To improve the degradation efficiency of cellulose distributed in livestock, poultry wastes and garden wastes, a high-efficiency cellulose-degrading fungus which was from bamboo shavings, dead branches, and rotted leaves, and sheep dung was screened with Congo red staining, filter paper disintegration test and the endoglucanase [carboxyl methyl cellulose (CMC)] activity was tested. The physiological and molecular identification of the strain was carried out. The results showed that a high-efficiency cellulose-degrading fungus was screened in this study, which was identified as Trichoderma longibrachiatum by morphological observation and fungus species identification, and named as T. longibrachiatum ZJ-10. Single factor test showed that the conditions for achieving the maximum enzyme production activity showed as follows: 3% inoculation, initial pH 6.5, rotation speed of 160 r/min, 40 ℃, and cultured for 5 d. According to Plackett-Burman experimental design, Box-Benhnken steepest climbing path method and response surface methodology, the optimal enzyme production medium formula was 5 g/L NaCl, 7 g/L peptone, and 12 g/L CMC-Na. Under the optimal conditions, the CMC enzyme activity of strain ZJ-10 could reach 80.32 U/mL, which was 26.45% higher than that of the former optimization. In conclusion, strain of T. longibrachiatum ZJ-10 with strong CMC enzyme activity was screened in this study, which provides a good strain resource for the utilization of livestock, poultry and garden waste resources.
In order to explore the migration and enrichment law of uranium (U) and its related elements in farmland soils (aeolian sandy soils) and plants in Qianjiadian U mining area of Inner Mongolia, the roots, stems, leaves and rhizosphere soil samples of zoysiagrass, sorghum, peanut, corn, willow and poplar were collected systematically. The contents of 13 kinds of heavy metal elements such as uranium (U), arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), manganese (Mn), molybdenum (Mo), nickel (Ni), lead (Pb), antimony (Sb), thorium (Th) and zinc (Zn) were analyzed, as well as their bioconcentration factors and translocation factors among the soils and plants. The results showed that: 1) The content of heavy metal elements in the aeolian sandy soil of Qianjiadian U mining area was low, and the concentration coefficient was mostly lower than one. Uranium was significantly positive correlation with other elements. 2) The contents of heavy metal elements in the zoysiagrass and its rhizosphere soil were higher than those of other plants. 3) The plants had selective absorption of heavy metal elements, among which poplar had the strongest enrichment effect on Cd, while zoysiagrass, peanut and willow could enrich Cu, Mo and Zn, respectively. 4) The absorption of heavy metal elements by various organs was generally in the order of leaf＞root＞stem. On the whole, the content of heavy metal elements in the aeolian sandy soil is low, and the plants have strong selective absorption capacities of Cd and Zn in soil, and strong tolerance to heavy metal elements. Zoysiagrass, sorghum and peanut can be used as candidate plants for ecological restoration after mining.
Islands have special geographical landscapes and complex soil forming conditions, where the soil formation is different from that in mainland areas. To understand the genesis characteristics and taxonomic classification of island hilly soils in Zhejiang Province, 80 soil profiles were surveyed combining with historical literature data in this study. The results showed that the geomorphic structures, parent materials, climatic conditions, and vegetation types of the soils were relatively single, but the soils were frequently affected by the island scales, distances from land, tide, and human activities. The terrain slope was large; the lithification was obvious; the clayization was weak; the desilicification-allitization was changeable; the weathering-leaching coefficient was medium; the restoring base cations were obvious; the pH value and base saturation percentage were higher than those in the mainland at the same latitude; and the soil forming environment was affected by both ancient and modern factors. Four soil orders, namely Ferrosols, Argosols, Cambosols, and Primosols, were identified from the islands of Zhejiang Province, including 7 suborders of Ustic Ferrosols, Udic Ferrosols, Ustic Argosols, Udic Argosols, Ustic Cambosols, Udic Cambosols, and Orthic Primosols, as well as 10 soil groups, 11 subgroups and 25 soil families. In conclusion, the direction of soil formation from the islands of Zhejiang Province is basically the same as that of mainland hilly soil at the same latitude, belonging to the traditional ‘red soil zone’.
Under the iron-deficiency condition, roots of graminaceous plants secrete mugineic acids into the soil. To determine the effects of rice root exudate 2′-deoxymugineic acid (DMA) on rhizosphere and root endosphere bacterial community, wild type rice named as Nipponbare and osbhlh156 and iro2 mutant rices that loss the ability to secrete DMA were used as experimental materials in this study. The rhizosphere and root endosphere microorganisms were sampled for DNA extraction and 16S rRNA gene amplicon sequencing and data analysis. The results showed that soil types and cultivation conditions had significant impacts on rhizosphere and root endosphere bacterial community composition. In contrast, the root exudate DMA had relatively less impact, but not negligible. The bacterial species and diversity decreased from rhizosphere to root endosphere, which confirmed that the root endosphere bacteria were gradually selected and colonized inside root by interacting with plants. Nine microbial taxa, including Bradyrhizobium and Dictyobacter, etc., were selected as biomarkers, to distinguish whether there is DMA secretion in the rice rhizosphere. Through functional prediction, it was found that the bacterial taxa with adenosine triphosphate-binding cassette (ABC) transporter function may be involved in plant iron transport and related function. This study clarifies the effects of DMA on the composition of rhizosphere and root endosphere bacterial community of rice and provides data support for the comprehensive analysis of the role of microorganisms in response to iron deficiency in rice.
Mulberry sclerotial disease is a devastating disease in mulberry production. In order to understand the existent situation of pathogens and their microecology in the soil of the mulberry field, we collected the soil samples from mulberry fields in four plots of different regions in Zhejiang Province [namely Deqing County (DQ), Changxing County (CX), Jinhua Duohu Residential District (JD) and Jiangdong Town (JJ)]. Among them, CX mulberries were cultivated in greenhouse, and the others were cultivated in open field. The experiment took one plot in Sichuan Province as a control (CK), which was rarely or never found the sclerotial disease. Then, we identified the soil fungi and bacteria through high-throughput sequencing of internal transcribed spacer (ITS) and 16S rRNA. The results showed that the relative abundance (RA) of genus Ciboria in the mulberry fields of DQ, JJ and JD were 28.84%, 60.17%, and 70.15%, respectively. No diseased fruit of mulberry sclerotinia was found in CX and CK fields, and the relative abundance of Ciboria was 0.02% and 0.06?, respectively. The main microorganisms in CX field were Mortierella, Chaetomium, and Humicola, with the relative abundance of 36.46%, 21.59%, and 15.93%, respectively; the main microorganisms in CK field were Penicillium, Fusarium, and Fusicolla, and their relative abundances were 24.05%, 15.35%, and 9.75%, respectively. Among the bacteria, Pseudomonas was the only genus identified in all five field samples, and the highest relative abundance of Pseudomonas was found in the JJ field (but only 6.81%), highlighting a rich bacterial diversity. Collectively, the relative abundance of the genus Ciboria and the diversity of fungi and bacteria reveal the complex relationship between the relative abundance of Ciboria and the soil microecology in mulberry fields. It also further implies the possibility of preventing and controlling mulberry sclerotial disease by changing the soil microecological structure.
Polychlorinated biphenyls (PCBs) are typical pollutants in soil. Nanoscale zero-valent iron (nZVI) can effectively dechlorinate high-chlorinated PCBs into low-chlorinated PCBs which can be more easily degraded by microorganisms. In this study, soil samples contaminated by PCBs were collected from an e-waste recycling site in Taizhou, Zhejiang Province. The remediation of combined nZVI and PCBs-degrading strain Rhodococcus pyridinovorans R04 was carried out to investigate the removal effect of PCBs in soil. The results showed that the combined treatment of nZVI and degrading strain R04 had better effects than the treatment of nZVI or R04 alone in removing PCBs or various chlorinated PCB congeners in soil. After combined treatment with nZVI and degrading strain R04 for 32 d, the removal rate of PCBs in soil reached 59.4%, which was higher than 46.1% of nZVI treatment and 34.4% of degrading strain R04 treatment (P＜0.05). Therefore, the combination of nZVI and degrading bacteria in the remediation of PCBs contaminated soil has good application potential.
To explore the effects of seabuckthorn fruit residue on soil physicochemical properties, greenhouse gas (CO2, CH4, N2O) emissions, and the microbial numbers, a 28-day soil pot experiment was conducted. Three groups of materials were used, including seabuckthorn fruit residue (R), biochar (B), and biological ceramsite (T) in the experiment, and a natural culture was used as the control group (CK). The results showed that the seabuckthorn fruit residue significantly promoted the contents of soil nutrients such as total carbon, total nitrogen, and available potassium, and the average increase rates were 16.31%, 14.99%, and 46.15%, respectively. Besides, the soil pH was also enhanced from 0.25 to 0.69. The microbial numbers in the soils treated with seabuckthorn fruit residue were promoted significantly. The average growth rate of microorganisms in the first 14 days was 335.6% higher than that of the control. The CO2 emissions and global warming potential (GWP) with the treatment of seabuckthorn fruit residue were higher of biochar (R) treatment, while the CH4 and N2O emissions were both lower than those of biochar (B) and biological ceramsite (T) treatments. In general, the seabuckthorn fruit residue showed relatively high returning value, but its risk of greenhouse gas emission should also be considered. This study can provide some references for the practice of returning seabuckthorn fruit residue into the field.
To evaluate phytotoxicity of zinc oxide nanoparticles (ZnO NPs) on plants, the effects of 0, 5, 50, 250 mg/L ZnO NPs on nutrient uptake and photosynthesis of lettuce were studied using hydroponic culture with Zn2+ andbulk ZnO as comparisons. The results showed that ZnO NPs inhibited the growth of lettuce, and biomass of lettuce decreased obviously with the increase of ZnO NPs concentration. Under the 5-250 mg/L ZnO NPs treatments, the contents of magnesium (Mg), iron (Fe), manganese (Mn) and copper (Cu) in the shoots of lettuce were reduced by 18.0%-33.3%, 19.0%-28.6%, 17.2%-28.3% and 17.4%-33.8%, respectively. Further-more, 50 and 250 mg/L ZnO NPs treatments significantly decreased the chlorophyll content and chloroplast activity of lettuce. Under the 5-250 mg/L ZnO NPs treatments, net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular carbon dioxide concentration (Ci) and transpiration rate (Tr) of lettuce decreased by 33.7%-75.0%, 21.3%-36.7%, 11.2%-29.0% and 30.7%-83.4%, respectively; the maximum photochemical efficiency (Fv /Fm), photochemical quenching coefficient (qP), actual photochemical quantum yield (ΦPSⅡ), and electron transport rate decreased by 6.3%-18.8%, 7.0%-14.0%, 5.0%-20.0% and 5.8%-20.7%, respectively. The inhibition of 250 mg/L ZnO NPs on the photosynthesis of lettuce was much greater than that of the corresponding Zn2+ release amount and bulk ZnO with the same concentration. These results indicate that ZnO NPs can inhibit the photosynthesis of lettuce by affecting the mineral nutrient absorption, hindering the chlorophyll synthesis, and reducing the photosystem Ⅱ activity.
This paper studied the effects of different seedling quality traits of Sedum plumbizincicola on the removal rate of cadmium (Cd). By the methods of correlation analysis, principal component analysis and clustering analysis, it was found that seedling quality had a great impact on Cd removal efficiency and remediation cost, and stem diameter, branch number, seedling height and Cd content were the important indexes to determine the quality of seedlings. The shoot Cd uptake of the Ⅰ or Ⅱ grade seedling with stem diameter≥5.0 mm, branch number per plant≥2, seedling height≥6.0 cm and seedling Cd content≤5 mg/kg, was more than 200 g/hm2 after 90 d of planting. The remediation efficiencies of the Ⅰ and Ⅱ grade seedlings were over 3.4 times higher than the Ⅳ grade seedling (stem diameter＜4.0 mm, branch number per plant of 0-1, seedling height＜6.0 cm, seedling Cd content≤5 mg/kg), and using Ⅰ and Ⅱ grade seedlings could effectively save labor cost, and reduce or avoid herbicide application. A case of large-area heavy metal contaminated soil remediation was carried out to test this quality classification standard for S. plumbizincicola seedlings, and it was found that the shoot Cd uptake of the Ⅰ or Ⅱ grade seedling was 222.35 g/hm2 after 120 d of planting, and the remediation effect could reach or even higher than that of 6-8 months in previous experiments. In summary, the high-quality S. plumbizincicola seedlings is an important basis for improving remediation efficiency and reducing remediation cost. This study clarifies the quality traits and remediation efficiencies of different grades of seedlings. This standard for grading S. plumbizincicola seedlings is helpful to promote the standardization and mechanization of remediating heavy metal contaminated soil with this plant.
The high degree of intensive utilization of vegetable field soils is prone to nutrient imbalance and excessive accumulation, which hinders the sustainable development of vegetable production. Based on the analysis of fertility status and main obstacle factors of vegetable field soils under the open land and facility cultivation patterns in the Xitiaoxi watershed, the threshold of soil phosphorus (P) loss was explored in this study. The results indicated that the soil pH value under the open land cultivation pattern was significantly lower (P＜0.05) than that under the facility cultivation pattern. The contents of soil total potassium (K), available K, available P, and water-extractable P under the facility cultivation pattern were significantly higher (P＜0.05) than those under the open land cultivation pattern, as well as the total soluble salt content and electrical conductivity. It was also found that the fertility grades of vegetable field soils under the two cultivation patterns were mostly (95.8%) Grade Ⅱ. The correlation between soil water-extractable P and Mehlich 3-P was well illustrated with the piecewise linear regression equation. The threshold of Mehlich 3-P for controlling P loss from the open land and facility vegetable field soils was estimated to be 102.7 mg/kg and 128.7 mg/kg, respectively. Thus, the soil samples exceeding this threshold accounted for 65.0% and 83.3% of the total number of samples, respectively. In conclusion, the soil acidification and the risk of P loss under the open land and facility cultivation patterns in the Xitiaoxi watershed are serious, and the soil salinization under the facility cultivation pattern is an outstanding issue.
By selecting a typical blue clayey paddy soil with planting single-season rice in the southeast coast, we studied the effects of urea fertilizer containing N-(n-butyl) thiophosphoric triamide (NBPT, urease inhibitor) and 3, 4-dimethylpyrazole phosphate (DMPP, nitrification inhibitors) biochemical inhibitors on the nitrogen transformation in the surface water and soil and rice growth under the different fertilization times and levels. The results showed that: compared with the conventional urea fertilizer treatment, when the urea added with NBPT and DMPP combined biochemical inhibitors was applied twice as 50% base fertilizer and 50% topdressing, the concentrations of ammonium, nitrate and nitrite in field surface water decreased by 7.0% and 13.2%, 46.5% and 50.5%, 75.4% and 58.2% at the regreening stage and early tillering stage of rice, respectively; the ammonium concentration in soil decreased by 21.8% at the regreening stage and increased by 27.5% and 9.3% at the later tillering stage and jointing stage of rice; besides, the plant height, tiller number and chlorophyll content of rice were increased by 4.8% and 4.1%, 4.9% and 11.8%, 17.8% and 15.9% at the tillering stage and jointing stage, respectively. Furthermore, the yield and biomass of rice increased by 6.8% and 12.5%, 9.2% and 12.6%, respectively, at the mature stage, when the urea added with NBPT and DMPP combined biochemical inhibitors was applied once as base fertilizer or twice as 50% base fertilizer and 50% topdressing. In conclusion, the combined application of NBPT and DMPP biochemical inhibitors can effectively inhibit the rapid increase of ammonium and nitrate nitrogen in soil and field surface water, delay the transformation rate of nitrogen form, and maintain the relatively low nitrate nitrogen concentration in the surface water and soil in the rice fields, which can reduce the risk of nitrogen loss in paddy fields, promote rice growth and increase rice yield.
Rhizosphere microorganisms play an important role in plant growth and adaptation to the environment. In order to reveal the characteristics of rhizosphere bacterial community of endangered plant Cupressus gigantea in Tibet, we employed 16S rRNA gene high-throughput amplicon sequencing technology combined with soil chemical properties to examine the rhizosphere bacterial composition and diversity in Bayi District, Milin County, and Langxian County of Nyingchi City in Tibet and their influencing factors. The results showed that the diversity of bacteria in the rhizosphere of C. gigantea was rich, and the dominant bacterial phylum were Actinobacteriota, Proteobacteria, and Acidobacteriota. There were 757 shared genera (65.83%) of rhizosphere bacteria in C. gigantea in Langxian County, Bayi District, and Milin County, with 125 (10.87%), 39 (3.39%) and 41 (3.56%) unique genera, respectively, and the β-diversity analysis of non-metric multidimensional scaling based on Bray-Curtis distance revealed significant differences among populations. The positive correlation of the co-occurrence network of bacterial communities was more than 68%, and the cooperative relationship was greater than the competitive relationship. Soil available phosphorus (AP), total phosphorus (TP), and ammonium nitrogen (NH4+-N) were important factors driving changes in the structure of rhizosphere bacterial community. In order to adapt to different growth environments, various groups of C. gigantea have formed unique rhizosphere bacterial communities. The above results can provide a reference for studying the role of rhizosphere microorganisms in the growth and environmental adaptation of C. gigantea and the protection of C. gigantea resources.
Non-point source nitrogen (N) pollution is one of the major environmental threats of water quality degradation in agricultural watersheds. Based on the monitoring data of N output at riverine outlet section and the calculation of net anthropogenic nitrogen input (NANI) in the Changle River watershed of Shengzhou City, Zhejiang Province from 2003 to 2016, the response relationships of riverine water quality to NANI and meteorological factors driving non-point source pollution were explored, and a response model was established to evaluate riverine N pollution sources in this study. The results showed that, during the study period, the average NANI was 95.77 kg/(hm2·a), among which chemical fertilizer N, net human food and animal feed N, atmospheric N deposition, biological N fixation and seed N contributed 53.90, 25.62, 11.94, 4.18 and 0.13 kg/(hm2·a), respectively. The average riverine N export was 2 178.78 t/a, which was positively correlated with NANI and precipitation, and negatively correlated with evaporation and wind speed in the studied watershed. Accordingly, the simulated results of the response model [R2=0.801 0, Nash-Sutcliffe efficiency coefficient (NSE)=0.799 1] showed that the historical remained N in the watershed, the NANI of the current year and the riverine background N accounted for 66.8%, 30.8% and 2.4% of the riverine N export, respectively. These results indicated that the historical remained N in the watershed was the largest contributor to riverine N pollution with a long-term impact on riverine water quality, which implied the existence of lag effect of riverine water quality in response to the measures of N emission reduction in the watershed. Therefore, the implementation of long-term N control measures should be an important strategy to prevent and control riverine N pollution in agricultural watershed.
As a processing technology that can rapidly fabricate customized products in small batches, three-dimensional (3D) printing has great application potential in horticultural gardens. On the basis of existing studies on controlled releasing materials for 3D printing, the carrier materials for solo nutrition were developed after a range of formulation screening. The new formulations were suitable for material extrusion 3D printing and the single-material carrier formulation fertilizer contained sodium alginate or xanthan gum as a binder, mannitol as a filler, ethanol/water with fixed ratio as a solvent, sepiolite as a thickening agent, and urea as the core fertilizer. It was confirmed that the maximum adding ratio of urea could reach 1∶4 [m (urea)∶V (solvent)] when using sodium alginate as a binder, while the maximum adding ratio could reach 3∶4 [m (urea)∶V (solvent)] when using xanthan gum as a binder. It was confirmed that the developed formulation could also be used as the carrier of other types of nutrients including KCl, K2HPO4, and ZnSO4. This work also demonstrated that it was possible to combine different nutrients and achieve element couplings by using multi-material extrusion 3D printing technology. Through the printing parameter adjustment experiment, the optimal printing was achieved when the printing speed was 200 mm/min, and the extrusion speed was 0.02 mm/s, and the extrusion height was 1 mm, and the nozzle diameter was 1 mm. The controlled release period of different formulations were further studied by the sand column leaching method. There were significant differences between the controlled release period of single-material carrier formulation fertilizers under different formulations and their post-treatments. The modified formulation with sepiolite can obviously change the release rate of single-material carrier formula fertilizer and the longest controlled release period reached 30 d.
Bacterial leaf blight in rice is a significant disease, and understanding the effects of straw burning on pathogens and antibiotic resistance genes (ARGs) in paddy fields is crucial. Soil and rice stubble samples were collected from bacterial leaf blight outbreak areas in Ningbo City of Zhejiang Province, and these samples were subjected to high-throughput metagenomic sequencing to investigate the effects of straw burning. The results indicated that the relative abundance of pathogens in the rice stubble was significantly higher than that in the soil. After straw burning, except for the significant increase in available potassium content, there were no significant changes in the other physicochemical properties of the soil. Overall, there were no significant differences in pathogen community diversity after straw burning, but straw burning led to a sharp decrease in the relative abundance of Xanthomonas oryzae in the rice stubble. The relative abundances of ARGs in the soil and rice stubble increased after straw burning, but there were no significant differences compared with those before straw burning (P＞0.05), while the relative abundance of mobile genetic elements (MGEs) in the rice stubble decreased significantly after straw burning (P＜0.05). The proportion of positively correlated links in the coexisting networks of pathogens-ARGs decreased after straw burning. Mantel analysis revealed that the water content (r=0.642, p＜0.01), pH value (r=0.582, p＜0.05), total organic carbon content (r=0.325, p＜0.05), total nitrogen content (r=0.570, p＜0.01), and available phosphorus content (r=0.311, p＜0.05) were closely related to the soil ARG subtypes; the dissolved organic carbon (DOC) content (r=0.275, p＜0.05) and available potassium content (r=0.312, p＜0.05) were correlated with the ARG subtypes, and the DOC content (r=0.201, p＜0.05) significantly affected the pathogen community structure in the rice stubble. In summary, straw burning can reduce the relative abundance of X. oryzae in the rice stubble, which suggests that it may be a viable option for preventing and controlling rice bacterial leaf blight; moreover, a reduction in the positive correlation ratio of pathogens-ARGs and in the relative abundance of MGEs after straw burning may inhibit the formation of potentially resistant pathogens. However, given the complexity of soil biological compound pollution, the effects of straw burning on pathogens and ARGs in paddy fields need to be further explored by long-term location experiments.
In the highly acidic soil pilot area contaminated by cadmium (Cd) in Yongkang City of Zhejiang Province, we screened low-Cd-accumulating rice cultivars and soil passivators in the field and performed the combined effect tests for two consecutive years to explore the safe utilization technology model suitable for local Cd-polluted paddy fields. The results showed that ‘Xiushui 519’ (XS519), ‘Zhenuo 106’ (ZN106), ‘Zhongzheyou 1’ (ZZY1H) and ‘Zhongjia 8’ (ZJ8H) could be recommended as low-Cd-accumulating rice cultivars suitable for local planting. Among them, ‘Xiushui 519’ had the lowest and most stable Cd accumulation ability, and the average bioconcentration factors (BCFs) of Cd in the rice grains in the two years were 0.090 and 0.159, respectively; in the screening tests of passivators, the improvement effect of lime (L) on soil pH was significant. Lime, iron-modified biochar (FeC) and calcium-magnesia phosphate fertilizer (CaMgP) could reduce soil available Cd contents to a certain extent (passivation rates were 14.8%, 7.1% and 6.9%, respectively). In addition, 1 800 kg/hm2 iron-modified biochar and 2 400 kg/hm2 soil conditioner had better effects on reducing the Cd content in the rice grains of ‘Zhongjia 8’, which decreased by 32.2% and 29.0%, respectively, after application. According to the results of the combination tests of the low-Cd-accumulating cultivars and passivators, both the application of 2 250 kg/hm2 iron-modified biochar and 2 250 kg/hm2 soil conditioner increased obviously the soil pH values at the tillering stage and filling stage, the soil conditioner of which had a better improvement effect. The Cd contents in the rice grains of ‘Xiushui 519’ and ‘Zhenuo 106’ were extremely significant correlations with the soil pH values (5.19-5.61) at the mature stage. Within the range of soil pH values involved in the test, except for the combination of ‘Xiushui 519’ and the 1 500 kg/hm2 soil conditioner, the Cd content in the rice grains increased with increasing application amount of passivators. Therefore, planting ‘Xiushui 519’ (a low-Cd cultivar) directly is the best choice for the safe utilization of Cd-contaminated paddy fields in this area, which is both economical and convenient.
To understand the community structure composition and dynamic change characteristics of human pathogenic bacteria (HPB) in soils after manure application, laboratory cultivation experiments were conducted on agricultural soils with long-term application of chicken manure, pig manure, or chemical fertilizer in five regions of Hangzhou, Jiaxing, Quzhou, Jinhua, and Longyou in Zhejiang Province, and the community compositions of the soil bacteria and HPB were analyzed by high-throughput sequencing and sequence alignment methods. The results showed that a total of 75 HPB were detected in 160 soil samples and two manure samples, and the dominant HPB were Bacillus_megaterium_QM_B1551 (24.2%) and Clostridium_beijerinckii_NCIMB_8052 (23.1%). The Shannon indexes of bacteria and HPB in the soils decreased after the application of pig manure, while the diversities of bacteria and HPB in the soils with the application of chicken manure or chemical fertilizer had no significant changes. The results of the principal coordinate analysis showed that there was a significant difference in the bacterial community composition of soils between the manure treatment and the unfertilized control, especially in the pig manure treatment (P＜0.001); 22.7% of all HPB were shared among the soil samples; and the relative abundance of most HPB in the soils treated with manure was higher than that in the unfertilized control, and it decreased continuously with the extension of cultivation time. The results of the variance partitioning analysis showed that soil physicochemical properties, bacterial communities, and their interactions were important factors contributing to the variation of HPB in the soils. In summary, the HPB variation characteristics in soils treated with manure are influenced mainly by manure types, soil types, soil physicochemical properties, and inherent bacterial communities.
Non-flooding plastic film mulching cultivation (PM) for rice is a comprehensive and innovative technology that utilizes plastic film covering as the core to achieve water-saving rice production. However, after mulching with plastic film, nitrogen (N) fertilizer can only be applied once as a basal fertilizer before transplanting, which will lead to excessive vegetative growth at the early stage and potential N deficiency at the late growth stage, thereby limiting the high yield of rice. Polymer coated urea (CR) is a controlled release N fertilizer that has become one of the best management measures for improving crop yield and N use efficiency under a traditional flooding cultivation (TF) pattern, but it has not been evaluated in a long-term positioning test under the PM pattern. In this study, taking the high-yielding and medium-maturing indica hybrid rice cultivar ‘Liangyoupeijiu’ as a test material, the effects of applying CR and urea (UR) on rice yield, N use efficiency and soil nutrient contents were compared under the PM and TF patterns. The results showed that, compared with applying UR, applying CR under the TF and PM patterns improved the N use efficiency by 9.2% and 15.4%, respectively (P＜0.05), and increased the rice yield by 8.6% and 15.0%, respectively (P＜0.05). Compared with the TF pattern, the PM pattern accelerated the decomposition of soil organic matter and reduced the contents of total N and alkali-hydrolyzable N in the soil. Compared with applying UR, applying CR under the PM pattern alleviated the decrease of the total N and alkali-hydrolyzable N contents in the soil and increased the economic benefits by 16.8%. In summary, applying CR is an effective way to solve the problem of N deficiency at the late growth stage of rice under the PM pattern.
