Effects Of Long-term Fertilization Research Articles

Effects of Long-term Fertilization on Soil Microbial Diversity and Community Structure in the Agro-pastoral Ecotone

To explore the effects of different long-term fertilization treatments on soil microbial diversity and community structure in the drylands of an agro-pastoral ecotone, a long-term fertilization experiment at the Inner Mongolia cultivated land conservation science observation and experiment station, Ministry of Agriculture, and rural areas was taken as the research object. Four treatments, including no fertilizer (CK), single nitrogen fertilizer (NF), single chemical fertilizer (CF), and the combined application of organic manure and chemical fertilizer (CFM), were selected for the collection of 0-10 cm and 10-20 cm soil at potato maturity 16 years after the experiment (2019). High-throughput sequencing technology was used to assess the soil bacterial and fungal communities to explore the effects of different fertilization measures on soil quality from the perspective of microorganisms, and the partial least squares path model (PLS-PM) was used to reveal the key environmental driving factors of soil microbial community alternation and crop yield improvement in dryland during fertilization mode transformation. The results showed that:① the CF and CFM treatments significantly improved soil fertility, but the effect of the latter was significantly better than that of the former. Soil available nitrogen, available phosphorus, and available potassium in the CFM treatment increased by 131.9%-174.7%, 216.9%-283.3%, and 103.3%-109.3%, respectively, and organic matter and total nitrogen content also increased significantly. The CF treatment still maintained a high soil pH, whereas the NF treatment significantly decreased soil pH and had little effect in improving soil fertility. ② Compared with that under CK, the NF treatment significantly reduced the soil bacterial Chao1 and Shannon index, and the CFM treatment significantly increased the soil bacterial species richness, Chao1 index, and soil fungal Shannon index, whereas soil bacterial and fungal diversity in the CF treatment did not reach a significant difference level with CK. ③ The soil microbial community composition at 0-10 cm and 10-20 cm was similar. The CFM treatment increased the relative abundance of soil beneficial bacteria and decreased the relative abundance of pathogenic bacteria. The relative abundance of dominant bacteria such as Proteobacteria, Bacteroidetes, and Gemmatimonadetes increased. The relative abundances of Actinobacteria, Ascomycota, and Basidiomycota were decreased, whereas the NF and CF treatments showed the opposite trend. ④ PLS-PM analysis showed that with the gradual change in fertilization mode from CK→NF→CF→CFM, the driving factors affecting microbial community succession and yield increase were also changed from soil pH→soil NPK content→soil pH, SOM, and NPK content. In general, long-term fertilization had significant effects on soil chemical properties and microbial communities in drylands in the agro-pastoral ecotone. As the optimal fertilization choice, CFM was significantly better than NF and CF in improving soil fertility and inhibiting the growth of pathogenic microorganisms. The number of pathogens in long-term non-fertilization and unbalanced fertilization soil was significantly increased, and the risk of crop infection to indigenous diseases was increased. The research results can provide scientific reference for farmland nutrient balance management and soil microenvironment improvement of the agricultural ecosystem in the agro-pastoral ecotone in North China.

PhoD Harboring Microbial Community and Alkaline Phosphatase as Affected by Long Term Fertilization Regimes on a Calcareous Soil

Organic phosphorus (Po) may play a vital role in phosphorus availability via its mineralization by alkaline phosphatase (ALP), being encoded by phoD gene, in calcareous soil. Understanding the effects of long-term fertilization on the community of phoD harboring bacteria and the related alteration of the P availability owing to the changes in ALP secretion may offer a chance to elucidate the Po contribution to soil available P. Based on a long-term experiment, we analyzed the phoD gene harboring microbial diversity, abundance and composition, ALP and Po forms, and their relationship. The treatments involved were control without any fertilizers (CK), synthetic nitrogen and potassium (NK), synthetic nitrogen, phosphorus and potassium (NPK), NPK and crop stalk return (SNPK), and NPK plus organic manure (MNPK). Fertilization increased the abundance and diversity of phoD gene harboring microbial over CK. Those receiving NPK and NPK treatments integrated with organic supplements significantly improved the relative abundance of Proteobacteria but decreased Gemmatimonadetes at the phylum level, while all fertilized treatments appreciably increased the relative abundance of Lysobacter but decreased that of Gemmatirosa and Afipia, at the genus level. SNPK and MNPK treatments noticeably increased the relative abundance of Methylobacter but reduced Pseudomonas and Streptomyces relative to those receiving synthetic fertilizer treatments. Long-term fertilization markedly raised ALP activity, which was significantly and positively correlated with the relative abundance of the phylum Proteobacteria as represented by the genera Methylobacterium and Lysobacter. ALP was closely associated with moderately labile Po, followed by enzyme P, recalcitrant Po, and labile Po. The changes in phoD bacteria and ALP were mainly driven by soil organic carbon, Olsen P and pH. We concluded that the long-term fertilization, especially the addition of organic supplements, profoundly modified the soil properties and subsequently changed the diversity and relative abundance of phoD gene harboring bacteria, which promoted the activity of ALP, and thus the mineralization of various forms of Po (mainly moderately labile Po) to enhance the P availability.

Soil addition of MnSO4 reduces wheat Cd accumulation by simultaneously increasing labile Mn and decreasing labile Cd concentrations in calcareous soil: A two-year pot study

Cadmium (Cd) pollution of wheat fields is a serious environmental and health problem that warrants attention. Manganese (Mn)-containing materials are considered effective for inhibiting Cd accumulation in Cd-contaminated acidic soils. However, information on the long-term remediation effects of Mn fertilizers on Cd accumulation in wheat and on the microbial community in calcareous soils remain limited. Here, a two-year pot experiment was conducted to assess the performance of 0.05–0.2% MnSO4 addition in Cd-contaminated calcareous soils (total Cd concentration: 3.65 mg/kg) on Cd accumulation in wheat as well as on the soil bacterial community. The formation of Mn oxides and transformation of exchangeable Cd to stable Cd fractions confirmed that the application of MnSO4 significantly decreased CaCl2-extractable Cd concentrations in soil (0–47.08%). In addition, MnSO4 addition improved the antagonistic effect of Cd and Mn ions in the wheat rhizosphere by increasing the available Mn concentration in the soil (1.04–3.52 times), thereby significantly reducing wheat Cd accumulation by 24.66–54.70%. Notably, the addition of MnSO4 did not affect the richness and diversity (P > 0.05) but altered the composition and function of bacterial communities, especially those involved in metabolism and genetic information processing. Importantly, the effects of MnSO4 on Cd immobilization in soil (10.66–47.08%) and the inhibition of Cd accumulation in wheat (12.13–54.30%) can last for two years after one addition. Furthermore, the maximum decrease in Cd concentration in grains was found in the low-Cd wheat cultivar, with values of 31.39–54.70% and 19.94–54.30% in the first and second years, respectively. Based on the present findings, the combination of MnSO4 with a low-Cd wheat cultivar is effective for the safe utilization of Cd-contaminated calcareous soils.

Phosphorus speciation and colloidal phosphorus responses to short-term cessation of fertilization in a lime concretion black soil

Long-term excessive mineral fertilizer application led to soil acidification and phosphorus (P) accumulation, increasing the risk of P loss and environmental pollution. The cessation of fertilization was widely considered as a cost-effective management strategy to relieve the situation, however, how the fertilization cessation influences the speciation and concentrations of P in bulk soil and the colloidal fractions, and whether the declining P concentration could maintain soil fertility are unclear. In this study, the effect of long-term fertilization (~40 years) and short-term cessation of fertilization (~16 months) on inorganic P, organic P, and colloidal P in lime concretion black soil were investigated with P sequential fractionation and 31P nuclear magnetic resonance spectroscopy (NMR). After long-term fertilization, available P, Ca2-P, Fe-P, orthophosphate monoesters, and orthophosphate diesters increased significantly, but soil pH decreased by ~2.8 pH units, indicating that long-term fertilization caused soil acidification and P accumulation as well as changed P speciation dramatically. In contrast, fertilization cessation in short term brought the increase of soil pH (~0.8 pH units) and decreased slightly for available P and inorganic P. The available P after fertilization cessation was 22.9-29.8 mg kg−1, which was still sufficient for crop growth requirements. In addition, fertilization cessation brought increases in the proportions of fine colloids (100-450 nm, including nontronite and some amorphous Fe oxides) and drove the significant release of Fe/Al oxides nanoparticles (1-100 nm) and associated P with the species of orthophosphate and pyrophosphate. In summary, fertilization cessation in short term could alleviate soil acidification and inorganic P accumulation effectively, at the same time maintain soil P fertility and improve the potential mobilization of P associated with microparticles.

Evaluating the Effects of Sustainable Chemical and Organic Fertilizers with Water Saving Practice on Corn Production and Soil Characteristics

The rapidly growing world population, water shortage, and food security are promising problems for sustainable agriculture. Farmers adopt higher irrigation and fertilizer applications to increase crop production resulting in environmental pollution. This study aimed to identify the long-term effects of intelligent water and fertilizers used in corn yield and soil nutrient status. A series of field experiments were conducted for six years with treatments as: farmer accustomed to fertilization used as control (CON), fertilizer decrement (KF), fertilizer decrement + water-saving irrigation (BMP1); combined application of organic and inorganic fertilizer + water-saving irrigation (BMP2), and combined application of controlled-release fertilizer (BMP3). A significant improvement was observed in soil organic matter (14.9%), nitrate nitrogen (106.7%), total phosphorus (23.9%), available phosphorus (26.2%), straw yield (44.8%), and grain yield (54.7%) with BMP2 treatment as compared to CON. The study concludes that integrating chemical and organic fertilizers with water-saving irrigation (BMP2) is a good approach to increasing corn productivity, ensuring water safety and improving soil health. The limitations of the current study include the identification of fertilizer type and its optimum dose, irrigation water type, and geographical position.

Effect of Long-Term Inorganic Fertilization on Diversity and Abundance of Bacterial and Archaeal Communities at Tillage in Irrigated Rice Field

Short Retraction Notice The paper does not meet the standards of "Advances in Bioscience and Biotechnology". This article has been retracted to straighten the academic record. In making this decision the Editorial Board follows COPE's Retraction Guidelines. The aim is to promote the circulation of scientific research by offering an ideal research publication platform with due consideration of internationally accepted standards on publication ethics. The Editorial Board would like to extend its sincere apologies for any inconvenience this retraction may have caused. Editor guiding this retraction: Prof. Abass Alavi (EiC of ABB). Please see the article page for more details. The full retraction notice in PDF is preceding the original paper which is marked "RETRACTED".

Climate change impacts on long-term field experiments in Germany

CONTEXTLong-Term Field Experiments (LTEs) were implemented to study the long-term effects of different management practices, including tillage, fertilization and crop rotation under otherwise constant conditions. Climate change is expected to change these conditions, challenging interpretation of LTE data with regard to the distinction between climate change and management effects. OBJECTIVEThe objective of the study was to quantify the expected, spatially differentiated changes of agroclimatic conditions for the German LTE sites as a precondition for modelling and LTE data interpretation. METHODSWe developed a framework combining spatially distributed climate data and LTE metadata to identify the possible climatic changes at 247 LTE sites with experiments running for 20 years or more. The LTEs were classified using the following categories: fertilization, tillage, crop rotation, field crops or grassland, conventional or organic. We utilized climate variables (temperature, precipitation) and agroclimatic indicators (aridity, growing degree days, etc.) to compare a baseline (1971–2000) with future periods (2021−2100) under the IPCC's Shared Socio-economic Pathways (SSP). A comprehensive LTE risk assessment was conducted, based on changes in climate variables and agroclimatic indicators between baseline and future scenarios. RESULTS AND CONCLUSIONSUnder the most extreme scenario (SSP585), 150 LTEs are expected to shift from humid and dry sub-humid to semi-arid conditions. Frost days in LTE areas are expected to decline by 81%, and the growing season to lengthen by up to 92%. The spatial differentiation of expected climate change also facilitates the identification of suitable sites for future agricultural practices and may inform the design of new LTEs. SIGNIFICANCEOur results may guide the interpretation of LTE data regarding the effect of climate change, facilitating future soil crop modelling studies with LTE data and providing information for planning new LTE sites to support future agricultural research and/or adapting management on existing LTE sites. The framework we developed can easily be transferred to LTE sites in agricultural regions worldwide to support LTE research on climate change impacts and adaptation.

Effects of long-term fertilization with contemporary Danish human urine, composted household waste and sewage sludge on soil nematode abundance and community structure

It is desirable to recycle the urban waste products human urine, composted household waste and sewage sludge as fertilizers to agricultural fields. This could minimize the use of NPK fertilizer, improve soil structure and store carbon. However, waste products may contain heavy metals, persistent organic pollutants (POP) and plastics, and there are concerns that long-term build-up of these substances will cause unwanted effects on soil health.Nematodes are ubiquitous and numerous in soil ecosystems. Abundance and community structure of soil nematodes can be used as indicators of soil health, as some species are vulnerable to pollution. There are well-developed methods for detecting environmental changes based on nematode community structure.At the long-term CRUCIAL field experiment, where alternative fertilizer products have been applied since 2003, we measured effects of long-term fertilization with human urine, composted household waste and sewage sludge on soil properties (pH, soil organic matter and nitrogen availability), abundance of soil microorganisms (bacteria, fungi, small protozoa and ciliates) and nematode trophic groups compared to plots with unfertilized, NPK and cattle manure treatment. Sampling and assessments were done three times during a growth season. Further, we assessed the composition of nematode communities using metabarcoding.Treatments with a high input of organic matter (cattle manure, composted household waste and sewage sludge) had high abundances of bacteria and thus bacterial grazers (small protozoa, ciliates, and bacterial feeding nematodes). We found a significant correlation between nematode community structure and pH and organic matter. We calculated the nematode Maturity Index 2–5 (pollution indicator) based on metabarcoding data, which did not differ significantly between the treatments.We conclude that long-term fertilization with different types of contemporary Danish urban waste products affects both soil properties and abundance of soil organisms, the latter largely reflecting the organic matter input of the fertilizer treatments. We found no adverse effect on nematode communities that could indicate pollution-induced stress on nematofauna or decreased soil fertility.

Response of Long-Term Application of Fertilizers and Manure on P Pools in Inceptisols

ABSTRACT Soil phosphorous (P) can limit plant growth due to its fixation which stipulates the changes occuring due to imbalanced fertilization in pearl millet-wheat system. The study was aimed to identify the long-term effect of fertilizers and manures on availability of P due to changes in soil inorganic (Pi) and organic P (Po) pools at 0–15, 15–30, 30–60, and 60–90 cm. A sequential methodology was used to determine the effect of fertilizers and manures w.r.t. control (CK) on pools of P and their distribution in soil profile. Fertilizers and manures significantly increased the total and available P concentration. Labile (LOP) and moderately labile (MLOP) organic phosphorous concentrations significantly (P < .05) impacted throughout the soil profile. However, moderately and highly stable organic P pools (MSOP & HSOP) were significantly higher at surface soils. Integrating manures with fertilizers (NPKM) for 10 years increased the LOP and MLOP by 121.5 and 50.0%, while the concentration of MSOP and HSOP was higher under fertilizer treatments (NPK and BFSTCR) at surface soils. The Pi associated with Saloid-P, Aluminium-P, and Iron-P showed decreasing concentration, while calcium-phosphorous concentration increased at all soil depths. The increase in residual-P was more pronounced at lower depths. The proportion of Pi to the total P increased to 16.8% in fertilizer treatments at 30–60 and 60–90 cm soil, while Po proportions increased to 21.0% at 0–15 cm soil. Integrating manures with fertilizers could be a viable nutrient management practice of enhancing the Po and Pi and their availability to plants in sandy soils of Inceptisols.

Effect of long-term fertilization on zinc distribution and its uptake by wheat (Triticum aestivum)

Zinc (Zn) is one of the seventeen essential nutrients required for proper growth and development of plants. Majority of soils of India (about 43% of its cultivated soil) are deficient in Zn. Long-term fertilizer experiments (LTFE) are the perfect platform to investigate the impact of integrated nutrient management (INM) over a long period of time on Zn availability and uptake by crops. With this aim, soil samples were collected from an on-going 47 year-old longterm fertilizer experiment at ICAR-Indian Agricultural Research Institute (ICAR-IARI), New Delhi after harvesting of wheat during April, 2018. The selected fertilizer and manurial treatments includes control, N alone, NP, NPK, 150% NPK, NPK+Zn and NPK+FYM were studied. Results of the study reveal that yield of wheat, Zn content and uptake varied from 1.95-5.58 t/ha, 29.8-42.3 mg/kg, and 96.5-368 g/ha, respectively, across the nutrient management practices. It was also found that residual Zn was the major fraction in soil which accounted for 86-90% of the total Zn followed by oxide bound Zn (5.4-9.2%), organically bound Zn (1.9-3.8%), carbonate bound Zn (0.34-0.82%) and water soluble plus exchangeable Zn (0.26-0.58%). Grain yield of wheat was at par in NPK+Zn and NPK+FYM indicating that similar response of the applied Zn as compared to integrated nutrient management. Thus, NPK+Zn are the best option for producing Zn-fortified grains and sustainable crop production.

Soil Chemical Properties Depending on Fertilization and Management in China: A Meta-Analysis

The long-term overuse of fertilizers negatively affects soil chemical properties and health, causing unsustainable agricultural development. Although many studies have focused on the effects of long-term fertilization on soil properties, few comparative and comprehensive studies have been conducted on fertilization management over the past 35 years in China. This meta-analysis (2058 data) evaluated the effects of the fertilizer, climate, crop types, cultivation duration and soil texture on the soil chemical properties of Chinese croplands. NPKM (NPK fertilizers + manure) led to the highest increase in pH (−0.1), soil organic carbon (SOC) (+67%), total nitrogen (TN) (+63%), alkali-hydrolysable nitrogen (AN) (+70%), total phosphorus (TP) (+149%) and available potassium (AK) (+281%) compared to the unfertilized control, while the sole nitrogen fertilizer (N) led to the lowest increase. The SOC (+115%) and TN (+84%) showed the highest increase under the influence of NPKM in an arid region. The increase in the chemical properties was higher in unflooded crops, with the maximum increase in the wheat–maize rotation, compared to rice, under NPKM. The SOC and TN increased faster under the influence of organic fertilizers (manure or straw) compared to mineral fertilization. Fertilizers produced faster effects on the change in the SOC and TN in sandy loam compared to the control. Fertilizers showed the highest and lowest effects on change in pH, organic C to total N ratio (C/N), TP and TK in clay loam with the cultivation duration. NPKM greatly increased the C/N compared to NPK in an arid region by 1.74 times and in wheat by 1.86 times. Reaching the same SOC increase, the lowest TN increase was observed in wheat, and the lowest increase in TP and AK was observed in rice, compared to the other crops. These results suggest that organic fertilizers (manure or straw) play important roles in improving soil fertility and in acidification. NPKM greatly increased the potential for soil C sequestration in wheat and in the arid region. The small increases in TP and TK can increase the SOC in rice and in the humid region. Therefore, considering the crop types and climatic conditions, reduced fertilization and the combination of mineral fertilizers with manure may be the best ways to avoid agricultural soil deterioration and increase soil carbon sequestration.

The Composition of the Organic Matter Fractions of Loamy Sand after Long-Term FYM Application without Liming

The key to soil organic matter management is understanding the transformation processes of fresh organic matter to permanent humus that control soil organic carbon dynamics. This paper presents the results of the effect of long-term soil fertilization with increasing doses of (manure) FYM and ammonium nitrate on the composition of humus compounds not limed of loamy sand. The study showed that both crop rotation and manure fertilization significantly affected organic matter fractions and humus humification index. The soil in crop rotation B (with enriching effect) accumulated significantly larger amounts of soil organic carbon in 0–30 cm layer despite a lower soil pH, but had lower soil organic quality compared to the soil in crop rotation A (with depleting effect). In both rotations, FYM was applied once per 4-year rotation at a dose of 40 t·ha−1 which improved the soil organic carbon content. Depleting crop rotation (A) showed no increase in soil accumulation of humins fractions (H), while the “enriching” crop rotation (B) had such a tendency. Mineral nitrogen fertilization significantly affected the composition of the humic acids fraction. The soil in crop rotation B was characterized by a significantly higher content of fulvic acid (FA) and lower of humins (H) carbon fraction. The large input of organic matter into the soil under lower content pH conditions may hinder its transformation into permanent humus. Changes in the humification index were the consequence of changes in the carbon content of humic and fulvic acids, under the influence of plant selection in crop rotation and manure fertilization. According to the criterion of this parameter, soil in crop rotation A and soil fertilized with manure had lower loss of the more labile FA fraction (lower value of humification index—1.48).

CORRELATION OF AVAILABLE NUTRIENTS WITH YIELD OF RICE IN CALCAREOUS SOIL

Soil fertility is the function of nutrient availability in the soil. Soil properties and crop production are liable to change due to continuous cropping with long term fertilization. Correlation study is used for the study of available nutrients of agricultural soil with yield of crops. The objective of this study is to investigate the correlation between soils available nutrients and the yield of rice. The long term effect of fertilizers and manures on response of rice-wheat cropping rotation and changes in physical and chemical properties of sandy loam Typic Calciorthents was stated during rabi 1988-89 in split plot design with three replication. Four levels of chemical fertilizer were taken as main plot treatment and four levels of organic sources on nutrients were taken as sub plot treatments. The results showed that integrated use of compost and crop residue either alone or in combination of inorganic sources of nutrients augmented higher build of soil available nutrients. Soil available N, P, P2O5, K2O and S were positively and significantly correlated and available Zn and B were negatively correlated with yield of rice crop.

Polycyclic Aromatic Hydrocarbons in Soil at Different Depths under a Long-Term Experiment Depending on Fertilization.

The aim of this study was to assess the effect of long-term fertilization with manure and mineral fertilizers on the content and distribution of selected polycyclic aromatic hydrocarbons (PAHs)—the content of a sum of 16 polycyclic aromatic hydrocarbons, light and heavy PAHs in two soil layers (0–30 cm and 30–60 cm). The material for the study was composed of soil samples collected from the sixth rotation in a long-term, controlled field experiment, conducted in Bałcyny since 1986. The content of 16 polycyclic aromatic hydrocarbons was determined on a gas chromatographer coupled with an FID detector. In order to evaluate the significance of differences between the mean effects on the tested characteristics, a non-parametric Mann–Whitney U test for two independent samples was applied. A higher content of the sum (16) of PAHs was found in the 0–30 cm than in the 30–60 cm soil layer. The research results also demonstrated a higher content of the sum of light PAHs in the 30–60 cm than in the 0–30 cm soil layer. The content of heavy PAHs, in turn, was significantly higher in the upper than in the deeper soil layer. This dependence appeared in both the soil fertilized with manure and soil nourished only with mineral fertilizers.

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

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

Canary in the coal mine: Lessons from the Jarrah Forest suggest long-term negative effects of phosphorus fertilizer on biodiverse restoration after surface mining

Despite nutrient enrichment having widely reported negative impacts on biodiversity, fertilizer is routinely applied in post mining restoration to enhance plant growth and establishment. Focusing on surface mine restoration (predominately bauxite and mineral sands), we outline the long-term negative impacts of fertilizer, particularly phosphorus fertilizer, on plant community composition, species richness, fire fuel loads, and belowground impacts on nutrient-cycling. We draw from extensive research in south-western Australia and further afield, noting the geographical coincidence of surface mining, phosphorus impoverished soil and high plant biodiversity. We highlight the trade-offs between rapid plant-growth under fertilisation and the longer-term effects on plant communities and diversity. We note that the initial growth benefits of fertilisation may not persist in water-limited environments: growth of unfertilised forests can eventually match that of fertilised forest, throwing doubt on the premise that fertilisation is necessary at all.

Root stoichiometry explains wheat endophytes and their link with crop production after four decades of fertilization

Fertilization can impact root endophytic microbiomes and food production. However, the impacts of decades of continued fertilization on root microbiomes, and their link with ongoing crop production, remain poorly understood. Here, we used a four decade-long fertilization experiment, including contrasting types of organic and inorganic fertilization, to investigate the effects of long-term fertilization on multi-kingdom root endophytic microbiomes, including keystone species (modules within microbial networks), and their indirect associations with the production of wheat, which is one of the most important crops worldwide. We found that long-term inorganic (nitrogen, phosphorus, potassium (NPK)) and organic (NPK with straw (NPKS) and NPK with cow manure (NPKM)) fertilization had significant impacts on the community composition of endophytic arbuscular mycorrhizal fungi (AMF), bacteria, and non-mycorrhizal fungi. In addition, compared with NPK fertilization, NPKS and NPKM amendments significantly decreased the microbial network complexity, which was associated with changes in the root iron content. Finally, we identified an important subset of keystone root endophyte species within the microbial network (Module #2), which was positively correlated with wheat yield, and affected by changes in root carbon to phosphorus ratio. This study provides evidence that long-term fertilization can affect keystone root endophytic species in the root microbiome, with implications for food security in an over-fertilized world.

Long-term (nearly a century) effects of fertilizer, lime and rice straw compost application on active aluminum and iron and available phosphorus in paddy fields

In paddy soils, plant availability of phosphorus (P) increases during the flooding period due to the reductive dissolution of iron (Fe)-bearing minerals on which P is sorbed. Soil chemical properties are a determining factor of P availability and are subject to change after prolonged paddy rice cultivation. The purpose of this study was to evaluate the effects of long-term application of rice straw compost and slaked lime on changes in soil chemical properties, particularly focusing on the increase in available P under reductive conditions. The rice cultivation experiment was launched in 1926 to clarify the effects of mineral fertilizer (NPK), rice straw compost, and slaked lime application on soil properties. The amount of P solubilized under reductive conditions was evaluated by the difference in the P extracted by the Bray II method with and without reductive treatment of the soil. Continuous application of NPK mineral fertilizer without slaked lime resulted in higher amounts of aluminum extracted by acid ammonium oxalate and P extracted by the Bray II method until the 92nd cropping, while the increase in the proportion of available P under reductive conditions was low. In contrast, the amounts of Fe extracted by acid ammonium oxalate and P solubilized under reductive conditions were higher with increasing application of compost. The application of the compost caused strongly reductive conditions in the soil during the flooding period, and the dissolution of P in the Fe-bound fraction was facilitated. However, excessive application of compost led to the dissolution of high amounts of Fe-bound P, resulting in a loss of Fe and P from the cultivated soil. These results suggest that excessive application of rice straw compost and no application of slaked lime may cause a decrease in available P in paddy soils.

Potential Nitrogen Mineralization and Its Availability in Response to Long-Term Fertilization in a Chinese Fluvo-Aquic Soil

The determination of organic nitrogen (N) mineralization is crucial for estimating N availability, quantifying exogenous inputs, and estimating associated environmental impacts. The objective of this study was to explore the effect of long-term various fertilization on soil organic N mineralization potential (NMP), which influences plant N accessibility. Treatments from a 26-year long-term field experiment with no fertilization (CK), chemical fertilizer N at 165 kg N ha−1 and P at 82.5 kg P2O5 ha−1 (NP), NP with K fertilizer at 165, 82.5, 82.5 kg ha−1 N, P2O5 and K2O (NPK), NPK at 165, 82.5, 82.5 kg ha−1 N, P2O5 and K2O with manure at 7857.14 kg ha−1 (NPKM), and NPKM at 165, 82.5, 82.5 kg ha−1 N, P2O5 and K2O with manure at 1.5× application rate (11,785.71 kg ha−1) (1.5NPKM) were examined for potentially mineralizable N by aerobic incubation at 35 °C for 30 weeks. Three pools (Pools I, II, and III) of mineralizable N were recognized. Pool I, the mineralization flush on rewetting in the first 2 weeks; Pool II, gross N mineralization between weeks 2 and 30; and Pool III, the potentially mineralizable N, predicted from the fitted curve, that did not mineralize during the incubation period. Soil microbial biomass carbon (SMBC) and N (SMBN) as well as fixed ammonium (NH4+) contents and relationship with N mineralization rate (k) were also studied. Long-term manure application yielded a significantly higher k (0.32 week−1) than other treatments (0.12–0.22 week−1) but not a significantly higher NMP. Nitrogen mineralization during the wheat and maize-growing seasons was predicted to be 8.7–26.3 (mg N kg−1 soil) and 25.9–42.1 (mg N kg−1 soil), respectively. Both labile mineralizable N pools (Pools I and II) followed the same patterns in the treatments: 1.5NPKM &gt; NPKM &gt; NPK &gt; NP &gt; CK, while the reverse was true for stable N (Pool III). The significant positive correlation between k with SMBC and SMBN (R2 = 0.93, p = 0.008 and R2 = 0.94, p = 0.006) suggested that the higher mineralization rate might be contributed by the higher soil microbial biomass in NPKM. The trends of fixed NH4+ and mineralized N were coupled. Long-term manure application significantly improved the N mineralization rate in soil. Manure application is an effective strategy to enhance soil microbial biomass and soil N availability and has the potential to reduce the dependence upon chemical N fertilization.

Fertilization Rapidly Alters the Feeding Activity of Grassland Soil Mesofauna Independent of Management History

Nitrogen fertilization of permanent grasslands affects soil fauna communities by modifying their taxonomic composition, population dynamics and feeding activity. However, it is not well understood if the edaphic fauna adapts to these external inputs so that the immediate response to fertilizer application depends on the long-term nutrient management strategy. We performed a field experiment in permanent grasslands under agricultural management in three regions across Germany. We used experimental fertilization with an organic plant-sourced fertilizer along a long-term nutrient management gradient to study the immediate and long-term effects of fertilization and their interdependence on the taxonomic composition and feeding activity of the soil mesofauna (Nematoda, Oribatida, and Collembola). Sampling season, soil properties, vegetation structure, and geographic location were considered as additional predictor variables to reflect heterogeneity in environmental conditions. The taxonomic composition, richness and total abundance of soil mesofauna communities were significantly affected by long-term nutrient management, but not by experimental fertilization. However, N pulses rapidly (within days) reduced the feeding activity estimated with bait-lamina strips independent of long-term nutrient management strategies. Experimental addition of organic plant-sourced fertilizer may have led to a rapid build-up of microbial biomass, providing alternative food sources for the soil mesofauna and causing a shift away from the bait-lamina substrate. Our study indicates that community changes associated with the long-term nutrient management regime in permanent grasslands do not alter the strong functional response of the soil mesofauna to N pulses. There is an urgent need to develop nutrient management strategies for permanent grasslands that take into account both the conservation of the edaphic faunal community and changes of ecosystem functions caused by rapid responses of the soil mesofauna to fertilizer inputs.