Long-term Application Of Organic Fertilizers Research Articles

Molecular Composition of Humic Acids of Different Aged Fallow Lands and Soils of Different Types of Use in Northwest of Russia

Post-agrogenic transformation of fallow soils leads to changes in soil carbon content, the molecular composition of humic substances, and rates of organic matter stabilization, which can affect climate change on the planet. In this regard, we analyzed the molecular composition of humic acids isolated from natural and fallow soils in the southern Taiga zone of northwest Russia. Different-aged soils on fallow lands represent a model of soil transformation in time, and data on the transformation of soil humic acid molecular composition make a significant contribution to the understanding of soil organic matter stabilization aspect issues. In this case, the molecular structure of humic acids isolated from natural and fallow soils in northwest Russia was analyzed. To study the molecular composition of HAs, the elemental composition was analyzed, and 13C (CP/MAS) NMR spectroscopy of HAs isolated from different aged abandoned soils and soils of different types of use was carried out. The obtained data showed that with the increasing age of soils in the fallow state, there is an increase in the carbon content of humic acids as well as a decrease in nitrogen content. As a result of the increasing age of soils in the fallow state, there are dynamics in the content of aromatic structural fragments in humic acids: 34% for 40 years old, 28% for 80 years old, and 31% for 120 years old. This is due to changes in the precursors of humification and the further transformation of plant residues in the soil. Re-involved fallow land soils lead to an increase in the content of aromatic structural fragments in the composition of HA in relation to HA extracted from mature soils. The lowest content of aromatic structural fragments was observed in the humic acids of 130-year-old agricultural soil, which is associated with the long-term application of organic fertilizers.

Biological Interactions Mediate Soil Functions by Altering Rare Microbial Communities.

Soil microbes, the main driving force of terrestrial biogeochemical cycles, facilitate soil organic matter turnover. However, the influence of the soil fauna on microbial communities remains poorly understood. We investigated soil microbiota dynamics by introducing competition and predation among fauna into two soil ecosystems with different fertilization histories. The interactions significantly affected rare microbial communities including bacteria and fungi. Predation enhanced the abundance of C/N cycle-related genes. Rare microbial communities are important drivers of soil functional gene enrichment. Key rare microbial taxa, including SM1A02, Gammaproteobacteria, and HSB_OF53-F07, were identified. Metabolomics analysis suggested that increased functional gene abundance may be due to specific microbial metabolic activity mediated by soil fauna interactions. Predation had a stronger effect on rare microbes, functional genes, and microbial metabolism compared to competition. Long-term organic fertilizer application increased the soil resistance to animal interactions. These findings provide a comprehensive understanding of microbial community dynamics under soil biological interactions, emphasizing the roles of competition and predation among soil fauna in terrestrial ecosystems.

The addition of organic fertilizer can reduce the dependence of dryland yield on rainfall-based on a 32-year long-term study

Clarifying the synergistic effect between rainfall and fertilization in rainfed farming and joint effect on crop yield can provide theoretical basis for improving the sustainable productivity of farmland in dry farming. A 32-year fertilizer regulation experiment was conducted in the dry farming region of the Loess Plateau. According to the precipitation, it was divided into dry, normal and high rainfall years. The influence of long-term fertilization regulation on crop yield and farmland moisture changes under different rainfall years was analyzed, and the regulation mechanism of fertilization and precipitation coordination on crop yield under different rainfall years was explored. The results showed that effects of fertilization on crop yield and water use efficiency (WUE) were closely related to experimental years. In the early stage, the increase in treatments with higher amounts of nitrogen was more significant, while in the later stage, the increase in treatments with less organic fertilizer was more significant. The correlation of crop yield, the whole rainfall (WR), growth period rainfall (GPR), fallow period rainfall (FPR), water storage during sowing (SWS), evapotranspiration (ET), WUE and utilization efficiency of precipitation (PUE)under different rainfall years and treatments was analyzed. The results showed that the crop yield showed that the correlation with PUE showed high> dry> normal rainfall year, and the correlation with WUE showed the law of dry> high> normal rainfall year. The correlation of organic fertilizer treatments was lower than that of single chemical fertilizer. With the years extension of application organic fertilizer, application low amount of organic fertilizer can improve crop yield by improving PUE, and can achieve the effect of application high amount of organic fertilizer. No matter what the rainfall years, the long-term application of organic fertilizer can make full use of the rainfall to improve the WUE, and then ensure the sustainability of crop yield.

Long-term application of organic fertilizer prompting the dispersal of antibiotic resistance genes and their health risks in the soil plastisphere

Microplastic (MP) pollution is a rapidly growing global environmental concern that has led to the emergence of a new environmental compartment, the plastisphere, which is a hotspot for the accumulation of antibiotic resistance genes (ARGs) and human bacterial pathogens (HBPs). However, studies on the effects of long-term organic fertilizer application on the dispersal of ARGs and virulence factor genes (VFGs) in the plastisphere of farmland soil have been limited. Here, we performed a field culture experiment by burying nylon bags filled with MPs in paddy soil that had been treated with different fertilizers for over 30 years to explore the changes of ARGs and VFGs in soil plastisphere. Our results show that the soil plastisphere amplified the ARG and VFG pollution caused by organic fertilization by 1.5 and 1.4 times, respectively. And it also led to a 2.7-fold increase in the risk of horizontal gene transfer. Meanwhile, the plastisphere tended to promote deterministic process in the community assembly of HBPs, with an increase of 1.4 times. Network analysis found a significant correlation between ARGs, VFGs, and bacteria in plastisphere. Correlation analysis highlight the important role of mobile genetic elements (MGEs) and bacterial communities in shaping the abundance of ARGs and VFGs, respectively. Our findings provide new insights into the health risk associated with the soil plastisphere due ARGs and VFGs derived from organic fertilizers.

Response of Soil Absolute and Specific Enzyme Activities to Long-Term Application of Organic Fertilizer to Solonetz in Northeast China

Soil organic carbon (SOC) and microbial biomass carbon (MBC) are highly correlated with enzyme activities. Specific enzyme activities can exclude the autocorrelation between enzyme activity and SOC and MBC. However, the responses of absolute and specific enzyme activities to saline–alkali properties remains unclear. In this study, the absolute and specific enzyme activities of cellobiose hydrolase, β-glucosidase, arylsulfatase, alkaline phosphatase, and urease were measured in soils with 10, 15, 18, 21, and 26 years of organic fertilizer application in contrast to soils without organic fertilizer application. The results showed that long-term organic fertilizer application led to significantly increased in the absolute and specific enzyme activity and decrease in pH, electrical conductivity (EC), exchangeable sodium percentage (ESP), as well as sodium adsorption ratio (SAR5:1). In the structural equation model (SEM), the EC extremely limited the geometric mean of specific enzyme activity per unit of MBC (MBC-GMSEA) (path coefficient, −0.84, p < 0.001). Pearson’s correlation analysis showed that the correlations between EA/MBC and pH, EC, ESP, and SAR5:1 were higher than between the absolute soil enzyme activity and pH, EC, ESP, and SAR5:1. Of the parameters tested, EA/MBC was a more sensitive index to reflect the improvement effect of organic fertilizer on soils and evaluate the saline–alkali barrier.

Long-Term Application of Organic Fertilizers in Relation to Soil Organic Matter Quality

The quality of soil organic matter plays a central role in soil structure, carbon sequestration and pollutant immobilization. The effect of 16–23 years of fertilization on the quality of soil organic matter was studied in field experiments at ten experimental sites in Central Europe. Soil samples were collected in 2016 after barley harvest. Six crops were rotated: pea–canola–winter wheat–spring barley–beet/potato–spring barley. Six treatments were studied: unfertilized control, mineral fertilization (NPK), farmyard manure, farmyard manure + NPK, straw incorporation, and straw incorporation + NPK. Although carbon input did not significantly correlate with any soil organic carbon fractions, the C/N ratio of applied organic fertilizers significantly correlated with the content of humic acid carbon (C-HA), the C-HA/C-FA ratio and humification index in soil. The combination of farmyard manure + NPK resulted in a higher humic acid carbon content in soil, humification rate, and humification index compared to the application of NPK, straw return, and the combination of straw return + NPK. Although straw return led to a lower E4/E6 (A400/A600, Q4/6) ratio compared to farmyard manure application, the C-HA/C-FA ratio was unchanged among these treatments. The application of farmyard manure with and without the addition of NPK led to higher values of carbon sequestration efficiency in soil compared to the straw return with and without the addition of NPK.

Long-term application of organic compost is the primary contributor to microplastic pollution of soils in a wheat–maize rotation

Microplastics (MPs) are posing new threats to soil ecosystems. Organic fertilizers are considered as an emerging contributor to MPs accumulation in agricultural soils. However, few studies have focused on the MPs fate in soils under long-term organic fertilizer application. Based on an 11-year field test with wheat-maize cropping rotation, this study investigated the characteristics of MPs in pig manure and cow manure composts, and examined the impact of long-term compost application on soil MPs accumulation, surface morphology, and distribution. The MPs contents in pig manure and cow manure composts were 3547 and 4520 items kg−1, respectively. Microplastics abundances in soils under long-term use of these two composts were 144 to 287 and 140 to 316 items kg−1, respectively, which increased significantly with increasing compost application amount and was substantially higher than that in soils without compost. Accumulated soil MPs sourced from long-term compost application were 1.73 × 108 to 7.22 × 108 items ha−1, accounting for 43.0 %–75.9 % of the total, and the contribution value doubled as the compost application rate doubled. The proportion of MPs <1 mm in composts (31.0 %) was lower when compared with that in compost-amended soils (43.8 %), and size and abundance reduced with increasing soil depth. Microplastics shapes and polymer types in composts and compost-amended soils were similar and mostly included fragments of polyethylene and polypropylene and fibers of polyethylene terephthalate. Microplastics in compost-amended soils showed complicated weathered surface morphologies, and soil mineral colloids were attached. These results demonstrate that compost-derived MPs in soils can be gradually weathered and degraded into smaller particles under long-term compost application. These findings provide key insights into the pollution level of soil MPs with organic fertilizer application and serve as a scientific basis for developing MPs mitigation measures in agricultural soils.

Characteristics of Greenhouse Gas Emissions from Yellow Paddy Soils under Long-Term Organic Fertilizer Application

Reducing greenhouse gas emissions from rice fields is essential to respond to the national “dual-carbon” strategy, achieve green agricultural development, and ensure food security. The substitution of organic fertilizers for chemical fertilizers is an important means to achieve zero growth and has a positive impact on crop yield and soil nutrients; however, the impact on the greenhouse effect is inconsistent. The effects of organic fertilizers on soil greenhouse gas emissions vary depending on factors such as soil, geography, ecological environment, and human management. However, previous research has shown that the combined application of organic fertilizer can increase soil carbon storage and increase crop yield, and may be an effective fertilization measure to reduce greenhouse gas emissions from yellow paddy fields. To clarify the effects of different ratios of organic fertilizer on the greenhouse gas emission characteristics of Guizhou yellow paddy soil, CH4, CO2, and N2O emissions from rice fields were monitored by static opaque chamber-gas chromatography, and the effects of different fertilization treatments on the cumulative greenhouse gas emissions and global warming potential (GWP) were investigated. Results showed that organic fertilizer application increased CH4 emissions from rice fields, and the effect increased with increasing organic fertilizer application. The peak period was from the heading stage to the filling and ripening stage, and there was almost no emission during the fallow period. Compared with the balanced application of chemical fertilizer (NPK), the treatment with organic fertilizer alone (M) significantly increased CO2 emissions, but the replacement of 1/2 chemical fertilizer nitrogen with 1/2 organic fertilizer (1/2 M + 1/2 N-PK) and the replacement of 1/4 chemical fertilizer nitrogen with 1/4 organic fertilizer (1/4 M + 3/4 N-PK) did not significantly increase CO2 emissions; emissions were 5% lower in the 1/2 M + 1/2 N-PK treatment than in the NPK treatment. Compared with the NPK treatment, the application of organic fertilizer alone significantly reduced N2O emissions by 32.16%, while the 1/2 M + 1/2 N-PK and 1/4 M + 3/4 N-PK treatments increased N2O emissions by 6.31% and 16.02%, respectively. However, there were no significant differences between the organic–inorganic combined treatments and NPK. During the flooding period, N2O emissions were relatively low, but the emissions increased rapidly after field drying. The application of organic fertilizer increased the GWP of rice fields. Compared with the NPK treatment, the M treatment increased GWP by 47.07%, 1/2 M + 1/2 N-PK increased GWP by 10.16%, and the 1/4 M + 3/4 N-PK treatment increased GWP by 2.93%. Except for the M treatment, the differences between treatments were not significant. Our results concluded that replacement of chemical fertilizers with organic fertilizers at a ratio of 1/4 to 1/2 did not significantly increase greenhouse gas emissions in rice fields, besides, it mitigate the greenhouse effect and increase soil carbon sequestration and yield in rice fields.

Reactive N emissions from cropland and their mitigation in the North China Plain

Excessive application of chemical nitrogen (N) fertilizer and inefficient N management are still common in the North China Plain, leading to large reactive N (Nr) losses and pollution, threatening environmental security and public health. Three improved N management practices (33% reduction in N applied (OU), OU combined with partial organic fertilizer substitution (UOM) and the urea in UOM amended with a urease inhibitor (ULOM)) together with no N application (CK) and farmers’ conventional practice (CU) were tested on a maize-wheat rotation at Quzhou, Hebei, North China Plain (NCP). Nr emissions were related to WFPS (Water Filled Pore Space), soil mineral N (NH4+-N and NO3−-N) and soil temperature. Nr emissions and yield-scaled Nr emissions were significantly reduced by partial substitution of organic fertilizer for chemical fertilizer: NH3 emissions were reduced by 55.8–62.4%. Using a urease inhibitor (Limus®), further reduced NH3 emissions by 40.2–64.5%. Yield-scaled NH3 emissions were, on average, reduced by 60.0% and 55.2% in the maize and wheat growing season, respectively, relative to the UOM treatment. Long-term application of organic fertilizer had a significant positive effect on N use efficiency (NUE). Overall, the study shows that appropriated N management such as reducing the N application rate, partial substitution of chemical N by organic N and using a urease inhibitor can reduce Nr emissions and promote NUE in the North China Plain. The methods corresponding to the ULOM and UOM treatments were the most and second most effective, respectively, with high net economic benefits.

15-year fertilization increased soil organic carbon stock even in systems reputed to be saturated like permanent grassland on andosols

Previous long-term experiments conducted more than 10 years ago, showed that long-term application of organic fertilizer increased soil organic carbon (SOC) of grasslands. However, it was usually assumed that, independent of the successive additions of fertilizer, soils have an upper limit to their SOC due to the inability of the soil mineral phase to fix additional carbon. Andosols of the volcanic Reunion Island are typically very rich in carbon and are usually considered as saturated in SOC. To assess the long-term effect of different types of fertilization on SOC in these soils, SOC concentrations were recorded at yearly intervals for 15 years in one arenosol site and in two andosols sites across a topo-sequence. The types of fertilization tested included inorganic, organic, and a mix of inorganic and organic nutrient sources. The addition of organic fertilizers increased soil carbon in the top (0–15 cm) horizon in both the arenosol and the two andosols (up to +250% in the arenosol and up to +41% in the andosol), whereas inorganic fertilizers and the control treatment did not always result in a significant increase in SOC. After 15 years, no plateau was reached in C stocks even with the highest fertilization rates. Our results suggest that SOC build-up was mainly due to inputs of organic fertilizer C, rather than to increased C inputs due to the fertilizer-induced increased crop yield. In the andosol, all the fertilization treatments led to higher concentrations of carbon in the deeper layers. This suggests that SOC inputs lead to downward migration of OC to deep horizons. For C-rich soils like andosols, assessing the variations in carbon in the deep horizon is thus critical in estimating the effects of soil management on carbon sequestration.

Long-term manure inputs induce a deep selection on agroecosystem soil antibiotic resistome

Although the enrichment of antibiotic resistance genes (ARGs) in diverse organic soils have been explored, understanding of the ecological processes governing the composition of ARGs in long-term organically fertilized soils still remains limited across typical agricultural regions. Thus, the distribution and assembly of ARG profile in three typical agricultural soils (black soil, fluvo-aquic soil, and red soil) under long-term contrasting fertilization regimes (chemical-only vs organic-only) were investigated using high-throughput qPCR (HT-qPCR). The application of organic manure significantly increased the abundance and number of ARGs across soils, as compared to those with chemical fertilizer. Organic manure application enriched the abundance of mobile genetic elements (MGEs), which were positively associated with ARGs. In addition, it is long-term organic fertilizer that enriched the number and abundance of opportunist and specialist ARGs in the fluvo-aquic and red soils, but not black soils. The number and abundance of most generalist ARGs did not change significantly among different fertilization or soil types. The assembly process of the ARG profiles tends to be more deterministic in organically fertilized soils than in chemically fertilized soils. These results suggest that long-term organic fertilizer application may contribute to the persistence and health risk of the soil antibiotic resistomes (especially specialist ARGs).

Macroaggregation is promoted more effectively by organic than inorganic fertilizers in farmland ecosystems of China—A meta-analysis

Fertilizers can affect formation, size distribution and stability of soil aggregates in agricultural ecosystems. Although many independent studies have been recently carried out to understand the effects of fertilizers on soil aggregates in farmland ecosystems of China, the results remain widely contradictory. A meta-analysis was conducted using a total number of 1286 observations from 100 publications between 2005 and 2020 to quantitatively analyze the effects of different fertilizer treatments, duration of fertilizer application, regional heterogeneity, soil texture, and aeration conditions on the composition of soil aggregates. Results showed that long-term annual single application of organic fertilizer, inorganic fertilizer (N and NPK) and combined application of organic and inorganic fertilizers increased the proportion of > 2 mm fractions, but decreased the proportion of 0.25–0.053 mm and < 0.053 mm fractions, respectively. The promotion of macroaggregates (> 0.25 mm) by long-term application of organic fertilizer and the combined application of organic and inorganic fertilizers were significantly stronger than inorganic fertilizer, but the opposite for microaggregate (< 0.25 mm). The application of organic and inorganic fertilizer and straw return should be applied in sandy loam and silty loam, and clay loam was applied mainly manure (M), nitrogen plus manure (NM), nitrogen, phosphorus and potassium plus manure (NPKM) and nitrogen, phosphorus and potassium plus straw return (NPKS), while reducing the single application of inorganic nitrogen (N). Inorganic fertilizers and combined with organic-inorganic fertilizer increased the proportion of > 2 mm fractions in anaerobic soil significantly more than that in well-aerated soil. Long-term annual single application of N and M promoted the proportion of > 2 mm and 2–0.25 mm fractions significantly more than that of combined application of nitrogen and phosphorus and potassium (NPK), NM, NPKM and NPKS in experiments conducted in the Northeast of China. In addition, our results also showed that the proportion of macroaggregates did not increase linearly with continuous fertilizer input, but with the extension of fertilization durations, the macroaggregates transformed to microaggregates gradually after reaching the saturation state. Organic fertilizer and organic-inorganic combined application had longer time to promote macroaggregates than inorganic fertilizer.

Effect of Long-Term Fertilization on Aggregate Size Distribution and Nutrient Accumulation in Aeolian Sandy Soil.

Soil aggregates are the material basis of soil structure and important carriers of nutrients. Long-term application of organic and inorganic fertilizers can affect the composition of soil aggregates to varying degrees, which in turn affects the distribution and storage of soil nutrients. We report the results of a 15-year long-term field-based test of aeolian sandy soil and used the wet sieve method to analyze the stability of water-stable aggregates, as well as the distribution characteristics of nutrients in different particle size aggregates. Our results show that long-term application of organic fertilizer (M3) and combined organic–inorganic treatments (NPK1-M1, NPK1-M2, and NPK1-M3) help to increase the amount of organic carbon, inorganic carbon, and cation exchange in the macro-aggregates, and the improvement rates are 92–103%, 8–28%, and 74–85%, respectively. The organic content of the fertilizers also promotes the formation of macro-aggregates, and the stability of aggregates increase from 0.24 to 0.45. In contrast, the application of inorganic fertilizers (NPK1, NPK2, and NPK3) has no marked effect on the formation and stability of macro-aggregates; the application of inorganic fertilizers can merely maintain the organic carbon content of the soil. Correlation analysis shows that the application of organic fertilizers and chemical (inorganic) fertilizers containing phosphorus and potassium can markedly increase the content and reserves of available phosphorus and potassium across all aggregate sizes, and there is a significant positive correlation between these parameters and the amount of applied fertilizer (p < 0.05). Aggregates of various sizes in aeolian sandy soils in arid areas have the potential for greater nutrient storage. Therefore, organic fertilizers can be used in the agricultural production process to improve soil structure and fertility.

长期施肥黄土旱塬农田土壤-微生物-植物系统碳氮磷生态化学计量特征

探讨长期不同施肥制度对农田土壤、植物生态系统的碳（C）、氮（N）、磷（P）含量及其生态化学计量比的影响，可为揭示该系统能量平衡和养分循环，实现农业生态系统元素平衡及可持续发展提供参考意义。以位于黄土高原半干旱地区的长武国家黄土高原农业生态实验站长期施肥试验为研究对象，选取不施肥（CK）、单施氮肥（N）、单施磷肥（P）、施氮磷肥（NP）、单施有机肥（M）、氮肥配施有机肥（NM）、磷肥配施有机肥（PM）、氮磷肥配施有机肥（NPM）8个处理，分析了黄土旱塬典型农田土壤-微生物-植物生态系统中C、N、P含量及其生态化学计量变化规律。研究结果表明：1）长期单施有机肥和化肥配施有机肥处理可显著提高土壤和有机质C、N、P含量。2）氮、磷肥的输入显著降低了土壤和小麦C：N、N：P，施P显著降低了有机态C：P和小麦C：P；有机肥配施对微生物生物量和小麦C：N：P的影响更为明显。3）长期有机肥配施条件下土壤养分和小麦化学计量比存在较强的相关关系。微生物生物量碳与有机C、N、P呈显著正相关，土壤微生物生物量氮与土壤N、P总量呈显著正相关，微生物生物量磷与土壤C、N、P总量含量呈显著负相关；植株碳含量与微生物生物量氮呈显著正相关，植物磷含量与土壤有机磷呈显著正相关。黄土区农田生态系统土壤TC：TP与TC：TN，TN：TP呈正相关，土壤TN：TP与有机碳和有机磷比呈正相关，植物植株C：N与BC：BP、BN：BP呈正相关。长期施肥明显改变了土壤和植物C、N、P含量及化学计量比。氮肥配施有机肥可明显提高微生物对土壤碳素的转化分解，导致有机质和微生物量的化学计量比发生变化，进而提高作物对土壤碳素的固定能力，增强植株对外源养分的输入。;To explore the effects of different fertilization systems on carbon, nitrogen and phosphorus contents and ecological stoichiometric ratio of farmland soil and plant ecosystem in a long time can provide reference for revealing the energy balance and nutrient cycle of the system and realizing the balance and sustainable development of agricultural ecosystem elements. In this study, the long-term fertilization experiment at the Loess Plateau agricultural ecology experimental station of Changwu, located in the semi-arid region of the Loess Plateau, was taken as the research object. No fertilization (CK), single application of nitrogen (N), single application of phosphate (P), single application of nitrogen and phosphate (NP), single application of organic fertilizer (M), combined application of nitrogen and organic fertilizer (NM),application of phosphate and organic fertilizer(PM), and combined application of nitrogen and phosphate and organic fertillizer were selected. The contents of C, N and P in soil, microbe and plant in typical agricultural ecosystem of the Loess Plateau were analyzed, and the change rule of stoichiometry and its influencing factors were analyzed. The results showed that:(I) compared with CK, long-term single application of organic fertilizer and fertilizer combined with organic fertilizer treatment could significantly improve the carbon, nitrogen and phosphorus content of soil and organic matter. (II) With the input of exogenous nitrogen and phosphate fertilizer, compared with CK treatment, N and P treatment significantly reduced soil and wheat C:N and N:P, respectively, and P treatment significantly reduced organic matter and wheat C:P. However, the effect of organic fertilizer combination on microbial biomass and wheat C:N:P was more obvious. (III) There was a significant correlation between soil nutrients and the stoichiometric ratio of wheat under the condition of long-term organic fertilizer application, compared with no fertilization. The results showed that long-term fertilization significantly changed soil carbon, nitrogen and phosphorus contents and stoichiometric ratio, and fertilizer combined with organic fertilizer could significantly improve soil fertility in the xeroxic farmland of loess, resulting in the change of stoichiometric ratio of organic matter and microbial biomass, which had a significant impact on the stoichiometric ratio of wheat plants.

Effect of Different Agricultural Farming Practices on Microbial Biomass and Enzyme Activities of Celery Growing Field Soil.

Soil quality is directly affected by alterations in its microbiological, biological, biochemical, physical, and chemical aspects. The microbiological activities of soil can affect soil fertility and plant growth because it can speed up the cycling of nutrients, enzymes, and hormones that are needed by plants for proper growth and development. The use of different agricultural management practices can influence microbial biomass and enzyme activities by altering soil microclimate, soil microorganism habitat, and nutrient cycling. Based on this, the present work planned to evaluate the impact of conventional, low-input, and organic farming systems in a vegetable field growing celery on microbial biomass and different soil enzyme activities. The present study showed a comparison of the effect of different practices on biological soil quality indicators during two sampling times, i.e., one month after colonization and one month before harvesting. It was observed that the soil microbial biomass in the organic farming system was significantly higher than that found in conventional and low-input practices. Under an organic farming system, the soil microbial biomass in December was significantly higher than that in October. The soil microbial biomass carbon in the 0–20 cm soil layer showed higher variation compared to that in the 20–40 cm layer for all the three of the farming management practices that were used in the study. Additionally, the soil total carbon and total organic carbon were recorded as being higher in the December samples than they were in the October samples. Under all the three of the management practices that were applied, the soil catalase activity was higher in the October samples than it was in the December soil samples that were collected the from 20–40 cm soil layer compared to those that were taken from the 0–20 cm layer. The application of organic fertilizer (chicken and cowmanure compost) resulted inincreases in the soil urease and in the protease activity. The protease activity of the soil samples that were extracted from the 0–20 cm and 20–40 cm soil layers in October was higher in the samples that were taken from farms using conventional practices than it was in the samples that were taken from farms using organic and low-input practices, while the samples that were collected during December from both of the soil layers showed higher protease activity when organic methods had been used. No significant variation in the soil urease activity was observed between the two soil layer samples. Urease activity was the highest when organic management practices were being used, followed by the low-input and the conventional modes. For the conventional and low-input practices, the soil urease activity showed an obvious trend of change that was related to thetime of sampling, i.e., activity in December was significantly higher than activity in October. The novelty of this study was to determine the microbial biomass carbon and enzymatic activity in a six-field crop rotation (tomato, cucumber, celery, fennel, cauliflower, and eggplant) using three management practices: low-input, conventional, and organic systems. The present study showed that the long-term application of organic fertilizers plays a large role in maintaining excellent microbial and enzyme activitythat result in improved soil quality.

Effect of long-term application of organic fertilizers on improving organic matter quality in acid soil

ABSTRACT Soil organic carbon (SOC) content can greatly affect soil quality by determining and maintaining important soil functions. The study examined SOC, humic substances and molecular composition characteristics of acid soil (Dystric Retisol) with different long term (54 years) fertilization in Western Lithuania. Farmyard manure (FYM 60 t ha−1) and alternative organic fertilizers (wheat straw, green mass of lupine and oats, rape stubble and straw) applied on the two soil backgrounds – acid and limed. The experimental design included the following treatments: 1) unlimed soil; 2) unlimed soil + FYM; 3) unlimed soil + alternative organic fertilizers; 4) limed soil (1.0 rate every 5 years); 5) limed soil + FYM; 6) limed soil + alternative organic fertilizers. The result indicates that application of organic fertilizers exerted a significant positive effect on SOC accumulation (0.1–0.4% more carbon than the control). The combination of soil liming and FYM resulted in the accumulation of valuable humic acids. The higher amount of humic acids (0.67% of C) was maintained under FYM applied plots. The application of organic fertilizers and liming exerted the transformation of carbon compounds changes in the direction of polymerization of humic acids, which creates more favourable conditions for carbon sequestration.

The response of agronomic characters and rice yield to organic fertilization in subtropical China: A three-level meta-analysis

Organic fertilizer plays a critical role in developing sustainable cropping systems due to its positive impacts on soil fertility, crop productivity, and environmental sustainability. Yet, a systematic and quantitative analysis on how organic fertilization affects soil physicochemical properties, nutrient uptake and physiological use efficiency, agronomic characteristics, yield, and yield components of rice (Orzya sativa L.) is lacking. In this study, a synthesized three-level meta-analysis from 74 peer-reviewed papers which concentrated on rice production with organic fertilizer application at 85 sites in subtropical China was conducted to investigate how organic manure affects soil fertility and rice productivity. The results showed that organic fertilization significantly increased soil organic carbon (SOC) by 15.6 %, and available nutrients varied from 2.3%–20.2%. Moreover, organic fertilization significantly increased leaf area index, content of chlorophyll, and total biomass accumulation at grain-filling and ripening stages, which was favorable to the promotion of grain filling. Overall, organic fertilization significantly increased rice yield by 8.3 %, which was attributed to the higher nutrient uptake and physiological use efficiency. In addition, the response of rice yield was various under different subcategories. The magnitude of the increase in rice yield was the greatest under the treatment with animal manure (10.5 %), followed by biochar (8.3 %) and crop straw (7.2 %) due to the higher SOC sequestration and nitrogen use efficiency with animal manure incorporation compared with biochar and crop straw amendment. In addition, organic fertilization was most effective at improving the rice yield when the content of SOC was <10 g kg−1, indicating that it was an effective way to improve the crop production of infertile soil. The response of rice yield to organic fertilization increased as the experimental duration increased, which was of great significance as the rice yield could be improved through long-term application of organic fertilizer. The results of the present study indicated that organic fertilization is an effective practice for rice production in subtropical China.

Effects of different fertilization managements on microbial necromass and plant lignin accumulation in a Mollisol

Fertilization is an effective management to maintain and increase soil organic carbon (SOC) level in agroecosystems. Both microbial metabolism and plant component retention control SOC sequestration. Here, we used amino sugars and lignin as biomarkers to investigate the responses of distribution of microbial necromass and plant debris in a long-term cultivated soil (30 years) and SOC accumulation to different fertilization regime. The results showed that, compared with unfertilized treatment, inorganic fertilizer application (N fertilizer-only or the combination of organic or inorganic fertilizers) increased crop production and soil amino sugar accumulation, but did not affect the concentrations of lignin and SOC, indicating that inorganic fertilizer stimulated the assimilation of microbial substrate and accelerated the turnover of SOC and lignin in the plough layer. Compared with inorganic fertilizer treatment, long-term organic fertilizer application promoted SOC accumulation (38.3%), but did not affect amino sugar concentration in SOC, which indicated that soil could reach a 'saturation' state with respect to microbial residue accumulation. In contrast, the application of organic fertilizer increased the proportion of lignin in SOC,indicating that the contribution of plant residues to SOC persistence was enhanced. Compared with the manure-only treatment, organic-inorganic combined application mainly increased the contribution of amino sugar to SOC accumulation. Our findings indicated that long-term fertilization could affect SOC dynamics through modulating the accumulation processes of microbial necromass and plant debris.

Manure application increased crop yields by promoting nitrogen use efficiency in the soils of 40-year soybean-maize rotation

It is great of importance to better understand the effects of the long-term fertilization on crop yields, soil properties and nitrogen (N) use efficiency in a rotation cropping cultivation system under the conditions of frequent soil disturbance. Therefore, a long-term field experiment of 40 years under soybean-maize rotation was performed in a brown soil to investigate the effects of inorganic and organic fertilizers on crop yields, soil properties and nitrogen use efficiency. Equal amounts of 15N-labelled urea with 20.8% of atom were used and uniformly applied into the micro-plots of the treatments with N, NPK, M1NPK, M2NPK before soybean sowing, respectively. Analyses showed that a total of 18.3–32.5% of applied N fertilizer was taken up by crops in the first soybean growing season, and that the application of manure combining with chemical fertilizer M2NPK demonstrated the highest rate of 15N recovery and increased soil organic matter (SOM) and Olsen phosphorus (Olsen P), thereby sustaining a higher crop yield and alleviating soil acidification. Data also showed that no significant difference was observed in the 15N recovery from residue N in the second maize season plant despite of showing a lower 15N recovery compared with the first soybean season. The recovery rates of 15N in soils were ranged from 38.2 to 49.7% by the end of the second cropping season, and the residuals of 15N distribution in soil layers revealed significant differences. The M2NPK treatment demonstrated the highest residual amounts of 15N, and a total of 50% residual 15N were distributed in a soil layer of 0–20 cm. Our results showed that long-term application of organic fertilizers could effectively promote N use efficiency by increasing SOM and improving soil fertility, and thus leading to an increase in crop yields. This study will provide a scientific reference and guidance for improving soil sustainable productivity by manure application.

Influence of Long-Term Application of Organic Fertilization on the Effects of DCD in Brown Soil

Nitrification (DCD) inhibitor has been proved to be effective in retarding nitrification process of nitrogen in the soil. Application of nitrification inhibitors to the field is considered to be a major method in controlling nonpoint pollution induced by nitrogen fertilizer in agricultural production. Thus a simulating experiment was carried out to study the Influence of long-term application of organic fertilization on the effects of different concentrations of Dicyandiamide in brown soil, and the best application rate was screened to provide references for agricultural practice. Soil samples (0-20cm) were taken from two treatments in October 2017: (1) no fertilization (CK); (2) pig manure input (M). The samples were sieved while still fresh and incubated at a constant temperature (25°C) and soil moisture in different treatments remained 60 percent of field water capacity for 42 days with periodic subsamplings. The experiment included unfertilized control, soil appended with urea nitrogen of 0.4g/kg alone, soil appended with urea nitrogen of 0.4g/kg and 1%DCD, soil appended with urea nitrogen of 0.4g/kg and 2%DCD and soil appended with urea nitrogen of 0.4g/kg and 5%DCD (The Percents represents the percentage of DCD depended on the amount of applied pure N). During the experimental period, the contents of ammonium nitrogen (NH4 +-N), nitrite nitrogen (NO3 --N), pH and nitrification potential were measured. Results of laboratory incubations indicated that DCD effectively inhibited the transformation from ammonium nitrogen to nitrate nitrogen in brown soil and the trends were N+5%DCD > N+2%DCD > N+1%DCD>N. It was found that nitrification was always greater in long-term application of organic fertilizer soil than in long-term unfertilized soil. Long-term application of organic fertilizer reduced the inhibitory effect of DCD.