure.  Three-dimensional excitation-emission matrix fluorescence analysis and enzymatic activity assay were used to determine the features of soil DOM molecular structure and the associated microbial reactions.  The results showed that P input increased the biodegradability of DOM, indicating by the increased lower molecular weight components and decreased humic degree in the DOM.  P input also reduced the structural complexity of DOM with blue shifts of fluorescent signals.  The fluorescence index and β/α index of DOM increased with increasing P application by 4–5% and 3–11%, respectively, while humification index decreased by 8–13%.  The P input increased the abundance of bacteria and fungi by 34–167% and 159–964%, respectively, while 29–54% increments were found for the β-1,4-glucosidase activities.  These results implicated that P fertilization accelerated the soil DOM cycle, although the structural complexity of DOM declined, which potentially benefits soil C sequestration in paddy fields and may be a C sequestration mechanism in the P-dependent paddy. 
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    Dynamics of organic carbon and nitrogen in deep soil profile and crop yields under long-term fertilization in wheat-maize cropping system
    Muhammad QASWAR, LI Dong-chu, HUANG Jing, HAN Tian-fu, Waqas AHMED, Sehrish ALI, Muhammad Numan KHAN, Zulqarnain Haider KHAN, XU Yong-mei, LI Qian, ZHANG Hui-min, WANG Bo-ren, Ahmad TAUQEER
    2022, 21 (3): 826-839.   DOI: 10.1016/S2095-3119(20)63501-8
    Abstract96)      PDF in ScienceDirect      
    Soil organic carbon (SOC) and nitrogen (N) are two of the most important indicators for agricultural productivity.  The primary objective of this study was to investigate the changes in SOC and N in the deep soil profile (up to 100 cm) and their relationships with crop productivity under the influence of long-term (since 1990) fertilization  in the wheat-maize cropping system.  Treatments included CK (control), NP (inorganic N and phosphorus (P) fertilizers), NPK (inorganic N, P and potassium fertilizers), NPKM (NPK plus manure), and M (manure).  Crop yield and the properties of topsoil were measured yearly from 2001 to 2009.  C and N contents were measured at five different depths in 2001 and 2009.  The results showed that wheat and maize yields decreased between 2001 and 2009 under the inorganic fertilizer (NP and NPK) treatments.  The average yield between 2001 and 2009 under the NP, NPK, NPKM, and M treatments (compared with the CK treatment) increased by 38, 115, 383, and 381%, respectively, for wheat and 348, 891, 2 738, and 1 845%, respectively, for maize.  Different long-term fertilization treatments significantly changed coarse free particulate (cfPOC), fine free particulate (ffPOC), intramicroaggregate particulate (iPOC), and mineral-associated (mSOC) organic carbon fractions.  In the experimental years of 2001 and 2009, soil fractions occurred in the following order for all treatments: mSOC>cfPOC>iPOC>ffPOC.  All fractions were higher under the manure application treatments than under the inorganic fertilization treatments.  Compared to the inorganic fertilization treatments, manure input enhanced the stocks of SOC and total N in the surface layer (0–20 cm) but decreased SOC and N in the deep soil layer (80–100 cm).  This reveals the efficiency of manure in increasing yield productivity and decreasing risk of vertical loss of nutrients, especially N, compared to inorganic fertilization treatments.  The findings provide opportunities for understanding deep soil C and N dynamics, which could help mitigate climate change impact on agricultural production and maintain soil health.

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    Effects of a decade of organic fertilizer substitution on vegetable yield and soil phosphorus pools, phosphatase activities, and the microbial community in a greenhouse vegetable production system
    ZHANG Yin-Jie, GAO Wei, LUAN Hao-an, TAND Ji-wei, LI Ruo-nan, LI Ming-Yue, ZHANG Huai-zhi, HUANG Shao-wen
    2022, 21 (7): 2119-2133.   DOI: 10.1016/S2095-3119(21)63715-2
    Abstract146)      PDF in ScienceDirect      
    Partial substitution of chemical fertilizers by organic amendments is adopted widely for promoting the availability of soil phosphorus (P) in agricultural production.  However, few studies have comprehensively evaluated the effects of long-term organic substitution on soil P availability and microbial activity in greenhouse vegetable fields.  A 10-year (2009–2019) field experiment was carried out to investigate the impacts of organic fertilizer substitution on soil P pools, phosphatase activities and the microbial community, and identify factors that regulate these soil P transformation characteristics.  Four treatments included 100% chemical N fertilizer (4CN), 50% substitution of chemical N by manure (2CN+2MN), straw (2CN+2SN), and combined manure with straw (2CN+1MN+1SN).  Compared with the 4CN treatment, organic substitution treatments increased celery and tomato yields by 6.9−13.8% and 8.6−18.1%, respectively, with the highest yields being in the 2CN+1MN+1SN treatment.  After 10 years of fertilization, organic substitution treatments reduced total P and inorganic P accumulation, increased the concentrations of available P, organic P, and microbial biomass P, and promoted phosphatase activities (alkaline and acid phosphomonoesterase, phosphodiesterase, and phytase) and microbial growth in comparison with the 4CN treatment.  Further, organic substitution treatments significantly increased soil C/P, and the partial least squares path model (PLS-PM) revealed that the soil C/P ratio directly and significantly affected phosphatase activities and the microbial biomass and positively influenced soil P pools and vegetable yield.  Partial least squares (PLS) regression demonstrated that arbuscular mycorrhizal fungi positively affected phosphatase activities.  Our results suggest that organic fertilizer substitution can promote soil P transformation and availability.  Combining manure with straw was more effective than applying these materials separately for developing sustainable P management practices. 
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    Organic matter fractions within macroaggregates in response to long-term fertilization in calcareous soil after reclamation
    CAO Han-bing, XIE Jun-yu, HONG Jie, WANG Xiang, HU Wei, HONG Jian-ping
    2021, 20 (6): 1636-1648.   DOI: 10.1016/S2095-3119(20)63354-8
    Abstract66)      PDF in ScienceDirect      
    Soil organic carbon (SOC) plays a key role in improving soil quality and optimizing crop yield.  Yet little is known about the fate of macroaggregates (>0.25 mm) under long-term fertilization and their relative importance in SOC sequestration in reclaimed calcareous soil.  Therefore, the effects of mineral fertilizers and organic manure on the mechanisms of organic carbon (OC) stabilization in macroaggregates were investigated in this study.  Four treatments were used: unfertilized control (CK), mineral fertilizer (NPK), compost chicken manure alone (M), and mineral fertilizers plus manure (MNPK).  Samples from the 0–20 cm layer of soil receiving 11-year-long fertilization were separated into four fractions based on the macroaggregates present (unprotected coarse and fine particulate organic matter, cPOM and fPOM; physically protected intra-microaggregate POM, iPOM; and biochemically protected mineral associated OM, MOM) by the physical fractionation method.  Compared with the control, the long-term application of NPK had little effect on SOC content, total nitrogen (TN) content, and OC and TN contents of macroaggregate fractions.  In contrast, incorporation of organic manure (MNPK) significantly increased SOC (45.7%) and TN (24.3%) contents.  Application of MNPK increased OC contents within macroaggregate-extracted fractions of cPOM (292.2%), fPOM (136.0%) and iPOM (124.0%), and TN contents within cPOM (607.1%), fPOM (242.5%) and iPOM (127.6%), but not the mineral associated organic carbon (MOM-C) and nitrogen (MOM-N) contents.  Unprotected C fractions were more strongly and positively correlated with SOC increase than protected C fractions, especially for cPOM-C, indicating that SOC sequestration mainly occurred via cPOM-C in the studied calcareous soil.  In conclusion, MNPK increased the quantity and stability of SOC by increasing the contents of cPOM-C and cPOM-N, suggesting that this management practice (MNPK) is an effective strategy to develop sustainable agriculture.
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    Response of carbon footprint to plastic film mulch application in spring maize production and mitigation strategy
    CHEN Bao-qing, Shahar BARAM, DONG Wen-yi, HE Wen-qing, LIU En-ke, YAN Chang-rong
    2021, 20 (7): 1933-1943.   DOI: 10.1016/S2095-3119(20)63278-6
    Abstract107)      PDF in ScienceDirect      
    Producing more food with a lower environmental cost is one of the most crucial challenges worldwide.  Plastic mulching has developed as one of the most dominant practices to improve crop yields, however its impacts on greenhouse gas (GHG) emissions during the production life cycle of a crop are still unclear.  The objective of this work is to quantify the impacts of plastic film on GHG emissions and to reduce GHG emissions with innovative agronomic practices.  Carbon footprint per unit of area (CFa), per unit of maize grain yield (CFy), and per unit of economic output (CFe) were evaluated for three maize cultivation systems: a no mulch system, a conventional plastic mulching system (PM) and a biennial plastic mulching pattern, namely a ‘one film for 2 years’ system (PM2), during 2015–2018 in a maize field located on the Loess Plateau of China.  The results suggested that PM induced a 24% improvement in maize yields during the four experimental years compared to a no-mulch treatment (NM).  However, PM dramatically increased the CFa by 69%, 59% of which was created by the input of the plastic film material, and 10% was created by increases in the soil N2O emissions.  The yield improvements from PM could not offset the increases in CFa, and CFy and CFe were both increased by 36%.  Shifting from PM to PM2 did not reduce crop yields, but it led to a 21% reduction in CFa and 23% reductions in CFy and CFe due to the reduced input amount of plastic film, decreased soil N2O emissions, and less diesel oil used for tillage.  Compared to NM, CFy and CFe were only 5% higher in PM2.  This study highlights the necessity of reducing the amount of plastic film input in the development of low-carbon agriculture and shifting from conventional PM cultivation to PM2 could be an efficient option for mitigating GHG emissions while sustaining high crop yields in plastic mulched fields. 
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    The impacts of oxytetracycline on humification during manure composting can be alleviated by adjusting initial moisture contents as illustrated by NMR
    FENG Yao, WANG Gui-zhen, LIU Yuan-wang, CHENG Deng-miao, FAN Shuang-hu, ZHAO Quan-sheng, Jianming XUE, ZHANG Shu-qing, LI Zhao-jun
    2021, 20 (8): 2277-2288.   DOI: 10.1016/S2095-3119(20)63332-9
    Abstract93)      PDF in ScienceDirect      
    Oxytetracycline (OTC) residues have been found in soil and water, and they may pose potential risks to agricultural ecological environments.  One of the most impactful ways for OTC to enter the soil and water environments is through excrement used as organic fertilizer.  Therefore, it is important to remove OTC during manure composting and to understand the transformation of the organic materials during composting in the presence of OTC.  In the present paper, chicken manure and wheat sawdust spiked with OTC were composted under different initial moisture contents (MC) to evaluate the degradation of OTC and  changes of organic matter during the composting process.  The MC has a significant effect on OTC degradation during composting.  A higher MC of 65% was more conducive to OTC degradation (77.4%) and compost maturity compared to the lower MC.  However, the higher MC of 65% could increase the ammonia volatilization by promoting nitrification compared to the lower MC.  An increase in the initial MC could improve the composting temperature.  NMR results illustrated that the presence of OTC could affect the internal transformation of aliphatics, and OTC inhibited compost humification.  Thus, an initial MC of 55–65% can alleviate the impacts of OTC on humification during manure composting.
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    Integrated management of crop residue and nutrients enhances new carbon formation by regulating microbial taxa and enzymes
    WU Hong-liang, CAI An-dong, XING Ting-ting, HUAI Sheng-chang, ZHU Ping, HAN Xiao-zeng, XU Ming-gang, LU Chang-ai
    2022, 21 (6): 1772-1785.   DOI: 10.1016/S2095-3119(21)63752-8
    Abstract187)      PDF in ScienceDirect      
    Although returning crop residue to fields is a recommended measure for improving soil carbon (C) stocks in agroecosystems, the response of newly formed soil C (NFC) to the integrated supply of residue and nutrients and the microbial mechanisms have not been fully understood. Therefore, an 84-day incubation experiment was conducted to ascertain the microbial mechanisms that underpin the NFC response to inputs of residue and nitrogen (N), phosphorus (P), and sulfur (S) in two black soils. The results showed that adding residue alone accelerated microbial nutrient mining, which was supported by decreases of 8–16% in the ratios of C:N and C:P enzyme activities (relative to soils with nutrient inputs). The NFC amounts increased from 1155.9 to 1722.4 mg kg−1 soil in Gongzhuling and increased from 725.1 to 1067.5 mg kg−1 soil in Hailun as the levels of nutrient supplementation increased. Boosted regression tree analysis suggested that β-glucosidase (BG), acid phosphatase (AP), microbial biomass C (MBC), and Acidobacteria accounted for 27.8, 18.5, 14.7, and 8.1%, respectively, of the NFC in Gongzhuling and accounted for 25.9, 29.5, 10.1, and 13.9%, respectively, of the NFC in Hailun. Path analysis determined that Acidobacteria positively influenced NFC both directly and indirectly by regulating BG, AP, and MBC, in which MBC acquisition was regulated more by AP. The intensity of NFC was lower in Hailun soil than in Gongzhuling soil and was directly affected by AP, thereby indicating the importance of soil status (e.g., SOC and pH) in determining NFC. Overall, our results reveal the response of NFC to supplementation by N, P, and S, which depends on Acidobacteria and Proteobacteria, and their investment in BG and AP in residue-amended soil.
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    Changes in soil organic carbon pools following long-term fertilization under a rain-fed cropping system in the Loess Plateau, China
    WANG Ren-jie, SONG Jia-shan, FENG Yong-tao, ZHOU Jiang-xiang, XIE Jun-yu, Asif KHAN, CHE Zong-xian, ZHANG Shu-lan, YANG Xue-yun
    2021, 20 (9): 2512-2525.   DOI: 10.1016/S2095-3119(20)63482-7
    Abstract133)      PDF in ScienceDirect      
    Understanding the mechanism of soil organic carbon (SOC) sequestration is of paramount importance in sustaining crop productivity and mitigating climate change.  Long-term trials were employed to investigate the responses of total SOC and its pools, i.e., mineral-associated OC (MOC), particulate OC (POC, containing Light-POC and Heavy-POC), to fertilization regimes at Yangling (25-year), Tianshui (35-year) and Pingliang (37-year) under a rain-fed cropping system in the Loess Plateau.  The fertilization regimes in each trial included three treatments, i.e., control (no nutrient input, CK), chemical fertilizers (CF), and organic manure plus chemical fertilizers (MCF).  Relative to the CK, long-term fertilization appreciably increased SOC storage by 134, 89 and 129 kg ha–1 yr–1 under CF, and 418, 153 and 384 kg ha–1 yr–1 under MCF in plough layer soils (0–20 cm), respectively, at the Yangling, Tianshui and Pingliang sites.  The MOC pools accounted for 72, 67 and 64% of the total SOC at the above three sites with sequestration rates of 76, 57 and 83 kg ha–1 yr–1 under CF and 238, 118 and 156 kg ha–1 yr–1 under MCF, respectively.  Moreover, the MOC pool displayed a saturation behavior under MCF conditions.  The POC accordingly constituted 27, 33 and 36% of SOC, of which Light-POC accounted for 11, 17 and 22% and Heavy-POC for 17, 16 and 15% of SOC, respectively.  The sequestration rates of POC were 58, 32 and 46 kg ha–1 yr–1 under CF, and 181, 90 and 228 kg ha–1 yr–1 under MCF at the three respective sites, in which Light-POC explained 59, 81 and 72% of POC under CF, and 60, 40 and 69% of POC under MCF, with Heavy-POC accounting for the balance.  Compared with CK, the application of CF alone did not affect the proportions of MOC or total POC to SOC, whereas MCF application markedly reduced the proportion of MOC and increased the POC ratio, mainly in the Light-POC pool.  The distribution of SOC among different pools was closely related to the distribution and stability of aggregates.  The present study confirmed that organic manure amendment not only sequestered more SOC but also significantly altered the composition of SOC, thus improving SOC quality, which is possibly related to the SOC saturation level.
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    Changes in organic C stability within soil aggregates under different fertilization patterns in a greenhouse vegetable field
    LUAN Hao-an, YUAN Shuo, GAO Wei, TANG Ji-wei, LI Ruo-nan, ZHANG Huai-zhi, HUANG Shao-wen
    2021, 20 (10): 2758-2771.   DOI: 10.1016/S2095-3119(21)63646-8
    Abstract96)      PDF in ScienceDirect      
    Knowledge of the stability of soil organic C (SOC) is vital for assessing SOC dynamics and cycling in agroecosystems.  Studies have documented the regulatory effect of fertilization on SOC stability in bulk soils. However, how fertilization alters organic C stability at the aggregate scale in agroecosystems remains largely unclear.  This study aimed to appraise the changes of organic C stability within soil aggregates after eight years of fertilization (chemical vs. organic fertilization) in a greenhouse vegetable field in Tianjin, China.  Changes in the stability of organic C in soil aggregates were evaluated by four methods, i.e., the modified Walkley-Black method (chemical method), 13C NMR spectroscopy (spectroscopic method), extracellular enzyme assay (biological method), and thermogravimetric analysis (thermogravimetric method).  The aggregates were isolated and separated by a wet-sieving method into four fractions: large macroaggregates
    (>2 mm), small macroaggregates (0.25–2 mm), microaggregates (0.053–0.25 mm), and silt/clay fractions (<0.053 mm).  The results showed that organic amendments increased the organic C content and reduced the chemical, spectroscopic, thermogravimetric, and biological stability of organic C within soil aggregates relative to chemical fertilization alone.  Within soil aggregates, the content of organic C was the highest in microaggregates and decreased in the order microaggregates>macroaggregates>silt/clay fractions.  Meanwhile, organic C spectroscopic, thermogravimetric, and biological stability were the highest in silt/clay fractions, followed by macroaggregates and microaggregates.  Moreover, the modified Walkley-Black method was not suitable for interpreting organic C stability at the aggregate scale due to the weak correlation between organic C chemical properties and other stability characteristics within the soil aggregates.  These findings provide scientific insights at the aggregate scale into the changes of organic C properties under fertilization in greenhouse vegetable fields in China.
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    Quantifying in situ N2 fluxes from an intensively managed calcareous soil using the 15N gas-flux method
    LIU Yan, WANG Rui, PAN Zhan-lei, ZHENG Xun-hua, WEI Huan-huan, ZHANG Hong-rui, MEI Bao-ling, QUAN Zhi, FANG Yun-ting, JU Xiao-tang
    2022, 21 (9): 2750-2766.   DOI: 10.1016/j.jia.2022.07.016
    Abstract189)      PDF in ScienceDirect      

    Denitrification-induced nitrogen (N) losses from croplands may be greatly increased by intensive fertilization.  However, the accurate quantification of these losses is still challenging due to insufficient available in situ measurements of soil dinitrogen (N2) emissions.  We carried out two one-week experiments in a maize–wheat cropping system with calcareous soil using the 15N gas-flux (15NGF) method to measure in situ N2 fluxes following urea application.  Applications of 15N-labeled urea (99 atom%, 130–150 kg N ha−1) were followed by irrigation on the 1st, 3rd, and 5th days after fertilization (DAF 1, 3, and 5, respectively).  The detection limits of the soil N2 fluxes were 163–1 565, 81–485, and 54–281 μg N m−2 h−1 for the two-, four-, and six-hour static chamber enclosures, respectively.  The N2 fluxes measured in 120 cases varied between 159 and 2 943 (811 on average) μg N m−2 h−1, which were higher than the detection limits, with the exception of only two cases.  The N2 fluxes at DAF 3 were significantly higher (by nearly 80% (P<0.01)) than those at DAF 1 and 5 in the maize experiment, while there were no significant differences among the irrigation times in the wheat experiment.  The N2 fluxes and the ratios of nitrous oxide (N2O) to the N2O plus N2 fluxes following urea application to maize were approximately 65% and 11 times larger, respectively (P<0.01), than those following urea application to wheat.  Such differences could be mainly attributed to the higher soil water contents, temperatures, and availability of soil N substrates in the maize experiment than in the wheat experiment.  This study suggests that the 15NGF method is sensitive enough to measure in situ N2 fluxes from intensively fertilized croplands with calcareous soils.

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    Apparent variations in nitrogen runoff and its uptake in paddy rice under straw incorporation
    Muhammad Amjad BASHIR, ZHAI Li-mei, WANG Hong-yuan, LIU Jian, Qurat-Ul-Ain RAZA, GENG Yu-cong, Abdur REHIM, LIU Hong-bin
    2022, 21 (11): 3356-3367.   DOI: 10.1016/j.jia.2022.08.062
    Abstract169)      PDF in ScienceDirect      

    Straw incorporation is a widespread practice to promote agricultural sustainability.  However, the potential effects of straw incorporation with the prolonged time on nitrogen (N) runoff loss from paddy fields are not well studied.  The current study addresses the knowledge gap by assessing the effects of straw incorporation on the processes influencing N runoff patterns and its impacts on crop yield, N uptake, total N (TN), and soil organic matter (SOM).  We conducted field experiments with rice (Oryza sativa L.)–wheat (Triticum aestivum L.) rotation, rice–tobacco (Nicotiana tabacum L.) rotation, and double-rice cropping in subtropical China from 2008 to 2012.  Each rotation had three N treatments: zero N fertilization (CK), chemical N fertilization (CF), and chemical N fertilization combined with straw incorporation (CFS).  The treatment effects were assessed on TN runoff loss, crop yield, N uptake, soil TN stock, and SOM.  Results showed that TN runoff was reduced by substituting part of the chemical N fertilizer with straw N in the double rice rotation, while crop N uptake was significantly (P<0.05) decreased due to the lower bioavailability of straw N.  In contrast, in both rice–wheat and rice–tobacco rotations, TN runoff in CFS was increased by 0.9–20.2% in the short term when straw N was applied in addition to chemical N, compared to CF.  However, TN runoff was reduced by 2.3–19.3% after three years of straw incorporation, suggesting the long-term benefits of straw incorporation on TN loss reduction.  Meanwhile, crop N uptake was increased by 0.8–37.3% in the CFS of both rotations.  This study demonstrates the challenges in reducing N runoff loss while improving soil fertility by straw incorporation over the short term but highlights the potential of long-term straw incorporation to reduce N loss and improve soil productivity.

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    Partial organic substitution weakens the negative effect of chemical fertilizer on soil micro-food webs
    LIU Han-wen, ZHANG Xiao-ke, ZHANG Gui-zong, KOU Xin-chang, LIANG Wen-ju
    2022, 21 (10): 3037-3050.   DOI: 10.1016/j.jia.2022.07.043
    Abstract137)      PDF in ScienceDirect      
    Soil biotic communities play vital roles in enhancing soil nutrient cycling and soil fertility.  Long-term excessive nitrogen (N) application is disadvantageous to the stability of soil food webs and affects arable soil health and sustainable utilization.  Proper organic substitution is essential to improve soil health and alleviate the disadvantages of excessive chemical fertilization.  However, the biological effects of various organic amendments on soil micro-food webs are poorly understood.  In order to explore the effects of various organic amendments including stover, biochar and manure on soil micro-food webs (microbial and nematode communities), a field plot experiment with maize having five treatments viz., 100% urea (100% N), 70% urea (70% N), 70% urea plus stover (Stover), 70% urea plus cattle manure (Manure) and 70% urea plus biochar (Biochar) was conducted.  Manure treatment increased the carbon (C) to N use efficiency of soil microbes, which contributed to the retention of soil C, while Biochar treatment elevated soil organic C (SOC) and soil pH.  Additionally, Biochar treatment mitigated the negative effects of soil acidification on the soil micro-food web and reduced the abundance of plant parasites.  Overall, the biological effect of organic amendments was distinguished from chemical fertilization (100% N and 70% N) through principal co-ordinates analysis.  Negative relationships among soil properties, microbial and nematode biomass in the 100% N treatment were diminished in treatments where chemical fertilizer was reduced.  The bottom-up effects on soil food webs were observed in organic substitution treatments.  In conclusion, organic amendments improved soil fertility by regulating soil microbial and nematode communities in the cropland ecosystem, alleviated the negative effects of chemical fertilizer on the micro-food webs and controlled the trophic cascades among soil biota.
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    Bentonite-humic acid improves soil organic carbon, microbial biomass, enzyme activities and grain quality in a sandy soil cropped to maize (Zea mays L.) in a semi-arid region
    ZHOU Lei, XU Sheng-tao, Carlos M. MONREAL, Neil B. MCLAUGHLIN, ZHAO Bao-ping, LIU Jing-hui, HAO Guo-cheng
    2022, 21 (1): 208-221.   DOI: 10.1016/S2095-3119(20)63574-2
    Abstract124)      PDF in ScienceDirect      
    A bentonite-humic acid (B-HA) mixture added to degraded soils may improve soil physical and hydraulic properties, due to effects such as improved soil structure and increased water and nutrient retention, but its effect on soil physicochemical and biological properties, and grain quality is largely unknown.  The effect of B-HA, added at 30 Mg ha−1, was studied at 1, 3, 5 and 7 years after its addition to a degraded sandy soil in a semi-arid region of China.  The addition of B-HA significantly increased water-filled pore space and soil organic carbon, especially at 3 to 5 years after its soil addition to the soil.  Amending the sandy soil with B-HA also increased the content of microbial biomass (MB)-carbon, -nitrogen and -phosphorus, and the activities of urease, invertase, catalase and alkaline phosphatase.  The significant effect of maize (Zea mays L.) growth stage on soil MB and enzyme activities accounted for 58 and 84% of their total variation, respectively.  In comparison, B-HA accounted for 8% of the total variability for each of the same two variables.  B-HA significantly enhanced soil properties and the uptake of N and P by maize in semi-arid areas.  The use of B-HA product would be an effective management strategy to reclaim degraded sandy soils and foster sustainable agriculture production in northeast China and regions of the world with similar soils and climate.

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    Long-term straw return influenced ammonium ion retention at the soil aggregate scale in an Anthrosol with rice-wheat rotations in China
    ZHANG Wen-zhao, CHEN Xiao-qin, WANG Huo-yan, WEI Wen-xue, ZHOU Jian-min
    2022, 21 (2): 521-531.   DOI: 10.1016/S2095-3119(20)63592-4
    Abstract120)      PDF in ScienceDirect      
    Soil aggregates are an important controlling factor for the physico-chemical and biological processes such as ammonium (NH4+) retention.  Straw return to the field is increasingly recommended to promote soil carbon (C) sequestration and improve crop yields.  However, the effects of straw return on NH4+ retention at soil aggregate level in agricultural soils have seldom been investigated.  This study aimed to evaluate the influences of long-term straw return on NH4+ adsorption and fixation in microaggregates (<0.25 mm) with or without soil organic carbon (SOC) oxidization.  Soil samples were collected from plots of three treatments, i.e., no fertilizer (CK), inorganic NPK fertilizers (NPK), and inorganic NPK fertilizers with rice straw return (NPKS), from a 20-year-old field trial with rice-wheat rotations in Taihu Lake Region, China.  Soil aggregates were separated using wet-sieving method.  The SOC of microaggregates was oxidized by H2O2.  The results showed that long-term straw return significantly increased SOC and NH4+ adsorption, but inhibited NH4+ fixation in microaggregates.  NH4+ adsorption potential and strength - obtained from adsorption isotherms - increased, but NH4+ fixation decreased along with increasing SOC in microaggregates, indicating the important role of SOC in NH4+ adsorption and fixation.  This was verified by the SOC oxidization test that showed a relative decrease in NH4+ adsorption potential for the NPKS treatment and an increase in NH4+ fixation in all three treatments.  Therefore, long-term straw return influences NH4+ adsorption and fixation by enhancing SOC content and could improve N availability for crop uptake and minimize applied N fertilizer losses in rice-wheat cropping systems.
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    Substituting nitrogen and phosphorus fertilizer with optimal amount of crop straw improved rice grain yield, nutrient use efficiency and soil carbon sequestration
    XIE Jun, Blagodatskaya EVGENIA, ZHANG Yu, WAN Yu, HU Qi-juan, ZHANG Cheng-ming, WANG Jie, ZHANG Yue-qiang, SHI Xiao-jun
    2022, 21 (11): 3345-3355.   DOI: 10.1016/j.jia.2022.08.059
    Abstract289)      PDF in ScienceDirect      

    Crop straw return after harvest is considered an important way to achieve both agronomic and environmental benefits.  However, the appropriate amount of straw to substitute for fertilizer remains unclear.  A field experiment was performed from 2016 to 2018 to explore the effect of different amounts of straw to substitute for fertilizer on soil properties, soil organic carbon (SOC) storage, grain yield, yield components, nitrogen (N) use efficiency, phosphorus (P) use efficiency, N surplus, and P surplus after rice harvesting.  Relative to mineral fertilization alone, straw substitution at 5 t ha–1 improved the number of spikelets per panicle, effective panicle, seed setting rate, 1 000-grain weight, and grain yield, and also increased the aboveground N and P uptake in rice.  Straw substitution exceeding 2.5 t ha–1 increased the soil available N, P, and K concentrations as compared with mineral fertilization, and different amounts of straw substitution improved SOC storage compared with mineral fertilization.  Furthermore, straw substitution at 5 t ha–1 decreased the N surplus and P surplus by up to 68.3 and 28.9%, respectively, compared to mineral fertilization.  Rice aboveground N and P uptake and soil properties together contributed 19.3% to the variation in rice grain yield and yield components.  Straw substitution at 5 t ha–1, an optimal fertilization regime, improved soil properties, SOC storage, grain yield, yield components, N use efficiency (NUE), and P use efficiency (PUE) while simultaneously decreasing the risk of environmental contamination.

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    Fractionation of soil organic carbon in a calcareous soil after long-term tillage and straw residue management
    LI Teng-teng, ZHANG Jiang-zhou, ZHANG Hong-yan, Chrisite PHRISITE, ZHANG Jun-ling
    2022, 21 (12): 3611-3625.   DOI: 10.1016/j.jia.2022.08.072
    Abstract119)      PDF in ScienceDirect      

    No tillage (NT) and straw return (S) collectively affect soil organic carbon (SOC).  However, changes in the organic carbon pool have been under-investigated.  Here, we assessed the quantity and quality of SOC after 11 years of tillage and straw return on the North China Plain.  Concentrations of SOC and its labile fractions (particulate organic carbon (POC), potassium permanganate-oxidizable organic carbon (POXC), microbial biomass carbon (MBC) and dissolved organic carbon (DOC)), components of DOC by fluorescence spectroscopy combined with parallel factor analysis (PARAFAC) and the chemical composition of SOC by 13C NMR spectroscopy were explored.  Treatments comprised conventional tillage (CT) and NT under no straw return (S0), return of wheat straw only (S1) or return of both wheat straw and maize residue (S2).  Straw return significantly increased the concentrations and stocks of SOC at 0-20 cm depth but no tillage stratified them with enrichment at 0-10 cm and a decrease at 10-20 cm in comparison to CT, especially under S2.  Labile C fractions showed similar patterns of variation to that of SOC, with POC and POXC more sensitive to straw return and the former more sensitive to tillage.  Six fluorescence components of DOC were identified comprising mostly humic-like substances with smaller amounts of fulvic acid-like substances and tryptophan. Straw return significantly decreased the fluorescence index (FI) and autochthonous index (BIX) and increased the humification index (HIX).  No tillage generally increased HIX in topsoil but decreased it and increased the FI and BIX below the topsoil.  The chemical composition of SOC was: O-alkyl C>alkyl-C>aromatic-C>carbonyl-C.  Overall, NT under S2 effectively increased SOC and its labile C forms and DOC humification in topsoil and microbially-derived DOC below the topsoil.  Return of both wheat and maize straw was a particularly strong factor for promoting soil organic carbon in the plough layer, and the stratification of SOC under no tillage may confer long-term influence on carbon sequestration.

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    Estimation of soil organic carbon stock and its controlling factors in cropland of Yunnan Province, China
    SUN Tao, TONG Wen-jie, CHANG Nai-jie, DENG Ai-xing, LIN Zhong-long, FENG Xing-bing, LI Jun-ying, SONG Zhen-wei
    2022, 21 (5): 1475-1487.   DOI: 10.1016/S2095-3119(21)63620-1
    Abstract102)      PDF in ScienceDirect      
    Soil organic carbon (SOC) is the most important indicators of soil quality and health.  Identifying the spatial distribution of SOC and its influencing factors in cropland is crucial to understand the terrestrial carbon cycle and optimize agronomic management.  Yunnan Province, characterized by mountainous topography and varied elevation, is one of the highest SOC regions in China.  Yet its SOC stock of cropland and influencing factors has not been fully studied due to the lack of adequate soil investigation.  In this study, the digital mapping of SOC at 1 km resolution and the estimation of total SOC stock in cropland of Yunnan Province was undertaken using 8 637 topsoil (0–20 cm) samples and a series of spatial data through Random Forest (RF) model.  It was showed that across the cropland of Yunnan Province, the mean SOC density and total stock were 4.84 kg m–2 and 337.5 Mt, respectively.  The spatial distribution indicated that relatively high SOC density regions resided in the northwest and northeast parts of Yunnan Province.  Elevation (19.5%), temperature (17.3%), rainfall (14.5%), and Topographic wetness index (9.9%) were the most important factors which controlled spatial variability of SOC density.  Agronomic practices (e.g., crop straw treatments, fertilizer management) should be optimized for the sustainable development of crop production with high SOC sequestration capacity in Yunnan Province.
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    Long-term straw addition promotes moderately labile phosphorus formation, decreasing phosphorus downward migration and loss in greenhouse vegetable soil
    ZHANG Yin-Jie, GAO Wei, LUAN Hao-an, TANG Ji-wei, LI Ruo-nan, LI Ming-Yue, ZHANG Huai-zhi, HUANG Shao-wen
    2022, 21 (9): 2734-2749.   DOI: 10.1016/j.jia.2022.07.028
    Abstract152)      PDF in ScienceDirect      
    Phosphorus (P) leaching is a major problem in greenhouse vegetable production with excessive P fertilizer application.  Substitution of inorganic P fertilizer with organic fertilizer is considered a potential strategy to reduce leaching, but the effect of organic material addition on soil P transformation and leaching loss remains unclear.  The X-ray absorption near-edge structure (XANES) spectroscopy technique can determine P speciation at the molecular level.  Here, we integrated XANES and chemical methods to explore P speciation and transformation in a 10-year field experiment with four treatments: 100% chemical fertilizer (4CN), 50% chemical N and 50% manure N (2CN+2MN), 50% chemical N and 50% straw N (2CN+2SN), and 50% chemical N and 25% manure N plus 25% straw N (2CN+2MSN).  Compared with the 4CN treatment, the organic substitution treatments increased the content of labile P by 13.7–54.2% in the 0–40 cm soil layers, with newberyite and brushite being the main constituents of the labile P.  Organic substitution treatments decreased the stable P content; hydroxyapatite was the main species and showed an increasing trend with increasing soil depth.  Straw addition (2CN+2SN and 2CN+2MSN) resulted in a higher moderately labile P content and a lower labile P content in the subsoil (60–100 cm).  Moreover, straw addition significantly reduced the concentrations and amounts of total P, dissolved inorganic P (DIP), and particulate P in leachate.  DIP was the main form transferred by leaching and co-migrated with dissolved organic carbon.  Partial least squares path modeling revealed that straw addition decreased P leaching by decreasing labile P and increasing moderately labile P in the subsoil.  Overall, straw addition is beneficial for developing sustainable P management strategies due to increasing labile P in the upper soil layer for the utilization of plants, and decreasing P migration and leaching.

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    Low soil carbon saturation deficit limits the abundance of cbbL-carrying bacteria under long-term no-tillage maize cultivation in northern China
    YIN Tao, QIN Hong-ling, YAN Chang-rong, LIU Qi, HE Wen-qing
    2022, 21 (8): 2399-2412.   DOI: 10.1016/S2095-3119(21)63800-5
    Abstract225)      PDF in ScienceDirect      

    The responses of cbbL-carrying bacteria to different levels of soil carbon saturation deficits (SCSD) under tillage managements are largely unknown.  We assessed the influence of SCSD on the abundance and diversity of cbbL-carrying bacteria under long-term no-tillage with residue retention (NT) and conventional tillage without residue retention (CT) cultivation systems in maize.  We found SCSD was smaller under NT than under CT in the 0–15 cm soil layer.  The abundance and the Shannon diversity of cbbL-carrying bacteria in the NT treatment were lower than in the CT treatment.  Soil carbon saturation and cbbL gene abundance showed a significant positive correlation, but there was no correlation between soil carbon saturation and cbbL gene diversity.  However, the long-term NT practice decreased cbbL-carrying bacteria diversity and altered the community structure of the cbbL-carrying bacteria.  Our results indicated that low SCSD limited the abundance of cbbL-carrying bacteria, but there was no relationship between low SCSD and diversity of cbbL-carrying bacteria.  We suggest that further studies of cbbL-carrying bacteria carbon sequestration rates and capacity should be based on the effect of management practices on cbbL-carrying bacteria abundance and diversity.  Our study has important implications for the relationship between the biological and physicochemical mechanisms in CO2 fixation.

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