Soil Fertilization Research Articles

Effects of water and fertilizer regulation on soil microbial community, fruit nutrients, and saponin content of Panax notoginseng: A three years field experiment

In pursuit of maximum yield and economic benefits of Panax notoginseng, farmers usually apply excessive fertilizer and irrigation. Which easily induce the decline of Panax notoginseng quality, fertilizer and water use efficiencies and soil health. From 2021–2023, a field experiment was conducted in Dali Village, Luxi County, Honghe Prefecture, Yunnan Province, to study the response of soil microbial community, root nutrient content, and ginsenoside content of Panax notoginseng to different water and fertilizer regulation. The experiment including three irrigation levels (F1: 120 mm, F2: 240 mm, and F3: 360 mm) four fertilization rates(F1: 48 kg ha−1, F2: 72 kg ha−1, F2: 96 kg ha−1, and 120 kg ha−1),and a CK treatment (no fertilizer and no irrigation) The results showed that the average N, P, and K contents across all treatments were greater in 2023 than those in 2021 and 2022. W3F4 treatment significantly increased N absorption. W2F4 treatment significantly increased P and K absorption. W2F4 treatment significantly increased the Panax notoginseng yield, and W3F2 treatment significantly increased the saponin content. The Panax notoginseng yield ranged from 1165 to 3006 kg∙ha−1, with a maximum average yield in 2023. The Re content averaged 81.5 % in 2023 over 2021, and the highest Re content in W3F2 treatment in 2023 was 108.54 mg∙g−1. In 2023, W2F3 treatment had the highest R1 content of 15.34 mg∙g−1, W2F3 treatment had the highest content of Rg1 of 44.65 mg∙g−1, and W3F2 treatment had the highest Rb1 content of 52.52 mg∙g−1. From 2021–2023, the total number of unique OTUs in W1F1 was the largest, out followed by W3F2, W3F4, and W3F1. The treatment that significantly increased the bacterial Chao1 index was W3F1 and W2F2 in 2021, W3F3, W2F1, W2F1 and W2F3 in 2022, and W2F3 and W2F4 in 2023. The Shannon nor Simpson indices were not varied significantly from CK. At the phylum level, W1F3 in 2021 and W3F1 in 2022 and 2023 improved the relative abundance of Proteobacteria, Acidobacteriota At the genus level, W1F1 in 2021 and 2023 improved the relative abundance of Vicinamibacteraceae_norank and Vicinamibacterales_norank. LEfSe analysis of soil microbial communities showed the most divergent species in 2021 with W3F2, W1F1 in 2022, and W2F1 in 2023. Different water and fertilizer treatments affected the total OTU number of bacterial communities and changed the bacterial community structure. W3F1 and W2F3 treatments significantly increased soil bacterial diversity, and soil microbial diversity regulated plants N as well as R1 and Rg1 content, and the quality of Panax notoginseng is related to microbial diversity. N, P, K, and R1 had a significant positive correlation with microbial community diversity (P<0.05). The W1F1 treatment communities were relatively abundant, and the community species showed high similarity in W3F1 and W2F3.

Optimization of fertilizer use efficiency, soil quality and oil palm (Elaeis guineensis Jacq.) growth with biochar under drip irrigation conditions irrigation conditions

Biochar (BC) is an eco-friendly product characterized with high content of carbon and usually obtained by heating biomass without oxygen. Utilizing BC as organic material to amend the problematic soils and improve plant growth and yield has been proved previously. This study investigated the effect of vetiver grass biochar (VGB) on fertilizer use efficiency, soil quality, and oil palm growth performance. A net house experiment was conducted at the Farm Unit, UiTM Sarawak Branch, between August 2022 and March 2023. A factorial randomized complete block design (RCBD) with five treatments and four replications was devised. Treatments applied were: T0) absolute control; T1) 100% NPK fertilizer; T2) 100% vetiver grass biochar; T3) 50% vetiver grass biochar + 50% NPK fertilizer; and T4) 25% vetiver grass biochar + 75% NPK fertilizer. The BC application significantly improved the fertilizer use efficiency through reducing the rate of fertilizer applied. It also significantly enhanced most soil-measured chemical properties and soil nutrients. The growth performance of oil palm plant was significantly enhanced by BC application in terms of plant height, hump diameter, leaf number, chlorophyll content, and plant biomass. The BC application demonstrated its usefulness in managing soil and cultivating oil palm plant sustainably by reducing the rate of fertilizer applied and improve the fertilizer use efficiency. Based on the output, we suggest that treatment T3 (50% vetiver grass biochar + 50% NPK) can be used to improve the growth performance of oil palm.

Developments in biochar incorporated geopolymers and alkali activated materials: A systematic literature review

Annually, industries related to agricultural products generate substantial volumes of waste biomass, presenting critical challenges for solid waste management due to its environmental and health implications. Pyrolysis emerges as a significant technique for converting such waste into biochar (BC), a material with notable internal microstructure, porosity, and chemical properties, contingent on the feedstock and processing conditions. BC is recognized for its exceptional water retention and alkalinity, primarily utilized for soil enhancement and fertilization. Its application across various fields, particularly in enhancement for sustainability, has gained momentum. This review meticulously explores BC's role in sustainable composites, focusing on geopolymers and alkali-activated binders through a comprehensive examination of existing literature, underscored by bibliometric analysis. This pioneering review, leveraging the PRISMA framework and VOSviewer for bibliometric insights, aims to bridge the research gap in this evolving domain, offering a critical assessment of BC's integration in sustainable construction materials, its challenges, and future research directions. Hence, this pioneering systematic review represents the first-ever exploration within the research domain of BC's applications in geopolymers and alkali-activated materials, marking a foundational step toward understanding its potential and challenges in sustainable engineering practices.

Heavy Metal Accumulation in Soil and Plants Using Municipal Solid Waste Compost in Variable pH Conditions

ABSTRACT Municipal solid waste composts (MSWC) are extensively utilized as organic soil conditioners and fertilizers in agricultural fields across many countries. However, the use of MSWC can lead to heavy metal pollution in soil and plants, which may adversely affect plant growth. This study examined the impact of MSWC on the heavy metal content in plants and soil across various pH levels. The experiment was conducted in a pot setting with three replications. The research findings indicated that MSWC application increased the levels of copper (Cu) and zinc (Zn) in soils but had no significant effect on lead (Pb), nickel (Ni), manganese (Mn), and iron (Fe) levels. Additionally, increases were observed in the Cu, Zn, and Fe content in plants, while Pb and Ni content remained unchanged. Cu, Zn, and Fe are essential for plant growth, and their enhancement in both soil and plants is a direct result of their relatively high presence in the MSWC used. The soil-plant transfer coefficients show that the transfer of heavy metals from soil to plants is highest under acidic conditions, indicating that the heavy metal content in MSWC can vary depending on soil pH and application rate. Therefore, it is crucial to carefully analyze and evaluate the heavy metal contents of soil and compost samples before employing MSWC in agricultural fields.

Biochemical and biophysical drivers of the hydrogen isotopic composition of carbohydrates and acetogenic lipids.

The hydrogen isotopic composition (δ2H) of plant compounds is increasingly used as a hydroclimatic proxy; however, the interpretation of δ2H values is hampered by potential coeffecting biochemical and biophysical processes. Here, we studied δ2H values of water and carbohydrates in leaves and roots, and of leaf n-alkanes, in two distinct tobacco (Nicotiana sylvestris) experiments. Large differences in plant performance and biochemistry resulted from (a) soil fertilization with varying nitrogen (N) species ratios and (b) knockout-induced starch deficiency. We observed a strong 2H-enrichment in sugars and starch with a decreasing performance induced by increasing NO3-/NH4+ ratios and starch deficiency, as well as from leaves to roots. However, δ2H values of cellulose and n-alkanes were less affected. We show that relative concentrations of sugars and starch, interlinked with leaf gas exchange, shape δ2H values of carbohydrates. We thus provide insights into drivers of hydrogen isotopic composition of plant compounds and into the mechanistic modeling of plant cellulose δ2H values.

Inhibition of nitrate accumulation in vegetable by Chroococcus sp. and related mechanisms

Vegetable nitrate accumulation is a major threat to food security and human health. The application of a non-toxic and non-nitrogen-fixing cyanobacterium, Chroococcus sp., was found to reduce soil nitrate content; however, the influence of Chroococcus sp. on vegetable growth and nitrate accumulation remains unclear. In this study, Chroococcus sp. was introduced to soil fertilized with NaNO3, (NH4)2SO4, and CO(NH2)2. Variations in growth performance and nitrate content of pakchoi (Brassica chinensis L.), coupled with changes in soil fertility, were investigated through pot experiments. The varied abundance of rhizosphere bacteria and differential expression of bacterial functional genes were studied using 16S rRNA and meta-transcriptomic sequencing analyses, respectively. Chroococcus sp. reduced vegetable nitrate content by 42.29%, 21.34%, and 27.10% in pakchoi planted in soil fertilized with NaNO3, (NH4)2SO4, and CO(NH2)2, respectively. This reduction was mainly attributed to regulation of the rhizosphere bacterial community by Chroococcus sp. First, Chroococcus sp. stimulated denitrifying bacteria (such as Methylotenera, Gemmatimonas, Nitrosomonas, Nocardioides, Gaiella, Lysobacter and Sphingomonas) that contributed to a reduction in soil nitrate content. Second, Chroococcus sp. stimulated several rhizosphere bacteria such as Methylibium, Micromonospora, Bacillus, Pedomicrobium, Hyphomicrobium, Steroidobacter, Pseudolabrys, Streptomyces, Methylobacillus and Pseudomonas that directly participated in the reduction of vegetable nitrate accumulation, according to their negative correlation with vegetable nitrate content. Chroococcus sp. increased soil fertility and consequently promoted the growth of pakchoi by reducing soil salinity and increasing soil polysaccharide content, available phosphorus, and functional enzyme activity. The increased abundances of various rhizosphere bacteria genera also contributed to an increase in soil fertility and the promotion of vegetable growth. In general, this study demonstrated the effectiveness of Chroococcus sp. in reducing vegetable nitrate accumulation and explored the related mechanisms.

Differences in Soil Fertility and Bacterial Community Structure Between Carbon Inputs such as Biochar and Organic Fertilizer and Their Relationship

The potato planting area of Guizhou Province ranks second in China. However, due to factors such as climatic conditions and unbalanced fertilization, soil organic matter in potato fields is consumed rapidly and has a large deficit, which affects soil biological function and soil fertility. Biochar and organic fertilizer are effective ways to supplement foreign aid organic matter to improve soil quality. However, the differences in soil fertility and microbial community structure and their relationships under the conditions of organic fertilizer or biochar combined with chemical fertilizer are not clear. In this study, three treatments of conventional fertilization （NPK）, increased application of biochar （NPKB）, and increased application of organic fertilizer （NPKO） were set up to investigate the characteristics of potato rhizosphere soil, bacterial community composition, and diversity； to analyze the effects of these factors on the soil integrated fertility index； and to explore the direct and indirect effects of IFI on soil fertility and bacterial community structure differences between treatments and their driving factors. The results showed that soil pH, available phosphorus （AP）, available potassium （AK）, total nitrogen （TN）, organic carbon （SOC）, and C/N ratio were significantly higher in the NPKB and NPKO treatments than in the NPK treatment （P<0.05）. Soil IFI was greatest for NPKO, followed by NPKB and least for the NPK treatment. A total of 8 214 ASVs were obtained from all the soil samples, belonging to 26 phyla, 75 classes, 165 orders, 176 families, and 251 genera （excluding unidentified fungi）. Proteobacteria, Actinobacteria, and Chloroflexi were the dominant phyla, accounting for 54.85% of all ASVs. Compared to that in the NPK and NPKB treatments, the NPKO treatment had the highest bacterial diversity and number of significantly different taxa, and soil AN, AP, AK, SOC, TN, and IFI were significant correlates of bacterial diversity index （P<0.05）. Additionally, pH, TN, and SOC were significant influencers of bacterial taxa differences （P<0.05）, with importance ranked as TN （70.59%） &gt; SOC （49.42%） &gt; pH （27.08%）. Structural equations suggested that pH-related soil properties and bacterial community diversity were the direct pathways influencing IFI, and soil pH-related soil characteristics could also indirectly affect IFI by affecting bacterial Shannon diversity. These results indicate that soil fertility and bacterial community structure were significantly different and correlated between the biochar and organic fertilizer addition treatments and that pH and bacterial community diversity were the key factors influencing IFI, with the NPKO treatment in particular having the best effect on improving IFI. Considering the effect of soil fertilization and the functional group of bacteria, NPKO is the recommended combination for the best synergistic effect of soil fertilization, that is, N 150 kg·hm-2+P2O5 135 kg·hm-2+K2O 135 kg·hm-2+organic fertilizer 6.6 t·hm-2.

Elaeis guineensis phenotypic traits and non-enzymatic antioxidant responses to the combination of biofertilizer and chemical fertilizer in infertile soil

A 7-month glasshouse study was conducted to assess the growth responses, nutrient status, and non-enzymatic antioxidant properties of E. guineensis seedlings grown on infertile Ultisol which were subjected to different combinations of chemical fertilizers (CF) and commercial biofertilizer (IBG) as follows: [T1] 100% CF [T2] 70% CF + 30% IBG biofertilizer [T3] 50% CF + 50% IBG biofertilizer [T4] 70% CF only and [T5] Absolute Control. A combination of CF70 and IBG30 led to 15.8% increase in the growth of seedlings as compared to CF100, presenting significantly higher fresh shoot and root weights as well as an ideal root-to-shoot ratio. Absolute control seedlings on the other hand, showed less desirable phenotypical traits across all the observed parameters. Significantly higher levels of relative chlorophyll were recorded for the seedlings treated with CF70 + IBG30, which positively correlated with the chlorophyll a/b ratio. Moreover, the biofertilizer and chemical fertilization allowed increased uptake of nutrients where higher uptake of B and P was positively correlated (p < 0.05) with enhanced frond production, while larger roots mass was associated with primary growth traits. The positive impacts of the combined IBG biofertilizer and chemical fertilizer application were likely attributed to enhanced accumulation of non-enzymatic antioxidants to counteract the effects of soil infertility, with seedlings in CF70 + IBG30 mostly recorded the highest phenolic, anthocyanin, flavonoid, photosynthetic pigments, DPPH radical activity and proline levels.

Long-term fertilization and liming increase soil fertility but reduce carbon stratification and stocks of paddy rice soils

Long-term fertilization and liming increase soil fertility but reduce carbon stratification and stocks of paddy rice soils

Nitrogen fertilizers affecting the efficiency of mineral and organic phosphorus fertilizers in tropical soils cultivated with maize

Most conventional phosphorous (P) fertilizers are highly soluble, which favors P retention in the solid phase of the soil, and this condition hinders P availability to plants. Alternative P fertilizers, such as organominerals and struvite, have a slow release of nutrients into the soil, which in turn favors P uptake by plants; nevertheless, soil acidification caused by nitrogen (N) fertilizers can reduce P availability in the soil. In his study, we assessed the effect of N fertilizers on P availability for maize (Zea mays) grown in tropical soils with alternative P fertilizers. An experiment was set up in columns under greenhouse conditions with maize in two cultivation cycles in two soils with contrasting textures (medium and clayey textures), two N fertilizers (calcium nitrate - CN - and ammonium sulfate - AS), three P fertilizers (triple superphosphate - TSP -, organomineral - OM - and struvite - ST), and a control treatment (without addition of P and N fertilizers). At 45 days after emergence, we measured the biomass production and the N and P contents in plants to calculate fertilization efficiency as well as the soil P content. AS promoted the highest aboveground N accumulation, whereas the highest efficiency was obtained with CN. The alternative P sources did not differ in terms of P availability when combined with both N sources. Soil textures were sensitive to fertilizer combination. Further studies are needed to assess struvite interaction with other elements in the soil and the P release kinetics to plants.

Soil Fertility, Fertilizers, and Crop Nutrition: Past, Present, and Future

AbstractThe 20th century saw the development of a highly efficient nutrient industry producing affordable fertilizers that contributed greatly to increased food, feed, fiber, and fuel production for a growing global population. Plant nutrient production and use in the 21st century faces pressure to improve efficiency and outcomes. The nutrient industry has historically operated with large volumes and low margins, and has, at times, been slow to embrace innovations. However, the landscape has changed, driven by the demand for superior products, practices, and environmental stewardship. This transition marks the advent of what experts term “responsible plant nutrition” (International Fertilizer Association, 2024). This is the third and final article in a series on the past, present, and future of the North American fertilizer industry. Earn 1.5 CEUs in Nutrient Management by reading this article and taking the quiz at https://web.sciencesocieties.org/Learning‐Center/Courses.

Effect of Soil and Foliar Nitrogen Fertilization on Performance and Economics of Linseed (Linum usitatissimum L.) Cultivation under Rainfed Conditions of Nagaland

Background: Crop production relies heavily on essential nutrients. Balanced soil-applied fertilizers, along with foliar sprays, can improve input efficiency and crop performance, particularly in rainfed areas prone to moisture stress. Method: A field investigation was conducted at the experimental farm of School of Agricultural Sciences, Nagaland University, Medziphema campus, during rabi season of 2021. The experiment was laid out in split plot design with three replications with four main factors comprising of soil-application of different doses of N (nitrogen) in two splits (based on RDF of 40 kg N ha-1) viz., 100 % N, 75% N, 50% N and 25% N and five sub-factors comprising of foliar sprays of N viz. Control (water spray), single spray of Nanourea @ 3 ml liter-1, two sprays of Nanourea @ 3 ml liter-1, single spray of Urea @ 2% and two sprays of Urea @ 2 %. Result: Among the different soil application treatments, significantly highest NUE (Agronomic Efficiency), seed yield (996.80 kg ha-1) and stover yield (3032.10 kg-1) was recorded with soil application of 100 % N ultimately recording the highest net return (Rs. 26004 ha-1) and IBCR (5.80). Whereas, two sprays of Nanourea @ 3 ml L-1, among foliar treatments, recorded the highest NUE (Agronomic Efficiency), seed and stover yield (918.44 kg ha-1 and 3032.26 kg ha-1 respectively) as well as net returns (Rs. 22988 ha-1) and IBCR (5.5).

Impact of nitrapyrin on urea‐based fertilizers in a Mediterranean calcareous soil: Nitrogen and microbial dynamics

AbstractNitrification inhibitors, such as nitrapyrin (NI), are increasingly co‐applied with nitrogen (N) fertilizers as part of sustainable agricultural practice. Several studies in temperate regions have documented the effectiveness of NI in retaining soil ammonium (NH4+), minimizing N loss and increasing crop yields. However, less is known about the effects of NI in Mediterranean regions, where agricultural production is challenging and requires intensive irrigation and fertilization. We investigated the short‐term impact of the nitrification inhibitor nitrapyrin (2‐chloro‐6‐(trichloromethyl)pyridine) in a two‐factor mesocosm experiment, using a typical Mediterranean soil, where NI was co‐applied with a selection of urea‐based fertilizers: urea (U), U with urease inhibitors (U + UI), methylene urea (MU) and zeolite‐coated urea (ZU). NI co‐applied with urea fertilizers resulted in higher availability of soil NH4+ and a concurrent increase in NH3 volatilization. Net cumulative soil NH4+ availability was 1.5–3.3 fold greater when NI was applied. Concurrently, net cumulative nitrate (NO3−) and nitrite (NO2−) availability was reduced by 10%–60%; this was found for all the tested fertilizer types except MU fertilizer, where the net cumulative soil NO3− and NO2− doubled. Nitrous oxide (N2O) emissions from urea fertilization were reduced by 40% with UI, 50% with NI and 66% with NI + UI. Interestingly, after 28 d, the composition of soil microbial communities was distinctly different, due to NI application. Specifically, NI application dramatically reduced the abundance of ammonia‐oxidizing and denitrifying bacterial functional groups. NI was effective in reducing N2O emissions in this calcareous soil; however, NH3 emissions were remarkably enhanced. These findings have important implications for the large‐scale adoption of inhibitor technologies in Mediterranean agroecosystems and for the reduction of greenhouse gas emissions.

Soil organic carbon fractions and storage potential in Finnish arable soils

AbstractUnderstanding the factors affecting the total amount and distribution of soil organic carbon (OC) across different functional carbon pools is important to better define the future management of soil OC stocks. The interactions between soil management practices, local physicochemical soil properties and climate are essential for determining the OC content of the soil. Nevertheless, how these factors affect the total amount of OC and its distribution across carbon pools, i.e., more labile particulate (POC) and more stable mineral‐associated (MAOC) organic carbon, is only partly known. In this study, we assessed topsoil (0–20 cm) samples from 93 arable farms in the southern half of Finland to determine the total amount of OC, and its distribution in MAOC and POC, along with relevant soil properties (amount of clay and silt, aluminium and iron oxides and pH), climate (precipitation and temperature) and fertilization (mineral versus organic). The fertilization did not affect the total soil carbon content (12–58 g OC kg−1 soil). The share of OC in the MAOC fraction (on average 86% of total OC) was relatively stable across the large range of OC contents and clay contents (2%–68%). We assessed the highest feasible MAOC of the soils with boundary line analyses and their OC saturation state with Hassink's equation (Hassink, 1997). Only soils with the lowest clay content (&lt;10% clay) were assumed to be carbon‐saturated, suggesting that most of the studied soils have a capacity to accrue more MAOC. Simple linear regression showed that clay, aluminium and iron oxides explained 9%, 21% and 22% of the variation in MAOC, respectively. Multiple regression analyses including the amount of clay, clay+silt, aluminium and iron oxides, pH, type of fertilization, precipitation and temperature as explanatory variables explained 33%–53% of the variation in OC and MAOC. In all soils, aluminium oxides were important explanatory variable for MAOC, whereas Fe oxides were significant only in soils with higher clay content (&gt;30%). In soils with a low clay content (&lt;30%), pH had added value in explaining MAOC. Altogether, it seems that various climatic, edaphic and soil management‐related factors are context‐dependently controlling OC and that soil textural information alone is not necessarily an adequate predictor to assess the MAOC saturation state of the soil.

Responses of soil fungal and bacterial communities to long-term organic and inorganic nitrogenous fertilizers in an alpine agriculture

Although nitrogen fertilizer is an important measure to increase grain yield, response of soil microbial community to nitrogen fertilizer is still unclear in alpine regions. Based on a long-term (>10 years) nitrogen fertilizer experiment (control, CF: chemical fertilizer, SM: sheep manure; CS: chemical fertilizer + sheep manure) in an alpine agroecosystem of the Lhasa, Xizang, responses of soil bacteria and fungi communities to nitrogen fertilizer was investigated. The CF treatment reduced fungi operational taxonomic unit (OTU) by 13.08 %, phylogenetic diversity by 11.13 % at 10–20 cm, but increased fungi guild number at 0–10 cm by 17.71 %. The SM treatment reduced fungi OTU at 10–20 cm by 11.82 %. Compared to CF and SM treatments, CS treatment had stronger positive effects on bacterial α-diversity, considering that CS treatment but not CF and SM treatments increased bacterial mean nearest taxon distance, species Shannon and Simpson at 10–20 cm. The CF, SM and CS treatments altered fungal community composition at 0–10 and 10–20 cm, bacterial community composition at 10–20 cm, and bacterial species composition at 0–10 cm. The CF and CS treatments altered bacterial phylogenetic composition at 0–10 cm, and the SM and CS treatments altered bacterial functional composition at 0–10 cm. The decreased magnitude of the relative abundance of symbiotroph fungi caused by CS treatment (90.44 %) was stronger than that (65.14 % and 53.62 %) caused by CF and SM treatments at 10–20 cm. Therefore, the SM and CS treatments had stronger effects on soil bacterial functional composition, but the CF treatment had stronger effects on fungal α-diversity. Compared with single application of organic or inorganic nitrogen fertilizer, mixed application of organic and inorganic nitrogen fertilizer was more beneficial to the maintenance and improvement of soil bacterial diversity, but caused more reduction of soil symbiotic fungi and in turn greater potential risk. These scientific findings observed by this study can provide guidance for fertilizer management and soil fertility improvement.

Topsoil dilution by subsoil admixture had less impact on soil organic carbon stock development than fertilizer form and erosion state

Enhancing the agroecosystems carbon (C) sink function for climate mitigation faced challenges, particularly with traditional measures with limited suitability for increasing soil organic carbon (SOC) stocks. Inducing a SOC undersaturation in the topsoil by abrupt subsoil admixture is a way to create an additional C sink. However, the deep tillage traditionally used for this topsoil dilution was not always successful. It was due to a lack of knowledge and suitable approaches to record the effect of all relevant factors in SOC recovery, including soil conditions and fertilizer forms.We addressed these problems by establishing a three-factorial experiment: I) “moderate topsoil dilution,” II) “N fertilization form,” and III) “soil erosion state,” representing three soil types in the hummocky ground moraine landscape of NE Germany. SOC dynamics were determined over a year of winter rye cropping using a novel robotic chamber system capable of measuring CO2 exchange on 36 experimental plots with a reduced methodological bias than previous measuring systems.The averaged net ecosystem carbon balance, a proxy for SOC stock change, indicated that topsoil dilution only reduced further SOC losses. The N fertilizer form had a significantly stronger and more differentiated effect. While the mineral N fertilization consistently produced only C sources, the organic fertilization, in combination with the diluted topsoil, led to a C sink. This C-sink function was, however, more pronounced in the eroded soil than in the non-eroded soil. Overall, the results have made clear that the impact of topsoil dilution on the further development of the SOC stock is only possible if the effect of other relevant factors, such as N fertilizer form and erosion state, are taken into account.

Biochar Amendment was Less Effective for Rice Yield Improvement but More Effective for Soil Quality Relative to Inorganic Fertilization in a Low Fertility Paddy Soil

Biochar Amendment was Less Effective for Rice Yield Improvement but More Effective for Soil Quality Relative to Inorganic Fertilization in a Low Fertility Paddy Soil

Soil amendment and N fertilization strategies to improve C sequestration and storage in soil aggregates

AbstractManagement can affect soil quality through changes in carbon (C) stock, especially in protected C fractions of soil aggregates. Soil aggregation and C sequestration may be improved with soil correction (liming and gypsum) and nitrogen (N) fertilization, but it is not clear how these factors might interact to affect humic substances. The objective of the study was to evaluate the effects of calcium (Ca), magnesium (Mg), and N fertilizatilizer amendments on the accumulation of C, N, and humic substances in soil aggregates from an Oxisoil in Brazil. The production system was no‐till soybean [Gycine max (L.) Merr] double‐cropped with maize (Zea mays L.) and intercropped with forage grass since 2016. Treatments were no amendment, lime only, and lime + phosphogypsum, factorially arranged with and without annual N fertilization of maize. Soil was collected at 0–10, 10–20, 20–40, and 40–60 cm 6 years after initiation of the experiment. The combination of lime, gypsum, and N led to 13% greater total C stock and 20% greater total N stock within the 0–60 cm soil profile than the control. Levels of fulvic acid (FA) and humic acid (HA) were similar among aggregate classes, but humin was greatest in larger aggregates. Liming plus N decreased FA and HA, but gypsum application mitigated this negative effect. Application of limestone, gypsum, and N increased humin, mainly in the soil surface (0–10 cm). Soil C storage and stabilization was enhanced in large soil aggregates with the combined use of lime, gypsum, and N fertilization in humid tropical soils.

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.

Exploring the Effects of Nitrogen Fertilization Management and Soil Factors on the Yield and Quality of Flue-Cured Tobacco in China—A Quantitative Research

Tobacco, a pivotal economic crop in China, faces the challenge of securing high-quality raw materials for its industry due to unbalanced and inefficient nitrogen (N) application. To assess the impact of fertilizer management and soil factors on the yield and quality of flue-cured tobacco (FCT), a meta-analysis was conducted across 82 peer-reviewed research studies. The findings demonstrated that both fertilizer management and soil properties exerted a significantly greater influence on yield (63.13% and 62.05%, respectively) than the proportion of superior and medium tobacco (PSMT) (23.57% and 23.83%, respectively). Multiple models were conducted to analyze the N application rate for maximum yield and PSMT, respectively, resulting in an optimum range from 90 to 100 kg N ha−1. The highest yield and PSMT increments were observed with fertilizer timing (FT) applied twice, a basal fertilizer ratio (BFR) exceeding 50%, and a soil pH below 6.5. The nicotine content escalated with increasing N application rates (NR) and soil nitrogen content, peaking at NR over 120 kg N ha−1 and soil total nitrogen (TN) above 2 g kg−1. Stepwise regression modeling indicated that nicotine content was positively influenced by fertilizer management factors (including NR, fertilizer timing, and BFR), as well as initial soil nitrogen content (AN and TN). However, it was negatively correlated with available potassium (AK). Therefore, the results of this meta-analysis suggest that effective fertilizer management, slightly acidic soils enriched with AK, and lower N supply capacity are crucial for enhancing leaf quality while reducing nicotine content. This approach promises improved economic and environmental returns for the tobacco industry in China.