Citrus Orchard Soil Research Articles

The influence of urban environmental effects on the orchard soil microbial community structure and function: a case study in Zhejiang, China.

The urban environmental effects can have multifaceted impacts on the orchard soil microbial community structure and function. To specifically study these effects, we investigated the soil bacterial and fungal community in the laxly managed citrus orchards using amplicon sequencing. Ascomycota demonstrated significant dominance within the citrus orchard soils. The increased presence of beneficial Trichoderma spp. (0.3%) could help suppress plant pathogens, while the elevated abundance of potential pathogenic fungi, such as Fusarium spp. (0.4%), might raise the likelihood of disorders like root rot, thereby hindering plant growth and resulting in reduced yield. Moreover, we observed significant differences in the alpha and beta diversity of bacterial communities between urban and rural soils (p < 0.001). Environmental surveys and functional prediction of bacterial communities suggested that urban transportation factors and rural waste pollution were likely contributing to these disparities. When comparing bacterial species in urban and rural soils, Bacillus spp. exhibited notable increases in urban areas. Bacillus spp. possess heavy metal tolerance attributed to the presence of chromium reductase and nitroreductase enzymes involved in the chromium (VI) reduction pathway. Our findings have shed light on the intricate interplay of urban environmental effects and root systems, both of which exert influence on the soil microbiota. Apart from the removal of specific pollutants, the application of Bacillus spp. to alleviate traffic pollution, and the use of Trichoderma spp. for plant pathogen suppression were considered viable solutions. The knowledge acquired from this study can be employed to optimize agricultural practices, augment citrus productivity, and foster sustainable agriculture.

The underlying mechanisms by which boron mitigates copper toxicity in Citrus sinensis leaves revealed by integrated analysis of transcriptome, metabolome and physiology.

Both copper (Cu) excess and boron (B) deficiency are often observed in some citrus orchard soils. The molecular mechanisms by which B alleviates excessive Cu in citrus are poorly understood. Seedlings of sweet orange (Citrus sinensis (L.) Osbeck cv. Xuegan) were treated with 0.5 (Cu0.5) or 350 (Cu350 or Cu excess) μM CuCl2 and 2.5 (B2.5) or 25 (B25) μM HBO3 for 24wk. Thereafter, this study examined the effects of Cu and B treatments on gene expression levels revealed by RNA-Seq, metabolite profiles revealed by a widely targeted metabolome, and related physiological parameters in leaves. Cu350 upregulated 564 genes and 170 metabolites, and downregulated 598 genes and 58 metabolites in leaves of 2.5μM B-treated seedlings (LB2.5), but it only upregulated 281 genes and 100 metabolites, and downregulated 136 genes and 40 metabolites in leaves of 25μM B-treated seedlings (LB25). Cu350 decreased the concentrations of sucrose and total soluble sugars and increased the concentrations of starch, glucose, fructose and total nonstructural carbohydrates in LB2.5, but it only increased the glucose concentration in LB25. Further analysis demonstrated that B addition reduced the oxidative damage and alterations in primary and secondary metabolisms caused by Cu350, and alleviated the impairment of Cu350 to photosynthesis and cell wall metabolism, thus improving leaf growth. LB2.5 exhibited some adaptive responses to Cu350 to meet the increasing need for the dissipation of excessive excitation energy (EEE) and the detoxification of reactive oxygen species (reactive aldehydes) and Cu. Cu350 increased photorespiration, xanthophyll cycle-dependent thermal dissipation, nonstructural carbohydrate accumulation, and secondary metabolite biosynthesis and abundances; and upregulated tryptophan metabolism and related metabolite abundances, some antioxidant-related gene expression, and some antioxidant abundances. Additionally, this study identified some metabolic pathways, metabolites and genes that might lead to Cu tolerance in leaves.

Assessing horticulture-based land management impacts on carbon dynamics and soil quality

The present study was carried during 2020 and 2021 at School of Agricultural Sciences and Rural Development (Nagaland University), Medziphema, Nagaland to study the effects of different horticulture-based land use systems on carbon stock, soil fertility and soil biological health in acidic hill soils of Nagaland. Average values of bulk density of the soils were 1.20 and 1.21 g/cm3 in surface and sub-surface soils, respectively irrespective of type of orchards. The maximum and minimum carbon stock was recorded in pineapple [Ananas comosus (L.) Merr.] (46.77 and 43.38 mg/ha) and citrus (Citrus spp.) (33.07 and 32.42 mg/ha) orchard soils. Soil microbial biomass carbon in pineapple (270.13 and 244.23 µg/g) and citrus orchard soils (165.64 and 152.49 µg/g) was recorded in surface and sub-surface layers, respectively. Banana (Musa spp.) orchard soils had greater values of dehydrogenase activity (15.26 and 9.83 µg TPF/g/h). Soils of banana orchard also recorded highest acid phosphatase activity (176.0 and 165.5 µg PNP/g/h), which was at par with mango (Mangifera indica L.) orchard soils (175 and 166 µg PNP/g/h). Minimum acid phosphatase activity (162.0 and 150.0 µg PNP/g/h) was recorded in citrus orchard soils. Maximum earthworm population density was recorded in banana orchard (12–20 number/m2) and minimum (4–12 number/m2) in citrus orchards.

Evaluating the long-term effects of best management practices on pollution reduction and soil quality improvement in sloping farmland of the Three Gorges Reservoir area

Reducing nonpoint-source pollution and improving soil quality by applying best management practices (BMPs) on sloping farmland are essential for ensuring water environmental safety and sustainable agricultural development. However, little is known about the accumulative effect of the long-term application of BMPs on reducing pollution and improving soil quality in major land use types of sloping farmland in watersheds. We conducted a nine-year field experiment for citrus orchard and cropland of sloping farmland in the Three Gorges Reservoir area of China. The treatment settings for the citrus experimental plots were as follows: (1) citrus intercropped with white clover (WC), (2) citrus orchard soil mulched with straw (SM), (3) citrus intercropped with Hemerocallis flava contour hedgerows (HF) and (4) conventional citrus planting pattern (C-CK). The treatment settings for the crop experimental plots were as follows: (1) wheat-peanut rotation intercropped with Toona sinensis contour hedgerows (TS), (2) wheat-peanut rotation intercropped with alfalfa contour hedgerows (AF), (3) ryegrass-sesame rotation (RS) and (4) conventional wheat-peanut rotation (W-CK). We found that compared with C-CK and W-CK, (1) runoff, sediment, total nitrogen and total phosphorus losses were reduced by 18.0 %, 66.1 %, 35.6 % and 40.2 %, respectively, in WC; by 22.4 %, 61.2 %, 43.9 % and 52.4 %, respectively, in SM; by 25.4%, 69.5 %, 52.0 % and 58.1 %, respectively, in HF; by 45.1 %, 73.7 %, 64.6 % and 66.0 %, respectively, in TS; by 41.8 %, 67.4 %, 59.3 % and 60.8 %, respectively, in AF; and by 24.1 %, 42.9 %, 39.3 % and 40.3 %, respectively, in RS; (2) the soil quality index values of the BMP treatments increased; and (3) the application of these BMPs did not significantly affect yield or product value. We suggest the application of these BMPs on sloping farmland to (1) efficiently reduce total runoff, total sediment, and soil total nitrogen and total phosphorus losses; (2) improve soil quality; and (3) have no significant effect on output, of which the BMP HF applied to citrus orchard and the BMP TS applied to cropland are the most effective.

Occurrence and distribution of trisiloxane ethoxylates in citrus orchard soils in China: Analytical challenges

Trisiloxane ethoxylates (TSEOn) are widely used as agricultural surfactants due to their significant synergism with the active ingredients of pesticides, generally, including three typical end groups which are hydroxyl (TSEOn-H), methoxy (TSEOn-CH3), and acetoxy (TSEOn-COCH3), respectively. However, the potential ecotoxicological and endocrine-disrupting risks of TSEOn congeners have recently attracted ever-growing concern. Above all, there is limited research on the concentration levels of TSEOn in agroecosystems. This study, simultaneous analysis of 39 TSEOn oligomers in citrus orchard soils in China was implemented by the modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) extraction coupled with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The method detection limits (MDLs) and the method quantification limits (MQLs) for TSEOn were 0.003–0.07 μg/kg and 0.01–0.20 μg/kg, respectively. The recoveries for TSEOn oligomers in soils ranged from 81 % ∼ 106 % with related standard deviations (RSDs) < 7 %. This newly developed UPLC-MS/MS method with high sensitivity and stability allows us to successfully trace the occurrence of TSEOn congeners in the citrus orchard soils from 3 provinces and 1 municipality in China. The detected concentrations of TSEOn-H oligomers in the sampled soils ranged from 0.02 to 0.288 μg/kg (dry weight). The congener profiles of TSEOn-H were dominated by TSEOn-H (n = 6– 8) in the soils. Additionally, the total concentrations of TSEOn-H congeners (ΣTSEOn-H) in the soils were in the range of 0.03 to 1.49 μg/kg. A comparison of ΣTSEOn-H distribution among the different citrus orchard soils indicated a higher level of ΣTSEOn-H in the soil samples collected from Zhejiang Province. Notably, TSEOn-CH3 or TSEOn-COCH3 oligomers were not detected in the tested soils. To the best of our knowledge, this is the first report on the occurrence and distribution of TSEOn congeners in agricultural soils.

The relationship between overwintering peach fruit fly pupae Bactrocera zonata (Saunders) (Diptera: Tephritidae) and some pathogenies in citrus orchard soils in Diyala province

A field and laboratory study was conducted for soil samples in citrus orchards in the Muqdadiya region - Diyala province in year 2021, for three depths (3, 5, and 7) cm, to detect overwintering peach fruit fly pupae Bactrocera zonata (Saunders) its infecting by Beauveria bassiana (Bals) Vuill. . The results showed that inverse (negative) correlation between the rates of the numbers of fungal colonies and the different soil depths, as the correlation value was (-0.906).

Virulence of Local Isolates of The Entomopathogenic Fungus Beauveria bassiana on Egg and Adult Stages of Tomato Leaf Miner, Tuta absoluta

Hasan, A.H., M. Ahmad, O. Hamoudi and M. Moufleh. 2024. Virulence of Local Isolates of The Entomopathogenic Fungus Beauveria bassiana on Egg and Adult Stages of Tomato Leaf Miner, Tuta absoluta. Arab Journal of Plant Protection, 42(3): 340-348. https://doi.org/10.22268/AJPP-001252 The efficacy of four local isolates of the entomopathogenic fungus Beauveria bassiana (Ascomycota: Hypocreales), (b6 isolated from citrus orchard soil (Harisoon), b7 from greenhouse soil (Alkhrab), b8 from palm weevil pupae (Lattakia) and b10 from olive orchard soil (Mengella), were tested on the egg and adult stages of the tomato leafminer Tuta absoluta by direct spraying for each stage with three different concentrations of fungal spore suspensions 2×104 , 2×106 and 2×108 spores/ml. The results obtained showed that both insect stages were very sensitive to fungal infection to varying degrees and there were significant differences in the hatching rate and adult mortality rate caused by the four isolates in comparison with the control treatment. The b8 and b10 isolates were the most effective on both insect stages at all concentrations tested. Corrected mortality rates at the highest concentration (2×108 spore/ml) were 82.59% for b8 isolate and 86.30% for b10 isolate on eggs and LC50 was 1×106 spores/ml for b8 isolate and 8×105 spores/ml for b10 isolate, whereas the corrected mortality rate for both were 100% on adults, 8 days after treatment, and by using the highest spore concentration. The LT50 was 3.2 days for both isolates and the LC50 was 2×104 spores/ml for b8 isolate and 1×105 spores/ml for b10 isolate under laboratory conditions. Keywords: Biological control, Beauveria bassiana, Tuta absoluta, mortality, LT50, LC50

Effect of Different Parameters (Treatment Administration Mode, Concentration and Phenological Weed Stage) on Thymbra capitata L. Essential Oil Herbicidal Activity

The essential oil (EO) of Thymbra capitata has been demonstrated to possess herbicidal activity and could be used as an alternative to synthetic herbicides with reduced persistence in soil and new mode of action. Nevertheless, it is necessary to determine the adequate doses for its use, the proper way for its application and the best phenological stage of weeds and crops in which the EO should be applied to obtain maximum efficacy against weeds without compromising crop production. In this work, T. capitata EO was tested at three different concentrations against weeds grown from a citrus orchard soil seedbank untreated with herbicides and against three important weed species grown in substrate to determine the efficacy of the concentrations on different weed species. All experiments were carried out under greenhouse conditions. To find out the best way for applying the EO, it was applied by irrigation and by spraying on the targeted weeds, and to verify the influence of timing, it was tested on Lolium rigidum at two different phenological stages and on wheat at a later phenological stage than weeds. The highest concentration tested (12 µL·mL−1) showed the best performance to control weeds. The more effective mode of application was by spraying on dicotyledons and by irrigation on monocotyledons at the earliest phenological stage. T. capitata EO was phytotoxic for wheat. More trials in different crops are needed to determine the best conditions for its use.

Nitrogen-deficient leaves and roots can keep high abilities to scavenge reactive oxygen species and methylglyoxal, and protect them against oxidative damage in Citrus sinensis seedlings

Nitrogen-deficiency (ND) usually occurs in some citrus orchard soils in China. The roles of reactive oxygen species (ROS) and methylglyoxal (MG) generation and their detoxification systems in ND tolerance of horticultural woody plants still need to be revealed. For the first time, we examined the effects of ND on ROS and MG generation and their detoxification systems in leaves and roots of Citrus sinensis seedlings. The objectives are to test the hypotheses that N-deficient leaves and roots can keep high abilities to scavenge ROS and MG, thereby protecting them from oxidative damage, and that ND-induced alterations of ROS and MG formation and their detoxification systems in leaves and roots are different. ND augmented superoxide anion production rate and MG concentrations, but it decreased malondialdehyde (MDA) concentrations and electrolyte leakage in leaves and roots. ND increased the activities of most enzymes involved in ROS (ascorbate-glutathione cycle-related enzymes, antioxidant enzymes, and sulfur metabolism-related enzymes) and MG (glyoxalases) detoxification expressed on a protein basis with a few exceptions, and the concentrations of ascorbate, phytochelatins, and total non-protein thiols in leaves and roots. These results suggested that nitrogen-deficient leaves and roots could keep high abilities to detoxify ROS and MG, and protect them from oxidative damage. Generally viewed, ND affected the production and removal of ROS and MG more in roots than in leaves.

Accumulation and Origin of Phosphorus and Heavy Metals in Citrus Orchard Soils in Jeju Island, South Korea: Potential Ecological Risks and Bioavailability

This study investigated the accumulation of total phosphorus (TP) and heavy metals (HMs; Pb, Zn, Cu, Cd, Cr, and Ni) in citrus orchard soils in Jeju Island, Korea, identifying potential soil pollution sources using statistical analysis. Anthropogenic HM pollution was evaluated using the geoaccumulation index and enrichment factors, whereas HM bioavailability was assessed via single extraction. TP, Zn, Cu, and Cr concentrations in citrus orchard topsoil were significantly higher than those in forestland soils, indicating their accumulation in the surface layer. Statistical analyses confirmed that elements with high concentrations were closely related to potential pollution sources accumulated on the surface layer of citrus orchards owing to agricultural activities. Particularly, Zn and Cu accumulation was confirmed to originate from intensive compost and pesticide use in citrus orchards. Cu showed the highest contamination and enrichment of all HMs. However, Zn and Cu fractions, determined via an availability assessment, were dominated by acid or complex compounds, indicating that labile Zn and Cu have potential bioavailability for plants. Nevertheless, their fractions accounted for a small proportion (mean &lt; 15%). Therefore, despite the high pollution levels of Zn and Cu, their availabilities were extremely low, indicating a negligible bioavailability in crops and no impact on aquatic ecosystems.

Effects of Orange Peel Biochar and Cipangopaludina chinensis Shell Powder on Soil Organic Carbon Transformation in Citrus Orchards

In view of the continuous decline in organic carbon content in citrus orchard soil, to explore the effects of biochar and farmland waste on the transformation of organic carbon in citrus orchard soil. In this study, the soil of a citrus orchard in Yangshuo County, Guilin, Guangxi, China, was collected. The citrus peel and the Cipangopaludina chinensis shell were used as raw materials, the citrus peel was used to prepare biochar, and the Cipangopaludina chinensis shell was powdered. The materials were added to the soil in different proportions. A 30-day indoor incubation soil was conducted to investigate the effects of adding different proportions of citrus peel biochar and Cipangopaludina chinensis shell powder on the transformation of organic carbon in citrus orchard soil. Compared with the control group, the addition of 4% orange peel biochar, 2% orange peel biochar + 2% Cipangopaludina chinensis shell powder, 2.6% orange peel residue biochar + 1.3% Cipangopaludina chinensis shell powder, and 3% orange peel biochar + 1% Cipangopaludina chinensis shell powder increased soil organic carbon by 22.49%, 20.06%, 19.81%, and 21.35%, respectively. Compared with the control, 2.6% orange peel biochar + 1.3% Cipangopaludina chinensis shell powder had the best effect on the improvement of soil organic carbon components, and microbial biomass carbon (MBC), dissolved organic carbon (DOC) and readily oxidized organic carbon (ROC) increased by 19.81%, 64.88%, 67.81%, and 19.44%, respectively. Different proportions of orange peel residue biochar and Cipangopaludina chinensis shell powder were applied to the soil of the citrus orchard to effectively increase the soil organic carbon component content and enzyme activities. This study provides a theoretical basis for the carbon sequestration mechanism of citrus orchard soil using different proportions of orange peel residue biochar and Cipangopaludina chinensis shell powder.

Effects of magnesium-modified biochar on soil organic carbon mineralization in citrus orchard.

In order to investigate the carbon sequestration potential of biochar on soil, citrus orchard soils with a forest age of 5 years was taken as the research object, citrus peel biochar (OBC) and magnesium-modified citrus peel biochar (OBC-mg) were selected as additive materials, and organic carbon mineralization experiments were carried out in citrus orchard soil. OBC and OBC-Mg were applied to citrus orchard soils at four application rates (0, 1, 2, and 4%), and incubated at a constant temperature for 100 days. Compared with CK, the cumulative mineralization of soil organic carbon decreased by 5.11% with 1% OBC and 2.14% with 1% OBC-Mg. The application of OBC and OBC-Mg significantly increased the content of soil organic carbon fraction, while the content of soil organic carbon fraction was higher in OBC-Mg treated soil than in OBC treated soil. Meanwhile, the cumulative mineralization of soil organic carbon was significantly and positively correlated with the activities of soil catalase, urease and sucrase. The enzyme activities increased with the cumulative mineralization of organic carbon, and the enzyme activities of the OBC-Mg treated soil were significantly higher than those of the OBC treated soil. The results indicated that the OBC-Mg treatment inhibited the organic carbon mineralization in citrus orchard soils and was more favorable to the increase of soil organic carbon fraction. The Mg-modified approach improved the carbon sequestration potential of biochar for citrus orchard soils and provided favorable support for the theory of soil carbon sink in orchards.

Screening and Identification of the Rhizosphere Fungal Communities Associated with Land Reclamation in Egypt

Soil fungi are a wide range of microorganisms that play an essential role in enhancing the available nutrients in the soil for plants. In the current study, to study the fungal association with newly reclaimed land in Egypt, 22 composite soil samples were screened and characterized from citrus and olive orchard soil in contrast to a control soil that had never been cultivated (a nearby desert). The isolates were identified and tested for P solubilization and IAA production to highlight their potential as biofertilizers while the sampled soil was characterized. The physicochemical characteristics of the orchard’s soil sample had a high relative mean moisture content, and the C/N ratio were 45.24% and 16.8% compared with desert lands of 32.80% and 8.12%, respectively, while a higher pH was recorded for desert lands. A total of 272 fungal isolates yielded 27 filamentous fungal species. Based on ITS molecular identification, the 27 isolates belonged to phyla Ascomycota, from eight genera. Twelve species were positive in producing a phosphate clearance zone around the fungal colony growth, while ten species were able to release IAA in vitro with different tryptophan concentrations under different pH values. When known pathogenic fungi were excluded, Aspergillus tubingensis and A. fumigatus were the highest IAA producers and can solubilize phosphorus. The screening and identification of the fungal diversity of the newly reclaimed land provided insights into potential phosphate solubilizers and plant phytohormones producers (i.e., IAA). Overall, the obtained results can provide primary knowledge that indicates the great potential fungal ability to develop biofertilizers for application in improving the production of immature soil for agriculture reclamation processes and practices.

Effect of bio-organic fertilizers partially substituting chemical fertilizers on labile organic carbon and bacterial community of citrus orchard soils

Effect of bio-organic fertilizers partially substituting chemical fertilizers on labile organic carbon and bacterial community of citrus orchard soils

Effects of Chemical Fertilizer Combined with Organic Fertilizer Application on Soil Properties, Citrus Growth Physiology, and Yield

Chemical fertilizer has been excessively used for high yield of citrus around the world, especially in China; meanwhile, it deteriorates the citrus orchard soil environment. To resolve the conflict, the use of organic fertilizer provides a promising solution. However, the data about organic fertilizer used in citrus orchard is rarely available. Here, four treatments including CK (no fertilizer), CF (chemical fertilizer), OF + CF (chemical fertilizer reduction combined with organic fertilizer; application of N, P2O5, K2O fertilizer and organic fertilizer is 0.564, 0.236, 0.336 and 10 kg/plant), and BF + CF (chemical fertilizer reduction combined with bioorganic fertilizer; application of N, P2O5, K2O fertilizer and bioorganic fertilizer is 0.508, 0.320, 0.310 and 10 kg/plant) were performed in a ‘Ponkan’ (Citrus reticulata Blanco) orchard to evaluate the effect of organic fertilizer on citrus yield, growth, soil properties etc. when nutrients of fertilizer of each treatment were equal except CK. The data obtained in 2019 and 2020 showed that both OF + CF and BF + CF were beneficial to improve soil fertility (soil physicochemical and microbe properties) and citrus growth physiology (growth, nutrient and photosynthesis), alleviate NO3−-N leaching, and promote yields. Comprehensive evaluation indicated that BF + CF was more effective than OF + CF. Together, organic fertilizer has the potential to substitute partial chemical fertilizer with improvement in soil properties, growth physiology, and yield of citrus.

Effects of Microplastics Addition on Soil Organic Carbon Mineralization in Citrus Orchard

To investigate the effects of microplastics on soil organic carbon mineralization and the changes in soil enzyme activities, an incubation experiment was conducted whereby single applications of either microplastics or straw, and combined application of both, were added to Dangyang citrus orchard soil. The results showed that the combined application of straw and microplastics significantly affected organic carbon mineralization in the soil, but the single addition of microplastics had no significant effect. Compared with straw alone, the application of a small combined amount of microplastics and straw significantly increased soil organic carbon mineralization by 8.20%, while medium and high amounts of the combined application significantly inhibited soil organic carbon mineralization. The lowest amount of organic carbon mineralization occurred with the highest amount of combined microplastics and straw, 10.13% lower than with straw alone. The addition of microplastics significantly reduced the activity of β-glucosidase. In particular, a high amount of microplastics significantly decreased the activity of β-glucosidase, compared with the control, by 20.52%, 43.93%, and 17.79% on the day 1, 6, and 35, respectively. However, straw application alleviated the inhibition effect of microplastic application on soil β-glucosidase activity. The soil organic carbon mineralization rate was significantly positively correlated with DOC, MBC and β-glucosidase activity.

Bacterial Diversity and Community in Response to Long-Term Nitrogen Fertilization Gradient in Citrus Orchard Soils

Citrus orchards receive increasing amounts of nitrogen fertilizer for the purpose of optimal yields and good quality of citrus fruits. Although the effects of increased nitrogen fertilizer on citrus fruit trees have been reasonably well studied, few comparable studies have examined impacts on soil bacterial communities and diversity, even though they play critical roles in orchard ecosystem functioning. In our study, Illumina MiSeq sequencing was used to investigate bacterial community structure and diversity under 5-years long-term nitrogen fertilization gradients (N0, N1, N2, N3, N4, and N5) in citrus orchard soils. The sequencing result showed that nitrogen fertilizer addition increased bacterial diversity along the N0 to N3 gradient but decreased bacterial diversity along the N3 to N5 gradient. The increase in the nitrogen fertilizer rate altered bacterial community composition by increasing the relative abundance of Delta-proteobacteria, Nitrospirae, SBR1093, and Latescibacteria and decreasing the relative abundance of Alpha-proteobacteria. Finally, regression analysis revealed that bacterial diversity and the relative abundance of Nitrosomonadales, Rhodobiaceae, Gemmatimonas, and Variibacter exhibited a significant positive correlation with citrus yield. The study revealed that a reasonable nitrogen fertilizer rate applied to citrus orchards could improve bacterial community structure and diversity and increase citrus yield.

Dissipation of tiafenacil in five types of citrus orchard soils using the HPLC-MS coupled with the quick, easy, cheap, effective, rugged, and safe method.

Tiafenacil is a new contact herbicide and its environmental behavior after field application remains poorly understood. In order to understand the dissipation of tiafenacil in the soil, the tiafenacil dissipation experiment was conducted at citrus orchard sites in five provinces of China (Gansu, Shandong, Sichuan, Jiangxi, and Hainan) in 2019 and 2020 (July-August) and the relevant determination methods were optimized. The results showed that the established method showed good linearity in the concentration range of 0.01-0.5mg/kg. The average recoveries of tiafenacil from the five soils were 86.31-101.66%, with coefficients of variation of 0.28-10.79%. The dissipation of tiafenacil at the five experimental sites conformed to the first-order kinetic equation, Ct =C0 exp- kt (R2 =0.8130 - 0.9967). The half-life of tiafenacil ranged from 0.26 to 4.19 days. The dissipation rate of tiafenacil was positively correlated with soil organic matter content and negatively correlated with soil pH, while monthly average temperature and total rainfall were less influential than soil properties. Therefore, the established method was simple and effective for tiafenacil residue analysis in citrus orchard soils. Tiafenacil could readily dissipate in soil and might be a safe alternative to glyphosate for weed control in citrus orchards.

Soil Chemical Properties of Citrus Orchards in Jeju

This study is conducted to be used as data for soil nutrient management and fertilizer application improvement by examining the chemical characteristics of citrus orchard soils in the Jeju region. The soil samples were collected from 50 sites of dark brown soils (DBS), 50 sites of very dark brown volcanic ash soils (VDBAS), and 50 sites of black volcanic ash soils (BVAS) in Jeju Island from February to March 2018. Soil chemical properties such as pH, organic matter, available phosphate (Av. P₂O5), exchangeable potassium (Ex. K), exchangeable calcium (Ex. Ca), exchangeable magnesium (Ex. Mg), and lime requirement were analyzed. The average pH of DBS, VDBAS, and BVAS were 5.4, 5.0, and 5.3, respectively. Organic matter contents were 42 g kg-1 for DBS, 98 g kg-1 for VDBAS, and 154 g kg-1 for BVAS, which showed that the darker the soil color, the higher the organic matter contents. Av. P₂O5 and Ex. K contents became lower as the soil color get darker, and the lime requirement became higher as the soil color get darker. When compared to the optimal range of ideal citrus orchard soils, the insufficient ratio of pH, Ex. Ca, and Mg were quite high, with more than 58% in all soils, thus requiring the use of calcium magnesium fertilizer. The excessive ratio of Av. P₂O5 and Ex. K were high in DBS with 90% and 62%, respectively, and the insufficient ratio of Av. P₂O5 and Ex. K in BVAS were high with 46% and 56%, respectively. As for the correlation between citrus orchard soil chemical components, the pH and Ex. cations (K, Ca, and Mg) showed a positive correlation, and the pH and lime requirement showed a negative correlation. Organic matter showed a negative correlation with Av. P₂O5 and a positive correlation with lime requirement. In conclusion, the fertilizer management of the soil in Jeju needs to be managed differently depending on the soil color.

Effects of Fertilization on the Nitrogen Residual Amounts and Leaching from Citrus Orchard Soil in the Three Gorges Reservoir Area

This experiment has the citrus orchard soil in the basin of the Zigui County Ecological Station in the Three Gorges Reservoir Area as its research object. Leaching tests of an undisturbed soil column at 0-20, 0-40, and 0-60 cm depth were performed in a citrus orchard. The effects of nitrogen leaching and residual amounts in the soil were studied. Four kinds of fertilization treatments were set up in the experiment:no fertilization treatment (CK), low nitrogen fertilization treatment (T1:250kg·hm-2), medium nitrogen fertilization treatment (T2:500kg·hm-2), and high nitrogen fertilization treatment (T3:750kg·hm-2). The results showed that:① The main form of nitrogen leaching in citrus orchard soil was nitrate nitrogen (NO3--N), accounting for 36.93%-60.07% of total nitrogen (TN) leaching. The ratio of TN to ammonium nitrogen (NH4+-N) was 4.40% to 5.79%. The ratio of NO3--N residues in soil to TN residues was 11.31‰-45.66‰, and the ratio of NH4+-N residues to TN residues was 1.051‰-2.07‰. ② Nitrogen leaching and residual amounts in citrus orchards at the same depth showed significant positive correlation with the amount of fertilizer applied. The leaching losses and residual amounts of TN in soil at different fertilization rates were 11.35-30.11 kg·hm-2and 0.30-1.86 g·kg-1, respectively. Among them, the ratio of leaching losses of NO3--N and NH4+-N to TN leaching amounts peaked under T2 treatment, and the peaks of NO3--N and NH4+-N residues in TN residual amounts appeared in T1 and T2 treatment, respectively. ③ Given the same fertilization amounts, the leaching amounts and residual amounts of different forms of nitrogen in the soil were greatly affected by soil depth. After fertilization, the peaks of NO3--N leaching and residual amounts appeared at 20 cm and 40 cm, respectively, and the peaks of NH4+-N leaching and residual amounts mainly appeared at 20 cm depth. Inferred from the results of the experiment, the neutral nitrogen treatment in the 0-40 cm soil column is more conducive to the conversion of fertilizer nitrogen to inorganic nitrogen for plant absorption, and reduces the risk of nitrogen leaching after fertilization.