Changing soil available substrate primarily caused by fertilization management contributed more to soil respiration temperature sensitivity than microbial community thermal adaptation.

Substrate depletion and microbial community thermal adaptation are major mechanisms that regulate the temperature sensitivity (Q10) of soil microbial respiration. Traditionally, the Q10 of soil microbial respiration is measured using laboratory incubation, which has limits in the continuous input of available substrates and the time scale for microbial community thermal adaptation. How the available substrate and the soil microbial community regulate the Q10 of soil microbial respiration under natural warming conditions remains unclear. To fill this gap in knowledge, a long-term field experiment was conducted consisting of two years of soil respiration observations combined with a soil available substrate and microbial community thermal adaptation analysis under seasonal warming conditions. The Q10 of soil respiration was calculated using the square root method, and it was more affected by the available substrate than by microbial community thermal adaptation. Fertilization management has a stronger effect on soil available substrate than temperature. As the temperature increased, NH4-N proved itself to be important for the bacterial community in the process of Q10 regulation, while dissolved organic carbon and nitrogen were key factors for the fungal community. Based on the niche breadth of microbial community composition, the changing Q10 of the soil respiration was not only closely associated with the specialist community, but also the generalist and neutralist communities. Furthermore, bacterial community thermal adaptation primarily occurred through shifts in the abundances of specialists and neutralists, while changes in species richness and species replacement occurred for the fungal generalists and neutralists. This work indicates that changing available nitrogen and DOC primarily caused by fertilization management contributed more in regulating the Q10 of soil microbial respiration than microbial community thermal adaptation, and there are different mechanisms for bacterial and fungal community thermal adaptation under warming.

G-quadruplex in the TMV Genome Regulates Viral Proliferation and Acts as Antiviral Target of Photodynamic Therapy.

Plant viruses seriously disrupt crop growth and development, and classic protein-targeted antiviral drugs could not provide complete protection against them. It is urgent to develop antiviral compounds with novel targets. Photodynamic therapy shows potential in controlling agricultural pests, but nonselective damage from reactive oxygen species (ROS) unexpectedly affects healthy tissues. A G-quadruplex (G4)-forming sequence in the tobacco mosaic virus (TMV) genome was identified to interfere the RNA replication in vitro, and affect the proliferation of TMV in tobacco. N-methyl mesoporphyrin IX stabilizing the G4 structure exhibited inhibition against viral proliferation, which was comparable to the inhibition effect of ribavirin. This indicated that G4 could work as an antiviral target. The large conjugate planes shared by G4 ligands and photosensitizers (PSs) remind us that the PSs could work as antiviral agents by targeting G4 in the genome of TMV. Chlorin e6 (Ce6) was identified to stabilize the G4 structure in the dark and selectively cleave the G4 sequence by producing ROS upon LED-light irradiation, leading to 92.2% inhibition against TMV in vivo, which is higher than that of commercial ningnanmycin. The inhibition of Ce6 was lost against the mutant variants lacking the G4-forming sequence. These findings indicated that the G-quadruplex in the TMV genome worked as an important structural element regulating viral proliferation, and could act as the antiviral target of photodynamic therapy.

Brincidofovir is a robust replication inhibitor against African swine fever virus in vivo and in vitro.

African swine fever virus (ASFV) infection is a major public and socioeconomic concern that has a serious impact on the global swine industry. Unfortunately, there are currently no commercially available vaccines or antiviral agents that are both safe and effective against ASFV. In the study, we use primary porcine alveolar macrophages to screen a kinase inhibitor library for anti-ASFV compounds. Six candidate compounds that inhibited ASFV infection with inhibition of > 90% were identified, among which brincidofovir exhibited optimal inhibitory effects on ASFV. Brincidofovir reduces ASFV replication in a dose-dependent manner (IC50 = 2.76 nM) without cytotoxicity (CC50 = 58 µM). It possesses the ability to reduce viral titres and inhibit viral structural protein expression. Time-of-addition assays suggest that the compound interferes with the post-invasion stage of the viral infection cycle. In pig challenge experiments, brincidofovir was indicated to protect pigs against ASFV-induced lethality by decreasing the viral load in organs and peripheral blood, while it alleviated the histopathological changes associated with ASFV infection. Furthermore, brincidofovir also decreased viral shedding in pigs with ASFV infection. Our data together demonstrate that brincidofovir may serve as a potentially effective agent for the prevention and control of ASFV infection, whereas further investigations are still required.

Long-term chemical fertilization results in a loss of temporal dynamics of diazotrophic communities in the wheat rhizosphere.

Diazotrophs are potential bacterial biofertilizers with efficacy for plant nutrition, which convert atmospheric N2 into plant available nitrogen. Although they are known to respond strongly to fertilization, little is known about the temporal dynamics of diazotrophic communities throughout plant developmental under different fertilization regimes. In this study, we investigated diazotrophic communities in the wheat rhizosphere at four developmental stages under three long-term fertilization regimes: no fertilizer (Control), chemical NPK fertilizer only (NPK), and NPK fertilizer plus cow manure (NPKM). Fertilization regime had greater effect (explained of 54.9 %) on diazotrophic community structure than developmental stage (explained of 4.8 %). NPK fertilization decreased the diazotrophic diversity and abundance to one-third of the Control, although this was largely recovered by the addition of manure. Meanwhile, Control treatment resulted in significant variation in diazotrophic abundance, diversity, and community structure (P = 0.001) depending on the developmental stage, while the NPK fertilization resulted in the loss of temporal dynamics of the diazotrophic community (P = 0.330), which could be largely recovered by the addition of manure (P = 0.011). Keystone species identified in this study were quite different among the four developmental stages under Control and NPKM treatment but were similar among stages under NPK treatment. These findings suggest that long-term chemical fertilization not only reduces diazotrophic diversity and abundance, but also results in a loss of temporal dynamics of rhizosphere diazotrophic communities.

Open access databases available for the pesticide lead discovery.

Pesticide research is a multi-disciplinary collaborative study, and big data analysis based on integrating information from databases benefits decision-making in pesticide research. In the last 40 years, dozens of pesticide-related databases have been built up to describe their biological activities, toxicity, modes of action, and environmental risks, etc. However, these data are scattered and overlapping in different databases in multiple inconsistent formats, which is not convenient for information analysis and comparison. In this study, the content of 26 open access databases related to pesticide research was illustrated according to the information provided for the ligand-based drug design (LBDD) and receptor-based (or structure-based drug design, SBDD), and was summarized into three categories:1) the correspondence between the chemical structures and functional properties (biological activity, resistance, toxicity, environmental adaptation); 2) action mode study (target identification, target structures, and biological pathways); 3) computational servers for pesticide design. To our knowledge, this is the first review about the open access databases for pesticide research. The data classification could facilitate the information accessibility for pesticide research, and speed up the decision-making process in pesticide discovery.

Root stoichiometry explains wheat endophytes and their link with crop production after four decades of fertilization.

Fertilization can impact root endophytic microbiomes and food production. However, the impacts of decades of continued fertilization on root microbiomes, and their link with ongoing crop production, remain poorly understood. Here, we used a four decade-long fertilization experiment, including contrasting types of organic and inorganic fertilization, to investigate the effects of long-term fertilization on multi-kingdom root endophytic microbiomes, including keystone species (modules within microbial networks), and their indirect associations with the production of wheat, which is one of the most important crops worldwide. We found that long-term inorganic (nitrogen, phosphorus, potassium (NPK)) and organic (NPK with straw (NPKS) and NPK with cow manure (NPKM)) fertilization had significant impacts on the community composition of endophytic arbuscular mycorrhizal fungi (AMF), bacteria, and non-mycorrhizal fungi. In addition, compared with NPK fertilization, NPKS and NPKM amendments significantly decreased the microbial network complexity, which was associated with changes in the root iron content. Finally, we identified an important subset of keystone root endophyte species within the microbial network (Module #2), which was positively correlated with wheat yield, and affected by changes in root carbon to phosphorus ratio. This study provides evidence that long-term fertilization can affect keystone root endophytic species in the root microbiome, with implications for food security in an over-fertilized world.

Phosphorus and Zinc Are Strongly Associated with Belowground Fungal Communities in Wheat Field under Long-Term Fertilization.

Belowground fungi are closely related to crop growth, and agricultural fertilization is widely known to affect soil fungal communities. Yet it remains unclear whether fungal communities in differing belowground habitats-root endosphere, rhizosphere soil, and bulk soil-respond differently to long-term fertilization. Here we investigated the variation in fungal communities of root endosphere, rhizosphere soil, and bulk soil under 35 years of fertilization in wheat fields. Specifically, the fertilization regimes were applied as five treatments: soils receiving NPK fertilizer, NPK and cow manure (NPK+CM), NPK and pig manure (NPK+PM), NPK and wheat straw (NPK+WS), and no fertilizer (Control). Long-term fertilization significantly impacted fungal community composition in all three habitats, and these effects were stronger in the rhizosphere and bulk soils than root endosphere. Mantel test results showed that fungal community composition was significantly correlated with phosphorus and zinc contents. Further, fungal alpha diversity was lowest in the NPK+PM treatment and was negatively correlated with both phosphorus and zinc contents. Moreover, NPK+PM treatment had the lowest complexity of fungal co-occurrence network, and in general network complexity was significantly negatively correlated with the zinc and phosphorus contents. Taken together, these results suggest that long-term fertilization can impact fungal communities not only in soils but in root endosphere, and this is strongly associated with the contents of phosphorus and zinc there, a finding important for guiding fertilization management practices and supporting sustainable agriculture. IMPORTANCE Fungi, an essential component in nutrient cycling and plant growth, are highly sensitive to fertilization. However, there are limited studies on fungi in root endosphere under long-term fertilization management. Our research extended the study on the endophytic fungal community of crop roots under agricultural management and found that its responses were similar to the communities in soil habitats. In addition, the type of organic materials was reported as the main driver affecting soil fungal community under long-term fertilization. Our research further revealed that the underlying mechanism of affecting the fungal communities in the soils and roots was the differences in phosphorus and zinc contents caused by the application of different organic materials. Therefore, our results highlight that except for phosphorus, zinc content of the organic materials should be considered in long-term organic fertilization systems.

Differential Responses of Arbuscular Mycorrhizal Fungal Communities to Long-Term Fertilization in the Wheat Rhizosphere and Root Endosphere.

Arbuscular mycorrhizal fungi (AMF) provide essential nutrients to crops and are critically impacted by fertilization in agricultural ecosystems. Understanding shifts in AMF communities in and around crop roots under different fertilization regimes can provide important lessons for improving agricultural production and sustainability. Here, we compared the responses of AMF communities in the rhizosphere (RS) and root endosphere (ES) of wheat (Triticum aestivum) to different fertilization treatments, nonfertilization (control), mineral fertilization only (NPK), mineral fertilization plus wheat straw (NPKS), and mineral fertilization plus cow manure (NPKM). We employed high-throughput amplicon sequencing and investigated the diversity, community composition, and network structure of AMF communities to assess their responses to fertilization. Our results elucidated that AMF communities in the RS and ES respond differently to fertilization schemes. Long-term NPK application decreased the RS AMF alpha diversity significantly, whereas additional organic amendments (straw or manure) had no effect. In contrast, NPK fertilization increased the ES AMF alpha diversity significantly, while additional organic amendments decreased it significantly. The effect of different fertilization schemes on AMF network complexity in the RS and ES were similar to their effects on alpha diversity. Changes to AMF communities in the RS and ES correlated mainly with the pH and phosphorus level of the rhizosphere soil under long-term inorganic and organic fertilization regimes. We suggest that the AMF community in the roots should be given more consideration when studying the effects of fertilization regimes on AMF in agroecosystems. IMPORTANCE Arbuscular mycorrhizal fungi are an integral component of rhizospheres, bridging the soil and plant systems and are highly sensitive to fertilization. However, surprisingly little is known about how the response differs between the roots and the surrounding soil. Decreasing arbuscular mycorrhizal fungal diversity under fertilization has been reported, implying a potential reduction in the mutualism between plants and arbuscular mycorrhizal fungi. However, we found opposing responses to long-term fertilization managements of arbuscular mycorrhizal fungi in the wheat roots and rhizosphere soil. These results suggested that changes in the arbuscular mycorrhizal fungal community in soils do not reflect those in the roots, highlighting that the root arbuscular mycorrhizal fungal community is pertinent to understand arbuscular mycorrhizal fungi and their crop hosts' responses to anthropogenic influences.

Biodiversity of key-stone phylotypes determines crop production in a 4-decade fertilization experiment.

Cropping systems have fertilized soils for decades with undetermined consequences for the productivity and functioning of terrestrial ecosystems. One of the critical unknowns is the role of soil biodiversity in controlling crop production after decades of fertilization. This knowledge gap limits our capacity to assess how changes in soil biodiversity could alter crop production and soil health in changing environments. Here, we used multitrophic ecological networks to investigate the importance of soil biodiversity, in particular, the biodiversity of key-stone taxa in controlling soil functioning and wheat production in a 35-year field fertilization experiment. We found strong and positive associations between soil functional genes, crop production and the biodiversity of key-stone phylotypes; soils supporting a larger number of key-stone nematode, bacteria and fungi phylotypes yielded the highest wheat production. These key-stone phylotypes were also positively associated with plant growth (phototrophic bacteria, nitrogen fixers) and multiple functional genes related to nutrient cycling. The retrieved information on the genomes clustered with key-stone bacterial phylotypes indicated that the key-stone taxa had higher gene copies of oxidoreductases (participating most biogeochemical cycles of ecosystems and linking to microbial energetics) and 71 essential functional genes associated with carbon, nitrogen, phosphorus, and sulfur cycling. Altogether, our work highlights the fundamental role of the biodiversity of key-stone phylotypes in maintaining soil functioning and crop production after several decades of fertilization, and provides a list of key-stone phylotypes linking to crop production and soil nutrient cycling, which could give science-based guidance for sustainable food production.

Suppressed N fixation and diazotrophs after four decades of fertilization.

BACKGROUND: N fixation is one of the most important microbially driven ecosystem processes on Earth, allowing N to enter the soil from the atmosphere, and regulating plant productivity. A question that remains to be answered is whether such a fundamental process would still be that important in an over-fertilized world, as the long-term effects of fertilization on N fixation and associated diazotrophic communities remain to be tested. Here, we used a 35-year fertilization experiment, and investigated the changes in N fixation rates and the diazotrophic community in response to long-term inorganic and organic fertilization. RESULTS: It was found that N fixation was drastically reduced (dropped by 50%) after almost four decades of fertilization. Our results further indicated that functionality losses were associated with reductions in the relative abundance of keystone and phylogenetically clustered N fixers such as Geobacter spp. CONCLUSIONS: Our work suggests that long-term fertilization might have selected against N fixation and specific groups of N fixers. Our study provides solid evidence that N fixation and certain groups of diazotrophic taxa will be largely suppressed in a more and more fertilized world, with implications for soil biodiversity and ecosystem functions.

Divergent responses of bacterial activity, structure, and co-occurrence patterns to long-term unbalanced fertilization without nitrogen, phosphorus, or potassium in a cultivated vertisol.

Unbalanced fertilization lacking nitrogen (N), phosphorus (P), or potassium (K) is a worldwide phenomenon; however, whether they affect bacterial community composition and intraspecific interactions in a similar pattern and how they affect bacterial activity are not systematically compared. Soils under different kinds of unbalanced fertilization in a 21-year field experiment were collected to investigate the variation in dehydrogenase activity (DHA), bacterial community diversity, structure, composition, and possible interactions. Compared to the balanced fertilization of NPK, the DHA from unbalanced fertilization of NP, PK, and NK was 8.70, 11.59, and 14.17% lower, respectively, and from the unfertilized treatment (Nil) was 13.41% lower; however, the Shannon index from NP, PK, and Nil was 4.48-7.21% higher and from NK was 3.95% lower. Based on principal coordinate analyses (PCoA), bacterial community structure was separated by N application or not along PCo1 and was further separated by P application or not along PCo2, indicating a more influence by N deficiency. Moreover, the structure was mainly determined by soil pH, soil organic carbon (SOC), and total phosphorus (TP). The network complexity using co-occurrence analysis followed the order NP > NPK > PK > NK > Nil, indicating a more influence by P deficiency on intraspecific interactions. Structural equation modeling (SEM) revealed that the reduced DHA in NP was mainly regulated by the decreased SOC and increased Shannon index, in PK by the decreased SOC and increased Shannon index and pH, and in NK by the decreased SOC and TP and increased PCo2. The significantly lower abundance of Bacteroidetes and Chitinophagaceae in NK may also contribute to the reduced DHA. Our results imply that N deficiency had the greatest impact on bacterial community structure and composition, P deficiency had the greatest impact on network construction and bacterial activity, and K deficiency has minimal effect. Our results also suggest that main factors regulating the variation in soil functions may vary among different nutrient deficiencies.

The effect of 34-year continuous fertilization on the SOC physical fractions and its chemical composition in a Vertisol.

Reports regarding the effects of long-term organic and inorganic fertilization on the quantity and quality of soil organic carbon (SOC), particularly in Vertisols, are scarce. In this study, we combined SOC physical fractionation with 13C NMR spectroscopy technology to investigate the effect of 34 years of continuous fertilization on the SOC physical fractions and its chemical composition of 0-20 cm soil layer in a Vertisol. This study consisted of six treatments: no fertilization (control), chemical nitrogen, phosphorus and potassium fertilizers (NPK), low and high amounts of straw with chemical fertilizers (NPKLS and NPKHS), and pig or cattle manure with chemical fertilizers (NPKPM and NPKCM). Over 34 years of continuous fertilization, the SOC sequestration rate was from 0.08 Mg C ha-1 yr-1 in the control treatment to 0.66 Mg C ha-1 yr-1 in the NPKCM treatment, which was linearly related with the C input (P < 0.01). Of the five SOC physical fractions, two silt plus clay fractions (S + C_M, S + C_mM) dominated 74-92% of SOC, while three POM fractions (cPOM fPOM and iPOM) were only 8-26%. The two manure application treatments significantly increased all the SOC physical fractions except for the silt plus clay fraction within macroaggregates (S + C_M) compared with NPK treatment (P < 0.05), which was dependent on the larger amount of C input. Also, the two manure application treatments increased the levels of alkyl C and aromatic C but decreased O-alkyl C (P < 0.05), whereas the straw application (NPKLS and NPKHS) had no impact on the C functional groups (P > 0.05). Overall, the combination of animal manure with inorganic fertilization could enhance the SOC sequestration and alter its quantity and quality in Vertisols.

Does animal manure application improve soil aggregation? Insights from nine long-term fertilization experiments.

Manure application is widely recognized as a method of improving soil structure and soil fertility due to additional organic matter and nutrient inputs. However, the salinity of animal manure may have a detrimental effect on soil aggregation. The objective of this study was to determine the effects of long-term animal manure application on soil aggregation, binding agents (soil organic carbon, SOC and glomalin-related soil protein, GRSP), and dispersing agents (e.g., Na+) and their relationships based on nine long-term fertilization experiments (12 to 39 yr) across China. The two red soil experiments (Qiyang, QY and Jinxian, JX) and one paddy soil experiment in Jinxian (JX-P) were conducted in southern China (precipitation above 1200 mm yr-1), whereas the other six experiments were established in semi-humid or arid regions in China with precipitation in the range of 500-900 mm yr-1. Each experiment included three treatments as follows: no fertilization (Control), inorganic fertilizer (NP or NPK), and a combination of inorganic fertilizer and animal manure (NPM or NPKM). Long-term animal manure application not only significantly increased the biological binding agents (i.e., SOC and GRSP) in the nine experiments but also considerably increased the dispersing agents (i.e., exchangeable Na+) (P < 0.05), except for the paddy soil experiment. Consequently, soil aggregate stability increased after animal manure application in three experimental sites in southern China but not in the experimental sites in northern China. Aggregate stability had a positive relationship with SOC and GRSP in the experimental sites in southern China (P < 0.01) but a negative relationship with exchangeable Na+ in the experimental sites in northern China (P < 0.05). The Na+ accumulation in soils was negatively related to mean annual precipitation (P < 0.001). Our study demonstrates that the long-term application of animal manure may degrade soil structure via the Na+ accumulation.

Enhanced yields and soil quality in a wheat-maize rotation using buried straw mulch.

BACKGROUND: Straw return may improve soil quality and crop yields. In a 2-year field study, a straw return method (ditch-buried straw return, DB-SR) was used to investigate the soil quality and crop productivity effects on a wheat-corn rotation system. This study consisted of three treatments, each with three replicates: (1) mineral fertilisation alone (CK0); (2) mineral fertilisation + 7500 kg ha-1 wheat straw incorporated at depth of 0-15 cm (NPKWS); and (3) mineral fertilisation + 7500 kg ha-1 wheat straw ditch buried at 15-30 cm (NPKDW). RESULTS: NPKWS and NPKDW enhanced crop yield and improved soil biotical properties compared to mineral fertilisation alone. NPKDW contributed to greater crop yields and soil nutrient availability at 15-30 cm depths, compared to NPKWS treatment. NPKDW enhanced soil microbial activity and bacteria species richness and diversity in the 0-15 cm layer. NPKWS increased soil microbial biomass, bacteria species richness and diversity at 15-30 cm. CONCLUSIONS: The comparison of the CK0 and NPKWS treatments indicates that a straw ditch buried by digging to the depth of 15-30 cm can improve crop yields and soil quality in a wheat-maize rotation system. © 2016 Society of Chemical Industry.

Fungal community composition in soils subjected to long-term chemical fertilization is most influenced by the type of organic matter.

Organic matter application is a widely used practice to increase soil carbon content and maintain soil fertility. However, little is known about the effect of different types of organic matter, or the input of exogenous species from these materials, on soil fungal communities. In this study, fungal community composition was characterized from soils amended with three types of organic matter over a 30-year fertilization experiment. Chemical fertilization significantly changed soil fungal community composition and structure, which was exacerbated by the addition of organic matter, with the direction of change influenced by the type of organic matter used. The addition of organic matter significantly increased soil fungal richness, with the greatest richness achieved in soils amended with pig manure. Importantly, following addition of cow and pig manure, fungal taxa associated with these materials could be found in the soil, suggesting that these exogenous species can augment soil fungal composition. Moreover, the addition of organic matter decreased the relative abundance of potential pathogenic fungi. Overall, these results indicate that organic matter addition influences the composition and structure of soil fungal communities in predictable ways.

Productivity and sustainability of rainfed wheat-soybean system in the North China Plain: results from a long-term experiment and crop modelling.

A quantitative understanding of yield response to water and nutrients is key to improving the productivity and sustainability of rainfed cropping systems. Here, we quantified the effects of rainfall, fertilization (NPK) and soil organic amendments (with straw and manure) on yields of a rainfed wheat-soybean system in the North China Plain (NCP), using 30-years' field experimental data (1982-2012) and the simulation model-AquaCrop. On average, wheat and soybean yields were 5 and 2.5 times higher in the fertilized treatments than in the unfertilized control (CK), respectively. Yields of fertilized treatments increased and yields of CK decreased over time. NPK + manure increased yields more than NPK alone or NPK + straw. The additional effect of manure is likely due to increased availability of K and micronutrients. Wheat yields were limited by rainfall and can be increased through soil mulching (15%) or irrigation (35%). In conclusion, combined applications of fertilizer NPK and manure were more effective in sustaining high crop yields than recommended fertilizer NPK applications. Manure applications led to strong accumulation of NPK and relatively low NPK use efficiencies. Water deficiency in wheat increased over time due to the steady increase in yields, suggesting that the need for soil mulching increases.

Carbon sequestration efficiency of organic amendments in a long-term experiment on a vertisol in Huang-Huai-Hai Plain, China.

Soil organic carbon (SOC) sequestration is important for improving soil fertility of cropland and for the mitigation of greenhouse gas emissions to the atmosphere. The efficiency of SOC sequestration depends on the quantity and quality of the organic matter, soil type, and climate. Little is known about the SOC sequestration efficiency of organic amendments in Vertisols. Thus, we conducted the research based on 29 years (1982-2011) of long-term fertilization experiment with a no fertilizer control and five fertilization regimes: CK (control, no fertilizer), NPK (mineral NPK fertilizers alone), NPK+1/2W (mineral NPK fertilizers combined with half the amount of wheat straw), NPK+W (mineral NPK fertilizers combined with full the amount of wheat straw), NPK+PM (mineral NPK fertilizers combined with pig manure) and NPK+CM (mineral NPK fertilizers combined cattle manure). Total mean annual C inputs were 0.45, 1.55, 2.66, 3.71, 4.68 and 6.56 ton/ha/yr for CK, NPK, NPKW1/2, NPKW, NPKPM and NPKCM, respectively. Mean SOC sequestration rate was 0.20 ton/ha/yr in the NPK treatment, and 0.39, 0.50, 0.51 and 0.97 ton/ha/yr in the NPKW1/2, NPKW, NPKPM, and NPKCM treatments, respectively. A linear relationship was observed between annual C input and SOC sequestration rate (SOCsequestration rate  = 0.16 Cinput -0.10, R = 0.95, P<0.01), suggesting a C sequestration efficiency of 16%. The Vertisol required an annual C input of 0.63 ton/ha/yr to maintain the initial SOC level. Moreover, the C sequestration efficiencies of wheat straw, pig manure and cattle manure were 17%, 11% and 17%, respectively. The results indicate that the Vertisol has a large potential to sequester SOC with a high efficiency, and applying cattle manure or wheat straw is a recommendable SOC sequestration practice in Vertisols.

Impact of fertilizing pattern on the biodiversity of a weed community and wheat growth.

Weeding and fertilization are important farming practices. Integrated weed management should protect or improve the biodiversity of farmland weed communities for a better ecological environment with not only increased crop yield, but also reduced use of herbicides. This study hypothesized that appropriate fertilization would benefit both crop growth and the biodiversity of farmland weed communities. To study the effects of different fertilizing patterns on the biodiversity of a farmland weed community and their adaptive mechanisms, indices of species diversity and responses of weed species and wheat were investigated in a 17-year field trial with a winter wheat-soybean rotation. This long term field trial includes six fertilizing treatments with different N, P and K application rates. The results indicated that wheat and the four prevalent weed species (Galium aparine, Vicia sativa, Veronica persica and Geranium carolinianum) showed different responses to fertilizer treatment in terms of density, plant height, shoot biomass, and nutrient accumulations. Each individual weed population exhibited its own adaptive mechanisms, such as increased internode length for growth advantages and increased light interception. The PK treatment had higher density, shoot biomass, Shannon-Wiener and Pielou Indices of weed community than N plus P fertilizer treatments. The N1/2PK treatment showed the same weed species number as the PK treatment. It also showed higher Shannon-Wiener and Pielou Indices of the weed community, although it had a lower wheat yield than the NPK treatment. The negative effects of the N1/2PK treatment on wheat yield could be balanced by the simultaneous positive effects on weed communities, which are intermediate in terms of the effects on wheat and weeds.