Background and aims
It has been confirmed that the declines in arbuscular mycorrhizal fungi (AMF) populations and agroecosystem diversity are largely due to nutrient enrichment caused by ...fertilization. Replacing chemical-only fertilization with organic fertilization is widely considered a possible approach for maintaining soil biodiversity and a healthy functioning ecosystem. Here we aim to examine the effects of organic fertilizer on AMF occurrence.
Methods
We conducted a meta-analysis of 162 field experiments from 54 published studies conducted over the last 20 years. Our dataset included two groups: organic fertilization (OF)
vs
chemical-only fertilization (CF) and OF
vs
no fertilization (NF).
Results
We found that organic fertilizer increased AM fungal biomass and was less detrimental to AMF richness than mineral-only fertilization. AMF responses to organic fertilizer were generally positive when AMF and host plants had a strong mutualistic symbiosis such as in phosphorus-deficient soil, drought and semi-drought areas, at low latitudes, and at testing sites that contained two or more plant species or included legume. In conditions other than these, the responses were generally negative. Organic carbon input, increased soil phosphorus and the ratio of fertilizer N and P jointly explain the effects of organic fertilizer on AMF occurrence.
Conclusions
Our analysis indicates that, although some limiting factors exist, application of organic fertilizer can be an effective practice to protect AM symbiosis from the negative effects of nutrient enrichment in current cropping systems.
Potassium (K) deficiency is a common abiotic stress that can inhibit the growth of fruit and thus reduce crop yields. Little research has been conducted on pear transcriptional changes under low and ...high K conditions. Here, we performed an experiment with 7-year-old pot-grown "Huangguan" pear trees treated with low, Control or high K levels (0, 0.4, or 0.8 g·K
O/kg soil, respectively) during fruit enlargement and mature stages. We identified 36,444 transcripts from leaves and fruit using transcriptome sequencing technology. From 105 days after full blooming (DAB) to 129 DAB, the number of differentially expressed genes (DEGs) in leaves and fruit in response to low K increased, while in response to high K, the number of DEGs in leaves and fruit decreased. We selected 17 of these DEGs for qRT-PCR analysis to confirm the RNA sequencing results. Based on GO enrichment and KEGG pathway analysis, we found that low-K treatment significantly reduced K nutrient and carbohydrate metabolism of the leaves and fruit compared with the Control treatment. During the fruit development stages,
(
) played an important role on K
transport of the leaves and fruit response to K stress. At maturity, sucrose and acid metabolic pathways were inhibited by low K. The up-regulation of the expression of three
and two
genes involved in sorbitol metabolism was induced by low K, promoting the fructose accumulation. Simultaneously, higher expression was found for genes encoding amylase under low K, promoting the decomposition of the starch and leading the glucose accumulation. High K could enhance leaf photosynthesis, and improve the distribution of the nutrient and carbohydrate from leaf to fruit. Sugar components of the leaves and fruit under low K were regulated by the expression of genes encoding 8 types of hormone signals and reactive oxygen species (ROS). Our data revealed the gene expression patterns of leaves and fruit in response to different K levels during the middle and late stages of fruit development as well as the molecular mechanism of improvement of fruit sugar levels by K and provided a scientific basis for improving fruit quality with supplemental K fertilizers.
Severe early defoliation has become an important factor restricting the development of the pear industry in southern China. However, the assembly patterns of microbial communities and their ...functional activities in response to the application of bioorganic fertilizer (BIO) or humic acid (HA) in southern China’s pear orchards remain poorly understood, particularly the impact on the early defoliation of the trees. We conducted a 3-year field experiment (2017–2019) in an 18-year-old ‘Cuiguan’ pear orchard. Four fertilization schemes were tested: local custom fertilization as control (CK), CK plus HA (CK-HA), BIO, and BIO plus HA (BIO-HA). Results showed that BIO and BIO-HA application decreased the early defoliation rate by 50–60%, and increased pear yield by 40% compared with the CK and CK-HA treatments. The BIO and BIO-HA application significantly improved soil pH, available nutrient content, total enzyme activity and ecosystem multifunctionality, and also changed the structure of soil bacterial and fungal communities. The genus
Acidothermus
was positively correlated with the early defoliation rate, while the genus
Rhodanobacter
was negatively correlated. Additionally, random forest models revealed that the early defoliation rate could be best explained by soil pH, ammonium content, available phosphorus, and total enzyme activity. In conclusion, application of BIO or BIO mixed with HA could have assembled distinct microbial communities and increased total enzyme activity, leading to significant improvement of soil physicochemical traits. The increased availability of soil nutrient thus changed leaf nutrient concentrations and alleviated the early defoliation rate of pear trees in acid red soil in southern China.
To reveal the regulatory mechanisms underlying the productivity of long-term continuous cropping of processing tomato, a multi-year study was carried out to understand the effects of long-term ...continuous cropping on the community structures of the root zone microbes. Soil samples collected from continuous cropping of processing tomato after 3, 5 and 7 years were used for this study. Results showed that soil microbial biomass C (SMBC), N (SMBN) and microbial quotient (qMB) significantly decreased with longer cropping. After seven years of continuous cropping, the SMBC and SMBN contents, and qMB respectively significantly decreased by 52.3%, 78.8% and 48.2% (p < 0.01). In contrast, soil microbial biomass P (SMBP) increased during the first three years of continuous cropping, peaking to up to 1.6 times higher than that of the control, which also declined in the succeeding years. Continuous cropping significantly increased the PLFA of fungi, whereas the opposite trend was observed for bacteria, total PLFAs biomass, and the ratios of bacteria and fungi. The PLFA of actinomycetes have no change throughout. This suggests that fungi were better adapted to nutrient poor conditions than bacteria. Microbial diversity indices reached the highest after three years of continuous cropping, with the lowest observed after seven years. This indicated that microbial community diversity and uniformity decreased with increasing number of planting years. Furthermore, our results revealed that the microbial community structure in processing tomato soils changed with extended cropping, resulting to a decline in soil microbial biomass, which may be both a cause and a reflection of the poor soil quality.
The Masiluo-Zhangjiapingzi area is one of the most important target areas for ore exploration in western Sichuan, which has abundant gold and copper ore deposits. Substantial ore deposits in this ...area include the Masiluo gold deposit, Zhangjiapingzi gold deposit, Dongjia wuji specular hematite deposit, Gonglikong Cu-Au deposit, and Bazhe Cu-Au-Fe deposit. This study characterized the metallogenic regularity of the Masiluo-Zhangjiapingzi area using observations of the regional geological background and the characteristics of a typical deposit in this area. The ore deposits were found to be controlled by stratigraphy, geological structures, and magma with distinctive zoning characteristics-gold mineralization on the west part, Cu- Au mineralization on the northeastern part, and Fe-Cu-Au mineralization on the southeastern part.
Vegetation degradation caused by intense human disturbances poses a significant challenge to the preservation and improvement of ecosystem functions and services in the karst region of southwest ...China. Soil microorganisms are major regulators of ecosystem multifunctionality (EMF). Currently, there is a dearth of knowledge regarding the effects of vegetation degradation on soil microbial communities and their corresponding multiple ecosystem functions in karst regions. In this study, we selected the vegetation degradation sequences of second natural forest (NF), agroforestry (AS) and cropland (CL) to investigate the diversity of bacterial, fungal and protistan communities, and their hierarchical co-occurrence network, and EMF to explore the relationships between them. Compared to the NF, the carbon cycling index, nitrogen cycling index, soil water regulation power, and the EMF were significantly decreased by 8.2%–50.6%, 48.7%–86.8%, 19.8%–24.5%, and 31.4%–69.5% in the AS and CL, respectively. The development of EMF can be explained by the fungal, protistan and microbial hierarchical β-diversity, as well as the complexity (e.g. degree) of microbial hierarchical interactions during the process of vegetation degradation. Notably, correlations between the abundances of sensitive amplicon sequence variants (sASVs) for different karst vegetation types and EMF varied in distinct network modules, being positive in module 1 and negative in module 2. Moreover, the relative abundance of keystone taxa in fungal and protistan communities provided greater contributions to EMF than the bacterial communities. Additionally, random forest modeling showed that carbon and nitrogen sources, and soil water content, and trace elements (e.g. exchangeable magnesium, iron, manganese, and zinc) were identified as key driving factors of the EMF. Collectively, our findings demonstrate that vegetation degradation obviously alters soil microbial diversities and hierarchical interactions, emphasizing their key role in maintaining ecosystem functions and health in karst regions.
Display omitted
•Fungal and protistan α diversities had no impact on soil ecosystem multifunctionality (EMF).•Karst vegetation degradation enhanced the complexity of soil microbial hierarchical networks.•Leotiomycetes, Eurotiomycetes and Variosea classes are important in regulating EMF during vegetation degradation.
Utilization of arbuscular mycorrhizal (AM) resources to improve, or even maintain agroecosystem sustainability requires a thorough understanding of the biotic and abiotic factors that impact AM ...fungal communities. AM symbiosis is important in mango and litchi trees, two economically important fruit crops in China, but there is little information on the AM fungi associated with these trees or their responses to organic fertilizer. Using Illumina high-throughput sequencing we analyzed AM colonization, spore density, and community composition and diversity in the rhizospheric soil from 16 mango orchards and 16 litchi orchards located in southern China. Ours was a regional scale study and in general, we found that the majority of AM fungi OTUs belonged to the families Glomeraceae, followed by Gigasporaceae, Paraglomeraceae, Acaulosporaceae and Diversisporaceae. Glomus and Paraglomus were the genera that differed most in abundance between the rhizospheric soil of mango and litchi. AMF community composition was impacted by latitude and longitude and soil characteristics such as, NO3−-N, NH4+-N, available-P, and soil organic carbon (SOC). The sampling sites were in areas of medium to low altitude, and there was no significant correlation between altitude and AM fungal richness. We found that higher soil nutrient content, particularly available-P, was negatively correlated with AM colonization. Our results also showed that some of the AM genera responded differently to environmental variables. Structural equation modeling (SEM) demonstrated that SOC not only had a direct positive effect on AMF richness, but also an indirect negative effect, due to increased soil fertility. Our findings have enabled a deeper insight into the impacts of organic fertilizer on AM fungal communities, which will be valuable when considering AM symbiosis in orchard management.
•The abundance of Glomus and Paraglomus differed greatly between the rhizospheric soil of mango and litchi.•Geographical distances and soil properties jointly shaped the AM fungal communities.•Some AM genera responded differently to environmental variables.•SOC resulting from increased manure input had a direct positive effect on AMF richness.•Excessive use of manure is detrimental to AMF occurrence.
Pear trees with severe early defoliation usually suffer from weakened aboveground growth and a serious decrease of fruit quality and yield. Soil fertility and its microbial community and functional ...activity are significant factors impacting plant growth and yield, which also might be the very factors that influence the early defoliation of pear trees. To address the problems caused by chemical fertilizers, bioorganic fertilizer (BIO) and silicon amendment (SOA) are increasingly used as amendments to improve soil microbial activity and increase soil nutrient availability. However, how effective BIO and SOA are at improving the health of soils and reducing early defoliation remains unclear. Here, we conducted a 4-year field experiment (2016–2019) in a 25-year-old ‘Cuiguan’ pear orchard in Jianning county, Fujian province, comparing local custom fertilization (CK), local custom fertilization supplemented with SOA (CK-SOA), BIO, and BIO supplemented with SOA (BIO-SOA). At the end of the 4-year study we found that BIO and BIO-SOA treatments resulted in reduced leaf nitrogen content and increased leaf potassium (K), calcium (Ca), silicon (Si), and manganese (Mn) content. BIO and BIO-SOA treatments also resulted in a 50% reduction of the early deciduous rate and a 47% increase in pear yield. Compared with CK treated soil, BIO and BIO-SOA treated soils had higher nitrate nitrogen content (NO3−-N), available Si, Fe, Mn, and Zn content, and significantly improved microbial biomass nitrogen content (MBN), geometric mean enzyme activity (GMEA) and ecosystem multifunctionality (EMF). Network analysis revealed that BIO and BIO-SOA treatments had significantly altered the bacterial and fungal community composition in the orchard soil. Redundancy analysis (RDA) and the Mantel test indicated that soil available K, exchangeable Ca and Mg, and available Si, Fe, Mn and Zn content were the main factors influencing bacterial and fungal communities. The increased nutrient availability (e.g., NO3−-N and microelement contents), MBN, GMEA and EMF had negative effects on the early defoliation rate. Random Forest model identified soil available Si content, microbial biomass nitrogen content, EMF, and GMEA as the main predictors of early defoliation rate. Overall, this study demonstrates that application of BIO or BIO mixed with SOA can alleviate the early defoliation rate of pear trees by increasing the availability of microelements, microbial functional activity, and changing the soil microbial community composition.
Display omitted
•BIO and BIO-SOA significantly reduced the early defoliation rate of pear trees, and improved the pear yield.•BIO and BIO-SOA significantly increased soil available Si, Fe, Mn and Zn concentrations in pear orchard.•Soil microelements (e.g. Mg, Si, Fe and Zn) availability strongly affects microbial communities.•Belowground interactions significantly affects the growth of aboveground parts of pear trees.
Bioorganic fertilizers are widely used in fruit orchards to improve soil properties and increase productivity. To investigate the effects of bioorganic fertilizer (BIO) and chemical fertilizer (CF) ...on the root system architecture and above-ground growth of pear trees, a split-root experiment was conducted. To this end, six soil amendment combinations were investigated: NF–NF (no fertilizer), NF-CF, NF-BIO, CF-CF, BIO-BIO, and BIO-CF. Roots of 1-year old ‘Cuiguan’ pear trees were distributed as evenly as possible into split-root chambers containing the aforementioned amendment combinations and maintained for 210 days after budding. Results showed that in boxes containing the same fertilizer in both chambers (NF–NF, CF-CF and BIO-BIO), the BIO chambers had an improved soil pH, by 0.6–0.8 units, and 23%–65.5% greater SOM than the soils in the NF and CF chambers. We also found that in these BIO chambers the lateral root number was 2.1–3.5 times greater than in NF and CF chambers and the maximum order of lateral roots was greater than 9. BIO application promoted lateral root growth in the paired NF and CF chambers, increasing specific root length and reducing root tissue density. In BIO-CF boxes, the 4th to 6th lateral root number and length accounted for the largest proportion of total lateral root number and length respectively. Moreover, compared with trees grown in CF-CF, those grown in BIO-BIO and BIO-CF had greater mean xylem, phloem, and cork layer thicknesses, as well as greater mean vessel density and number. BIO-CF treated soils had significantly reduced (50%) available phosphorus content compared to CF-CF treated soils, and consistently, BIO-CF resulted in the greatest growth of trunk girth (by 5–29%) among all the treatments. Soil organic matter and nitrate nitrogen concentration had significantly positive effects on root growth and activity, while branching intensity was significantly related to available phosphorus content and total nitrogen, followed by available potassium content and ammonia nitrogen content. In conclusion, local application of bioorganic fertilizer is a promising technique to sustainably maintain pear tree productivity because it accelerates the root proliferation and activity in either nutrient-deficient or -sufficient soil.
Long-term application of chemical fertilizers has aggravated red soil acidification and caused severe early defoliation in pear-growing region of southern China. To investigate the effects of BIO and ...HA on the growth and activity of fine roots, and in turn the effect on leaf nutrient status and early defoliation of pear trees, we conducted a 2-year pot experiment (2018–2019) using 1-year-old pear (Pyrus pyrifolia) seedlings in a pear orchard in southern China. Four fertilization treatments were included: chemical fertilizer as control (CF), CF with humic acid (CF-HA), BIO, and BIO mixed with HA (BIO-HA). Results showed that BIO and BIO-HA treatments significantly decreased the early defoliation rate of pear trees about 18%–27% compared with CF and CF-HA treatments. For the growth status of the aboveground, the relative growth rate of pear trees treated by BIO and BIO-HA was 1.2 times higher than the CF treatment at 180 days after budding, and it was accompanied by an increase of leaf thickness, microelements content (e.g. calcium, manganese, iron and zinc), and a decrease of leaf temperature. Compared with CF treatment, BIO or BIO-HA significantly improved soil pH value by 0.9–1.1 units, and increased soil exchangeable calcium content by 50%–83%. BIO and BIO-HA treatments also significantly increased total lateral root number, length and root activity, which were negatively correlated with the early defoliation rate by the network analysis. Furthermore, structural equation model showed that root traits were the core factor to alleviate the early defoliation rate, which was directly or indirectly driven by the application of bioorganic fertilizer. In conclusion, BIO or BIO combined with HA can alleviate the early defoliation rate of pear trees by mitigating soil acidification to stimulate the lateral root growth and activity, and in turn increase leaf micronutrients content and aboveground growth. Our study shows that measuring root traits are at the core of plant responses to soil nutrient status and pH.
PDF
