Long-term Fertilization Experiment Research Articles

Long-term organic fertilization reshapes the communities of bacteria and fungi and enhances the activities of C- and P-cycling enzymes in calcareous alluvial soil

Soil microbial communities and extracellular enzymes are pivotal in governing the dynamics of soil carbon (C) and phosphorus (P) cycling. Nevertheless, comprehending the underlying regulatory factors and intricate interactions among these vital indicators remains an inadequately explored aspect, especially within the scenario of long-term fertilization. Long-term fertilization experiments were conducted on calcareous alluvial soil. The five fertilization regimes selected were as follows: without fertilization treatment (CK); inorganic NK fertilization treatment (NK); inorganic NPK fertilization treatment (NPK); organic fertilization treatment (M); and combined inorganic NPK with organic fertilization treatment (NPKM). The soil physicochemical properties, β-glucosidase (BG), and alkaline phosphomonoesterase (ALP) activities were determined, together with microbial (bacterial and fungal) community DNA sequences and subsequent bioinformatics analysis after 38 years of different fertilization. The results showed that the content of soil organic carbon (SOC) and available P and the activities of BG and ALP were the highest after M and NPKM treatments, which were 79–104 %, 26–36 times, 161–171 %, and 75–91 % higher than CK, respectively. Hierarchical clustering analysis showed that the bacterial and fungal community structures in M and NPKM treatments were similar, but the community structures in non-organic fertilization treatments (CK, NK, and NPK) were significantly different from those in organic fertilization treatments. The indicator species and correlation analysis combined revealed that most indicator species in organic fertilizer treatments were significantly positively correlated with soil BG and ALP, while most indicator species in non-organic fertilizer (CK and NK) treatments were significantly negatively correlated with soil BG and ALP. Organic fertilization treatments favored the growth of the bacterial genus Lysobacter and the fungal genera Acremonium and Mortierella and were significantly positively correlated with BG and ALP activities. Redundancy analysis revealed that SOC is the most important factor in shaping microbial community structure. Co-occurrence network analysis showed organic fertilization had higher network complexity, more keystone taxa, and more associations among microbial taxa compared with non-organic fertilization (CK + NK). Structural equation models revealed that microbial community structure is the direct driving factor of BG and ALP activities and their interactions, and SOC modulated the relationship between microbial community structure and BG and ALP activities. This study highlights how the application of organic fertilizer enhanced the C- and P-cycling enzyme activities, reshaped the soil microbial communities, and regulated these crucial indicators and their interactions by SOC.

Impact of Long-term Use of Fertilizers and Manure on Distribution of Soil-inorganic Phosphorus Fractions in a Vertisol

The field experiment was conducted during the kharif season under the AICRP on Long-Term Fertilizer Experiment at the Research Farm, Department of Soil Science and Agricultural Chemistry, JNKVV, Jabalpur (M.P.), India. The investigation was carried out to assess the distribution of P fractions in Vertisol after the harvesting of the soybean crop. Eight treatments were imposed with four replications in a simple randomized block design. The treatments were applied in combination with different doses of fertilizer viz., T1 (50% NPK), T2 (100% NPK), T3 (150% NPK), T4 (100% N), T5 (100% NP), T6 (100% NPK+FYM), T7 (100% NPK-S), and T8 (control). Through the findings, the soil pH and electrical conductivity (dS m-1) did not show significant changes even after the long-term application of various fertilizer levels compared to their initial values. The treatment with 100% NPK + FYM exhibited the highest organic carbon (g kg-1) content and available N, P, and K (kg ha-1) content over the control. The various forms of phosphorus in the soil were observed in the following order: Ca-P > Fe-P > Al-P > Occluded-P > Saloid-P . The Ca-P content was highest when 100% NPK fertilizer and farmyard manure (FYM) were used together. The analysis showed that the presence of saloid-P significantly influences the availability of phosphorus in Vertisol soil. Based on the current investigation, it is recommended to use integrated nutrient management, which includes both 100% NPK fertilizer and FYM, to prevent phosphorus deficiency in soybean cultivation in Vertisol.

Sustaining Soil Fertility: Exploring the Long-Term Effects of Chemical Fertilizers and Farmyard Manure Application

Long-term fertilizer and manure experiments serve as invaluable resources for investigating various aspects of agriculture and soil management. These experiments provide a wealth of information on yield trends, nutrient dynamics, and soil nutrient balances. They also help in predicting a soil’s carrying capacity, assessing soil quality, and evaluating the sustainability of agricultural systems. Long-term fertilizer experiments play a crucial role in separating the complex interactions among soils, plants, climate, and management practices and shedding light on their impacts on crop productivity. Long-term fertilizer experiments were initiated in the early 1970s, and they have been periodically evaluated since then. The continuous, long-term use of chemical fertilizers and manures is highly influencing the chemical nature and fertility status of the soil.

Long-term organic fertilization enhances potassium uptake and yield of sweet potato by expanding soil aggregates-associated potassium stocks

Crop straw return and organic manure application are effective and environmentally friendly methods used by farmers to improve soil structure, fertility and agricultural productivity. Sweet potato is a typical “potassium (K)-favoring” food crop and widely grown throughout the world. However, the regulation effects of long-term organic fertilization on soil aggregates-associated K stocks and K uptake by sweet potato are less understood. Herein, a long-term fertilization experiment since 2007 including chemical fertilizer (NPK), NPK combined with commercial manure (NPK+CM), NPK combined with pig manure (NPK+PM), and NPK combined with rice straw (NPK+RS) treatments under peanut-sweet potato crop rotation was employed. Long-term fertilizer application contributed to higher yield, yield stability, and K uptake of sweet potato. NPK+PM and NPK+RS treatments both showed the best promoting effect on plant growth. NPK+PM and NPK+RS treatments showed remarkable increasement of aggregate-associated exchangeable potassium (EK) and non-exchangeable potassium (NEK) stocks, particularly for small-macroaggregates (0.25–2 mm) and large-macroaggregates (> 2 mm). Total potassium (TK), EK and NEK stocks in large and small-macroaggregates displayed positive effects on K uptake and yield for sweet potato. Pearson's correlation and random forest model analysis revealed that EK and NEK stock in large-macroaggregate were the most key factors for K uptake and yield of sweet potato under long-term fertilization. Overall, our study highlights the prominent advantage of long-term organic fertilization.

Aggregate-Associated Carbon Fractions Under Forty-Eight Years of Fertilization in North-Western Himalayas

ABSTRACT The present investigation was carried out in an on-going long-term fertilizer experiment, initiated during 1972 at experimental farm of Department of Soil Science, CSK HPKV Palampur, to study the long-term effect of fertilizers and amendments on soil aggregate stability and carbon dynamics in an acid Alfisol under maize-wheat cropping system. The experiment comprised of eleven treatments. The soil of the experimental site was silt loam and classified taxonomically as “Typic Hapludalf” (subgroup). Soil samples were collected from surface (0–0.15 m) layer after the harvest of wheat (rabi, 2019–2020) and were analyzed for different aggerate size and their carbon fractions. The addition of FYM enhanced the macroaggregates (>0.25 mm) as compared to microaggregates (<0.25 mm). Incorporation of FYM alone or in combination with chemical fertilizers enhanced the accumulation of different C pools in all aggregate fractions over unfertilized control. Among the macroaggregates, 1–0.5 mm fraction had higher total organic carbon (TOC), organic carbon (OC), labile carbon (LC) and non-labile carbon (NLC) as compared to microaggregates. Aggregate-associated carbon is less susceptible to physical, microbiological, and enzymatic degradation, and is a potential carbon reservoir that is protected from mineralization. Addition of FYM along with 100% NPK recorded highest SOC stocks, SOC sequestration rate and highest carbon buildup. Different aggregate fractions of TOC, OC, LC and NLC were found to be positively and significantly correlated with available N, P and K and negatively and significantly correlated with bulk density whereas, positively and non-significantly correlated with soil pH and electrical conductivity. Different aggregate fractions of TOC, OC, LC and NLC were positively and significantly correlated with grain and straw yield of wheat.

Analysis on Change in Soil Organic Carbon Content of Farmland in Yangtze River Economic Belt Under Different Fertilizing Measures

The literature from a long-term fertilization experiment in the Yangtze River Economic Belt from January 1992 to May 2022 was collected, and the data of farmland soil organic carbon were extracted and integrated. Using the normalization treatment and the analysis method of relative annual variation, the overall change in soil organic carbon content in farmland in the Yangtze River Economic Belt under different long-term fertilization measures was studied, and the change differences of soil organic carbon content under three tillage modes were compared so as to judge and analyze the influence of the duration of the experiment on soil organic carbon dynamics. The results showed that under different long-term fertilization measures, the organic carbon content of farmland soil in the Yangtze River Economic Belt in China showed an overall upward trend. The NP, NPK, O, and NPKO treatments all increased the organic carbon content of agricultural soils, with that of the NPKO treatment being the largest. The sole application of inorganic nitrogen fertilizer reduced the organic carbon content of the soil. The rates of change in soil organic carbon content were 0.22 g·(kg·a)-1, 0.24 g·(kg·a)-1, and 0.16 g·(kg·a)-1for dryland, paddy, and water-dry rotation farmland, respectively. Additionally, the relatively rapid increase effect of organic carbon brought by the O and NPKO treatments could last for no more than 28 years in dryland soil but could still last for more than 28 years in paddy field and paddy-upland rotation soil. There was some variation in the rate of change of soil organic carbon content between soil types. The average rate of change of organic carbon was 0.25 g·(kg·a)-1for red soils, 0.14 g·(kg·a)-1 for brown soils, 0.19 g·(kg·a)-1 for tidal soils, and 0.15 g·(kg·a)-1 for rice soils. The trend of NPKO>O>NPK>NPK>NP>N was basically maintained for the rate of change in soil organic carbon content. The NPKO treatments were all significantly higher than the chemical fertilizer (N, NP, and NPK) treatments alone. The N treatment showed a reduction in organic carbon content in both red soil and rice soils. Considering the carbon fixation of farmland soil, the combined application of organic and inorganic fertilizers is a more suitable fertilization method in this area.

Long-term fertilization promotes soil organic nitrogen accumulation by increasing the abundance of keystone microbial cluster across aggregates

Nitrogen (N) in soil mainly occurs in organic forms, with soil organic nitrogen (SON) playing an essential role in supplying N to crops. However, it is unclear how the content and distribution of SON vary among different aggregate sizes, and how SON content is related to soil microorganisms. In this study, we investigated the associations between SON content and various microbial community characteristics across different aggregate sizes using data from a long-term field fertilization experiment in paddy soils. We also performed functional prediction to explore potential microbial mechanisms underlying SON accumulation. The results showed that SON content decreased as aggregate size decreased, with macroaggregates having the highest SON content and the silt-clay fraction having the lowest. Furthermore, our linear regression and structural equation modeling analysis revealed that keystone microbial clusters (highly interconnected taxa within Firmicutes, Proteobacteria, Chloroflexi, Actinobacteriota, and Ascomycota) were significantly correlated with SON content. Finally, functional prediction analysis suggested that this relationship may be due, at least in part, to the large number of metabolic pathways involved in biosynthesis of N-containing compounds present in keystone microbial clusters. Overall, our study highlights the importance of keystone microbial clusters in influencing the accumulation of SON and contributes to our understanding of soil N biogeochemical cycling.

Responses of total, reactive and dissolved phosphorus pools and crop yields to long-term fertilization

Maintaining an appropriate soil phosphorus level is key to ensure sustainable phosphorus management for crop production and to minimise phosphorus losses to water bodies. However, the effects of long-term fertilization on different soil phosphorus pools, crop yields and phosphorus loss risk remain unclear. This requires insights into the responses of soil phosphorus pools, crop phosphorus uptake with related crop yields and phosphorus loss to long-term phosphorus inputs. Changes in four soil phosphorus pools (PCACL2, POLSEN, POX and PTOTAL, respectively) and crop yield responses to various fertilization rates were examined in a 29-year long-term phosphorus fertilization experiment in China. Results showed that the increase in the four soil phosphorus pools was proportional to the accumulated phosphorus surplus, i.e., the input minus uptake. POLSEN and POX increased linearly with continuous phosphorus application and peaked at a phosphorus accumulation near 3200 kg P ha−1. Beyond this threshold, continuous phosphorus application caused a gradual increase in PTOTAL and a linear increase in PCACL2, which implies an increasing risk for leaching. The POX pool accounted for 87% of the accumulated phosphorus surplus until soil phosphorus saturation occurred. The crop yields of wheat and maize responded clearly to changes in PTOTAL, POX, POLSEN and PCACL2, with POX explaining most of the yield variation. Furthermore, POX was highly correlated with PCACL2, being a risk indicator for phosphorus leaching. Given that POX explains best how much of phosphorus surplus accumulates in soil, the variation in crop yield, and the risk for P leaching, it can be used as a valuable and reliable indicator to manage phosphorus sustainably.

Distinct characteristics of the bacterial community in the rhizosphere soils of sweet potato storage roots and fibrous roots following long-term fertilization

Sweet potato (Ipomoea batatas Lam.) has two special root systems, namely, storage roots and fibrous roots. However, the response of the bacterial community characteristics in the rhizosphere soils of the two types of roots to long-term fertilization is not clear. Here, a long-term fertilization experiment was established under wheat–sweet potato crop rotation in 2011. We sampled the rhizosphere soils of storage roots and fibrous roots under three fertilization treatments (i.e., NK, no P; NPK, chemical P fertilizer; and NPKM, inorganic combined with organic fertilizers). The diversity and composition of the bacterial community and the relative abundance of specific bacterial taxa and their relationships with soil properties were investigated at the stage of sweet potato expansion. The results showed that compared to the NK treatment, the NPK treatment significantly increased soil available P (AP) in the rhizosphere of storage roots and fibrous roots by 503 % and 668 %, dissolved organic carbon (DOC) by 25 % and 18 %, and available K (AK) by 3.5 % and 12.3 %, respectively. However, compared to the NK treatment, the Chao1 index was significantly decreased under the NPK treatment in both storage roots and fibrous roots. In addition, compared to storage roots, bacterial α-diversity and soil β-glucosidase and alkaline phosphatase activities significantly improved in the rhizosphere of fibrous roots (P < 0.001) under the NPKM treatment. Chryseobacterium, Acinetobacter and Myroides were the dominant bacterial genera in the rhizosphere soil of storage roots under the NPKM treatment. Furthermore, principal coordinate analysis (PCoA) indicated that the structure of the bacterial community was markedly altered in the rhizosphere soils of storage roots and fibrous roots under the NPKM treatment. Moreover, a complex network of bacterial communities was formed in the rhizosphere of storage roots rather than that of fibrous roots. Based on redundancy analysis (RDA) and structural equation modeling (SEM), the results revealed that the diversity and structure of the bacterial community were primarily driven by the AK concentration in the rhizosphere soil of the storage roots. In summary, long-term fertilization reshaped the bacterial community in the rhizosphere soils of two types of sweet potato roots by altering the properties of the rhizosphere soils.

Effects of long-term fertilization patterns on bacterial community structure and soil nutrients in dryland of yellow soil.

Understanding the responses of soil bacterial community to long-term fertilization in dryland of yellow soil could provide theoretical basis for establishing scientific fertilization system and cultivating healthy soil. Based on a 25-year long-term fertilization experiment on yellow soil, we collected soil samples from 0-20 cm layer under different fertilization treatments: no fertilization (CK), balanced application of N, P and K fertilizers (NPK), single application of organic fertilizer (M), combined application of constant organic and inorganic fertilizer (MNPK), and 1/2 organic fertilizer instead of 1/2 chemical fertilizer (MNP). Illumina MiSeq high-throughput sequencing technology was used to examine the effects of different fertilization patterns on soil bacterial community structure and soil nutrient content. The main driving factors of soil bacterial community were explored. The results showed that soil pH and organic matter content under treatments with organic fertilizer increased by 11.4%-13.5% and 28.8%-52.0%, respectively, compared to that under NPK treatment. Long-term fertilization did not affect soil bacterial α diversity, but significantly affected soil bacterial β diversity. Compared with CK and NPK treatment, treatments of M, MNP, and MNPK significantly changed soil bacterial community structure, and increased the relative abundance of Fusobacteria and Anaerobes. Four fertilization treatments increased the relative abundance of Bacteroidetes, and decreased the relative abundance of Actinomyces and Campylobacter, compared to CK. Soil pH was the most important factor affecting soil bacterial community structure. Fertilization-stimulated rare microbial taxa (Pumilomyces and Anaerobes) were more sensitive to changes in different environmental factors and were the main drivers of the formation of community versatility. In conclusion, organic fertilizer improved soil properties and fertility and changed soil bacterial community structure, which are conducive to cultivating healthy soil.

Long-Term Chemical Fertilization Drove Beneficial Bacteria for Rice Soil to Move from Bulk Soil to the Rhizosphere

Overuse of chemical fertilizer (CF) causes damage to soil and the environment. To reveal the process of the response of crop rhizospheric and bulk soil fertility and the bacterial community to long-term CF conditions, CF application and nonfertilization (CK, control) treatments were used in a long-term (12-year) fertilization experiment. Long-term CF application significantly increased the soil organic matter, total nitrogen, and available phosphorus contents (p &lt; 0.05), increased the available nitrogen (AN) and potassium (AK) contents to varying degrees, and decreased the soil pH in both rice rhizospheric soil and bulk soil. In addition, the bacterial Shannon and Ace indices in rice rhizospheric soil under the CF treatment were all higher than those under the control (CK) treatment, and the bulk soil bacteria showed the opposite trend. The LEfSe results showed that unidentified_Gammaproteobacteria and Geobacter (genera) were significantly enriched in the rhizospheric and bulk soil of rice under the CK treatment, respectively. Gemmatimonadetes (phylum) and Nitrospirae (phylum) + Thiobacillus (genus) were significantly enriched in the rice rhizospheric and bulk soil under the CF treatment. Only AK and AN had strong positive correlations with soil bacteria. Long-term CF application accelerated the migration of soil bacteria from the bulk soil to the rhizosphere, thus improving soil fertility and nutrient cycling.

Maize residue types and soil fertility levels influence sequestration of newly associated carbon in aggregates with in situ experiments

Soil physical structure plays a key role in the sequestration of organic carbon (C) and affects soil fertility and global climate change. However, the dynamics of the residue-derived C in different aggregate fractions are poorly understood. The objectives of this study were to explore the changes in soil aggregate composition and organic C distribution at different fertility levels after the addition of maize residues (roots, stems, and leaves, labeled with 13C). In this study, soil samples with high fertility (HF) and low fertility (LF) levels were formed through a long-term fertilization experiment (29 years), and different types of maize residues were added to the two types of soils. The 13C abundance was quantified in four fractions of soil aggregates large macroaggregates (>2 mm), small macroaggregates (0.25–2 mm), microaggregates (0.053–0.25 mm), and silt and clay (<0.053 mm) on the 60th, 90th, 180th and 540th day following the addition of residues. The findings indicate that the mass proportions of small macroaggregates and microaggregates in the LF soil were lower, whereas those of the other fractions were higher compared with HF soil. Moreover, greater amount of residue-derived C was found to be associated with soil aggregates in LF soil than that in HF soil, and the residue-derived C in different soil aggregate fractions differed with the residue type. The percentages of residue-derived C distributed in the large macroaggregate fractions averaged 19.9% and 15.3% in the LF and HF soils, respectively. Stem and leaf treatments of HF soil improved the stability of soil aggregates. The addition of roots significantly increased the soil organic C content in the aggregates; the residue-derived C content was the highest in the silt and clay fractions and the lowest in the large macroaggregate fraction (>2 mm). These results suggest that the potential benefits of adding maize residue to regulate SOC sequestration and stabilization of soil aggregates, especially in infertile soils.

Effect of Inorganic and Integrated Long-term Nutrient Management on DTPA-extractable Micronutrients in a Vertisol under Soybean-wheat Cropping System across the Soil Depth

The status of DTPA extractable micronutrient (Zn, Cu, Fe and Mn) in response of continuous application of different inorganic and organic fertilizer combination in a 48 years old ongoing long-term fertilizer experiment (AICRP-LTFE) were investigated in Vertisol at Department of Soil Science, and Agricultural Chemistry, JNKVV, Jabalpur under intensive cultivation of soybean- wheat cropping system in 2021. The treatments selected for the study were: control (T1); 100% NP(T2); 100% NPK (T3); 100% NPK+FYM (T4); 100% N(T5); 50% NPK (T6); 150% NPK (T7). Application of FYM along with balance fertilizer (100% NPK) significantly increased the micronutrients availability in soil. On contrast, Imbalance fertilization caused a lower level of micronutrients in soil even below to the critical limit in case of zinc. A decreasing trend with increase in soil depth irrespective of type of nutrient management and micronutrient type was evident in the study. Findings of the present study emphasized the application of balance fertilization along with organic sources like FYM for sustaining micronutrients availability in Vertisol under soybean-wheat cropping system.

Carbon Storage Potential and Carbon Dioxide Emissions from Mineral-Fertilized and Manured Soil

Two important goals of sustainable agriculture are food production and preserving and improving soil health. The soil organic carbon content is considered an indicator of soil health. The evaluation of the methods to increase the soil organic carbon content in long-term experiments is usually carried out without considering its environmental effects, (e.g., CO2–C soil emission). This study hypothesized that sandy soils have a low carbon storage potential, and that the carbon accumulation in the soil is accompanied by increased CO2–C emissions into the atmosphere. The study was carried out as a long-term fertilization experiment in Central Poland using a rye monoculture. The changes in the soil organic carbon content (SOC), CO2–C emissions from soil, and plant yields were examined for two soil treatments: one treated only with mineral fertilizers (CaNPK) and one annually fertilized with manure (Ca + M). Over the 91 years of the experiment, the SOC content of the manure-fertilized treatment increased almost two-fold, reaching 10.625 g C kg−1 in the topsoil, while the content of the SOC in the soil fertilized with CaNPK did not change (5.685 g C kg−1 in the topsoil). Unlike mineral fertilization, soil manuring reduced the plant yields by approximately 15.5–28.3% and increased the CO2–C emissions from arable land. The CO2–C emissions of the manured soil (5365.0 and 5159.2 kg CO2–C ha−1 in the first and second year of the study, respectively) were significantly higher (by 1431.9–2174.2 kg CO2–C ha−1) than those in the soils that only received mineral fertilizers (3933.1 and 2975.0 kg CO2–C ha−1 in the first and second year of the study, respectively). The results from this experiment suggest that only long-term fertilization with manure might increase the carbon storage in the sandy soil, but it is also associated with higher CO2–C emissions into the atmosphere. The replacement of mineral fertilizers with manure, predicted as a result of rising mineral fertilizer prices, will make it challenging to achieve the ambitious European goal of carbon neutrality in agriculture. The increase in CO2–C emissions due to manure fertilization of loamy sand soil in Central Poland also suggests the need to research the emissivity of organic farming.

Maize stalk incorporation increases N2O emissions that offset the benefit of SOC sequestration in a winter wheat-summer maize field: A four-year measurement in long-term fertilizer experiments

Soil organic carbon (SOC) sequestration, nitrous oxide (N2O) emissions, and net global warming potential (GWP) are variable following crop residue retention in agroecosystems. We measured the SOC content (from 1990 to 2018) and N2O fluxes (from October 2014 to September 2018) in a long-term fertilizer experiment with winter wheat-summer maize rotation (since 1990) in the Guanzhong Plain. The primary aim was to quantify the effects of maize stalk incorporation on N2O emissions, SOC sequestration (SOCSR), and net GWP during the measurement period. We examined two fertilizer management practices, i.e., synthetic fertilizers in both crop seasons (NF) and synthetic fertilizers in both crop seasons with maize stalk incorporation in the winter wheat season (NFS), and an unfertilized control (CK). Annual N2O emissions ranged from 0.11 to 0.27 kg N ha–1 yr–1 in CK. Fertilization significantly increased N2O emissions (p < 0.001), with values ranging from 1.65 to 5.65 and 3.08 to 7.85 kg N ha–1 yr–1 in NF and NFS, respectively. The emissions from NFS were 27–253% higher than those from NF, with significant differences (p < 0.05) during three out of four experimental years. The SOC contents linearly increased with the experimental year (p < 0.001), giving SOCSRs of 0.13, 0.45 and 0.60 t C ha−1 yr−1 in CK, NF and NFS, respectively. The net GWP averaged − 0.38, − 0.36, and 0.01 t CO2 equivalent ha−1 yr−1 in the three treatments, denoting that NFS was a minor greenhouse gas source during the measurement period. This study provided evidence that maize stalk incorporation increased both N2O emissions and SOC sequestration, while the N2O emissions offset the benefit of SOC sequestration. We conclude that maize stalk incorporation does not appear to be an effective approach to decrease net greenhouse gas emissions from the winter wheat-summer maize rotation in the Guanzhong Plain. This issue can probably be resolved by avoiding fertilizer application to wet soil in the winter wheat season and/or returning winter wheat straw in the summer maize season.

Effect of long-term fertilisation of Calcisols on organic carbon sequestration in marine climate in Estonia

ABSTRACT The aim of this work was to investigate the effect of long-term (45-year) fertilization of the crop rotation on soil organic carbon concentration (SOC%) changes in different periods of the experiment and its trend under conditions of more northerly marine climate changes. In this work, the data of the long-term NPK fertilization experiment of sandy loam Calcisols located in Northern Estonia (longitude 58.584816, latitude 24.422128) have been used. The crop rotation was divided into six blocks: potato-spring barley-spring barley under sowing with forage grasses – 1y and 2y forage grasses-winter rye. Different combinations of mineral (N 40—180; P 18—54; K 50—105 kg ha−1) and organic (manure (FYM) 30 and 60 Mg ha−1) fertilizers were used in the study. Two periods were observed: the last 20y vegetation period was 10% warmer and 15% less rainy than the earlier period. Under conditions of climate warming, the yield of barley and potatoes increased the most, especially with manure application. SOC% increased from 2.01 to 2.04 under the influence of mineral fertilizers, and from 2.08 to 2.22 with mineral + FYM. The soil is sustainable if manure is used at least 5–10 Mg ha−1 per y−1.

Soil fertilisation with 137Cs-contaminated and uncontaminated wood ash as a countermeasure to reduce 137Cs uptake by forest plants

The purpose of present study was to find out whether wood ash with a high pH value and neutralizing capacity reduces 137Cs uptake by forest plants many years after the radionuclide fallout. The effects of one-time point fertilisation with 137Cs-contaminated and uncontaminated wood ash alone or in combination with KCl on 137Cs transfer from soil to young leaves and green shoots of various dwarf shrubs and tree species were examined in a long-term fertilisation experiment (2012–2021) conducted in Bazar mixed forest, around 70 km from Chernobyl nuclear power plant. The results indicated minor effects of soil fertilisation, although there were differences between 137Cs uptake by species and years. Soil amendment with 137Cs-contaminated wood ash generally did not affect 137Cs uptake by young shoots and leaves of plants over the growing season in the first year and only slightly decreased Tag for 137Cs in the following years. The effect of a single application of 137Cs-uncontaminated wood ash on reducing 137Cs uptake by plants was generally negligible. Application of 137Cs-contaminated wood ash in combination with KCl reduced plant 137Cs uptake by about 45%, however, such reduction was only significant in some years for bilberry berries, young leaves and green shoots of lingonberry and alder buckthorn. Thus application of wood ash to 137Cs-contaminated forest soil many years after radionuclide fallout generally does not reduce 137Cs uptake by forest vegetation in a mixed forest ecosystem and this countermeasure should be applied with caution.

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.

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.

Competition model explains trends of long-term fertilization in plant communities.

Over 40 years ago, Kempton (Biometrics, 35, 1979, 307) reported significant modification to plant community structure following a long-term fertilization experiment. Many researchers have investigated this phenomenon in the years since. Collectively, these studies have shown consistent shifts in rank abundance relationships among species in communities following fertilization. The previous studies indicated that fertilization affects community structure through several critical processes, including trait-based functional response, reordering of species in rank abundance diagram (RAD), and niche dimensionality, although some questions have remained. How does the species reordering driven by the plant responses cause characteristic trends in temporal changes of RAD? Why are those trends ubiquitous in various systems? To answer those questions, we theoretically investigated the effects of fertilization on community structure based on a colonization model (or Levins model) with competition-fecundity trade-offs, which can result in the coexistence of multiple species under competition. The model represents characteristic RAD, which can be an adequate tool to study community composition. Our theoretical model comprehensively represents observed trends in rank abundance relationships following long-term fertilization and suggests that competitive interactions among species are a critical factor in structuring species diversity in plant communities.