Explore the vast range of titles available.

PurposeBiogas slurry (BS) is widely used as a valuable fertilizer for crop production. However, little is known about the effects of long-term BS application on potential pollution risk of heavy metals and bacterial community in paddy field. This study aimed to determine the accumulation and rice plant uptake of heavy metals (Cd, Cr, Pb, Cu, and Zn), as well as soil bacterial community composition following repeated BS application in a single rice cropping system.Materials and methodsIn this study, four treatments were included in a long-term field experiment: CK, no fertilizers; MF, mineral fertilizers, 270 kg urea-N ha–1; and two application rates of BS (BS1, 270 kg N ha–1 and BS2, 540 kg N ha–1). The heavy metals (Cd, Cr, Pb, Cu, and Zn) in soils and rice plants were measured by an inductively coupled plasma mass spectrometer and the soil bacterial community composition was analyzed using Illumina MiSeq sequencing of the 16S rRNA.Results and discussionSoil Zn concentrations were significantly greater in the BS treatments than in the MF treatment. Biogas slurry application significantly increased the heavy metals concentrations in rice plants, compared to the CK treatment. The concentrations of Cd and Pb in grain, and Cu and Zn concentrations in straw were significantly increased by the BS2 treatment compared to the MF treatment, respectively. However, the Cd, Cr, Pb, Cu, and Zn concentrations in grain and soil were all within the safety limits after long-term BS application. Application of BS and of MF resulted in similar bacterial alpha-diversities, and both increased them compared to the CK treatment. Fertilization significantly enhanced the relative abundances of phyla Proteobacteria, Actinobacteria, and Myxococcota but reduced that of Planctomycetota compared to the CK. While, there were no significant differences in those phyla among fertilized treatments. The relative abundances of genera Thiobacillus and Ellin6067 was decreased by the BS2 treatment compared to the MF treatment. Redundancy analysis (RDA) showed that soil organic carbon, available phosphorus and available potassium were the main factors shaping soil bacterial community composition. Spearman’s correlation demonstrated that soil Cd concentration had stronger correlation with some bacterial genera of Bryobacter, Vicinamibacteraceae, and Ellin6067.ConclusionsOverall, we conclude that BS application can be considered to substitute mineral fertilizers for rice production. However, the accumulation of heavy metals in paddy soil, especially for Zn, should be considered after long-term BS application.

Soil acidification often occurs when the concentration of ammonium (NH 4 + ) in soil rises, such as that observed in farmland. Both soil acidification and excess NH 4 + have serious adverse effects on crop growth and food production. However, we still do not know which of these two inhibitors has a greater impact on the growth of crops, and the degree of their inhibitory effect on crop growth have not been accurately evaluated. 31 wheat cultivars originating in various areas of China were planted under 5 mM sole NH 4 + (ammonium nitrogen, AN) or nitrate nitrogen in combined with two pH levels resembling acidified conditions (5.0 and 6.5). The results showed that the shoots and roots biomass were severely reduced by AN in both and these reduction effects were strengthened by a low medium pH. The concentration of free NH 4 + and amino acids, the glutamine synthetase activity were significantly higher, but the total soluble sugar content was reduced under NH 4 + conditions, and the glutamine synthetase activity was reduced by a low medium pH. Cultivar variance was responsible for the largest proportion of the total variance in plant dry weight, leaf area, nodal root number, total root length and root volume; the nitrogen (N) form explains most of the variation in N and C metabolism; the effects of pH were the greatest for plant height and root average diameter. So, soil acidification and excess NH 4 + would cause different degrees of inhibition effects on different plant tissues. The findings are expected to be useful for applying effective strategies for reducing NH 4 + stress in the field.

PurposeThe objectives of this study were to evaluate the effects of long-term organic materials incorporation on the soil aggregate and density-based fractions, and associated soil carbon (C) and nitrogen (N) conversion in the rice fields.Materials and methodsA long-term located experiment was conducted to study the effects of continuous application of organic materials (milk vetch, rice straw, and poultry manure) on the distribution characteristics of soil aggregate and density-based fraction, as well as its organic C and N, in rice fields. The soil aggregate was classified using the wet-sieving method. Light fraction (LF) and heavy fraction (HF) were classified according to density fractionation. Aggregate organic C (AC) and total N (AN), LF organic C (LFC) and N (LFN), and HF organic C and N concentrations were measured by using the Elementar Vario ISOTOPE elemental analyzer.Results and discussionApplication of organic materials increased the aggregate mass proportion of 2–0.25 mm (by 4.9–12.6%) and 0.25–0.053 mm (by 27.5–40.7%) fraction and its AC and AN concentration. The soil aggregate particulate organic C and total N were greatly improved with organic materials application. Furthermore, organic material had more obvious effect on the soil C and N in the LF than HF, which improved the LF particulate mass proportions by 75.1–177.0%, LFC by 51.7–68.4%, and LFN by 14.2–111.2%, respectively. Poultry manure had the greatest effect on increasing the AC, LFC, AN, and LFN, followed by milk vetch and rice straw.ConclusionsMilk vetch, rice straw, and poultry manure could effectively increase the soil intermediate aggregate and LF proportion, and stimulate the stabilization and fixation of C and N in rice fields. It is an effective agricultural practice by applying organic material to improve soil fertility and sustaining high crop productivity. The increases of intermediate aggregate and associated C and N may be the main factor for soil C and N sequestration under continual application of organic materials.

Understanding how organic amendments affect microbial carbon use efficiency (CUE) and necromass C (MNC) is crucial for understanding soil organic C (SOC) formation and accrual in paddy fields, but the underlying mechanisms remain largely unclear. In this study, the microbial CUE, MNC, and microbial community composition, as well as SOC fractions and chemical composition, were measured under long-term organic amendments: rice straw (RS), green manure (GM), and pig manure (PM) in paddy soils. Four treatments were included: (1) chemical fertilizers (CF); (2) CF plus RS (CF + RS); (2) CF plus GM (CF + GM); and (4) CF plus PM (CF + PM). The CUE, MNC, and microbial community were determined by 18O-H2O incubation, amino sugars levels, and phospholipid fatty acids (PLFAs) content, respectively. Results showed that SOC, particulate organic C (POC), and mineral-associated organic C (MAOC) concentrations were significantly increased by organic amendments compared with chemical fertilization alone. The O-alkyl C decreased, but aromatic C increased with long-term organic amendments, suggesting enhanced SOC hydrophobicity. GM and PM inputs significantly enhanced microbial CUE, but straw return did not affect microbial CUE compared to CF. Microbial growth and C uptake increased by 25.2–42.4% and 19.8–30.0% under organic amendments relative with CF. Microbial respiration was increased by RS and GM amendments. Turnover time was more rapid in CF + RS and CF + GM than in CF and CF + PM. Compared to CF, organic amendments increased the MNC concentration due to the increase in microbial biomass. In addition, CF + RS and CF + GM enhanced the MNC contribution to SOC, but PM had no effect, suggesting that PM contributed more organic C from non-microbial sources. The SOC, POC, and MAOC increased with microbial CUE and MNC, indicating that microbial traits play a crucial role in SOC accrual. Higher microbial CUE and biomass explained the increased MNC accumulation under organic amendments. Our study highlights the crucial role of microbe-mediated processes in SOC accrual under long-term organic amendments in paddy soils. Our findings show that organic amendments are an effective management practice for accumulating more SOC in paddy soils.

Biochar application is widely recognized as an effective approach for increasing soil organic carbon (SOC) and mitigating climate change in agroecosystems. However, the effects of biochar application on net accumulations and relative contributions of different SOC sources remain unclear. Here, we explored the effects of biochar application on plant‐derived (PDC) and microbial necromass C (MNC) in a 10‐year experimental rice–wheat rotation field receiving four different intensities of biochar application (0, 2.25, 11.5, and 22.5 t ha−1 for each crop season), using phospholipid fatty acids (PLFAs), lignin phenols and amino sugars as biomarkers of microbial biomass, PDC and MNC, respectively. Our results showed that biochar application increased SOC content and stock by 32.6%–203% and 26.4%–145%, respectively. Higher biochar application (11.5 and 22.5 t ha−1) increased soil pH, total nitrogen (TN), total phosphorus (TP), SOC/TN, and root biomass. In addition, higher biochar application enhanced bacterial, fungal, and total microbial biomass. Plant lignin phenols and MNC contents significantly increased, whereas their contributions to SOC significantly decreased with the increase in biochar application rates due to the disproportionate increase in PDC and MNC, and SOC. Fungal necromass had a greater contribution to SOC than bacterial necromass. The fungal/bacterial necromass decreased from 2.56 to 2.26 with increasing biochar application rates, because of the higher abundances of bacteria than that of fungi as indicated by PLFAs under higher biochar application rates. Random forest analyses revealed that pH, TP, and SOC/TN were the main factors controlling plant lignin and MNC accumulation. Structural equation modeling revealed that biochar application increased lignin phenols by stimulating root biomass, whereas enhanced MNC accumulation was primarily from increased microbial biomass and lignin phenols. Overall, our findings suggest that biochar application increases the accumulation of the two SOC sources but decreases their contributions to SOC in paddy soils. Long‐term successive biochar application increases lignin phenols accumulation by stimulating root biomass, whereas biochar application enhanced microbial necromass by increasing microbial biomass and plant lignin. Long‐term biochar application decreases the contributions of plant lignin and microbial necromass to soil organic carbon in paddy soils.

A 6-year field experiment was conducted to assess the effects of biogas slurry (BS) application on rice yield, soil nutrients, soil microbial activity (MicroResp™) and community composition (16S rRNA gene sequencing) in paddy field in southeast China. The experiment included five treatments: (1) 270 kg N ha−1 from urea (mineral fertilizers only, MF); (2) 135 kg N ha−1 from urea and 135 kg N ha−1 from BS (BS1); (3) 270 kg N ha−1 from BS (BS2); (4) 405 kg N ha−1 from BS (BS3) and (5) 540 kg N ha−1 from BS (BS4). Results showed that no significant differences were found in average rice yield between the MF and BS treatments (BS1–BS4). Both soil available phosphorus (AP) and soil available potassium (AK) increased with an increasing application rate of BS. The average substrate-induced respiration was significantly higher in the treatment with lower rate of BS (BS1 and BS2) than in other treatments and then decreased with increasing application rate of BS. Soil microbial communities were affected by BS application. Chloroflexi, Proteobacteria and Acidobacteria were the dominant bacterial phyla across all soil samples. The BS application resulted in a relative abundance of Nitrospirae 2.6–3.7 times than that in MF. Our results also indicated that AP and AK were the two main factors affecting soil microbial activity and community. Overall, the results suggest that the replacement of chemical fertilizer with BS may be an alternative management practice for improving soil quality, soil fertility and nutrient balance in paddy field.

Ammonia (NH 3 ) volatilization losses result in low nitrogen use efficiency (NUE) and various environmental impacts in agroecosystems. Machine-transplanted rice with side-deep fertilization (MRSF) has been recommended as an effective alternative to traditional transplantation with manual broadcasting of fertilizer. Controlled-release nitrogen fertilizer (CRF) can enhance rice yield and NUE in paddy fields. However, there is scarce information about combined effects of MRSF and CRF on NH 3 volatilization loss and rice grain yield, NUE, net economic benefit (NEB) in a double rice cropping system. In this study, a field experiment was conducted to evaluate the impact of MRSF with CRF on grain yields, NUE and economic returns of early rice and late rice from 2019 to 2021, as well as NH 3 emissions in two rice seasons (2019 and 2021). Six treatments were designed as no N fertilizer (N0), compound fertilizer broadcasting (CFB), compound fertilizer side-deep placement (CFD), CRF broadcasting (CRFB), CRF side-deep placement (CRFD1), and single side-deep placement of CRF (CRFD2). The results showed that the CFD and CRFB treatments decreased NH 3 volatilization while enhancing or maintaining rice yield and NUE compared to the CFB treatment. MRSF with CRF (CRFD1 and CRFD2) significantly reduced NH 3 emissions of early and late rice by 57.6–67.9% and 62.2–80.9% by decreasing the NH 4 + –N concentrations in the surface water compared to the CFB treatment, respectively. Rice grain yields in the MRSF with CRF treatments increased by 3.9–17.3% in early rice and 5.4–21.6% in late rice relative to the CFB treatment. In addition, MRSF with CRF treatments improved NUE for early and late rice from 32.1 to 36.2% and 21.3–28.4% in the CFB treatment to 48.4–61.2% and 39.7–62.3%, respectively. The yield-scale NH 3 volatilization losses were reduced under the MRSF with CRF treatments by 61.2–71.5% in early rice and 67.4–84.3% in late rice. Furthermore, MRSF with single basal application of CRF reduced time-consuming and labor-intensive while increasing rice yields and net economic benefits. Overall, co-application of MRSF and CRF can reduce NH 3 emissions, and improve rice yield, NUE and profitability in double rice cropping systems.

为探究猪粪和鸡粪有机肥部分替代化肥对椪柑橘园土壤培肥及果实产量品质的影响，通过2年定位试验，选用鸡粪和猪粪2种有机肥，开展7.5 t·hm-2和15 t·hm-2替代施用量对椪柑橘园土壤肥力、果实产量及品质的影响效果研究。结果表明，采用鸡粪和猪粪2种有机肥部分替代化肥的模式，可明显提升柑橘园土壤肥力。与全化肥处理相比，施用有机肥替代化肥处理的土壤酸化有所改善，全氮、有效磷、速效钾和有机质含量分别提高16.1%~54.7%、15.9%~30.1%、12.9%~36.9%和6.8%~39.6%。土壤微生物多样性的香农指数和均匀度增加，平均CO2产生率总体随着有机肥替代量的增加而提高，微生物数量明显增加。在同等有机肥替代化肥施用量条件下，猪粪有机肥培肥地力和增加土壤微生物数量及多样性的效果优于鸡粪有机肥。有机肥替代化肥处理较全化肥处理提高柑橘产量5.1%~19.5%，增加果实可溶性总糖2.7%~11.8%、维生素C 2.1%~10.8%、可溶性固形物5.9%~10.8%。7.5 t·hm-2猪粪有机肥替代化肥处理柑橘产量最高，而15 t·hm-2猪粪有机肥替代化肥处理柑橘品质最好。研究表明，采用有机肥部分替代化肥的施肥模式，有利于提高椪柑橘园土壤肥力和微生物多样性，进而提高果实产量、改善柑橘品质。This study investigated the effect of substituting chemical fertilizer with organic manure on soil fertility and the yield and quality of the fruit in a ponkan citrus orchard. A 2-year field experiment including two different application rates(7.5 t·hm-2 and 15 t·hm-2) of chicken manure and pig manure was conducted. Results showed that substituting chemical fertilizer with organic manure significantly improved soil fertility in a citrus orchard. The soil pH as well

This study investigated soil microbial responses to the application of tetracycline (TC), sulfamonomethoxine (SMM), and ciprofloxacin (CIP) alone and in combination in a soil culture pot experiment conducted at Hangzhou, China. Multiple approaches were applied for a better and complete depiction. Among the three antibiotics, SMM has a lowest dissipation and shows a most dramatic inhibition on microbial community and metabolism diversity. The combined application (AM) of SMM, CIP, and TC improved the dissipation of each antibiotic; similarly, SMM- and CIP-resistant bacteria showed larger populations in the AM than all single applications. Soils accumulated a large content of NO₃–N at day 20 after multi-antibiotics perturbation. All antibiotics stimulated soil basal respirations and inhibited soil metabolism diversity, whereas the interruption exerted by SMM and AM lasted for a longer time. Six nitrogen-cycling genes including chiA, amoA, nifH, nirK, nirS, and narG were quantified and found to decrease owing to both single- and multi-antibiotics perturbation. Overall, AM was most interruptive for soils, followed by SMM perturbation, while other antibiotics could be less interruptive. These results provide systematic insights into how soil microbial systems would shift under each single- or multi-antibiotics perturbation.

The application of nitrogen fertilizers leads to various ecological problems such as large amounts of nitrogen runoff loss causing water body eutrophication. The proposal that nitrification inhibitors could be used as nitrogen runoff loss retardants has been suggested in many countries. In this study, simulated artificial rainfall was used to illustrate the effect of the nitrification inhibitor DMPP (3,4-dimethyl pyrazole phosphate) on nitrogen loss from vegetable fields under combined organic and inorganic nitrogen fertilizer application. The results showed that during the three-time simulated artificial rainfall period, the ammonium nitrogen content in the surface runoff water collected from the DMPP application treatment increased by 1.05, 1.13, and 1.10 times compared to regular organic and inorganic combined fertilization treatment, respectively. In the organic and inorganic combined fertilization with DMPP addition treatment, the nitrate nitrogen content decreased by 38.8, 43.0, and 30.1 % in the three simulated artificial rainfall runoff water, respectively. Besides, the nitrite nitrogen content decreased by 95.4, 96.7, and 94.1 % in the three-time simulated artificial rainfall runoff water, respectively. A robust decline in the nitrate and nitrite nitrogen surface runoff loss could be observed in the treatments after the DMPP addition. The nitrite nitrogen in DMPP addition treatment exhibited a significant low level, which is near to the no fertilizer application treatment. Compared to only organic and inorganic combined fertilizer treatment, the total inorganic nitrogen runoff loss declined by 22.0 to 45.3 % in the organic and inorganic combined fertilizers with DMPP addition treatment. Therefore, DMPP could be used as an effective nitrification inhibitor to control the soil ammonium oxidation in agriculture and decline the nitrogen runoff loss, minimizing the nitrogen transformation risk to the water body and being beneficial for the ecological environment.