Long-term Fertilizer Application Research Articles

Long term combined fertilization and soil aggregate size on the denitrification and community of denitrifiers

Balanced fertilization strategies that combine the use of organic and inorganic fertilizers have been adopted to increase soil fertility and crop yield and to safeguard environment. However, knowledge on the influence of these fertilization strategies on microbe-mediated nitrogen cycling in the agricultural ecosystems remains limited. We analyzed the denitrifiers with nitrite reductase genes (nirK and nirS) in three soil aggregate classes (large macroaggregates, >2 mm; small macroaggregates, 0.25–2 mm; and microaggregates, <0.25 mm) in response to long-term application of inorganic fertilizers (NPK), NPK plus straw (NPKS), and NPK plus manure (NPKM) in the fluvo-aquic soil of North China Plain. Both fertilization and aggregate size had significant effects on the nirK and nirS gene abundances and soil potential denitrification activity (PDA). PDA in the combined fertilizer-treated soils (NPKS and NPKM treatments) was two times more than that in inorganic NPK-treated soil. PDA dramatically increased in small macroaggregates and microaggregates of NPKS treatment. The nirS gene abundance was significantly higher than that of the nirK gene abundance, and NPKS and NPKM treatments increased the nirS to nirK ratio in bulk soils and in microaggregates compared with NPK treatment and control. Correlation analysis and automatic linear modeling revealed a primary correlation between PDA and abundance of nirS-type denitrifiers. Soil properties, such as SOC, pH and TN, significantly affected the community structure of nirK- and nirS-type denitrifiers while only aggregate size significantly influenced the composition of nirK-type denitrifiers. Taken together, our results suggest that long-term combined fertilization increased the denitrification potential in small macroaggregate and microaggregate classes, and the increased gene abundance and the shift community structures of nirS- and nirK-type denitrifiers were potentially responsible for an increase in the promoted denitrification.

Long-term Use of Balanced and Integrated Nutrient Management Improved Soil Aggregation and Carbon Stabilization in a Maize-wheat Cropping Sequence

Sustainable nutrient management practices have the potential to enhance carbon (C) storage capacity of agricultural soils that may help offset increasing atmospheric CO2 concentration. Nutrient management practices on long-term basis differentially influence aggregates and distribution of soil organic C (SOC) present within aggregates, which in time may affect C stabilization. The present study assessed the impact of long-term application of fertilizers for 44 years either alone or integration with farmyard manure (FYM) on bulk density, SOC and C pools, potassium permanganate oxidizable C (KMnO4), aggregate stability and distribution of C fractions within different size aggregate under maize-wheat cropping sequence. The application of 100%NPK+FYM significantly (P&lt; 0.05) improved soil aggregation and mean weight diameter (MWD). The percent of macro-aggregates (MacroA) and meso-aggregates (MesoA) was maximum in 100%NPK+FYM followed by NPK and the minimum in the control treatment. Irrespective of aggregate classes, TOC (g kg-1 aggregate) was maximum in 100%NPK+FYM treatment with an average of 8.42 g kg-1 aggregate as compared to control (5.05 g kg-1 aggregate). If averaged across the treatments, TOC concentration in aggregates followed the order MacroA&gt; MesoA&gt;MicroA. Correspondingly, results for KMnO4-C were similar in different treatments and aggregate classes. Application of FYM with inorganic fertilizers (NPK) or NPK showed a significant increase in all oxidizable organic C fractions particularly recalcitrant C fraction, which reflects the stable nature of OC as compared to very labile and labile C fractions. In general, C present in mineral fraction and large-sized aggregates (MacroA) has higher recalcitrant fractions of SOC as compared to small-sized aggregates (MesoF and MicroF). The study concluded that long-term balanced and integrated nutrient management improved soil aggregation, C distribution within aggregates, and C storage capacity of soils under maize-wheat. Carbon associated with macro aggregate and a mineral fraction has more recalcitrant C fraction compared to meso and micro aggregate fractions.

Effect of long-term application of inorganic fertilizers, farm yard manure and lime on wheat (Triticum aestivum L.) productivity, quality and nutrient content in an acid alfisol

The effect of long-term addition of fertilizers and amendments on productivity, quality and nutrient content of wheat (Triticum aestivum L.) in an acid Alfisol was evaluated in field experiment at the research farm of the Department of Soil Science, Chaudhary Sarwan Kumar Himachal Pradesh Krishi Vishvavidyalaya (CSKHPKV) Palampur, Himachal Pradesh (India). The Long-Term Fertilizer Experiment was initiated during 1972 in randomized block design (RBD) with 11 treatments which were replicated three times. The soil of the experimental area was silt loam and classified taxonomically as “Typic Hapludalf”. The highest productivity of wheat (2822 kg ha−1) was recorded in the treatment comprising the recommended dose of fertilizer along with farmyard manure (FYM) @ 10t ha−1 and was statistically comparable with 100% NPK + lime (2589 kg ha−1). Continuous application of nitrogen (N) alone through urea (100%) in an acid alfisol has resulted in zero yield of wheat. Application of FYM and lime along with recommended doses of fertilizers improved all the crop quality parameters viz. crude protein, gluten, ash, fat, fiber and carbohydrate as compared to control and imbalanced fertilization for the last 45 years led to decline in crop quality parameters. Nutrient content in wheat grain i.e., phosphorus (P), magnesium (Mg) and iron (Fe) content was also the highest in FYM amended treatment and lowest in control. Whereas, calcium (Ca) content was the highest in lime amended plot and the lowest in control.

Carbon Mineralization and Inorganic Nitrogen Pools under Terminalia chebula Retz.-Based Agroforestry System in Himalayan Foothills, India

Abstract Soil organic matter is major terrestrial pool for soil organic carbon (C) and nitrogen (N), and their decomposition is sensitive to vegetation and climate change. Integrated nutrient management (INM) deals with the combined application of chemical fertilizers and organic manures for nutritional requirement of crops and avoid the adverse effect of long-term application of chemical fertilizer on crop production and their sustainability. The present study was carried out to investigate the influence of different nutrient sources on soil C mineralization and inorganic N pools in a Terminalia chebula Retz, based on a agroforestry system. The results showed that the highest CO2 evolution was recorded in 100 percent INM and minimum in farmyard manure treatment after 120 days of incubation. Inorganic N was higher under the agroforestry system than under the open system. Among the different nutrient sources, the highest inorganic N was recorded in a 100 percent INM nutrient source and minimal in wheat straw treatment. The yield of turmeric was higher under the T. chebula-based agroforestry system (20.87 t ha–1) than under the open system (19.27 t ha–1). Results suggest that agroforestry systems using the INM approach can enhance C mineralization and inorganic N concentration with improved crop productivity in the Himalayan foothills. Study Implications: Fertilizer has been used since ancient times, and if well managed it can be an asset, promoting sustainable agriculture and increasing crop production, particularly for smallholder farmers in the Himalayan region of India. We compared fertilizer application practices under an agroforestry system in a representative Himalayan region of India. The majority of farmers in the region of the Himalayan foothills having marginal land and they are not able to produce optimum food grains for their requirement. However, their demands are increasing day by day, so to fulfill their demand, they have to adopt agroforestry. Agroforestry may be fulfilling their demand in terms of food, fuel, fodder, and other intangible benefits. Moreover, to increase the production under agroforestry, we have to apply organic and inorganic fertilizer in the soil either as the sole application or as a combination of these fertilizers. The application of these fertilizers will improve the productivity and fertility of land, especially carbon mineralization and inorganic nitrogen. These two soil properties are important to study because these are limiting to land productivity. In addition, efforts to improve integrated nutrient management in the Himalayan region of India would strengthen farmers’ incomes by strengthening land fertility and productivity. The rapid increase in human population over the last century is putting a massive pressure on existing resources, namely soil and water, resulting in environmental degradation in some regions around the world. As productive land becomes scarce, marginalized farmers are pushed into fragile croplands and forest lands unsuitable for modern agriculture which, in turn, is vulnerable, to degradation. If the present trend in population growth persists, pasture and forest lands will be further reduced (Satterthwaite et al. 2010). At this stage, the value of growing trees becomes more significant, and participation in tree planting schemes should be encouraged. However, this option is most feasible when combined with agriculture. As a result, agroforestry is an important management strategy that not only helps to meet the world food requirements but also helps to protect soil from degradation (Ram et al. 2017) and can enhance soil organic matter levels by adding the quantity of above- and below-ground organic matter inputs to soils (Nair et al. 2009, Marone et al. 2017).

Short-Term Effects of Eco-Friendly Fertilizers on a Soil Bacterial Community in the Topsoil and Rhizosphere of an Irrigated Agroecosystem

Fertilizer application to arable soils could be effective for soil nutrients. However, there are many negative effects in croplands with long-term chemical fertilizer application. Whether eco-friendly fertilizer addition could enhance soil quality and soil microbial activity has been investigated before; however, how top- and rhizosphere soil bacterial communities respond to their short-term effects is not well known. Here, we used Illumina MiSeq sequencing to determine the changes of bacterial community structure in both topsoil and rhizoshpere after one month of the addition of three different eco-friendly fertilizers—biochar (B), microbial fertilizer (MF), fertilizer synergist (FS) and selected soil base fertilizer (CK) as a control, in an irrigated agroecosystem of cabbage crop (Brassica oleracea L. var. capitata L.). The results show that three different eco-friendly fertilizers significantly enhanced cabbage growth. The Shannon and Ace indexes of the bacterial community significantly decreased under the FS treatment in both soils, but the total abundance of bacteria was maximal under the FS treatment in the topsoil and the MF treatment in the rhizosphere. The addition of the three fertilizers led to significant differences in the relative abundance of bacteria community at the phylum level, such as Proteobacteria, Acidobacteria, Rokubacteria and Planctomycetes in the topsoil, and Chloroflexi, Actinobacteria, Firmicutes and Rokubacteria in the rhizosphere. The same phylum showed the inconsistent changes under different fertilizer treatments in both topsoil and rhizosphere. The dominant genera, i.e., Nitrosospira and Massilia in the topsoil, and Flavobacterium, Nitrosospira and Pseudomonas in the rhizosphere, were much higher under the FS treatment than others. Redundancy analysis showed that total nitrogen and available phosphorus were the key factors that shaped the bacterial community in this ecosystem. These results highlighted that the short-term addition of eco-friendly fertilizer had an improvement effect on the quality of both topsoil and rhizosphere in croplands with long-term chemical fertilizer 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.

Accumulation of potentially toxic elements in agricultural soil and scenario analysis of cadmium inputs by fertilization: A case study in Quzhou county

Fertilizer application has greatly increased crop yield, however impurities in mineral or organic fertilizers, such as heavy metals, are being added to agricultural soils, which would pose a high risk for soil and crop production. 115 soil samples were collected from Quzhou, a typical agricultural county in the North China Plain, to investigate the total content of cadmium (Cd), arsenic (As), lead (Pb), nickel (Ni), copper (Cu), zinc (Zn) and chromium (Cr) in soils. The contamination levels and source apportionment of studied elements were explored by the pollution indices, multivariate statistical approaches and geostatistical analysis. The ranges of Cd, As, Pb, Ni, Cu, Zn and Cr were between 0.08 and 0.35, 5.34–15.9, 7.34–38.9, 12.9–61.3, 7.80–27.0, 31.4–154, and 17.0–50.5 mg/kg and with the mean values 0.16, 9.20, 16.0, 24.7, 17.6, 61.1, and 29.5 mg/kg, respectively. The studied area was slightly polluted mainly by Cd, and higher pollution was found in soils under vegetable crops. The application of mineral phosphate fertilizer and livestock manure were the main source of Cd and Zn, and other elements (As, Pb, Ni and Cu) might originate from soil parent materials. Scenario analyses were performed using the R programming language, based on the cadmium contents in mineral phosphate fertilizers and livestock manures. The results showed that the long-term application of phosphate fertilizers would lead to some Cd enrichment in soil without risk of substantial pollution. Compared to pure mineral fertilizers, the long-term application of blended fertilizers (30% livestock manures and 70% phosphate fertilizers) or livestock manures would incur a higher Cd pollution risk within a short period, with a maximum probability of Cd risk of 55.21%. Mitigation measurements and scientific agronomic practices should be developed to minimize the risk of potential toxic elements in agricultural soil.

Effect of long-term organic amendments on the full-range soil water retention characteristics of a Vertisol

Enhancement of soil water holding capability is of great interest for the management of agro-ecosystems to increase water use efficiency and crop yields. Application of organic amendments has been reported to affect the wet range of the soil water retention characteristic (SWRC, pF ≤ 4.2) differently and knowledge of the impact on the dry range of the SWRC (pF > 4.2) is limited. In this study, we evaluated the effect of 33 years application of inorganic fertilizer and organic amendments, including wheat straw, cow and pig manure on the full range of the SWRC of a Vertisol. Results showed that long-term application of inorganic fertilizer did not significantly affect soil water retention. The addition of organic amendments, i.e. wheat straw, pig or cow manure in combination with inorganic fertilizer significantly increased the wet range of the soil water retention, which was attributed to improved soil structure by increased SOC content. However, plant available water content was not significantly improved by organic amendments. Application of organic amendments decreased or had no effect on soil water retention at pF > 5.5, indicating the hygroscopic water was less impacted by SOC content. Our results showed that the effects of organic amendments mainly improved the retention of the capillary water but not the adsorption of hygroscopic water. This provides new insights on the understanding of water behaviors in Vertisols.

Soil Chemical and Microbiological Properties Are Changed by Long-Term Chemical Fertilizers That Limit Ecosystem Functioning.

Although the effects of fertilization and microbiota on plant growth have been widely studied, our understanding of the chemical fertilizers to alter soil chemical and microbiological properties in woody plants is still limited. The aim of the present study is to investigate the impact of long-term application of chemical fertilizers on chemical and microbiological properties of root-associated soils of walnut trees. The results show that soil organic matter (OM), pHkcl, total nitrogen (TN), nitrate-nitrogen (NO3−), and total phosphorus (TP) contents were significantly higher in non-fertilized soil than after chemical fertilization. The long-term fertilization led to excessive ammonium-nitrogen (NH4+) and available phosphorus (AP) residues in the cultivated soil, among which NH4+ resulted in soil acidification and changes in bacterial community structure, while AP reduced fungal diversity. The naturally grown walnut trees led to an enrichment in beneficial bacteria such as Burkholderia, Nitrospira, Pseudomonas, and Candidatus_Solibacter, as well as fungi, including Trichoderma, Lophiostoma, Phomopsis, Ilyonectria, Purpureocillium, Cylindrocladiella, Hyalorbilia, Chaetomium, and Trichoglossum. The presence of these bacterial and fungal genera that have been associated with nutrient mobilization and plant growth was likely related to the higher soil OM, TN, NO3−, and TP contents in the non-fertilized plots. These findings highlight that reduced chemical fertilizers and organic cultivation with beneficial microbiota could be used to improve economic efficiency and benefit the environment in sustainable agriculture.

Effect of Organic Matter Promotion on Nitrogen-Cycling Genes and Functional Microorganisms in Acidic Red Soils

The application of exogenous organic matter is considered the main method of increasing the organic matter content of acidic red soils. Nitrogen is an important limiting factor for soil fertility. Changes to the soil ecosystem under organic matter promotion can affect soil nitrogen cycling and related functional microorganisms; however, there have been no studies on this aspect. Acidic upland red soils, with or without long-term organic fertilizer application, were chosen as the research materials in this study. Based on metagenomic sequencing and alignment in the nitrogen-cycling gene database, the present study aimed to investigate the effect of organic matter promotion on nitrogen-cycling genes and functional microorganisms in acidic red soils, which had been amended with exogenous organic matter for 32 years. The results showed that organic matter promotion in acidic soils increased the total organic carbon and total nitrogen content, and alleviated soil acidification. Organic matter promotion increased the soil net nitrification activity and potential for ammoxidation. Organic matter promotion increased the abundance of amoA genes (encoding ammonia monooxygenase) and nar, nap, nir, nor, and nos genes (encoding denitrification reductase); decreased the abundance of hao genes (encoding hydroxylamine oxidase) and nrf genes related to the dissimilatory nitrate reduction to ammonia; increased the abundance of glnA, gdh, glsA, ansB, and nao genes related to organic nitrogen metabolism; altered the abundance of functional genes related to assimilatory nitrate reduction; and changed the community composition of nitrogen-cycling microorganisms. After organic matter promotion, alleviation of soil acidification and enhancement of total organic carbon were the most important factors that affected the abundance of nitrogen-cycling genes and the community composition of functional microorganisms. Our results comprehensively investigated the inorganic and organic nitrogen-cycling genes, and correlated the functional genes, microbial populations, and functional activities in the ammonia oxidizing process, which provided supporting data to understand the nitrogen-cycling characteristics of acidic red soils and provided ideas for acidic soil improvement.

High manure load reduces bacterial diversity and network complexity in a paddy soil under crop rotations

Long-term application of chemical fertilizers causes soil degradation and nitrogen (N) loss, but these effects could be alleviated by organic fertilizers. In addition, crop rotation is a feasible practice to increase soil fertility, soil quality and crop yields comparing with monocultural cropping patterns. However, questions remain concerning how the soil microbiome responds to different manure application rates under crop rotations. Here, we collected soil samples from a rice-rape system to investigate the response of the soil microbiome to nine years of pig manure application at different rates (CK: 0 kg ha-1, M1: 1930 kg ha-1, M2: 3860 kg ha-1 and M3: 5790 kg ha-1). Our results revealed that the bacterial α-diversity (Chao1 and Shannon index) in the rape season increased first and then decreased with increasing manure application rates, and a high manure load tended to decrease the bacterial α-diversity in the rice season. Long-term manure application enriched some copiotrophic bacteria, such as Proteobacteria and Actinobacteria, while it decreased the relative abundance of Nitrospirae. Redundancy analysis (RDA) and the Mantel test indicated that soil pH, TC, TN, AP, C/P and N/P ratios were the main factors influencing bacterial communities. Moreover, network analysis showed that a low manure application rate shaped a complexly connected and stable bacterial community, while higher manure application rate decreased the stability of the bacterial network. These findings improve our understanding of bacterial responses to longterm manure application under crop rotations and their relationships with soil factors, especially in the context of increasing fertilizer inputs.

Поживний режим чорнозему вилугуваного та продуктивність зернової ланки за тривалого удобрення сівозміни

Goal. To study the effect of legumes predecessors and doses of nitrogen fertilizers on the nutritive regime of leached chernozem in agrocenose of winter wheat as well as grain chain productivity at long-term (over 50 years) application of different systems of organomineral fertilizing in conventional and alternative crop rotations. Methods. Long-term field and analytical. Results. Changes were fixed of the nutrient status of leached chernozem in agrocenose of winter wheat and productivity of grain link at the long-term application of organic and mineral fertilizers in crop rotation, as well as at introduction of different doses of nitrogen fertilizers under winter wheat, and its further cultivation after different legumes predecessors. The data were got concerning the content of mobile forms of nutrients in leached chernozem and their impact on the productivity of grain link. It was established that the fund of mineral nitrogen in soil depended mainly on the doses of nitrogen fertilizers which were entered under winter wheat, as well as on the legumes predecessor. The reserves of mobile phosphorus and potassium in leached chernozem depended on the duration and background of organic and mineral fertilizers which were used in crop rotation. Conclusions. The best conditions of the nitric mode of leached chernozem in agrocenose of winter wheat were formed for its cultivation after clover with the use of mineral fertilizers in the dose of N60P60K60. Fund of mobile phosphorus in the soil in agrocenose of winter wheat was formed mainly due to long-term (over 50 years) application of organic and mineral fertilizers in crop rotation. An annual application of 64 kg pf phosphorus (N43P43K43 + 8,3 t of manure for 1 ha of the area of crop rotation) with fertilizers (for 1 ha of crop rotation) had formed a high level of availability of soil phosphorus in the range of 309–323 mg/kg. That exceeded the control without fertilizer on 133–138 mg/kg of soil. Such a fertilizing system stabilized in crop rotation the content of mobile potassium in the soil at the level of 102–123 mg/kg. That corresponded to the average level of benefit and exceeded the control without fertilizers on 29–43 mg/kg of soil. The highest productivity of the grain crop rotation was achieved at the use of clover as the predecessor and long-term (50 years) entering of N43P43K43 + 8,3 tons of manure (or by-products) per 1 ha of crop rotation: yield of fodder units — 8.02 t/ha, the yield of grain — 3,33 t/ha of the link of crop rotation.

Effect of long term application of fertilizers on soil nutrient status in groundnut (Arachis hypogaea L)

An experiment was conducted in long term fertilizer experiments (initiated in 1981) plot with groundnut as testcrop to study the soil nutrient availability at harvest of groundnut. There were 11 treatments arranged in RBD with four replications. The highest value of available N (87 kg/ha) was recorded in treatment T10 [NPK + lime (100 kg/ha) at flowering]. Depletion of available P was seen in seven treatments when compared with initial P (47.6 P2O5 kg/ha). Available K content of the soil decreased in all the treatments as compared with the initial status (216 K2O kg/ha).

Health risk assessment associated with heavy metal accumulation in wheat after long-term phosphorus fertilizer application

Phosphorus (P) fertilizer is widely used to increase wheat yield. However, it remains unclear whether prolonged intake of wheat grain that received long-term P application may promote human health risks by influencing heavy metal(loid)s (HMs) accumulation. A 10-year field experiment was conducted to evaluate the effects of continuous P application (0, 25, 50, 100, 200, and 400 kg P ha−1) on human health risks of HMs, including zinc (Zn), copper (Cu), cadmium (Cd), lead (Pb), arsenic (As), nickel (Ni), and chromium (Cr), by ingesting wheat grain. The results showed that P application facilitated Zn, Pb, Cd, and As accumulation in the topsoil. The Zn, Cu, Pb, and Ni concentrations in grain were decreased, while Cd and As were increased by P application. All HMs concentrations of both soil and grain were in the ranges of corresponding safety thresholds at different P levels. The accumulation abilities of Zn, Cu, Pb, and Ni from soil and straw to grain were suppressed by P addition while of As was enhanced. There was no significant difference in the hazard index (HI) of the investigated HMs in all treatments except 25 kg ha−1. The threshold cancer risk (TCR) associated with As and Cd was enhanced, while that of Pb was alleviated as P application increased. Behaviors of Cr from soil to wheat and to humans were not affected by P application. Phosphorus application at a rate of 50 kg ha−1 decreased total non-cancer and cancer risks by 15% and 21%, respectively, for both children and adults, compared to the highest value. In conclusion, long-term optimal application of 50 kg P ha−1 to wheat did not result in additional adverse effects on the total non-carcinogenic or carcinogenic risk caused by the studied HMs to humans through the ingestion of wheat grain.

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Corn response to long-term manure and fertilizer applications on a preceding perennial forage crop

Abstract Removing solids from dairy slurry improves grass N response and reduces soil loading of P and organic N which makes this practice useful for sustainable farming. Therefore, it is important to understand the effects of long-term applications on grass of separated dairy slurry on the growth and N response of a subsequent corn crop. This two-year field study investigated the residual effects after 11 years with applications on a perennial grass (Festuca arundinacea Schreb.) of whole (WS), separated dairy slurry (LF) obtained from the second stage of a two stage lagoon system, mineral fertilizer (Fert), WS plus Fert (WS/Fert), and Control (no fertilizer), on two subsequent crops of silage corn (Zea mays L.). In addition to the legacy nutrients, the corn received commercial fertilizer at rates 0, 100, 200 kg N ha–1 or 200 kg N ha–1 plus starter P (40 kg ha–1) at time of planting. Whole-crop yield and N uptake were determined at harvest stage. Over two years, corn yielded more with greater N and P uptake after long-term applications of WS than LF, Fert and WS/Fert, regardless of current fertilizer applications. Additional mineral fertilizer N and P did not substitute for the historical effects. There was a significant linear relationship of corn N uptake with historical applications of organic-N but not with mineral-N or total-N across current fertilizer treatments. These results support farmer practice of supplementing first-year corn, after long-term manure application on grassland, with modest N and P as starter application only and then increasing N rates thereafter.

Soil nutrients and heavy metal availability under long-term combined application of swine manure and synthetic fertilizers in acidic paddy soil

Fertilization is a vital approach to increase the crop yield by enhancing soil fertility, but some of the fertilizer sources such as pig manure contain non-essential toxic heavy metals, which can produce the environmental and public health risk. Therefore, the purpose of this study was to investigate the soil fertility and heavy metal pollution risk under long-term fertilization in acidic paddy soil. Fertilizer treatments that were arranged in randomized complete block design (RCBD) included CK (no fertilization), NK (inorganic nitrogen and potassium fertilization), NPK (inorganic NK and phosphorus fertilization), NPKM1 (70% of NPK and 30% pig manure application), NPKM2 (50% of NPK and 50% of pig manure application), and NPKM3 (30% of NPK and 70% of pig manure application). The rice grain yield and soil nutrient contents were highest under NPKM3 treatment. Long-term addition of manure significantly (P ≤ 0.05) increased soil pH and SOC content compared to the NPK fertilization. Soil available and total Cr, Cd, and Hg contents were highest under NPKM3 treatments, while soil total and available Pb content was significantly (P ≤ 0.05) higher under NPK treatment. Highest ecological risk (IR) was (1904) under NPK treatment and highest pollution load index (PLI) was 1.5 under NPKM3 treatment. Cd concentration in rice grain exceeded the maximum permissible limit of 0.1 mg kg−1 under combined application of manure and inorganic fertilization treatments. Grain Cr, Hg, and Pb contents were within safe limits of their concentration in all treatments. Moreover, biological accumulation coefficients of Cr, Cd, Hg, Pb, Zn, and Cu were highest under NPK treatment. Redundancy analysis (RDA) showed that soil pH and nutrient contents showed significant correlation with heavy metal concentrations in soil. Soil pH showed significant (P ≤ 0.05) positive effect on Cd accumulation in rice grain. Heavy metals in pig manure should be monitored before application to the field to reduce the risk of heavy metal pollution in soil and plant. Furthermore, combined application at the rate of 70% inorganic fertilization and 30% of manure could be better strategy to produce high crop yield with minimum risk of heavy metal contamination in soil and food crops.

Discrimination of soil productivity and fertilizer-nitrogen use efficiency in the paddy field of subtropical China after 27 years different fertilizations

ABSTRACT To select optimal fertilization management for soil productivity and fertilizer-nitrogen use efficiency (NUE) improvement in rice fields, we conducted a microplot experiment by growing rice in soils from different long-term fertilizations with the same inorganic fertilizers. The NUE was accurately evaluated using 15N labeled urea. The variations of the chemical compositions of soil organic carbon (SOC) under different long-term fertilizations were investigated by three-dimensional fluorescence measurement. The results indicated that the treatments containing organic materials could maintain high soil productivities and displayed higher NUE than inorganic treatments. Total phosphorus (TP) was the most important soil factor for soil productivity and the SOC content ranked second, whereas SOC content was the primary soil factor affecting NUE and TP ranked second. Applying organic materials also significantly changed the chemical compositions of SOC as compared with inorganic treatments. Besides the SOC content, the chemical compositions of SOC also affect the soil productivity and NUE. In summary, long-term balanced application of inorganic fertilizers and organic materials increased the quantity and changed the chemical composition of SOC, and thus maintained high soil productivity and NUE.

Fifteen-Year Application of Manure and Chemical Fertilizers Differently Impacts Soil ARGs and Microbial Community Structure.

Manure, which contains large amounts of antibiotics and antibiotic resistance genes (ARGs), is widely used in agricultural soils and may lead to the evolution and dispersal of ARGs in the soil environment. In the present study, soils that received manure or chemical fertilizers for 15 years were sampled on the North China Plain (NCP), which is one of the primary areas of intensive agriculture in China. High-throughput quantitative PCR and sequencing technologies were employed to assess the effects of long-term manure or chemical fertilizer application on the distribution of ARGs and microbial communities. A total of 114 unique ARGs were successfully amplified from all soil samples. Manure application markedly increased the relative abundance and detectable numbers of ARGs, with up to 0.23 copies/16S rRNA gene and 81 unique ARGs. The increased abundance of ARGs in manure-fertilized soil was mainly due to the manure increasing the abundance of indigenous soil ARGs. In contrast, chemical fertilizers only moderately affected the diversity of ARGs and had no significant effect on the relative abundance of the total ARGs. In addition, manure application increased the abundance of mobile genetic elements (MGEs), which were significantly and positively correlated with most types of ARGs, indicating that horizontal gene transfer via MGEs may play an important role in the spread of ARGs. Furthermore, the application of manure and chemical fertilizers significantly affected microbial community structure, and variation partitioning analysis showed that microbial community shifts represented the major driver shaping the antibiotic resistome. Taken together, our results provide insight into the long-term effects of manure and chemical fertilization on the dissemination of ARGs in intensive agricultural ecosystems.

Combined Application of Organic and Inorganic Nitrogen Fertilizers Affects Soil Prokaryotic Communities Compositions

As a fundamental part of the soil ecosystem, prokaryotes are involved in the preservation of soil functions. However, little is known of how the combined application of long-term organic and inorganic nitrogen fertilizer affects the prokaryotic communities’ dynamics at a paddy field. A long-term positioning experiment initiated in 2013 with four treatments (NO: no N fertilizer, CN: 100% urea N with no organic fertilizer, PM: 80% urea N plus 20% N with pig manure, CM: 80% urea N plus 20% N with compost) were applied to detect the differential responses of soil physicochemical properties, and prokaryotic community structure and composition in different fertilization regimes. The results indicated that the long-term combined application of organic and inorganic nitrogen fertilizers altered the physicochemical properties to some extent and, simultaneously, established unique prokaryotic communities. In detail, the treatment of PM and CM significantly increased the content of soil organic carbon (SOC) and total nitrogen (TN) compared to NO. Moreover, a total of 31 indicator taxa were screened across the four treatments by LDA Effect Size (LEfSe) analysis following the principle of the greatest differences, which suggests that these indicator taxa were more sensitive to the fertilization. This research suggested that the combined application of long-term organic and inorganic nitrogen fertilizers not only contributed to the soil’s physicochemical properties but also changed the prokaryotic community composition.