Long-term Fertilizer Management Research Articles

Long-term manure fertilization increases rill erosion resistance by improving soil aggregation and polyvalent cations

Application of organic fertilizers is a potential practice to prevent soil erosion by changing the physicochemical properties of the soil, such as macroaggregates, soil organic carbon (SOC) content, and exchangeable cations. However, the practical performance of organic fertilizer in soil erosion after a long-term application has scarcely been reported. To reveal the response of soil erosion resistance (i.e., the soil susceptibility to resist external erosion force) to 43 years of organic fertilization, five treatments were investigated: (1) CK (no fertilizer), (2) NPK (mineral fertilizer), (3) M (pig manure), (4) MN1 (pig manure + 138 kg N ha−1), and (5) MN2 (pig manure + 276 kg N ha−1). The results showed that NPK, M, MN1, and MN2 significantly increased soil critical shear stress (τc) by 54 %, 87 %, 101 %, and 67 %, respectively, compared to CK. However, rill erodibility (kd) was increased significantly only in the MN2 treatment. The optimal partial least squares regression model showed that the increase in soil exchangeable Ca2+ was the dominant contributor to the τc increase, while soil mean weight diameter (MWD) had the greatest negative effect on kd. Compared with CK, the soil exchangeable Ca2+ in M and MN1 increased significantly by 123 % and 135 %, respectively. The MWD in M and MN1 increased by 86 % and 83 %, respectively, compared with that in CK. The application of pig manure was beneficial for decreasing exchangeable Na+ and increasing SOC content, which could improve MWD. Manure with a high N content did not increase MWD due to SOC decomposition. Our results indicate that the long-term application of manure, alone or combined with moderate N, improves rill erosion resistance.

Identification of Novel Viruses and Their Microbial Hosts from Soils with Long-Term Nitrogen Fertilization and Cover Cropping Management.

Soils are the largest organic carbon reservoir and are key to global biogeochemical cycling, and microbes are the major drivers of carbon and nitrogen transformations in the soil systems. Thus, virus infection-induced microbial mortality could impact soil microbial structure and functions. In this study, we recovered 260 viral operational taxonomic units (vOTUs) in samples collected from soil taken from four nitrogen fertilization (N-fertilization) and cover-cropping practices at an experimental site under continuous cotton production evaluating conservation agricultural management systems for more than 40 years. Only ~6% of the vOTUs identified were clustered with known viruses in the RefSeq database using a gene-sharing network. We found that 14% of 260 vOTUs could be linked to microbial hosts that cover key carbon and nitrogen cycling taxa, including Acidobacteriota, Proteobacteria, Verrucomicrobiota, Firmicutes, and ammonia-oxidizing archaea, i.e., Nitrososphaeria (phylum Thermoproteota). Viral diversity, community structure, and the positive correlation between abundance of a virus and its host indicate that viruses and microbes are more sensitive to N-fertilization than cover-cropping treatment. Viruses may influence key carbon and nitrogen cycling through control of microbial function and host populations (e.g., Chthoniobacterales and Nitrososphaerales). These findings provide an initial view of soil viral ecology and how it is influenced by long-term conservation agricultural management. IMPORTANCE Bacterial viruses are extremely small and abundant particles that can control the microbial abundance and community composition through infection, which gradually showed their vital roles in the ecological process to influence the nutrient flow. Compared to the substrate control, less is known about the influence of soil viruses on microbial community function, and even less is known about microbial and viral diversity in the soil system. To obtain a more complete knowledge of microbial function dynamics, the interaction between microbes and viruses cannot be ignored. To fully understand this process, it is fundamental to get insight into the correlation between the diversity of viral communities and bacteria which could induce these changes.

Effects of Different Long-Term Fertilizer Management Systems on Soil Microbial Biomass Turnover in a Double-Cropping Rice Field in Southern China

Soil microbial biomass content is usually regarded as an early indicator of changes in soil quality and soil fertility in paddy fields. Soil microbial biomass turnover is mainly influenced by the application of different fertilizer management systems. However, there is still a need to further investigate the effects of different long-term fertilizer management systems on soil microbial biomass turnover in paddy fields under the double-cropping rice (Oryza sativa L.) system. Therefore, the effects of different long-term (36 years) fertilizer practices on soil microbial biomass carbon (SMBC) and soil microbial biomass nitrogen (SMBN) contents, and the flux turnover rates of SMBC and SMBN at the 0–10 cm and 10–20 cm layers in a double-cropping rice field in southern China were investigated in the present paper. The field experiment included four different fertilizer treatments: MF, RF, OM, and CK. The results showed that SMBC and SMBN contents at the 0–10 cm and 10–20 cm soil layers with RF and OM treatments were increased compared with the MF and CK treatments. Compared with the CK treatment, SMBC contents at the 0–10 cm and 10–20 cm soil layers with RF and OM treatments increased by 35.72% and 50.28%, and 32.29% and 42.77%, respectively. SMBN contents at the 0–10 cm and 10–20 cm soil layers with RF and OM treatments increased by 15.52% and 22.70%, and 16.32% and 21.49%, respectively. The fluxes of SMBC and SMBN at the 0–10 cm and 10–20 cm soil layers with RF and OM treatments were significantly higher than those of the CK treatment. This result indicated that the flux turnover rates of SMBC and SMBN at the 0–10 cm and 10–20 cm soil layers with the MF, RF, and OM treatments were significantly higher than those of the CK treatment. Compared with the CK treatment, the flux turnover rates of SMBC and SMBN at the 0–10 cm and 10–20 cm soil layers with OM treatment increased by 46.10% and 48.59%, and 73.39% and 116.67%, respectively. SMBC and SMBN contents, and the flux turnover rates of SMBC and SMBN at the 0–10 cm layer were higher than those of the 10–20 cm layer under the same fertilizer treatment condition. Early rice and later rice yields with RF and OM treatments were significantly higher than those of the MF and CK treatments. As a result, the combined application of crop residue and organic manure with inorganic fertilizer management is a beneficial practice for increasing soil nutrients and rice yield under the double-cropping rice system in southern Chin.

Improvements in soil physical properties after long-term manure addition depend on soil and crop type

Manure application and crop rotation are common agricultural practices that can alter soil physical properties and affect soil functions. In this study, we assessed the effect of long-term manure fertilization (24 to 126 years) and crop type on soil hydraulic, aggregate and pore structural properties. Samples were collected from three long-term experiments (LTEs) in Sweden (silty clay, SiC), Germany (silt loam, SiL) and Denmark (sandy loam, SL). Measurements included water retention, air permeability and gas diffusivity measured at five matric potentials −3, −5, −10, −30 and −50 kPa, saturated hydraulic conductivity (Ksat), bulk density (ρb), and water-stable aggregates (WSA). The treatments at the three LTEs included various manure rates and crop sequences (winter wheat, maize, spring barley, and grass/clover). Results showed that long-term manure addition reduced ρb by an average of 3–6% for all three sites, and improved soil water retention, plant available water and WSA for most investigated plots. However, increasing manure rates for the SiL and SL sites did not result in further improvements in soil water retention, ρb and water-stable aggregates. The effect of manure on soil pore size distribution, gas transport, and Ksat varied with soil and crop type. Manure increased the porosity of pores < 30 µm in the two fine-textured sites and increased the porosity of pores > 30 µm for wheat and maize plots in the SL site. Manure improved gas transport and Ksat in the wheat plots and decreased these properties in the barley plots regardless of soil texture. The maize plots in the SL site had well developed pore structure, while the pore structure in the SiL site was relatively poor. Grass plots had poorer gas transport than maize plots in the SL site despite the manure addition. The study shows that improvements in soil physical and chemical properties arising from manure application largely depend on the crops grown and the soil texture.

Soil water repellency and micro-aggregate fractions in response to crop growth periods in a sloping cropland subjecting to long-term fertilization management

Fertilization management and crop growth can affect soil water repellency (SWR) through altering other soil properties such as micro-aggregate, soil organic carbon (SOC) and total nitrogen (TN). However, the extents and magnitudes of these effects remain unclear. This study aimed to determine the effects of different crop growth periods and long-term fertilization managements on SWR and selected soil physicochemical properties and their linkages. Soil samples were collected from agricultural plots experiencing different maize growth periods (ES, elongation stage; TS, tasseling stages; FS, filling stage; and MS, maturity stage) and fertilization managements (CK, no fertilizer with downslope cultivation; T1, combined manure and chemical fertilizers with downslope cultivation; T2, chemical fertilizer with downslope cultivation; T3, 1.5-fold chemical fertilizer with downslope cultivation; T4, chemical fertilizer with contour cultivation) in a representative sloping cropland with Entisols, southwest China. SWR, micro-aggregate fractions, and other physiochemical properties like soil organic carbon (SOC) and total nitrogen (TN) were determined. Results showed that SWR increased by 64.93% in T1 than in CK, and fertilization managements (i.e., T1, T2, T3, and T4) markedly increased soil 1000–250 μm fraction by 34.50–50.74% and reduced 250–50 μm fraction by 22.95–48.87% than CK did. SWR was 27.35%–78.74% higher in ES than that in other growth periods. The highest soil 250–50 fractions (30.80%) and the lowest <50 μm fractions (43.95%) both appeared in TS. SOC was both differed by fertilization management and growth period, while TN was only affected by the former. SWR was predicted well by TN alone. Our results indicate that long-term fertilizer application enhances SWR and have great significance for optimizing sustainable agricultural management in the similar sloping croplands.

Crop Yield, Nitrogen Recovery, and Soil Mineral Nitrogen Accumulation in Extremely Arid Oasis Cropland under Long-Term Fertilization Management

Crop yield stability and soil mineral nitrogen (Nmin) have rarely been evaluated from a long-term perspective in the extremely arid cropland regions of China. Therefore, a nationwide experiment aimed to optimize fertilizer application and increase productivity and nitrogen use efficiency in gray desert soils was initiated in 1990. Eight combinations of chemical fertilizers (CK, N, NK, NP, and NPK), straw return (NPKS), and manure amendments (NPKM and NPKM+) were tested for 24 years on spring wheat, winter wheat, and maize. The results displayed that the yield of three crops from balanced fertilizer treatments (NPK, NPKS, NPKM, and NPKM+) did not differ significantly after 24 years; however, reliable yield stability due to lower coefficient of variation (CV) and higher nitrogen harvest index (NHI) were recorded for manure amendment treatments. Compared to NPKM, NHI was lower for the NPKM+ treatment, but crop yield and stability did not improve, suggesting that the appropriate choice for manure amendment is important for guaranteeing food security in extremely arid regions. Balanced fertilizer treatments resulted in lower Nmin residual in the 300 cm soil profile, compared to unbalanced fertilizer treatments. The NPKS treatment gave the lowest value. In the 0–100 cm soil profile, Nmin was higher in NPKM than in the NPK treatment, suggesting that straw or manure amendment can effectively maintain Nmin in the topsoil undercurrent cropland management in arid areas. The NPKM treatment had the highest crop nitrogen recovery rate and the lowest nitrogen losses, further illustrating that manure amendment has higher N retention potential. Overall, although Nmin residues are relatively high in these regions, balanced fertilizer treatments, especially NPKM and NPKS, are the optimum strategies in extremely arid regions.

Thirteen Year Long Term Fertilization Effect on Soil P Balance and Sustainability of a Double Crop of Rice Grown in an Acidic Inceptisol under Sub-Tropical Climatic Situation

The goal of the study was to determine how long-term fertilizer management of a rice-rice production system affected the buildup or depletion of surface soil phosphorus (P) in a subtropical climate. The results showed that using FYM @ 5t ha-1 season-1 in conjunction with optimal NPK doses (80-40-60 kg ha-1season-1) resulted in significantly higher grain yield than using fertilizer alone at optimal, super optimal, or sub-optimal doses or optimal level along with lime/Zn/Zn+B/Zn+S. The use of NPK and FYM together resulted in the highest yield sustainability. Phosphorus balance measured by indirect method (apparent P- balance) and direct method (true P-balance) was positive in all the fertilized treatments and negative in control and 100% N treatment that received no P. High yielding treatments (NPK + FYM or NPK + FYM + Lime) maintained a relatively lower P balance than optimal or super optimal doses because of more removal through higher biomass production. The addition of 50% more phosphorus in 150% NPK treatment caused 9.77% more P accumulation than 100% NPK treatment. Between the two methods, the direct method registered more depletion in the two minus P treatments and less accumulation in all P-treated soils than the indirect method. In soil with a super optimal dose (150% NPK), there is the highest positive balance (25.18 kg ha-1 year-1) as compared to 16.5 kg ha-1year-1in the true method. Seasonal wet and dry grain yield and P uptake poorly correlated with apparent P balance, true P balance and total stock of P. Whereas, sustainability of dry season, wet season and system yield strongly correlated with apparent P balance (r=0.587*, 0.690** and 0.604*), true P balance (r=0.681**, 0.781** and 0.693**) and total stock of P (r=0.680**, 0.780** and 0.692**). Thus true P balance and the total stock of P in surface soil are better indicators of yield sustainability of each season and system as a whole; whereas, available P is closely related to the amount of residual fertilizer P in the soil. Consistent availability of the nutrient depends upon its total stock which in turn depends upon its balance. Knowledge of total stock and nutrient balance is very important for the sustainability of a particular cropping system and evaluating various nutrient management practices for their suitability. Further study on the composition of the total stock of P with respect to various P fractions and their relative contribution to P uptake will be useful for identifying the suitable management practice for P nutrition.

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

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

Visualizing Mineral-Associated Organic Matters in Long-Term Fertilization Treated Soils by NanoSIMS and SR-FTIR

Formation of mineral-associated organic matters is essential for long-term soil organic carbon preservation. However, the regulation pathways of mineral-associated organic matters in soils remains largely undescribed, especially at the submicron scale. Using a well-controlled long-term (32 years) field experiment at the Jiangxi Institute of Red Soils, Jinxian, China, we showed that long-term manure fertilization significantly (P &amp;lt; 0.05) increased the available Al and Fe concentrations over one order of magnitude in soil water dispersible colloids compared to no fertilization and chemical fertilization. Nano-scale secondary ion mass spectrometry (NanoSIMS) images and region of interest (ROI) analysis provided direct evidence demonstrating that long-term manure fertilization increased the 27Al16O−/12C−, 27Al16O−/12C14N−, 56Fe16O−/12C−, and 56Fe16O−/12C14N− ratios compared to no fertilization and chemical fertilization. This finding revealed that long-term manure fertilization may potentially enhance the stability of organic carbon and nitrogen. Synchrotron radiation based FTIR spectromicroscopy further supported that secondary minerals (&amp;lt;950 cm−1) were co-localized with amines, lipids, and proteins in the long-term manure fertilization, but only co-localized with proteins in the no fertilization and chemical fertilization. To summarize, our findings highlight the importance of manure inputs in increasing formation of mineral-associated organic matters and thus potentially increasing soil carbon persistence.

Influences of Long-term Crop Cultivation and Fertilizer Management on Soil Aggregates Stability and Fertility in the Loess Plateau, Northern China

Influences of Long-term Crop Cultivation and Fertilizer Management on Soil Aggregates Stability and Fertility in the Loess Plateau, Northern China

In-season phosphorus dynamics in rice-wheat cropping system under long-term fertilizer management in an inseptisol of North India

In-season phosphorus dynamics in rice-wheat cropping system under long-term fertilizer management in an inseptisol of North India

Long-Term Manure Fertilization Increases Rill Erosion Resistance by Improving Soil Aggregation and Polyvalent Cations

Long-Term Manure Fertilization Increases Rill Erosion Resistance by Improving Soil Aggregation and Polyvalent Cations

Soil Water Repellency and Micro-Aggregate Fractions in Response to Crop Growth Periods in a Purple Soil Sloping Cropland Subjecting to Long-Term Fertilization Management

Soil Water Repellency and Micro-Aggregate Fractions in Response to Crop Growth Periods in a Purple Soil Sloping Cropland Subjecting to Long-Term Fertilization Management

Molybdenum Bioavailability and Asymbiotic Nitrogen Fixation in Soils are Raised by Iron (Oxyhydr)oxide-Mediated Free Radical Production.

Nitrogen (N) fixation in soils is closely linked to microbially mediated molybdenum (Mo) cycling. Therefore, elucidating the mechanisms and factors that affect Mo bioavailability is crucial for understanding N fixation. Here, we demonstrate that long-term (26 years) manure fertilization increased microbial diversity and content of short-range ordered iron (oxyhydr)oxides that raised Mo bioavailability (by 2.8 times) and storage (by ∼30%) and increased the abundance of nifH genes (by ∼14%) and nitrogenase activity (by ∼60%). Nanosized iron (oxyhydr)oxides (ferrihydrite, goethite, and hematite nanoparticles) play a dual role in soil Mo cycling: (i) in concert with microorganisms, they raise Mo bioavailability by catalyzing hydroxyl radical (HO•) production via the Fenton reactions and (ii) they increase Mo retention by association with the nanosized iron (oxyhydr)oxides. In summary, long-term manure fertilization raised the stock and bioavailability of Mo (and probably also of other micronutrients) by increasing iron (oxyhydr)oxide reactivity and intensified asymbiotic N fixation through an increased abundance of nifH genes and nitrogenase activity. This work provides a strategy for increasing biological N fixation in agricultural ecosystems.

Soil organic matter and clay zeta potential influence aggregation of a clayey red soil (Ultisol) under long-term fertilization

The effect of soil organic matter (SOM) on aggregation of variably-charged red soils (Ultisol) through clay zeta potential is not fully understood. Therefore, the objectives of this study were to investigate the SOM effect on the clay zeta potential and soil aggregation after fertilization. Soils under 17 years of fertilization (manure, NPK + straw, NPK, and control (CK) were adjusted by KCl solution to reach varying soil pH and concentration in order to determine clay zeta potential, cations, and aggregate size distribution. The SOM content and C-functional groups by 13C-NMR analysis were also determined. Results showed that the negative zeta potential displayed a bell-shaped pattern with increasing concentration of KCl, but displayed different amplitude of variation among treatments. Manure had the highest zeta potential value and its degree of variation in relative to the value at KCl concentration of 0.1 mol L−1 (19%), NPK + straw and NPK treatments were similar, and CK was the least. Greater negative zeta potential for manure treatment was attributed to higher SOM content, aromatic-C functional groups, and their greater concentrations of Ca2+ and Mg2+ than did the CK. As a result, higher SOM and clay zeta potential yielded in less release of amount of soil particles (< 10 μm) (r = − 0.46*) and enhanced water stable macroaggregates for manure instead of NPK + straw. Long-term manure fertilization would be suggested as a conservation practice for red soil due to its increase in soil aggregate stability and negative zeta potential in subtropical climate.

Long-term nutrient management affects nitrogen dynamics and crop yield in rice (Oryza sativa)-wheat (Triticum aestivum) system

The present study was conducted to assess the in-season dynamics of nitrogen (N) in an Inceptisol under long-term fertilizer management in rice (Oryza sativa L.)-wheat (Triticum aestivum L.) cropping system at Punjab Agricultural University, Ludhiana. The treatments comprised combination of chemical fertilizers (100% NPK and 150% NPK) and organic manures (100% NPK+FYM, 100% NPK+GM and 100% NPK+SI) along with unfertilized control laid out in randomized complete block design with three replications. Soil samples were collected at 30, 60, 90 and 120 days after transplanting/sowing and at harvest of rice and wheat, respectively and analysed for available N, ammonical N, nitrate N and total N. Plant samples were also collected at corresponding time period to determine the N content, uptake and biomass. Application of 100% NPK+FYM had significantly higher contents of different N forms during growth of both rice and wheat compared to rest of the treatments. At harvest of rice, combined use of 100% NPK and FYM improved soil available N and total N over 100% NPK by 20 and 22%; respectively. Whereas at wheat harvest; the increase in available and total N amounted to 29 and 23%, respectively due to corresponding treatments. The gradual decrease in N forms was observed till crop harvest. The grain and straw yield, content and total uptake of N by rice and wheat increased significantly under the integrated fertilizer management. Integrated nutrient management practice improved the relative proportion of plant-available N forms and achieved higher rice-wheat productivity.

Effects of fertilizer practice on fungal and actinobacterial cellulolytic community with different humified particle-size fractions in double-cropping field

Cellulose plays an important role in maintaining or improving soil carbon (C) cycling and soil fertility of paddy field. There had close relationship between functional cellulose genes (cbhI and GH48) with characterize of soil organic matter chemical components (fulvic acid and humic acid) and soil physical fractions. However, there is still limited information about how functional cellulose degradation response to long-term fertilizer management and their relative importance for C sequestration under the double-cropping rice paddy field in southern of China. Therefore, the objective of this study were investigated the effects of 34-years long-term fertilizer regime on community abundance of cbhI and GH48 genes in five soil particle-size fractions (> 2000 μm, 2000–200 μm, 200–50 μm, 50–2 μm and 2–0.1 μm) by using polarization magic angle spinning 13C nuclear magnetic resonance spectroscopy. The field experiment was included four different fertilizer treatments: chemical fertilizer alone (MF), rice straw and chemical fertilizer (RF), 30% organic manure and 70% chemical fertilizer (OM), and without fertilizer input as a control (CK). The results showed that distribution of soil humus and cellulolytic microbial community abundance was significant increased under long-term application of crop residue and organic manure condition. And the FA, HA and HM C contents in > 2000 μm and 2000–50 μm fractions with MF, RF and OM treatments were significant higher than that of CK treatment. Meanwhile, the alkyl C and Oalkyl C groups of FA and HA in > 2000 μm fraction with MF, RF, OM and CK treatments were higher than that of the other fractions. There had higher AL% and lower ARO% of FA and HA in different particle-size fractions with MF, RF, OM and CK treatments. The results indicated that abundance of cbhI and GH48 genes in different particle-size fractions with RF and OM treatments were significant increased, compared with CK treatment. There had significant positive correlation between soil humus C components (FA and HA) with abundance of cbhI and GH48 genes, and the o-alkyl C and AL% of FA were positively correlated with abundance of cbhI and GH48 genes. As a result, the community abundance of cbhI and GH48 genes were significant increased under combined application of crop residue and organic manure with chemical fertilizer condition.

PH and ammonium concentration are dominant predictors of the abundance and community composition of comammox bacteria in long-term fertilized Mollisol

The newly-discovered complete ammonia-oxidizing bacteria (comammox) doubts our inherent understanding of nitrification. Herein, we study communities of comammox, ammonia-oxidizing bacteria (AOB) and archaea (AOA) in Mollisol after a 30-year fertilization history with four treatments: chemical nitrogen (N) and potassium (K) fertilizers (NK); chemical N, phosphorus (P), and K fertilizers (NPK); chemical NPK fertilizers plus organic manure (NPKM); and a control without fertilizers (CK). Compared with CK, chemical fertilizer treatments (NK and NPK) significantly reduced AOA amoA gene abundance and increased AOB and comammox amoA gene abundances. The highest values of AOA and AOB amoA gene abundances were found in the NPKM treatment and the highest value of comammox amoA gene abundance was observed in the NK treatment. The application of combined NPK and organic manure (NPKM) significantly increased AOA, AOB, and comammox amoA gene abundances compared to CK. Long-term chemical fertilization decreased the diversity of comammox community; whereas, the application of combined NPK with organic manure (NPKM) restored it to levels comparable to CK. Long-term fertilization management altered the community structure of comammox based on principal coordinate analysis (PCoA). Soil pH and NH4+-N concentration were the key factors affecting soil abundance and community structure of comammox. This study demonstrates the different responses of comammox community and canonical ammonia oxidizers to long-term fertilization practices in Mollisol.

Mineralization of Nitrogen Forms in Soil Cultivated with Yellow Melon under Organic and Mineral Fertilization

ABSTRACT The association of mineral and organic fertilization is a nitrogen supply system for the melon crop. Nitrogen (N) fractionation is an important tool to understand its dynamics in the soil and the contribution of each fraction to N bioavailability. This study aimed to evaluate the effects of organic and mineral fertilization on organic and inorganic forms of soil N of the cultivation of yellow melon. The experiment was conducted in the Experimental Field of Pacajus, belonging to Embrapa Agroindústria Tropical, in soil classified as Red Yellow Argisol. The experimental design was a split-plot randomized block. Fertilizer application was the main plot treatment and sampling time was arranged as subplots. The experimental results indicated that only organic fertilization was sufficient to significantly increase the total-N content (varying from 1,127 mg kg−1 to 967 mg kg−1) compared to only mineral fertilization (951 mg kg−1) and organic N represented 92 ± 2% of the total-N. In addition, the higher hydrolyzable N content was observed in the treatment with only bovine manure application (542 mg kg−1) which represents an N source for the mineralization and subsequent inorganic N for plants. Our results reveal that organic fertilization is efficient for long-term fertility management, increasing melon productivity.

Organic Manure Management Increases Soil Microbial Community Structure and Diversity in the Double-cropping Rice Paddy Field of Southern China

ABSTRACT The soil physicochemical properties and soil microbial community were affected by different fertilizer management. Fertilizer regime was closely related to soil texture and nutrient status in the double-cropping rice (Oryza sativa L.) paddy field of southern China. However, there was limited information about influence of long-term fertilizer management on soil microbial community in the double-cropping rice paddy field. Therefore, the effects of 39-years long-term fertilizer regime on soil bacterial and fungal diversity in the double-cropping rice paddy field of southern China were studied by using Illumina sequencing and quantitative real-time polymerase chain reaction (q-PCR) technology in the present paper. The experiment including four fertilizer treatments: chemical fertilizer alone (MF), rice straw and chemical fertilizer (RF), 30% organic manure and 70% chemical fertilizer (OM), and without fertilizer input as control (CK). The results showed that diversity indices of soil microbial community with RF and OM treatments were higher than that of CK treatment. Application of organic manure and rice straw management increase soil bacterial abundance of the phylum Proteobacteria, Actinobacteria, and Gammaproteobacteria, and soil fungi abundance of the phylum Basidiomycota, Zygomycota, and Tremellales were also increased. Compared with CK treatment, the value of Richness, Shannon and McIntosh indices, and taxonomic diversity were increased with RF and OM treatments. This finding demonstrated that RF and OM treatments modify soil bacterial and fungal diversity. Therefore, the combined application of organic manure or rice straw with chemical fertilizer management significantly increases the abundance of profitable functional bacteria and fungi species in the double-cropping rice paddy field of southern China.