Effects Of Long-term Fertilization Research Articles

Clay Minerals and Long-Term Fertilization Effects on Soil Organic Carbon Stocks, Soil Carbon Pools, and Soil Enzymes in an Inceptisol of Coimbatore, Tamil Nadu

ABSTRACT Soil Organic Carbon (SOC) is an important indicator for soil health and quality. The present study was conducted in five-decade-old Long-Term Fertilizer Experiment involving the finger millet−maize cropping sequence in an Inceptisol to examine the effects of inorganic fertilizers and manures on soil organic carbon stock in relation to C sequestration. This study was based on 10 treatments: 50%NPK, 100%NPK, 150%NPK, 100%NPK + HW, 100%NPK + ZnSO4, 100%NP, 100%N, 100%NPK + FYM, 100%NPK (− S), and control. We assess the clay mineral interaction with soil organic carbon stock and soil enzyme activity. The semi-quantification and characterization of clay minerals were sourced from X-ray diffraction (XRD) analysis, and the SOC stock was calculated based on SOC concentration, Bulk density, and Depth. From the study, results revealed that clay minerals were studied by XRD and FTIR spectroscopy analysis. The results revealed that dominant clay minerals in the experimental soil were in the order of Montmorillonite, 2:1 interstratified minerals, Vermiculite, and Illite, and the buildup of SOC stock raised from 6.3 Mg C ha−1 to 12.9 Mg C ha−1 over five decades. The maximum SOC stock of 12.9 Mg ha−1 was recorded in 100% NPK + FYM while the control registered 7.5 Mg C ha−1. The study conclude that balanced fertilization of 100% NPK with FYM contributed toward the increase in SOC, SOC stock, and carbon sequestration for improving soil fertility status.

Trade-off between soil enzyme activities and hotspots area depends on long-term fertilization: In situ field zymography

Mineral fertilizers and livestock manure have been found to impact the soil enzyme activities and distributions, but their trade-off and subsequent effects on soil functioning related to nutrient cycling are rarely evaluated. Here, we investigated the long-term effects of manure and mineral fertilization on the spatial distribution of enzyme activities related to carbon, nitrogen, and phosphorus under field-grown maize. We found that the legacy of mineral fertilizers increased the rhizosphere extension for β-glucosidase and N-acetylglucosaminidase by 16–170 %, and the hotspot area by 37–151 %, compared to manure. The legacy of manure, especially combined with mineral fertilizers, increased enzyme activities and formed non-rhizosphere hotspots. Furthermore, we found a trade-off between hotspots area and enzyme activities under the legacy effect of long-term fertilization. This suggested that plants and microorganisms regulate nutrient investments by altering the spatial distribution of enzyme activities. The positive correlation between hotspots area and nutrient contents highlights the importance of non-rhizosphere hotspots induced by manure in maintaining soil fertility. Compared to mineral fertilization, the legacy effect of manure expanded the soil functions for nutrient cycling in both rhizosphere and non-rhizosphere by >1.7 times. In conclusion, our findings indicate that the legacy of manure expands non-rhizosphere hotspots and enhances soil functioning, while mineral fertilization expands rhizosphere extension and intensifies hotspots area for nutrient exploitation.

Response of comammox Nitrospira clades A and B communities to long-term fertilization and rhizosphere effects and their relative contribution to nitrification in a subtropical paddy field of China

The recently discovered complete ammonia oxidation (comammox Nitrospira) containing clade A and clade B has further complemented our understanding of nitrification process. Nevertheless, understanding the community feature of comammox Nitrospira clades A and B and their relative contribution to nitrification in paddy rhizosphere are still in its infancy. In this study, we assessed the community diversity and structure of comammox Nitrospira clades A and B in paddy rhizosphere and bulk soils under thirty years of different fertilization strategies, i.e., non-fertilization control (CK), chemical fertilizers application (NPK), and NPK plus swine manure (NPKM), respectively. NPKM significantly increased the a-diversity (Chao1 and Shannon indices) of comammox Nitrospira clade A and altered the community structure (P < 0.05) but had little effect on clade B. A two-way analysis of variance (ANOVA) showed that the effect of long-term fertilization on soil comammox Nitrospira community and nitrification potential rate (PNR) was much greater than that of rhizosphere. Compared with NPK, soil PNR was greatly increased by 51.0% under the NPKM treatment in the rhizosphere (P < 0.05). Phylogenetic analysis showed that NPKM improved the relative abundances of sub-clade A.2.1 and sub-clade A.3.2 of the comammox clade A community, with an average increase of 212.2 and 210.4% in both rhizosphere and bulk soils relative to the NPK treatment. Soil organic matter, NH4+-N, and pH were significant soil drivers of comammox Nitrospira clades A and B community. Furthermore, linear regression and structural equation modeling clearly showed that comammox Nitrospira clade A a-diversity were significantly associated with soil PNR (P < 0.05). Our results suggest (i) that comammox Nitrospira clade A are sensitive to the organic fertilization; and (ii) that comammox Nitrospira clade A contribute more to nitrification than clade B under the long-term organic fertilized paddy soil.

Long-term effects of nitrogen and phosphorus fertilization on profile distribution and characteristics of dissolved organic matter in fluvo-aquic soil

Dissolved organic matter (DOM) drives numerous biogeochemical processes (e.g. carbon cycling) in agro-ecosystems and is sensitive to fertilization management. Nevertheless, changes in the quantity and quality of DOM in the vertical soil profile following long-term continuous nitrogen (N) and phosphorus (P) inputs remain unclear. In this study, the contents and optical characteristics of DOM along a 2-m soil profile were investigated using a 40-year wheat/maize rotation combined with experiments using different N and P fertilization rates in the North China Plain. The results revealed that the dissolved organic carbon (DOC) content decreased with an increase in soil depths. Compared with that in the control (no fertilization), 40-year N, P, and N + P additions increased the soil DOC content by 26%–69%, except for 270-kg N, and 67.5-kg P treatments. N + P application resulted in higher DOC contents than N-alone and P-alone applications. N, P, and N + P inputs increased or did not affect the aromaticity and hydrophobicity of DOM at 0–40 cm but reduced them from 40 to 200 cm. Compared with that in the control, N, P, and N + P inputs enhanced the content of humic acid-like substances (C1+C2+C3+C4) and decreased the content of protein-like substance (C5). C1 was the dominant component among the five DOM, representing the microbial humic component. Optical indices also indicated that soil DOM primarily originated from microbial sources. Nutrient addition accelerated transformation between complex C1 and simple C5 via promoting microbial activities. These results imply that N and P fertilizers increased the DOM content and altered its composition, thereby potentially affecting the stability of soil organic matter in the agroe-cosystems.

Effects of Long-term Fertilizations on the Organic Carbon Components of Soil Macroaggregates and the Yield of Wheat in Wheat Fields on the Loess Plateau

Soil macro-aggregates are the main location for soil organic carbon （SOC） sequestration, which is of great significance to improve soil fertility. This study aimed to understand the mechanisms of the organic carbon （OC） sequestration in macroaggregates and improve crop yield in wheat fields on the loess plateau. With the aggregate-density fractionation method, an eight-year experiment was conducted to investigate the following three factors： ① the effects of long-term fertilization on OC fractions within macroaggregates； ② the variation characteristics of OC fractions within macroaggregates, including coarse particulate organic carbon （cPOC）, fine particulate organic carbon （fPOC）, intra-microaggregate particulate organic carbon （iPOC）, free silt and clay particulate carbon （s+c_f）, and intra-microaggregate silt and clay particulate carbon （s+c_m）； ③ and the relationships between them and SOC input and yield formation. The treatments included no fertilization （CK）, farmer pattern （NP）, optimized fertilizers pattern （NPK）, optimized fertilizers + organic fertilizers pattern （NPKM）, and optimized fertilizers + biological organic fertilizers pattern （NPKB）. The results showed that the application of organic and chemical fertilizer （NPKM and NPKB） improved significantly the SOC content in macroaggregates compared with that in the single fertilizer treatment （NP and NPK）, which had a greater increase in SOC content in macroaggregates than that of the soil. All fertilization treatments had a tendency to increase the content of fractions iPOC, fPOC, and iPOC in macroaggregates, but silt and clay carbon （s+c_f and s+c_m） contents were decreased. The application of manure combined with chemicals markedly increased the allocations of fractions cPOC, fPOC, and iPOC reserves, but it greatly decreased （s+c_f） reserves allocation. However, the application of chemical fertilizers only significantly increased the proportion of cPOC reserves in macroaggregates. Correlation analysis showed that there were significant positive correlations among wheat grain yield and OC fractions （cPOC and fPOC） contents, SOC content, the OC content of &gt;0.25 mm macroaggregates, and SOC input, and the correlation coefficient was 0.645-0.883. In conclusion, long-term fertilization, especially combined with organic fertilizer, could promote the free silt and clay carbon fraction （s+c_f） to transfer into other forms of OC components through the increase in soil carbon input in the wheat field of the loess plateau. Furthermore, the OC content of macroaggregates was increased overall, providing a good soil environment for crop yield.

Divergent effects of long-term fertilization on the carbon management index across soil profiles in key Chinese croplands

Evidence for the variability of the carbon (C) management index (CMI) across surface and subsurface soil layers due to long-term fertilization in diverse agroecological settings is inadequate. Thus, our study aimed to explore the variations in soil organic C (SOC), CMI, and its response ratio (RR-CMI) along soil profiles (0–60 cm) across four croplands in China. These croplands represented two high-fertility sites in Gongzhuling (GZL) and Chongqing (CQ) and two low-fertility sites in Zhengzhou (ZZ) and Qiyang (QY). We evaluated various treatments: control (CK; no fertilizer), inorganic fertilizer (NPK), NPK combined with standard manure (MNPK), and 1.5 times the standard rate of manure and NPK (1.5MNPK). The results indicated a significant increase in SOC content across all depths, ranking as 1.5MNPK > MNPK > NPK > CK, with ranking for the pattern observed across sites as GZL > CQ ≈ QY > ZZ. This led to the most substantial increases, reaching 107, 86, 105, and 62 % more than CK across the soil profile (0–60 cm) under 1.5MNPK across all sites. Moreover, the same treatment showed a significantly higher CMI at 0–60 cm compared to CK, with increases of 37, 19, 65, and 25 % for ZZ, QY, GZL, and QY, respectively. Notably, for the low-fertility soils (ZZ and QY), a higher CMI was observed in the 0–20-cm soil layer), whereas the opposite was true for the high-fertility soil (GZL). Consequently, low-fertility soils exhibited a higher RR-CMI in the 0–20-cm soil layer, whereas the high fertility site (GZL) showed a higher RR-CMI in the 40–60-cm soil layer, suggesting differential accumulation and loss of SOC regulated by soil depth and inherent site fertility. Partial least squares regression analysis further indicated that soil and climatic factors predominantly influenced CMI under long-term fertilization in typical Chinese soils. In conclusion, the long-term application of manure combined with inorganic fertilizer promotes SOC sequestration and enhances CMI, presenting a viable management strategy for enhancing soil quality in the studied regions.

Съдържание на микроелементи (Mn, Zn, Cu, Pb, Ni и Cd) в почвата и ориенталски тютюн след продължително минерално торене

The effect of long-term mineral fertilization with different N, P and K rates on the concentration of Mn, Zn, Cu, Pb, Ni and Cd in soil and oriental tobacco (monoculture) was studied in 50-years stationary trail. Studies were conducted in 2014-2016 on rendzina soil at the Tobacco and Tobacco Products Institute - Markovo. The concentrations of total micronutrients in soil showed relatively small variation and they were not largely influenced by long-term mineral fertilization with different N, P and K rates. The accumulation of available Zn, Cu, Pb and Cd in the soil was also not significantly influenced by mineral fertilization. Available Mn and Ni were higher in fertilized treatments compared to unfertilized control. The long-term fertilization had no significant effect on Mn, Pb and Ni concentration in tobacco leaves. For lower and middle leaves, 225 kg P2 O5 ha-1 treatment resulted in lowest Zn concentration. The content of copper and cadmium in the leaves tended to decrease in mineral fertilizer treatments compared to the unfertilized control. When oriental tobacco was grown on rendzina soil with good buffering capacity, the risk of Mn, Zn, Cu, Pb, Ni and Cd accumulation in tobacco leaves associated with long-term mineral fertilization is low. These experimental conditions are adequate for the production of high quality sun-cured leaves with a low level of nicotine content, higher in reducing sugars and moderate in total nitrogen.

Divergent impacts of fertilization regimes on below-ground prokaryotic and eukaryotic communities in the Tibetan Plateau

Chemical nutrient amendment by human activities can lead to environmental impacts contributing to global biodiversity loss. However, the comprehensive understanding of how below- and above-ground biodiversity shifts under fertilization regimes in natural ecosystems remains elusive. Here, we conducted a seven-year field experiment (2011–2017) and examined the effects of different fertilization on plant biodiversity and soil belowground (prokaryotic and eukaryotic) communities in the alpine meadow of the Tibetan Plateau, based on data collected in 2017. Our results indicate that nitrogen addition promoted total plant biomass but reduced the plant species richness. Conversely, phosphorus enrichment did not promote plant biomass and exhibited an unimodal pattern with plant richness. In the belowground realm, distinct responses of soil prokaryotic and eukaryotic communities were observed under fertilizer application. Specifically, soil prokaryotic diversity decreased with nitrogen enrichment, correlating with shifts in soil pH. Similarly, soil eukaryotic diversity decreased with increased phosphorous inputs, aligning with the equilibrium between soil available and total phosphorus. We also established connections between these soil organism communities with above-ground plant richness and biomass. Overall, our study contributes to a better understanding of the sustainable impacts of human-induced nutrient enrichment on the natural environment. Future research should delve deeper into the long-term effects of fertilization on soil health and ecosystem functioning, aiming to achieve a balance between agricultural productivity and environmental conservation.

Effect of Longterm Fertilization and Manuring on Nutritional Quality of Maize Grain

A study on Effect of long term fertilization and manuring on soil quality and nutritional quality of maize (Zea mays L.) under finger millet-maize cropping system was carried out in LTFE plots which has been in progress since 1986 at UAS, GKVK, Bengaluru. Eleven treatments were laid in randomized block design with three replications. The hybrid maize was grown in LTFE plots during Rabi 2021-2022 (35th crop cycle) and qualities of grain were assessed. Application of 100 per cent NPK+ FYM+ lime recorded significantly higher grain quality viz., geometric mean diameter (7.63 mm), bulk density (791 kg m-3), 1000 grain mass (444.10 g), colour (L*72.91, a*4.68, b*27.48), crude protein (10.35%), ash (1.73%), moisture (8.19%) and crude fibre (1.85%). Inorganic fertilization alone, 100% N, 100% NP and control treatments recorded poor quality grain of maize. The conjoint use of organic manures along with chemical fertilizers in balanced form is essential to maintain good soil quality and for quality maize production.

The cooperative interaction of AOB and comammox clade A drives nitrification and N2O emissions in a long-term organic fertilized paddy soil

The newly discovered complete ammonia oxidizer (comammox Nitrospira) is able to single-step nitrification capability, and increased our understanding of soil nitrogen cycling. However, the response of comammox and ammonia-oxidizing bacteria (AOB) and archaea (AOA) to long-term fertilization and rhizosphere effects in paddy soils and their relative contribution to the nitrification-derived N2O emissions is still unclear. Here, we collected rhizosphere and bulk soils with thirty years of different fertilization strategies, i.e., non-fertilization (CK), chemical N, P, and K application (NPK), and NPK plus pig manure application (NPKM), respectively, to test changes in nitrification potential rate (PNR), N2O emission fluxes, abundance of ammonia oxidizers and their significant drivers. The result showed that NPKM significantly increased soil C and N levels, the proportion of soil middle-size particles (40.35–148.00 μm class), and soil PNR, but decreased soil N2O emissions, especially in the drying time of paddy (P < 0.05), compared to NPK fertilization. NPKM had the highest values of AOA, AOB, and comammox clade A amoA gene copy numbers (P < 0.05), but clade B was increased by the NPK in the rhizosphere soil. Furthermore, fertilization showed greater effects on ammonia oxidizers (except for clade B) than the rhizosphere effect. Mantel test showed that SOM, TP, pH, NH4+, and NO3− were main abiotic factors causing the niche separation among ammonia oxidizers. Linear regression analysis and structural equation model (SEM) showed that both PNR and N2O emission fluxes were significantly associated with the abundance of AOB and comammox clade A (P < 0.05). Therefore, our results underline the importance of AOB together with comammox clade A in nitrification and N2O production in long-term organic fertilized paddy fields, which could provide new ideas for the mitigation of N2O emission by adopting organic fertilization scenarios in Chinese paddy fields.

EFFECTS OF DIFFERENT TYPES OF ORGANIC FERTILIZER PLUS INDIGENOUS MICROORGANISM (IMO) ON THE GROWTH AND YIELD OF LOWLAND RICENSIC RC 160 VARIETY

The use of organic fertilizers has become increasingly popular due to their potential to improve soil fertility, reduce environmental pollution, and enhance crop yields. This study was carried out at Purok 2, Kipalili San Isidro Davao del Norte, Philippines, from December 2021 to April 2022. This experimental study aimed to investigate the effect of different organic fertilizers plus Indigenous microorganism (IMO) in the lowland with 160 rice variety, specifically, the study aimed: (1.) to determine the effect of different organic fertilizers plus Indigenous Microorganism (IMO) on the characteristics of rice NSIC RC 160 variety and yield components. (2.) to identify which treatment will give the optimum yield of rice NSIC RC 160 variety as affected by different organic fertilizer plus Indigenous Microorganism (IMO). (3.) to evaluate the economic profitability of rice NSIC RC 160 variety as affected by different organic fertilizer plus Indigenous Microorganism (IMO). Additionally, the study was laid out in a Randomized Complete Block Design with five treatments and three replications, Treatments were as follows. T1 (RR of NPK) T2 (Vermicast + IMO), T3 (Pig manure + IMO), T4 (Chicken Manure + IMO), T5 (Vermicast + Pig Manure + Chicken Manure + IMO). The different data gathered were statistically analyzed using the Analysis of Variance for comparison of means. However, results revealed that Organic Fertilizer plus Indigenous Microorganism (IMO), showed highly significant result in 2 of the data weight of 1000 grains and grain yield. The plant height, number of Panicle length and number of tillers, number of productive tillers showed no significant difference. In terms of economic analysis result revealed that treatment 4 with an RPC Value of 105. 64 % obtained the highest percentage of return on Production while T3 obtained the lowest RPC value. These findings suggest that organic fertilizer can be a viable alternative to chemical fertilizers in promoting sustainable rice production. Further studies on the long-term effects of organic fertilizer on soil quality and plant health are recommended. KEYWORDS: rice, organic fertilizer, Indigenous Microorganism (IMO), NSIC RC 160 variety

Nitrogen fertilization modulates rice phyllosphere functional genes and pathogens through fungal communities

The phyllosphere is a vital yet often neglected habitat hosting diverse microorganisms with various functions. However, studies regarding how the composition and functions of the phyllosphere microbiome respond to agricultural practices, like nitrogen fertilization, are limited. This study investigated the effects of long-term nitrogen fertilization with different levels (CK, N90, N210, N330) on the functional genes and pathogens of the rice phyllosphere microbiome. Results showed that the relative abundance of many microbial functional genes in the rice phyllosphere was significantly affected by nitrogen fertilization, especially those involved in C fixation and denitrification genes. Different nitrogen fertilization levels have greater effects on fungal communities than bacteria communities in the rice phyllosphere, and network analysis and structural equation models further elucidate that fungal communities not only changed bacterial-fungal inter-kingdom interactions in the phyllosphere but also contributed to the variation of biogeochemical cycle potential. Besides, the moderate nitrogen fertilization level (N210) was associated with an enrichment of beneficial microbes in the phyllosphere, while also resulting in the lowest abundance of pathogenic fungi (1.14 %). In contrast, the highest abundance of pathogenic fungi (1.64 %) was observed in the highest nitrogen fertilization level (N330). This enrichment of pathogen due to high nitrogen level was also regulated by the fungal communities, as revealed through SEM analysis. Together, we demonstrated that the phyllosphere fungal communities were more sensitive to the nitrogen fertilization levels and played a crucial role in influencing phyllosphere functional profiles including element cycling potential and pathogen abundance. This study expands our knowledge regarding the role of phyllosphere fungal communities in modulating the element cycling and plant health in sustainable agriculture.

Effects of Long-Term Controlled-Release Urea on Soil Greenhouse Gas Emissions in an Open-Field Lettuce System.

Controlled-release urea (CRU) fertilizers are widely used in agricultural production to reduce conventional nitrogen (N) fertilization-induced agricultural greenhouse gas emissions (GHGs) and improve N use efficiency (NUE). However, the long-term effects of different CRU fertilizers on GHGs and crop yields in vegetable fields remain relatively unexplored. This study investigated the variations in GHG emissions at four growth stages of lettuce in the spring and autumn seasons based on a five-year field experiment in the North China Plain. Four treatments were setup: CK (without N application), U (conventional urea-N application), ON (20% reduction in urea-N application), CRU (20% reduction in polyurethane-coated urea without topdressing), and DCRU (20% reduction in polyurethane-coated urea containing dicyandiamide [DCD] without topdressing). The results show that N application treatments significantly increased the GHG emissions and the lettuce yield and net yield, and DCRU exhibited the lowest N2O and CO2 emissions, the highest lettuce yield and net yield, and the highest lettuce N content of the N application treatments. When compared to U, the N2O emission peak under CRU and DCRU treatments was notably decreased and delayed, and their average N2O emission fluxes were significantly reduced by 10.20-20.72% and 17.51-29.35%, respectively, leading to a significant reduction in mean cumulative N2O emissions during the 2017-2021 period. When compared to U, the CO2 fluxes of DCRU significantly decreased by 8.0-16.54% in the seedling period, and mean cumulative CO2 emission decreased by 9.28%. Moreover, compared to U, the global warming potential (GWP) and greenhouse gas intensity (GHGI) of the DCRU treatment was significantly alleviated by 9.02-17.13% and 16.68-20.36%, respectively. Compared to U, the N content of lettuce under DCRU was significantly increased by 6.48-17.25%, and the lettuce net yield was also significantly increased by 5.41-7.71%. These observations indicated that the simple and efficient N management strategy to strike a balance between enhancing lettuce yields and reduce GHG emissions in open-field lettuce fields could be obtained by applying controlled-release urea containing DCD without topdressing.

Effect of long-term compost fertilization on the distribution of organic carbon and nitrogen in soil aggregates

Soil fertility is mainly related to soil total organic carbon (C) that should be preserved in order to optimize soil quality and functionality. Consequently, the use of organic amendments could be a possible strategy to increase soil C and nitrogen (N) storage particularly in orchard systems where the disturbance of soil is reduced thus making favorable conditions for C and N stabilization.The aim of this study was to evaluate the distribution and stabilization of organic C and total N in aggregate fractions after a 14-years-period of compost application to a peach orchard. The trial was conducted in the south-eastern Po valley, on a commercial nectarine orchard and the following treatments were compared in a complete randomized block design with four replicates: 1. unfertilized control; 2. mineral fertilization; 3. compost at a rate of 10 Mg dry weight ha−1 yr−1. At the end of orchard lifetime, soil was sampled from the row at four depths (0–0.15, 0.16–0.25, 0.26–0.45, and 0.46–0.65 m) and physically fractionated to separate macroaggregates (> 250 μm), microaggregates (250–50 μm) and silt and clay (< 50 μm) that were analyzed for organic C, total N, δ13C, and δ15N.Compost addition induced a significant increase of macroaggregates (66%), no changes in microaggregates and a decrease of silt and clay (22%) compared to control and mineral fertilization. With compost the accumulation of organic C and total N content in the macroaggregates was four-five times higher than the other two treatments in all the depths, therefore almost 50% of the soil organic C was in this fraction, compared to 20–24% in the control and mineral. In the micro-aggregates more C and N accumulated only in the two top layers, while no effect was observed in the silt and clay fraction. From macro-to microaggregates to the silt and clay fraction, the C/N ratio shifted from 9 to 7.5 to 6 on average indicating that the C and N stabilized in the finer fractions is mainly of microbial origin. The enrichment in C and N isotopic composition from macro-to micro to silt and clay is also indicative of the isotopic fractionation due to microbial metabolism and the consequent stabilization of microbial residues in the finer fractions. In the control and mineral, only receiving orchard litter, this change was observed in all the layers, on the contrary, with compost similar δ13C and δ15N values characterized the fractions in the top soil layer suggesting the occlusion of compost in all the fraction. With depth the macroaggregates maintained the same δ13C and δ15N values indicating consistent redistribution of compost in deep soil layers, while the finest fractions showed a progressive enrichment of δ13C due to the presence of C fractionated during microbial metabolism and progressively stabilized. In conclusion, compost supply leads to positive effects on C and N accumulation and stabilization also in the deeper layers favoring the increase of long-term soil fertility and C storage.

Effects of different long-term fertilization on rhizosphere soil nitrogen mineralization and microbial community composition under the double-cropping rice field

ABSTRACT Soil extracellular enzymes play an important role in regulating nitrogen (N) mineralization processes in paddy fields. Therefore, in this work, we determine the influence of a long-term fertilizer regime on rhizosphere soil N fertilization rates, soil enzymes, soil microbial community (bacterial ureolytic community (ureC), bacterial chitinolytic community (chiA)) under the double-cropping rice field in southern of China. The field experiment included the following fertilizer regimes: inorganic fertilizer alone (IF), rice straw and inorganic fertilizer (RF), 30% organic manure and 70% inorganic fertilizer (OM), without any fertilizer input as a control (CK). The results showed that rhizosphere soil N transformation rates in the paddy fields with OM and RF treatments were increased, compared with IF and CK treatments. Soil urease, β-glucosaminidase and arginase activities were significantly increased under OM and RF treatments. This result indicated that functional gene abundances of sub, npr and chiA were significantly greater under RF and OM treatments compared to IF and CK treatments. Soil bacterial ureolytic and chitinolytic communities were significantly changed by the different fertilization strategies. The practice of applying rice straw and organic manure seems beneficial for increasing rhizosphere soil N mineralization rates and microbial community diversity in the double-cropping rice fields.

Long-Term Fertilization Contributes to Carbon Saturation in Neutral-To-Alkaline Soils but not in Acidic Soils

ABSTRACT The study investigated the adsorption of dissolved organic carbon (DOC) on Chinese soils from four long-term experiments involving five treatments: (1) no fertilization (control), (2–4) inorganic nitrogen (N), phosphorus (P), and potassium (K) fertilization (N, NP, and NPK), (5) NPK plus manure (NPKM). The results showed that DOC adsorption followed a modified Langmuir isotherm model effectively (R2 = 0.912 ~ 0.991). The maximum adsorption capacity (Q max ) (i.e. saturation deficits) generally increased with increasing soil organic carbon (SOC) due to fertilization in Luvic Phaeozem, Haplic Gypsisols, and Eutric Cambisols. However, it decreased significantly in acidic soils (Haplic Acrisols) from 15.59 g/kg for control, to 13.96, 13.03, 9.30 and 8.02 g/kg for N, NP, NPK and NPKM, respectively. Moreover, long-term fertilization, particularly with organic fertilization (e.g. NPKM), resulted in an increase of carbon (C) saturation by 1.42 g/kg (5.52%) in Luvic Phaeozem, 9.27 g/kg (44.29%) in Haplic Gypsisols, and 3.75 g/kg (27.66%) in Eutric Cambisols; however, there was a slight decrease by 1.70 g/kg (−7.49%) in Haplic Acrisols. Canonical correlation analysis (CCA) revealed that clay content and soil available iron (AFe) might be the crucial factors controlling C deficits, and subsequently, C saturation, along with current SOC. In conclusion, long-term fertilization contributed to C saturation in neutral-to-alkaline soils, but not in acidic soils. Thus, further attention should be paid to the long-term effects of fertilization on C saturation.

Effects of long-term monocropping, rotation cropping, and fertilization on energy and fuel requirements for fall moldboard plowing in a clay-loam soil

With recent increases in energy costs, information on energy inputs is becoming a more important aspect in management decisions on selection of crop production systems. The effects of long-term (45–55 years) monocropping, rotation cropping, and fertilization on tillage energy (implement draft and tractor fuel consumption) were determined for a Brookston clay-loam soil in southwestern Ontario, Canada. Treatments included fertilized and unfertilized monocrop (continuous) corn (Zea mays L.), and a four year fertilized and unfertilized corn – oat (Avena sativa L.) – alfalfa (Medicago sativa L.) – alfalfa rotation with all phases of the rotation present in each year. The corn and second year alfalfa plots were moldboard plowed each fall after crop harvest, and then spring-tilled (disc, harrow) prior to planting; oat and first year alfalfa plots were not fall plowed or spring-tilled. Moldboard plow draft and tractor fuel consumption were measured annually from 2004 to 2014 using an instrumented tractor and the same plow and settings.Monocrop unfertilized corn consistently exhibited the greatest plow draft and tractor fuel consumption. Draft averaged over ten years was 13.0% higher for unfertilized than fertilized rotation corn, and 15.5% higher for fertilized than unfertilized second year alfalfa; fuel consumption was 10.4% higher for unfertilized than fertilized rotation corn and 5.1% higher for fertilized than unfertilized second year alfalfa. These differences were attributed to treatment-induced changes in soil strength. Both plow draft and fuel consumption were lower in rotation corn relative to monocrop corn, while plow draft was greater in fertilized alfalfa relative to unfertilized alfalfa due to greater root growth. This study demonstrated that long-term cropping systems can have substantial impacts on the energy required for tilling a clay loam soil.

Long-Term Experiences with Fertilizers on Wheat and Maize Crops in the Pedoclimatic Conditions of the Bârlad Plateau

A large number of long-term field experiments demonstrate that optimal application of nitrogen fertilizers to crops did not result in loss of organic matter, nor did it adversely affect soil microbial activity. Optimal use of fertilizers on agricultural crops reduces soil erosion, but repeated application of high doses of nitrogen fertilizer can lead to soil acidification, a negative trait of soil health. The main objective of this paper is to study the particular effect, interaction and complementarity of NP, NPK and organo-mineral fertilizers on the production of agricultural crops. This paper presents production data as well as references that can be used to define the scientific bases of the multi-year application of fertilizers. The experimental technique is specific to the polyfactorial character and the analytical methods used are specific and current in the field. In this scientific paper, we present the results obtained for the cultivation of wheat and corn, during the period 2018-2023, at the “Mircea Moțoc” Perieni Research-Development Station for Combating Soil Erosion, by fertilizing with several types of organo-mineral fertilizers. The results obtained come from the long-term experiences with fertilizers with 25 variants in the NP experience, respectively 16 variants in the NPK experience and the organo-mineral experience, all being placed according to the block method with parcels subdivided into 6 repetitions. The obtained results were interpreted by analysis of variance. From the results of this long-term experience, it is concluded that the effect of long-term fertilization with NP, NPK and organo-minerals responds to the maximization of profit and the optimization of the soil-plant system and environmental protection.

Seeds Act as Vectors for Antibiotic Resistance Gene Dissemination in a Soil-Plant Continuum.

Though the evidence for antibiotic resistance spread via plant microbiome is mounting, studies regarding antibiotic resistome in the plant seed, a reproductive organ and important food resource, are still in their infancy. This study investigated the effects of long-term organic fertilization on seed bacterial endophytes, resistome, and their intergenerational transfer in the microcosm. A total of 99 antibiotic resistance genes (ARGs) and 26 mobile genetic elements (MGEs) were detected by high-throughput quantitative PCR. The amount of organic fertilizer applied was positively correlated to the number and relative abundance of seed-associated ARGs and MGEs. Moreover, the transmission of ARGs from the rhizosphere to the seed was mainly mediated by the shared bacteria and MGEs. Notably, the rhizosphere of progeny seedlings derived from seeds harboring abundant ARGs was found to have a higher relative abundance of ARGs. Using structural equation models, we further revealed that seed resistome and MGEs were key factors affecting the ARGs in the progeny rhizosphere, implying the seed was a potential resistome reservoir for rhizosphere soil. This study highlights the overlooked role of seed endophytes in the dissemination of resistome in the soil-plant continuum, and more attention should be paid to plant seeds as vectors of ARGs within the "One-Health" framework.

Long-Term Effect of Wood Ash and Wastewater Sludge Fertilization on Tree Growth in Short-Rotation Forest Plantations on Abandoned Agricultural Land: A Case Study

Short-rotation forest plantations on former agricultural land capture CO2, provide bioeconomic materials, and mitigate climate change. This study aimed to enhance our understanding of the long-term effects of wood ash and wastewater sludge fertilization on various tree species (birch, hybrid aspen, grey alder, black alder, and hybrid alder) in short-rotation forestry plantations on abandoned agricultural land where tree growth measurements were taken over an 11-year period. After 11 years, the highest aboveground biomass (AGB) was observed for hybrid aspen clone No. 4 under wastewater sludge treatment (109.0 t ha−1), birch under wood ash treatment (34.3 t ha−1), black alder under wastewater sludge treatment (33.6 t ha−1), grey alder under wastewater sludge treatment (40.9 t ha−1), hybrid alder under control conditions (36.2 t ha−1), and hybrid aspen clone No. 28 under wood ash treatment (37.2 t ha−1). The average survival rate was 73% in control plots, 81% under wastewater sludge treatment, and 78% under wood ash treatment. Short-term positive impacts on tree growth were observed, effects that were not consistent over the long term. The impact of these treatments on tree growth varied between species, and the effects tended to diminish over time, which must be considered before fertilization.