Long-term Mineral Fertilization Research Articles

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.

Organic Phosphorus Fractions in Relation to Soil Aggregate Fractions of Black Soil

Knowledge of long-term phosphorus behavior is essential to improve soil structure, nutrient supply potential, and the sustainability of cropping systems. A 45-year long-term experimental trial was used to observe organic phosphorus fractionation and its effects on soil aggregation and nutrient distribution at three depths (0–20, 20–40, and 40–60 cm) in Vojvodina Province, Serbia, under maize monoculture and maize/barley rotation. Five fertilizing systems were studied, including Control, NPK, NPK + maize remains, NPK + manure, and NPK + manure in rotation. Soil aggregates were fractionated into four size categories (>2000, 2000–250, 250–53, and <53 μm) using a wet sieving method. The samples were analyzed for main indicators, including different forms of phosphorus, total and available (PT and PA), as well as its organic forms (Labile Po, Biomass Po, Mod. Labile Po, Fulvic acid Po, Humic acid Po, and Resistant Po), and other fertility parameters. Significant differences in total and available phosphorus as well as all observed organic phosphorus fractions were evident between treatments with and without organic amendments, particularly in the 0–20 and 20–40 cm soil layers. Moderately labile P forms were dominant across all treatments, while labile forms constituted a smaller proportion. The most notable differences between treatments were observed in the labile and moderately labile forms, as well as in the resistant form of organic phosphorus. Manure application led to increased nutrient content in macroaggregates (>250 μm) compared to microaggregates. Microaggregates (<250 μm) were predominant across all depths, while stable structural aggregates did not show a significant increase after manure application. PCA highlighted significant correlations between soil characteristics, including total and available P, total organic carbon, clay content, and enzyme activity, across different aggregate sizes and organic P fractions. Overall, long-term mineral fertilization combined with organic amendment application induced variations in phosphorus fractions and the content of carbon, nitrogen, and phosphorus associated with aggregates in the first two soil layers, except for aggregate size classes.

Replacing nitrogen in mineral fertilizers with nitrogen in maize straw increases soil water-holding capacity

Soil water-holding capacity decreases due to long-term mineral fertilizer application. The objective of this study was to determine how replacing mineral fertilizer with maize straw affected the soil water retention curve, soil water content, soil water availability, and soil equivalent pore size. Replacement treatments in which 25% (S25), 50% (S50), 75% (S75), and 100% (S100) of 225 kg ha−1 nitrogen from mineral fertilizer (CK) was replaced with equivalent nitrogen from maize straw were conducted for five years in the Loess Plateau of China. The Gardner model was used to fit the soil water retention curve and calculate the soil water constant and equivalent pore size distribution. The results indicated that the Gardner model fitted well. Replacing nitrogen from mineral fertilizer with nitrogen from straw increased soil specific water capacity, soil readily available water, soil delayed available water, soil available water, soil capillary porosity, and soil available water porosity over time. S25 increased field capacity and wilting point from the fourth fertilization year. S50 enhanced soil readily available water, soil delayed available water, soil available water, and soil available water porosity from the fifth fertilization year, whereas S25 and S75 increased these from the third fertilization year or earlier. Soil specific water capacity, soil readily available water, soil delayed available water, soil available water, soil capillary porosity, and soil available water porosity could better reflect soil water-holding capacity and soil water supply capacity compared with field capacity and wilting point.

Active microbial population dynamics and life strategies drive the enhanced carbon use efficiency in high-organic matter soils.

Microbial carbon use efficiency (CUE) is a critical parameter that controls carbon storage in soil, but many uncertainties remain concerning adaptations of microbial communities to long-term fertilization that impact CUE. Based on H218O quantitative stable isotope probing coupled with metagenomic sequencing, we disentangled the roles of active microbial population dynamics and life strategies for CUE in soils after a long-term (35 years) mineral or organic fertilization. We found that the soils rich in organic matter supported high microbial CUE, indicating a more efficient microbial biomass formation and a greater carbon sequestration potential. Organic fertilizers supported active microbial communities characterized by high diversity and a relative increase in net growth rate, as well as an anabolic-biased carbon cycling, which likely explains the observed enhanced CUE. Overall, these results highlight the role of population dynamics and life strategies in understanding and predicting microbial CUE and sequestration in soil.IMPORTANCEMicrobial CUE is a major determinant of global soil organic carbon storage. Understanding the microbial processes underlying CUE can help to maintain soil sustainable productivity and mitigate climate change. Our findings indicated that active microbial communities, adapted to long-term organic fertilization, exhibited a relative increase in net growth rate and a preference for anabolic carbon cycling when compared to those subjected to chemical fertilization. These shifts in population dynamics and life strategies led the active microbes to allocate more carbon to biomass production rather than cellular respiration. Consequently, the more fertile soils may harbor a greater microbially mediated carbon sequestration potential. This finding is of great importance for manipulating microorganisms to increase soil C sequestration.

Gross nitrogen mineralization and nitrification at an optimal phosphorus input level in southern Chinese red soil with long-term fertilization

In China, phosphorus (P) is recognized as a “key limiting nutrient” for crop production, and its overuse results in underground leaching, ecosystem alterations and risks to humans, such as degraded surface water quality. The coupling of nitrogen (N) and P implies that soil N dynamics are largely affected by P availability. However, how the addition of P affects soil N transformations remains less understood. To determine the optimal P-input level, we performed an incubation experiment on an upland soil from Jinxian in China after long-term mineral fertilizer application and P addition. The two treatments without N addition T1 (no fertilizer) and T2 (inorganic potassium fertilizer) and the two treatments with N addition T3 (inorganic nitrogen fertilizer) and T4 (inorganic nitrogen and potassium fertilizer) were selected from the long-term experiment that involved scientific management at five P-input levels (0, 25, 50, 75, and 100 kg P2O5 ha−1) with three replications. The results showed that soil organic matter (SOM) increased in the T3 and T4 treatments compared with the T1 and T2 treatments. The T4 treatment resulted in the maximum N concentration of 1.28 g kg−1, followed by that in the T3 treatment (1.25 g kg−1), T2 (0.16 g kg−1) and that in the T1 treatment (0.10 g kg−1), in the soil. Among the different treatments, soil microbial biomass carbon (SMBC) and nitrogen (SMBN) were significantly higher (492.69 mg kg−1 and 73.36 mg kg−1, respectively) in the T3 treatment than in the other treatments, while soil microbial biomass phosphorus (SMBP) was higher in the T4 treatment (17.55 mg kg−1). With the addition of P, the gross N mineralization rate was substantially enhanced when N and K were applied. After the 90-day incubation period, with higher concentrations of NO3--N and NH4+-N in the T4 treatment than in the other treatments, the concentrations were significantly increased by P addition, specifically T4P4 by 11.27% and 37.37%, T4P3 by 12.64% and 30.29%, T4P2 by 22.94% and 64.53%, and T4P1 by 3.93% and 11.09%, compared with those of T4P0, respectively; these results indicated a maximum N mineralization potential (No) and mineralization rate constant, k (NMR). As a result of the increased gross nitrogen mineralization rates and associated NH4+ substrate availability, the gross nitrification rate was also increased by P addition. Based on the polynomial regression analysis, the inclusion of P at the rate of 60 kg P2O5 ha−1 can be used effectively to obtain maximum gross N mineralization rates in soil. Additionally, to fully understand why P addition is more effective under specific soil and environmental conditions, more research is necessary to determine the underlying mechanisms.

The role of long-term mineral and manure fertilization on P species accumulation and phosphate-solubilizing microorganisms in paddy red soils

Abstract. Understanding soil phosphorus (P) transformation and turnover under various fertilization managements is important for evaluating sustainable P fertility and potential bioavailability in agriculture managements. Thus, long-term fertilization experiments (∼ 38 years) with the application of different inorganic and organic fertilizers in paddy red soils were conducted to determine the effect of different fertilizer applications on P pool accumulation and microbial communities, especially for phosphate-solubilizing microorganisms (PSMs). Long-term inorganic P (IP) fertilization increased the concentrations of total P (TP) (∼ 479 mg kg−1), available P (AP) (∼ 417 mg kg−1) and inorganic P (∼ 18 mg kg−1), but manure fertilization accelerated the accumulation of organic P, especially for orthophosphate monoesters (e.g., myo-IHP, ∼ 12 mg kg−1). Long-term mineral fertilization decreased bacterial richness, evenness and complexation of bacterial networks. In contrast, long-term manure fertilization and rhizosphere accumulated more amounts of total carbon, total nitrogen, and organic carbon, as well as regulated the soil pH, thus improving the separation of bacterial communities. Furthermore, PSM compositions were greatly influenced by fertilization managements and rhizosphere. For example, inorganic P fertilization increased the abundance of Thiobacillus (i.e., the most abundant phosphate-solubilizing bacteria (PSB) in this study) and shifted the community structure of PSB. Correspondingly, the concentrations of inorganic and total P were the key factors for the variation of the PSB community structure. These findings are beneficial for understanding the variation of inorganic and organic P pools and the microbial community, especially for PSMs under long-term inorganic and/or organic fertilization.

New Insights from Soil Microorganisms for Sustainable Double Rice-Cropping System with 37-Year Manure Fertilization

Long-term intensive use of mineral fertilizers in double rice-cropping systems has led to soil acidification and soil degradation. Manure fertilization was suggested as an alternative strategy to mitigate soil degradation. However, the effects of long-term mineral and manure fertilization on rice grain yield, yield stability, soil organic carbon (SOC) content, soil total nitrogen (TN) content, and the underlying mechanisms are unclear. Based on a long-term experiment established in 1981 in southern China, we compared four treatments: no fertilizer application (Control); application of nitrogen–phosphorus–potassium (NPK); NPK plus green manure in early rice (M1); and M1 plus farmyard manure in late rice and rice straw return in winter (M2). Our results showed that 37 years of NPK, M1, and M2 significantly increased rice grain yield by 54%, 46%, and 72%, and yield stability by 22%, 17%, and 9%, respectively. M1 and M2 significantly increased SOC content by 39% and 23% compared to Control, respectively, whereas there was no difference between Control and NPK. Regarding soil TN content, it was significantly increased by 8%, 46%, and 20% by NPK, M1, and M2, respectively. In addition, M2 significantly increased bacterial OTU richness by 68%, Chao1 index by 79%, and altered the bacterial community composition. Changes in soil nutrient availability and bacterial Simpson index were positively correlated with the changes in grain yield, while shifts in bacterial community were closely related to yield stability. This study provides pioneer comprehensive assessments of the simultaneous responses of grain yield, yield stability, SOC and TN content, nutrient availability, and bacterial community composition to long-term mineral and manure fertilization in a double rice-cropping system. Altogether, this study spanning nearly four decades provides new perspectives for developing sustainable yet intensive rice cultivation to meet growing global demands.

Long-Term Fertilization Strategy Impacts Rhizoctonia solani-Microbe Interactions in Soil and Rhizosphere and Defense Responses in Lettuce.

The long-term effects of agricultural management such as different fertilization strategies on soil microbiota and soil suppressiveness against plant pathogens are crucial. Therefore, the suppressiveness of soils differing in fertilization history was assessed using two Rhizoctonia solani isolates and their respective host plants (lettuce, sugar beet) in pot experiments. Further, the effects of fertilization history and the pathogen R. solani AG1-IB on the bulk soil, root-associated soil and rhizosphere microbiota of lettuce were analyzed based on amplicon sequencing of the 16S rRNA gene and ITS2 region. Organic fertilization history supported the spread of the soil-borne pathogens compared to long-term mineral fertilization. The fertilization strategy affected bacterial and fungal community composition in the root-associated soil and rhizosphere, respectively, but only the fungal community shifted in response to the inoculated pathogen. The potential plant-beneficial genus Talaromyces was enriched in the rhizosphere by organic fertilization and presence of the pathogen. Moreover, increased expression levels of defense-related genes in shoots of lettuce were observed in the soil with organic fertilization history, both in the absence and presence of the pathogen. This may reflect the enrichment of potential plant-beneficial microorganisms in the rhizosphere, but also pathogen infestation. However, enhanced defense responses resulted in retarded plant growth in the presence of R. solani (plant growth/defense tradeoff).

Changes in <em>Eutric Cambisol</em> due to long-term mineral fertilisation: A case study in Serbia

The paper presents the results of a 50-year fertilisation experiment on Eutric Cambisol with increasing doses of nitrogen and constant doses of phosphorus and potassium. The changes in main parameters of soil fertility were compared with the initial level at the beginning of the experiment in 1963 (baseline), as well as with the adjacent natural meadow soil. The long-term application of mineral fertilisers without replenishment of calcium resulted in strong acidification, an increase in clay content, an increase in the number of fungi, and a decrease in the number of ammonifiers and oligonitrophiles. In the fertilised treatments, an increase in the content of plant-available phosphorus and potassium and a significant decrease in the plant available boron and zinc with an increase in the N dose were observed. Long-term addition of high doses of N harmed the total number of microflora, actinomycetes, ammonifiers, and oligonitrophiles compared to untreated meadow soil. Significant changes in soil’s physical and chemical properties resulted in the transformation of Eutric Cambisol into Dystric Cambisol. Inappropriate agricultural practices, such as adding only mineral fertilisers, can lead to significant soil degradation even on the sites with favourable bioclimatic conditions for cropping. The results showed that causal chains between microbiological and chemical parameters need to be better researched and understood in the future. This and other long-term experimental results should be used to calibrate agro-ecosystem models in Serbia. Highlights - Due to a long-term mineral fertilisation Eutric Cambisol transformed into Dystric Cambisol. - A sharp drop in soil pH did not affect the yield of crops. - The total number of microflora correlated with the amount of fungi in the soil. - Degradation of soil fertility parameters persists under mineral fertilisation.

Effects of long-term mineral fertilization on silage maize monoculture yield, phosphorus uptake and its dynamic in soil

A long-term continuous silage maize ( Zea mays L . ) monoculture experiment (1993–2019) was conducted at Červený Újezd in the Czech Republic to assess the effects of different mineral fertilizers on phosphorus transformations and balance. An unfertilized control (C) was compared with i) ammonium sulfate (AS), ii) urea ammonium nitrate (UAN), iii) UAN + triple superphosphate and potassium chloride (UAN+PK), and iv) UAN + triple superphosphate and magnesium sulfate (UAN+PMg), respectively. The dry aboveground biomass yield (BY), P uptake by plants, bioavailable and stable soil P forms, soil P-sorption characteristics, as well as simple P-balance, sustainability yield index (SYI), and agronomic efficiency (AE) were evaluated. Maize P uptake, content, BY, AE, SYI, and P utilization over the 27 years increased in the order of UAN+PK > UAN+PMg > UAN > AS > C treatments. P uptake was positively correlated with bioavailable soil P and BY. AS and UAN only fertilizing caused a more negative P balance (on average −621 kg P ha –1 27 yrs –1 ) as compared to the control (–483 kg P ha –1 27 yrs –1 ). The bioavailable Al and Fe forms strongly influenced the soil P sorption parameters. As example, phosphorus sorption index increased to 137% for C, averagely to 183% for AS and UAN fertilizing treatments, and 124% for P fertilizing treatments in the year 2019 as compared to 1997 (=100%). Generally, almost all indices show that N only fertilizing (AS and UAN) significantly decreases the bioavailable and even the stable inorganic P forms and has a negative influence on P sorption parameters and thus, overall P-sustainability. The effect of this fertilizing system was even more negative than in the unfertilized control, due to the higher yield and P uptake in AS and UAN treatments. Although soil P was not a limiting nutrient for plant growth, it is possible to expect its direct influence on BY in AS and UAN treatments in the near future. • Although phosphorus was not limiting nutrient, P-sorption characteristics show low risk of P losses. • Unbalanced fertilizing with N, but without P, led to depletion of soil phosphorus, which was worse (–621 kg P ha –1 27 years –1 !) than at unfertilized control (–483 kg P ha –1 27 years –1 ). • Maize plants used even the stable inorganic P forms to maintain the biomass yield and phosphorus uptake. • Nitrogen appeared to be limiting nutrient in the experiment, which was one of the main reasons for yield decrease after 15 years after its establishment. • NPK fertilizing resulted in better sustainability index, P utilization as well as agronomic efficiency.

Эффективное использование фосфогипса отходов производства фосфора

Фосфор өндірісінің қалдығы болып табылатын фосфогипсті халық шаруашылығының түрлі салаларында, атап айтқанда, агроөнеркәсіп кешенінде қолдану үшін ұзақ мерзім бойы минералды тыңайтқыштың құрамына әсер ететін қолдану әдістері мен тәсілдеріне қысқаша шолу жасалды. Фосфогипстің физико-химиялық қасиеттерін зерттеу нәтижелері оның құрамындағы CaSO4, макро- және микроэлементтердің болуына байланысты қышқылданған топырақтарды кальцинациялауда мелиорант ретінде пайдалану мүмкіндігін негіздеу үшін ұсынылған. Фосфогипстің рентгендік фазалық талдауы бойынша ескі және жаңа үйінділердің құрамында: гипс CaSO4∙2H2O - 87,93% және 85,04%; кварц SiO2 - 9,10% және 10,58%; бассанит CaSO4 ∙ 0,67H2O - сәйкесінше 2,97% және 4,38%. «Қазфосфат» ЖШС Тараз филиалының ескі және жаңа үйінділерінен алынған фосфогипс үлгілерінің химиялық құрамы зерттелді. Көрсетілген үйінділердің фосфогипс үлгілеріне дифференциалды-термиялық және ИҚ талдаулары жүргізілді. Негізгі құрамдас бөліктердің құрамында ерекше айырмашылықтар жоқ екені анықталды. Жүргізілген зерттеулердің негізінде құрамында ұзақ әсер ететін өндірістік нысандардың қатты қалдықтарынан кешенді аралас тыңайтқыш қоспаларының жаңа түрлерін алудың мүмкіндігі зерттелді. Жоспардағы кешенді аралас тыңайтқыш қоспа құрамын фосфатты зат, ылғал сақтайтын компонент ретінде вермикулит, егіс алқаптарының қышқылдануын және тұздануын азайту үшін топырақ жамылғысын бейтараптандырғыш ретінде микроэлементтерді мазмұндайтын ішкі жыныстар және фосфогипс.

Short-term cellulose addition decreases microbial diversity and network complexity in an Ultisol following 32-year fertilization

Cellulose is an essential component of plant cell walls, and one of the major constituents of soil organic matter. Decomposition of cellulose, mediated by microorganisms, is critical to the sustainable development of arable soils. However, how exogenous cellulose addition, as a surrogate for organic material amendment, influences the diversity and community compositions of soil microorganisms and their network complexity remains largely unknown. To bridge this knowledge gap, we conducted a microcosm experiment incubated with soils that had been subjected to long-term mineral or organic fertilization. Cellulose addition increased the cumulative CO2 emission in all treatments, with the highest value found in the pig manure amended soils. Cellulose addition significantly reduced the alpha diversity of bacteria and fungi across all fertilization treatments, with a more pronounced effect observed for fungi. Moreover, cellulose addition strongly altered bacterial community structure by increasing the relative abundance of copiotrophic bacteria such as Actinobacteria and Proteobacteria while reducing that of oligotrophic bacteria (e.g., Chloroflexi). Compared with no-fertilizer treatment, the influence of cellulose addition on bacterial and fungal community structure was stronger in long-term mineral or organic fertilized soils. Cellulose addition altered the relative abundance of bacterial and fungal functional groups by generally enriching microbes involved in chemoheterotrophy and suppressing those involved in methylotrophy, pathotroph, saprotroph-symbiotroph, and saprotroph-pathotroph. In addition, cellulose addition decreased soil microbial complexity and the number of potential keystone species, but did not change the key role of Chloroflexi in soil microbial network. Overall, our results demonstrated that cellulose addition decreased soil microbial diversity and network complexity, with possible short-term negative consequences for ecosystem functioning in Ultisols.

Effects of Long-Term Mineral Fertilizer Application on Soil Nutrients, Yield, and Fungal Community Composition

Effects of Long-Term Mineral Fertilizer Application on Soil Nutrients, Yield, and Fungal Community Composition

Long-term mineral fertilizer substitution by organic fertilizer and the effect on the abundance and community structure of ammonia-oxidizing archaea and bacteria in paddy soil of south China

Ammonia oxidation in the soil is related to nitrogen (N) availability for plants, nitrate loss, and N fertilizer use efficiency, which is important for studies on the N cycle of paddy field ecosystems. Substitution of partial mineral N fertilizer with organic amendments is commonly considered to optimize fertilization practices and reduce the application of mineral N fertilizer in the paddy fields. However, little is known about the effects of this type of fertilization on the relative contribution of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) to soil nitrification. Therefore, a 34-year field trial including five fertilization regimes (CK, without fertilizer; NPK, mineral NPK fertilizer; NPKM1, 70% inorganic N + 30% organic N + PK; NPKM2, 50% inorganic N + 50% organic N + PK; NPKM3, 30% inorganic N + 70% organic N + PK; P: phosphorus, K: potassium) was conducted. AOA and AOB abundance and community structures were determined by quantitative PCR and high-throughput sequencing analyses. Although the abundance of AOA and AOB increased with the increase in the percentage (30%–70%) of organic N substitution, the abundance ratio of AOA to AOB (133.9–84.7) decreased. Soil potential nitrification rate (PNR) increased dramatically (p < 0.05) after replacing chemical N with organic N, and with the increase in the substitution ratio of organic N in paddy soils. AOA and AOB both correlated significantly (p < 0.05) with PNR, but the contribution of AOB to PNR exceeded that of AOA. Soil carbon (C) to N ratio was the best predictor (43.0%) for AOA abundance, while total N and NH4+-N incorporating models were the best predictors (90.3%) for AOB abundance. Variations in AOA composition correlated strongly with fertilizer-induced changes in soil pH and ammonia concentration, whereas the AOB community was only markedly correlated with pH (p = 0.004). The substitution of 30%–70% of mineral N with organic N could increase the soil pH to 5.54–5.87, and that of ammonia concentration to 8.37–24.1 μM, which was the main reason that AOB contributed more to PNR than AOA. These results indicate that the organic substitution fertilizer regime had much stronger effects on the abundance and composition of AOB than AOA, and the potential contribution of AOB to ammonia oxidation in paddy soils should not be ignored after mineral N partial substitution by organic N.

Impact of Long-Term Organic and Mineral Fertilization on Rhizosphere Metabolites, Root-Microbial Interactions and Plant Health of Lettuce.

Fertilization management can affect plant performance and soil microbiota, involving still poorly understood rhizosphere interactions. We hypothesized that fertilization practice exerts specific effects on rhizodeposition with consequences for recruitment of rhizosphere microbiota and plant performance. To address this hypothesis, we conducted a minirhizotron experiment using lettuce as model plant and field soils with contrasting properties from two long-term field experiments (HUB-LTE: loamy sand, DOK-LTE: silty loam) with organic and mineral fertilization history. Increased relative abundance of plant-beneficial arbuscular mycorrhizal fungi and fungal pathotrophs were characteristic of the rhizospheres in the organically managed soils (HU-org; BIODYN2). Accordingly, defense-related genes were systemically expressed in shoot tissues of the respective plants. As a site-specific effect, high relative occurrence of the fungal lettuce pathogen Olpidium sp. (76–90%) was recorded in the rhizosphere, both under long-term organic and mineral fertilization at the DOK-LTE site, likely supporting Olpidium infection due to a lower water drainage potential compared to the sandy HUB-LTE soils. However, plant growth depressions and Olpidium infection were exclusively recorded in the BIODYN2 soil with organic fertilization history. This was associated with a drastic (87–97%) reduction in rhizosphere abundance of potentially plant-beneficial microbiota (Pseudomonadaceae, Mortierella elongata) and reduced concentrations of the antifungal root exudate benzoate, known to be increased in presence of Pseudomonas spp. In contrast, high relative abundance of Pseudomonadaceae (Gammaproteobacteria) in the rhizosphere of plants grown in soils with long-term mineral fertilization (61–74%) coincided with high rhizosphere concentrations of chemotactic dicarboxylates (succinate, malate) and a high C (sugar)/N (amino acid) ratio, known to support the growth of Gammaproteobacteria. This was related with generally lower systemic expression of plant defense genes as compared with organic fertilization history. Our results suggest a complex network of belowground interactions among root exudates, site-specific factors and rhizosphere microbiota, modulating the impact of fertilization management with consequences for plant health and performance.

Active phoD-harboring bacteria are enriched by long-term organic fertilization

PhoD-harboring microorganisms are crucial for the regulation of soil phosphorus (P) cycling through the secretion of alkaline phosphomonoesterases and are also known to be sensitive to fertilizer inputs. However, the impacts of long-term mineral and organic fertilizer inputs on active phoD-harboring functional communities in soils remain largely unknown. In the present study, 18O-DNA-stable isotope probing coupled with high-throughput sequencing was utilized in order to characterize active phoD-harboring functional bacterial communities in soils subjected to long-term no-fertilizer (Control), mineral-only fertilizer (NPK), organic-only fertilizer (M), and the combination of mineral and organic fertilizer (NPKM) amendments. Total and active phoD gene abundance decreased in soils amended with long-term mineral fertilizer, but increased in soils under organic fertilizer amendment, compared with the non-fertilized soils. A total of 51 active phoD-harboring bacterial OTUs, mainly belonging to Actinobacteria, were identified in this study. Organically amended soils harbored a higher diversity of active bacterial community. In the active phoD-harboring functional community, Rhodococcus comprised approximately 99% of the total relative abundance in the unfertilized soil, whereas Nocardiopsis and Bacillus accounted for approximately 62% and 24%, respectively, in mineral-only fertilized soils. Active phoD-harboring communities were dominated by members of the genera Streptomyces (26–60%), Nocardia (5–9%) and Gordonia (23–41%) in all organically fertilized soils, including M and NPKM. Overall, these long-term fertilization regimes altered the abundance, richness and composition of the active phoD-harboring functional microbial community. This study provides novel insights into the responses of the active functional bacterial community that is responsible for soil P mineralization to differing long-term fertilization regimes.

Carbon, nitrogen, and phosphorus stoichiometry mediate sensitivity of carbon stabilization mechanisms along with surface layers of a Mollisol after long-term fertilization in Northeast China

Soil organic carbon (SOC) is an important parameter determining soil fertility and sustaining soil health. How C, N, and P contents and their stoichiometric ratios (C/N/P) regulate the nutrient availability, and SOC stabilization mechanisms have not been comprehensively explored, especially in response to long-term fertilization. The present study aimed to determine how the long-term mineral and manure fertilization influenced soil C/N/P ratios and various protection mechanisms underlying the stabilization of OC along with profile in a cropland soil. The soil was sampled from five depths, viz., 0–20 cm, 20–40 cm, 40–60 cm, 60–80 cm, and 80–100 cm, from plots comprising wheat-maize-soybean rotation system subjected to the long-term (35 years) manure and mineral fertilizer applications. Results revealed that the soil C, N, P stoichiometry and their contents in topsoil depths (0–20 and 20–40 cm) and subsoil depths (40–60, 60–80, and 80–100 cm) varied significantly (p < 0.01) among the soil layers. Compared with CK, the C, N, and P contents were significantly higher (p < 0.05) in NPKM in the topsoil layers, while M alone increased these contents throughout the subsoil. Overall, the C, N, and P contents and their stoichiometry decreased with the increase in depth. Regression analysis showed that C/N, C/P, and N/P ratios associated significantly with the OC fractions in the topsoil layers only. These negative correlations indicated that these ratios significantly influence the C stabilization in the surface layers. However, the results warrant further investigations to study the relationship between soil and microbial stoichiometry and SOC at various depths. Long-term manure applications improved the C sequestration not only in the topsoil but also in the deep layers; hence, these facts can be considered relevant for fertilizer recommendations in cropping systems across China.

Long-term effects of organic manure and inorganic fertilization on biological soil quality indicators of soybean-wheat rotation in the Indian mid-Himalaya

A field experiment was accompanied to scrutinize the effect of long-term (21-year) mineral and organic manure fertilizer treatments on carbon mineralization, glomalin related soil protein and some microbial characteristics of arable soils in Indian mid-Himalaya. The experiment was initiated in 1995 includes six treatments: Control, N 120, NPK, FYM, N + FYM and NPK + FYM. Long-term chemical fertilization has been reported to negative effects on soil biological properties, however, the impact of combined use of organic and inorganic fertilization on soil biological properties and its relationship remains poorly understood. Results showed that integrated use of organic and inorganic (NPK + FYM) for 21 years significantly increased in carbon mineralization, easily extractable glomalin related soil protein (EEGRSP) and total glomalin related soil protein (TGRSP). Soil microbial indices (microbial quotient: qMIC, microbial metabolic quotient: qCO2 and metabolic potential: MP) were enhanced in the NPK + FYM treatment as compared to rest of the treatments. The activities of seven enzymes, viz. dehydrogenase (DHA), β-glucosidase (β-GA), invertase (IA), acid phosphatase (Acid-PA), alkaline phosphatase (Alkaline-PA), arylsulphatase (ASA) and urease activity (UA) were significantly influenced by the application of NPK + FYM as compared rest of treatments. Soil fertilization with NPK and FYM was significantly higher fluorescein diacetate assay (FDA) activity as compared to other treatments. Soil microbial properties had strong positive correlation with qMIC, microbial biomass carbon (MBC) and soil organic carbon (SOC), while qCO2 had negative correlation under both soil layers. Results showed that the 21-year fertilization experiment clearly indicated that NPK + FYM embodied the best management practice (BMPs) for soil biological sustainability and for sustainable food production.

The Response of the Soil Microbiota to Long-Term Mineral and Organic Nitrogen Fertilization is Stronger in the Bulk Soil than in the Rhizosphere.

The effects of different agronomic practices, such as fertilization regimes, can be experimentally tested in long-term experiments (LTE). Here, we aimed to evaluate the effect of different nitrogen fertilizations on the bacterial microbiota in both rhizosphere and bulk soil of sugar beet, in the Giessen-LTE (Germany). Fertilization treatments included mineral-N, manure, mineral-N + manure and no N-amendment. Metabarcoding and co-occurrence analysis of 16S rRNA genes, qPCR of amoA, nirK, nirS, nosZ-I and nosZ-II genes and soil physico-chemical analyses were performed. The effect of the fertilization treatments was more evident in the bulk soil, involving 33.1% of the microbiota. Co-occurrence analysis showed a rhizosphere cluster, dominated by Proteobacteria, Actinobacteria and Verrucomicrobia (hub taxa: Betaproteobacteriales), and a bulk soil cluster, dominated by Acidobacteria, Gemmatominadetes and “Latescibacteria” (hub taxa: Acidobacteria). In the bulk soil, mineral N-fertilization reduced nirK, amoA, nosZ-I and nosZ-II genes. Thirteen Operational taxonomic units (OTUs) showed 23 negative correlations with gene relative abundances. These OTUs likely represent opportunistic species that profited from the amended mineral-N and outgrew the species carrying N-cycle genes. Our results indicate trajectories for future research on soil microbiome in LTE and add new experimental evidence that will be helpful for sustainable management of nitrogen fertilizations on arable soils.

Changes and Interactions between Grassland Ecosystem Soil and Plant Properties under Long-Term Mineral Fertilization

Grasslands intensification by use of mineral fertilization has contributed substantially to the increase in forage production. Intensification, however, can degrade the other beneficial functions or soil properties. The effects of mineral fertilization on soil and plant chemical qualities of a permanent wet grassland (Festucetum pratense association) were investigated in Slovakia. The grassland was treated using 3 different N, P, and K rates of mineral fertilizers in kg. ha−1. yr−1 plus the Control (0NPK) almost over 60-year period (1961–2017). The N, P, and K rates in low NPK treatment (LNPK) were N50, P15.4, and K 41.5, in the medium NPK treatment (MNPK) were N100, P30.8, and K83, and in the high NPK treatment (HNPK) were N200, P 61.6, and K 166, respectively. Overall, soil variables (pH, soil organic carbon, plant-available K) showed the most significant changes. A more balanced development was observed in case of soil total nitrogen, C:N ratio, and plant-available P. ANOVA revealed a significant effect between treatments only on plant-available P. In the case of plant functional group development, long-term mineral addition significantly disfavors legumes and forbs. However, analyses of the botanical composition over the last 5 years showed that legume cover significantly differs only in the HNPK treatment. Plant C:P, N:P, and N:K ratios were significantly reduced when fertilizers were added. In terms of grasslands yields, the highest biomass and content of macronutrients were obtained under the HNPK rates. However, with regard to the quality and quantity of the soil organic matter, the most appropriate treatment has been with the MNPK rates. Our findings demonstrate that medium fertilization seems to be an acceptable compromise to meet both productivity and environmental aspects and to connect ecological benefits with social benefits in the long term.