Publications by authors named "Xiaozeng Han"

13 Publications

  • Page 1 of 1

Long-term continuous cropping affects ecoenzymatic stoichiometry of microbial nutrient acquisition: a case study from a Chinese Mollisol.

J Sci Food Agric 2021 May 10. Epub 2021 May 10.

Key Laboratory of Mollisols Agroecology, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Harbin, China.

Background: Soil- and plant-produced extracellular enzymes drive nutrient cycling in soils and are assumed to regulate supply and demand for carbon (C) and nutrients within the soil. Thus, agriculture management decisions that alter the balance of plant and supplemental nutrients should directly alter extracellular enzyme activities (EEAs), and EEA stoichiometry in predictable ways. We used a 12-year experiment that varyied three major continuous grain crops (wheat, soybean, and maize), each crossed with mineral fertilizer (WCF, SCF and MCF, respectively) or not fertilized (WC, SC and MC, respectively, as controls). In response, we measured the phospholipid fatty acids (PLFAs), EEAs and their stoichiometry to examine the changes to soil microbial nutrient demand under the continuous cropping of crops, which differed with respect to the input of plant litter and fertilizer.

Results: Fertilizer generally decreased soil microbial biomass and enzyme activity compared to non-fertilized soil. According to enzyme stoichiometry, microbial nutrient demand was generally C- and phosphorus (P)-limited, but not nitrogen (N)-limited. However, the degree of microbial resource limitation differed among the three crops. The enzymatic C:N ratio was significantly lower by 13.3% and 26.8%, whereas the enzymatic N:P ratio was significantly higher by 9.9% and 42.4%, in MCF than in WCF and SCF, respectively. The abundances of arbuscular mycorrhizal fungi and aerobic PLFAs were significantly higher in MCF than in WCF and SCF.

Conclusion: These findings are crucial for characterizing enzymatic activities and their stoichiometries that drive microbial metabolism with respect to understanding soil nutrient cycles and environmental conditions and optimizing practices of agricultural management. © 2021 Society of Chemical Industry.
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http://dx.doi.org/10.1002/jsfa.11304DOI Listing
May 2021

Impacts of land-use changes on the variability of microbiomes in soil profiles.

J Sci Food Agric 2021 Feb 11. Epub 2021 Feb 11.

Key Laboratory of Mollisols Agroecology, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Harbin,, China.

Background: The conversion of arable land to grassland and/or forested land is a common strategy of restoration because the development of plant communities can inhibit the erosion of soil, increase biodiversity and improve associated ecosystem services. The vertical profiles of microbial communities, however, have not been well characterized and their variability after land conversion is not well understood. We assessed the effects of the conversion of arable land (AL) to grassland (GL) and forested land (FL) on bacterial communities as old as 29 years in 0-200-cm profiles of a Chinese Mollisol.

Results: The soil in AL has been a stable ecosystem and changes in the assembly of soil microbiomes tended to be larger in the topsoil. The soil properties and microbial biodiversity of arable land were larger following revegetation and reforestation. The conversion caused a more complex coupling among microbes, and negative interactions and average connectivity were stronger in the 0-20-cm layers in GL and in the 20-60-cm layers in FL. The land use dramatically influenced the assembly of the microbial communities more in GL than AL and FL. The bacterial diversity was an important component of soil multinutrient cycling in the profiles and microbial functions were not as affected by changes in land use.

Conclusion: The spatial variation of the microbiomes provided critical information on below-ground soil ecology and the ability of the soil to provide crucial ecosystem services. © 2021 Society of Chemical Industry.
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http://dx.doi.org/10.1002/jsfa.11150DOI Listing
February 2021

Keystone Microbiomes Revealed by 14 Years of Field Restoration of the Degraded Agricultural Soil Under Distinct Vegetation Scenarios.

Front Microbiol 2020 18;11:1915. Epub 2020 Aug 18.

National Observation Station of Hailun Agro-Ecology System, Key Laboratory of Mollisols Agroecology, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Harbin, China.

Agricultural intensification accelerates the degradation of cropland, and restoration has been managed by changing its vegetation. However, the keystone microbiome that drives the decomposition of plant-associated organic matter in the restoration is poorly understood. In this study, we established a 14-year field restoration experiment on a degraded cropland with four treatments: (1) bare land soil without biomass input (BL), (2) maize cropland (CL) without fertilization and biomass input, (3) natural grassland (GL), and (4) alfalfa cropland (AL) with biomass left in the fields. The activity of total soil microbiome was assessed by community-level physiological profiling (CLPP) with Biolog EcoPlates analysis, and keystone microbiome was identified as phylotypes showing statistically significant increase in the restored soils (GL and AL) relative to the degraded BL soil. The results showed that GL and AL treatments improved soil fertility as indicated by significant increase in soil organic carbon, total nitrogen, and available phosphorus when compared to BL treatment. The significant difference was not observed between CL and BL treatments except for pH and available phosphorus, indicating that the input and microbial decomposition of plant-associated organic matter were the key for restoration of soil fertility. Similar results were obtained for soil microbial activities of carbon utilization efficiency via CLPP analysis, and real-time quantitative polymerase chain reaction of 16S rRNA genes further revealed significantly higher abundance of total soil microbial community in GL and AL soils than in BL and CL. High-throughput sequencing of total 16S rRNA genes revealed the Bacteroidetes as the only keystone taxa at phylum level, and 106 and 120 genera were keystone phylotypes. Compared with BL and CL, the genera that increase significantly in GL and AL are called keystone genera of ecological restoration. The dominant keystone genera included , , , , , and . Significantly higher abundance of genus in BL soil implied it might serve as an indicator of agricultural land degradation. Statistical analysis showed that soil organic carbon and pH were significantly correlated with the input of plant-associated organic matters and dynamic changes of keystone taxa. These results suggest that the vegetation of natural grass (GL) and alfalfa plant (AL) and subsequent decomposition of plant-associated materials could serve as effective strategies for restoration of the degraded cropland by stimulating the keystone microbiomes and improving their physiological metabolisms of carbon utilization efficiency.
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http://dx.doi.org/10.3389/fmicb.2020.01915DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7461875PMC
August 2020

31-year contrasting agricultural managements affect the distribution of organic carbon in aggregate-sized fractions of a Mollisol.

Sci Rep 2020 06 3;10(1):9041. Epub 2020 Jun 3.

Key Laboratory of Mollisols Agroecology, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Harbin, 150081, P.R. China.

Evaluation of soil organic carbon (SOC) dynamics is often limited by the complexity of soil matrix. Quantitative information on the distribution of SOC within aggregate hierarchy will help elucidate the carbon flow in soil matrix. However, this knowledge still needs to be documented. Soils were sampled from a surface Mollisol with plots under 100 years of continuous cropping, 31 years of simulated overgrazing to severely degraded bareland, and grassland restoration from cropped soil. A combined density and chemical fractionation procedure within water-stable aggregate was utilized to quantify the distribution of OC after long-term different land use patterns. Results showed that grassland significantly increased total SOC and mean aggregate associated OC compared to initial soil in 1985 with total SOC (g kg soil) from 46.1 to 31.7 and mean aggregate associated OC (g kg aggregate) from 31.6 to 44.7. Converting cropland to grassland also enhanced the formation of macroaggregates (>0.25 mm) (from 34.7% to 52.2%) and increased the OC concentrations in density and humic fractions by 48.3%-75.9% within aggregates. But the proportions of OC in density and humic fractions to SOC only increased in macroaggregates in grassland. Alternatively, converting cropland to bareland caused substantial depletion of total SOC, macroaggregates and their associated OC concentrations. The SOC (g kg soil) and mean aggregate associated OC (g kg aggregate) significantly decreased from 31.7 to 25.7 and from 31.6 to 26.2, respectively. While the OC concentration of density and humic fractions within aggregates in bareland did not show significant decreases. Principal component analysis demonstrated that the soils were developed by contrasting land use changes, with the grassland soil being more associated with labile OC fractions within macroaggregats and bareland soil more associated with recalcitrant OC fractions within microaggregates and silt-clay units. These findings highlighted the favorable preservation of plant-derived carbon within soil aggregates, particularly in the labile OC fractions within macroaggregates under high plant inputs with 31 years of grassland conversion. For the cropland and bareland soils without organic inputs, more OC was stabilized within fine aggregates via organo-mineral interactions, tending to be more recalcitrant.
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http://dx.doi.org/10.1038/s41598-020-66038-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7271157PMC
June 2020

Response of Soil Fungal Community Structure to Long-Term Continuous Soybean Cropping.

Front Microbiol 2018 9;9:3316. Epub 2019 Jan 9.

National Observation Station of Hailun Agro-ecology System, Key Laboratory of Mollisols Agroecology, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Harbin, China.

Long-term continuous soybean cropping can lead to the aggravation of soil fungal disease. However, the manner in which the fungal community and functional groups of fungi are affected by continuous soybean cropping remains unclear. We investigated the fungal abundance, composition and diversity during soybean rotation (RS), 2-year (SS) and long-term (CS) continuous soybean cropping systems using quantitative real-time PCR and high-throughput sequencing. The results showed that the fungal abundance was significantly higher in CS than in SS and RS. CS altered the fungal composition. Compared with RS, SS had an increase of 29 and a decrease of 12 genera in fungal relative abundance, and CS increased 38 and decreased 17 genera. The Shannon index was significantly higher in CS and SS than in RS. The result of principal coordinate analysis (PCoA) showed that CS and SS grouped together and were clearly separated from RS on the PCoA1. A total of 32 features accounted for the differences in fungal composition across RS, SS, and CS. The relative abundance of 10 potentially pathogenic and 10 potentially beneficial fungi changed, and most of their relative abundances dramatically increased in SS and CS compared with RS. Our study indicated that CS results in selective stress on pathogenic and beneficial fungi and causes the development of the fungal community structure that is antagonistic to plant health.
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http://dx.doi.org/10.3389/fmicb.2018.03316DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6333693PMC
January 2019

Removal of ciprofloxacin from aqueous solutions by ionic surfactant-modified carbon nanotubes.

Environ Pollut 2018 Dec 24;243(Pt A):206-217. Epub 2018 Aug 24.

Stockbridge School of Agriculture, University of Massachusetts, Amherst, MA, 01003, USA. Electronic address:

Ionic surfactants may impact removal efficiency of organic contaminants from aqueous solution, but research regarding the adsorption mechanisms on surfactant-modified carbon nanotubes (CNTs) was limited. In this study, three multi-walled and one single-walled CNTs were used as adsorbents to investigate the adsorption behavior and mechanisms of ciprofloxacin (CIP) on CNTs modified by ionic surfactants (cationic CTAB (Cetyltrimethylamnonium bromide) or anionic SDS (Sodium dodecyl sulfate)). More than 80% (82-88%) of the total removed CIP on CTAB-modified CNTs occurred within the first 6 h, much higher than that on SDS-modified CNTs (57-78%). Modeling adsorption kinetics demonstrated that CIP adsorption on surfactant-modified CNTs was controlled by multiple and faster processes, and both external mass transfer and intraparticle diffusion are limiting factors. Relative to SDS, CTAB was significantly (P < 0.001) concentration-dependent in suppressing CIP removal. Besides, the increase in 1/n values of Freundlich model with increasing CTAB concentration suggested that CTAB could be a stronger competitor for CIP adsorption. Hydrophobic interactions predominated zwitterionic CIP adsorption on all CNTs tested, while electrostatic interactions could help control ionizable CIP adsorption on surfactant-modified CNTs depending upon pH. CIP adsorption on modified SWCNTs significantly declined with increasing ionic strength from 1 mM to 100 mM relative to those multi-walled CNTs because the more favorable aggregation of SWCNTs reduced the CIP adsorption, irrespective of which surfactant was added. Significant desorption hysteresis of adsorbed CIP released by SDS and water was observed, but not by CTAB, by which 32.6-54.4% of adsorbed CIP were removed. For SDS-modified CNTs, the mean release ratio (RR) followed an order of MWCNTs (0.075) > MHCNTs (0.058) > SWCNTs (0.057) > MCCNTs (0.049), significantly (P < 0.001) lower than CTAB-CNTs (0.37-0.56). It can be predicted that the tested surfactants co-existing with CNTs depress removal efficiency of diverse contaminants similar to CIP in aqueous systems.
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http://dx.doi.org/10.1016/j.envpol.2018.08.059DOI Listing
December 2018

Priming effects on labile and stable soil organic carbon decomposition: Pulse dynamics over two years.

PLoS One 2017 21;12(9):e0184978. Epub 2017 Sep 21.

Key Laboratory of Forest Ecology and Management, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, China.

Soil organic carbon (SOC) is a major component in the global carbon cycle. Yet how input of plant litter may influence the loss of SOC through a phenomenon called priming effect remains highly uncertain. Most published results about the priming effect came from short-term investigations for a few weeks or at the most for a few months in duration. The priming effect has not been studied at the annual time scale. In this study for 815 days, we investigated the priming effect of added maize leaves on SOC decomposition of two soil types and two treatments (bare fallow for 23 years, and adjacent old-field, represent stable and relatively labile SOC, respectively) of SOC stabilities within each soil type, using a natural 13C-isotope method. Results showed that the variation of the priming effect through time had three distinctive phases for all soils: (1) a strong negative priming phase during the first period (≈0-90 days); (2) a pulse of positive priming phase in the middle (≈70-160 and 140-350 days for soils from Hailun and Shenyang stations, respectively); and (3) a relatively stabilized phase of priming during the last stage of the incubation (>160 days and >350 days for soils from Hailun and Shenyang stations, respectively). Because of major differences in soil properties, the two soil types produced different cumulative priming effects at the end of the experiment, a positive priming effect of 3-7% for the Mollisol and a negative priming effect of 4-8% for the Alfisol. Although soil types and measurement times modulated most of the variability of the priming effect, relative SOC stabilities also influenced the priming effect for a particular soil type and at a particular dynamic phase. The stable SOC from the bare fallow treatment tended to produce a narrower variability during the first phase of negative priming and also during the second phase of positive priming. Averaged over the entire experiment, the stable SOC (i.e., the bare fallow) was at least as responsive to priming as the relatively labile SOC (i.e., the old-field) if not more responsive. The annual time scale of our experiment allowed us to demonstrate the three distinctive phases of the priming effect. Our results highlight the importance of studying the priming effect by investigating the temporal dynamics over longer time scales.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0184978PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5608328PMC
October 2017

Improving soil nutrient availability increases carbon rhizodeposition under maize and soybean in Mollisols.

Sci Total Environ 2017 Dec 23;603-604:416-424. Epub 2017 Jun 23.

Department of Animal, Plant & Soil Sciences, Centre for AgriBioscience, La Trobe University (Melbourne Campus), Bundoora, Vic 3086, Australia. Electronic address:

Rhizodeposited carbon (C) is an important source of soil organic C, and plays an important role in the C cycle in the soil-plant-atmosphere continuum. However, interactive effects of plant species and soil nutrient availability on C rhizodeposition remain unclear. This experiment examined the effect of soil nutrient availability on C rhizodeposition of C4 maize and C3 soybean with contrasting photosynthetic capacity. The soils (Mollisols) were collected from three treatments of no fertilizer (Control), inorganic fertilizer only (NPK), and NPK plus organic manure (NPKM) in a 24-year fertilization field trial. The plants were labelled with C at the vegetative and reproductive stages. The C abundance of shoots, roots and soil were quantified at 0, 7days after C labelling, and at maturity. Increasing soil nutrient availability enhanced the C rhizodeposition due to the greater C fixation in shoots and distribution to roots and soil. The higher amount of averaged below-ground C allocated to soil resulted in greater specific rhizodeposited C from soybean than maize. Additional organic amendment further enhanced them. As a result, higher soil nutrient availability increased total soil organic C under both maize and soybean systems though there was no significant difference between the two crop systems. All these suggested that higher soil nutrient availability favors C rhizodeposition. Mean 80, 260 and 300kgfixedCha were estimated to transfer into soil in the Control, NPK and NPKM treatments, respectively, during one growing season.
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http://dx.doi.org/10.1016/j.scitotenv.2017.06.090DOI Listing
December 2017

Genetic diversity of indigenous soybean-nodulating rhizobia in response to locally-based long term fertilization in a Mollisol of Northeast China.

World J Microbiol Biotechnol 2017 Jan 15;33(1). Epub 2016 Nov 15.

Key Laboratory of Mollisols Agroecology, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Harbin, 150081, China.

The influences of five different fertilizer treatments on diversity of rhizobia in soybean nodule were investigated in a long-term experiment with with four replicates: (1) control (without fertilization), (2) balanced NPK fertilizer (NPK), and (3-5) unbalanced chemical fertilizers without one of the major elements (NP, PK, and NK) in Mollisol in Northeast China. The highest soybean yield was observed in the NPK treatment. Total of 200 isolates were isolated and grouped into four Bradyrhizobium genospecies corresponding to B. japonicum, B. diazoefficiens, B. ottawaense and Bradyrhizobium sp. I, based upon the multilocus sequence analysis of 6 housekeeping genes. The Bradyrhizobium sp. I was extensively distributed throughout the study site and was recorded as the dominant soybean rhizobia (82.5-87.5%). Except the NK treatment, the other fertilizer treatments had no effect on rhizobial species composition. Compared with the CK treatment, all the fertilizer treatments decreased species richness, diversity and evenness. The soil organic carbon contents, available N content and pH were the key soil factors to rhizobial community structure. Results suggest that long-term fertilization can decrease rhizobial species diversity, while balanced fertilization with NPK is the most suitable fertilization regime if taking both soybean yields and rhizobial diversity into account.
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http://dx.doi.org/10.1007/s11274-016-2170-9DOI Listing
January 2017

Frozen cropland soil in northeast China as source of N2O and CO2 emissions.

PLoS One 2014 23;9(12):e115761. Epub 2014 Dec 23.

Department of Land, Air and Water Resources, University of California Davis, Davis, California, United States of America.

Agricultural soils are important sources of atmospheric N2O and CO2. However, in boreal agro-ecosystems the contribution of the winter season to annual emissions of these gases has rarely been determined. In this study, soil N2O and CO2 fluxes were measured for 6 years in a corn-soybean-wheat rotation in northeast China to quantify the contribution of wintertime N2O and CO2 fluxes to annual emissions. The treatments were chemical fertilizer (NPK), chemical fertilizer plus composted pig manure (NPKOM), and control (Cont.). Mean soil N2O fluxes among all three treatments in the winter (November-March), when soil temperatures are below -7°C for extended periods, were 0.89-3.01 µg N m(-2) h(-1), and in between the growing season and winter (October and April), when freeze-thaw events occur, 1.73-5.48 µg N m(-2) h(-1). The cumulative N2O emissions were on average 0.27-1.39, 0.03-0.08 and 0.03-0.11 kg N2O_N ha(-1) during the growing season, October and April, and winter, respectively. The average contributions of winter N2O efflux to annual emissions were 6.3-12.1%. In all three seasons, the highest N2O emissions occurred in NPKOM, while NPK and Cont. emissions were similar. Cumulative CO2 emissions were 2.73-4.94, 0.13-0.20 and 0.07-0.11 Mg CO2-C ha(-1) during growing season, October and April, and winter, respectively. The contribution of winter CO2 to total annual emissions was 2.0-2.4%. Our results indicate that in boreal agricultural systems in northeast China, CO2 and N2O emissions continue throughout the winter.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0115761PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4275265PMC
April 2016

Adsorption of antibiotic ciprofloxacin on carbon nanotubes: pH dependence and thermodynamics.

Chemosphere 2014 Jan 2;95:150-5. Epub 2013 Oct 2.

College of Plant Sciences, Jilin University of Agricultural Science & Technology, Jilin 132101, China; Stockbridge School of Agriculture, University of Massachusetts, Amherst, MA 01003, USA.

The environmental risks of antibiotics have attracted increasing research attention, but their environmental behaviors remain unclear. In this study, functionalized carbon nanotubes (CNTs), namely, hydroxylized (MH), carboxylized (MC), graphitized multi-walled CNTs (MG) and single-walled CNTs (SW) were used as adsorbents and ciprofloxacin (CIP) as an adsorbate to investigate the effect of pH and temperature on sorption and desorption processes. Sorption isotherms of CIP were fitted well by Freundlich and Dubinin-Ashtakhov models. Highly nonlinear isotherms of CIP were observed, indicating the highly heterogeneous site energy distribution on CNTs. At all pHs, SW had the highest sorption for CIP due to its largest surface area among all CNTs. Sorption distinction between MH and MC was explained by π-π electron donor-acceptor interactions. For SW, CIP sorption was thermodynamically favorable and endothermic associated with an entropy driven process, while the reverse process occurred for MC and MG. The rearrangement of CNTs bundles/aggregates and covalent bond formation may be responsible for CIP desorption hysteresis on CNTs. Desorption of antibiotics from CNTs may lead to potential exposure, particularly under changing environmental conditions such as temperature and pH.
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http://dx.doi.org/10.1016/j.chemosphere.2013.08.053DOI Listing
January 2014

[Fate of fertilizer nitrogen in paddy field of black soil region].

Ying Yong Sheng Tai Xue Bao 2003 Nov;14(11):1859-62

Northeast Institute of Geography and Agricultural Ecology, Chinese Academy of Sciences, Harbin 150040, China.

Taking the N application rate, method and main varieties applied in paddy field of black soil in Northeast China as the parameters, a micro-plot tracer isotope trial and a normal urea plot trial were conducted for two years to study the fate of fertilizer nitrogen in paddy field. The results showed that 22.2%-46.1% of applied chemical fertilizer nitrogen was absorbed and remained in the paddy plant, and averaged 37.68%. About 12.7% to 25.4% of applied N during the same year was remained in the soil. The determined nitrogen losses rate through ammonia volatilization in a closed chamber system was 19.0%-44.2%. The use efficiency of chemical fertilizer N was influenced by the application method. Higher use efficiency would be obtained with deeper or mixing application method. The amount of nitrogen remained in soil were related to the application method, and the remained rate was increased with the amount and application depth increasing. The experiment with 15N showed that no 15N residue was detected below 80 cm in depth, which was because the heavy texture of the black soil. The results of the tracer isotope trial and the plot experiments showed that there was a rough balance between the amount of residual nitrogen in soil and the priming effect from chemical fertilizer nitrogen.
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November 2003

[Changes of crop yield and soil fertility under long-term application of fertilizer and recycled nutrients in manure on a black soil III. Soil nutrient budget].

Ying Yong Sheng Tai Xue Bao 2002 Nov;13(11):1410-2

Heilongjiang Institute of Agricultural Modernization, Chinese Academy of Sciences, Harbin 150040.

The nutrient budget of fertilization models under different treatments was calculated using data from a field experiment over the period of 1985-1999. The results indicated that application of nitrogen fertilizer accelerated a large deficit of soil phosphorus, and the use of nitrogen and phosphorus accelerated the deficit of potassium. The experimental data demonstrated the appearance of a large area of soil deficit of phosphorus from 1970s and of potassium from 1980s in China. Nutrient recycled in farming system improved soil nutrient budget, but could not meet the nutrient requirements from high-yield crops. The use of recycled nutrients with an appropriate use of fertilizers according to the soil fertility could produce higher crop yields, balance soil nutrient budget, and not cause surplus nutrients to emit into environment.
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November 2002