NPK Treatment Research Articles

Mobilization of grassland soil arsenic stores due to agronomic management

The fate of arsenic in mineral soil stores over time is poorly understood. Here we examined arsenic loss over five decades from a managed grassland soil profile through analysing archived material from a long-term slurry (LTS) experiment at Hillsborough, Northern Ireland. A randomized block experiment was established in 1970 where a perennial ryegrass sward was seeded onto the site and subjected to control (no fertilization) and fertilization treatments using conventional (i.e. at farmers recommended application rate) mineral NPK fertilizer, and pig and cow slurry treatments. Soil (0–5, 5–10 and 10–15 cm), slurry applied, and sward off-take was archived each year. A mass-balance calculation found that control soils lost no arsenic down the 15 cm depth soil profile, the NPK treatment had a 10 % loss, while cow slurry caused 25 % loss, and a 35 % loss was observed for pig slurry. For treatments with arsenic loss, removal was linear over the 50 years of study in 2 out of the 3 blocks, with the 3rd block showing little or no change. Principal Component Analysis (PCA) found that arsenic was most positively associated with soil magnesium, manganese and nickel, while negatively associated with pH, organic carbon, phosphorus and silicon. Laser ablation – inductively coupled plasma – mass spectrometry (LA-ICP-MS) of soil found that arsenic association with lead mineralogy could potentially explain why there was a gradient in arsenic loss across the experimental plots. Slurry and atmospheric inputs, and sward off-take had little impact on the soil arsenic mass-balance. The findings suggest that leaching loss down the soil profile was the mechanism of loss of arsenic. The applicability of the LTS experimental site arsenic findings to other soils is discussed, as is the implication for the global biogeochemical cycling of those soils.

A comparative assesment of biostimulants in microbiome-based ecorestoration of polycyclic aromatic hydrocarbon polluted soil.

Polycyclic aromatic hydrocarbons (PAHs) pose severe environmental and public health risks due to their harmful and persistent nature. Therefore, developing sustainable and effective methods for PAH remediation is crucial. This study explores the biostimulation potential of various nutrient supplements in enhancing the metabolic activities of indigenous oleophilic bacteria to PAH degradation and removal. The physicochemical and microbiological characterization of the soil sample obtained from the aged crude oil spill site prior to bioremediation revealed the presence of PAH and other hydrocarbons, reduced nutrient availability as well as an appreciable population of PAH degrading bacteria such as strains of Pseudomonas, Enterobacter, Kosakonia and Staphylococcus. The polluted soil treatment was conducted in six microcosms representing each nutrient supplement: casmes-CM, cocodust-CCD and osmocote-OSM slow-release fertilizers, NPK 20:10:10, casmes + cow dung - CM + CD and a control (unamended soil). Each pot contained 4kg of soil spiked with 4% Escravos crude oil to a final concentration of 989mg/kg of PAH, respectively. All treatments enhanced the activity of the indigenous bacteria to promote PAH removal (> 50%) after 35days although CM + CD had the highest biostimulation effect (B. E.) of 56% with 71.77% PAH attenuation followed by NPK treatment with B. E. of 54.9% and 70.4% PAH removal, respectively. The order of degradation of PAHs from lowest to highest is: control > casmes > osmocote > cocodust > NPK > CM + CD. First-order kinetic model revealed soil microcosm amended with CM + CD had a higher k value (0.0342day-1) and lower t½ (18.48day) and this was relatively followed by NPK treated soil. Biostimulation is an effective bioremediation approach to PAH degradation, however, a combined nutrient regimen in the presence of PAH-degrading microbes is more potent and eco-friendly in driving this process.

Configuration of pore structure and related functions in macroaggregates following long-term organic and inorganic fertilization

Fertilization practices are vital for agricultural productivity and soil health. However, the impact of long-term organic and inorganic fertilization on pore structure and related functions in paddy soil is still under-explored. In this study, macroaggregates approximately 5 mm in diameter were collected from a 20-year long-term experiment with no fertilization (CK), and those treated with chemical fertilizer (NPK), organic fertilizer (RS), and a combination of both (RS+NPK). The pore structure of these macroaggregates was examined using synchrotron radiation-based X-ray tomography, alongside a pore network model and skeleton analysis. The soil functions concerning the pore structure at the aggregate scale were assessed through their physical and topological properties. Results indicated that the pore structure of the macroaggregates responded differently to organic versus inorganic fertilization. Specifically, the application of NPK significantly reduced the connected porosity, accessibility, and network complexity within the macroaggregates, whereas the opposite effects were observed with the RS treatment. Connectivity analysis showed that the critical pores in CK, NPK, and RS+NPK treatments originated from plant roots, while those in the RS treatment were likely formed through the decomposition of rice straw. Compared to CK, the NPK treatment exhibited fewer channels with high hydraulic conductance, indicating impaired transportability of water and nutrients under saturated conditions, while the opposite was true for the RS treatments. Furthermore, skeleton analysis highlighted that the NPK treatment has fewer paths for preferential and capillary flow compared to CK, indicating reduced accessibility of air, water, and nutrients under unsaturated conditions. These findings are essential for understanding the changes in soil functions related to pore structure following organic and inorganic fertilizer applications and for optimizing fertilization strategies to preserve soil structure and health.

Effects of Nutrient Deficiency on Crop Yield and Soil Nutrients Under Winter Wheat–Summer Maize Rotation System in the North China Plain

The wheat–maize rotation system in the North China Plain (NCP) has a large amount of crop straw. However, improper crop straw management and blind fertilization lead to nutrient imbalance and accelerated nutrient loss from the soil, ultimately leading to nutrient deficiency affecting the wheat–maize rotation system. In order to explore the effects of nutrient deficiency on the yield and nutrient use efficiency of wheat and maize, the experiment was conducted in a randomized complete block design consisting of five treatments with three replicates for each treatment: (1) a potassium fertilizer deficiency and appropriate nitrogen and phosphate fertilizer treatment (NP); (2) a phosphate fertilizer deficiency and appropriate nitrogen and potassium fertilizer treatment (NK); (3) a nitrogen fertilizer deficiency and appropriate phosphate and potassium fertilizer treatment (PK); (4) an adequate nitrogen, phosphorus, and potassium fertilizer treatment (NPK); and (5) a no-fertilizer treatment (CK). The results showed that, compared with CK, the yields of wheat and maize treated with NPK were increased by 21.5% and 27.5%, respectively, and the accumulation of the dry matter of the wheat and maize was increased by 42.5% and 57.3%. In all the deficiency treatments, the NK treatment performed better in terms of yield compared to the NP and PK treatments, while the NP treatment demonstrated a greater increase in dry matter accumulation. The NPK treatment significantly improved the nitrogen use efficiency (NUE) and nitrogen harvest index (NHI) of the wheat and maize, which resulted in higher nitrogen accumulation in the NPK treatment, and the NP treatment was the best among the other nutrient deficiency treatments. The inorganic nitrogen content showed a similar trend. In conclusion, nutrient deficiency can severely restrict crop growth. Nitrogen deficiency can significantly reduce crop yields. Phosphorus deficiency had a greater impact than potassium deficiency in terms of nutrient absorption and accumulation. Therefore, nitrogen fertilizer application should be emphasized in crop rotation systems, with moderate increases in phosphorus fertilizer application. This practice can effectively improve the nutrient deficiency under the wheat and maize rotation system in the NCP and complete a rational fertilization system.

Thinned slash pine (Pinus elliottii) stand response to midrotation vegetation control and fertilization on flatwoods sites

Midrotation management including vegetation control and fertilization can improve growth and yield of southern pine stands. This study investigated the 12-year response of slash pine (Pinus elliottii), thinned at midrotation to additional treatments of herbicide, fertilization, liming (one site), and combinations of these treatments in the Coastal Plain region of Georgia, USA. There was a significant treatment x stand age interaction observed at the Ware County site for height (p<0.001), dbh (p<0.001) and individual tree green weight (p<0.001). The herbicide + NPK and herbicide treatments resulted in the most consistent growth improvements 0 to 4 years post-treatment compared to the untreated control. The lime + NPK and herbicide treatment resulted in the longest lived (4 to 12 years) significantly improved growth response. Results revealed no tested treatments improved growth during the 12-year study duration at the Wayne County site. Results from this study suggest that thinned slash pine stands with diagnostics indicating midrotation fertilization or vegetation control may be beneficial do not always respond as expected to inputs. When stands are responsive, single application midrotation treatments can offer long-term growth improvements, yet growth response can differ depending on time since application.

Effects of exogenous nitrogen addition on soil organic nitrogen fractions in different fertility soils: Result from a 15N cross-labeling experiment

Exogenous nitrogen (N) addition serves as a pivotal nutrient management strategy, significantly enhancing agricultural production by regulating soil N availability and retention. However, the dynamics of soil organic nitrogen (SON) fractions in response to various forms of exogenous N addition across differing soil fertility levels remain inadequately understood. This study utilized data from a 25-year fertilization experiment and a 15N cross-labeling experiment in Northeast China to assess and quantify the effects of mineral N fertilizers and organic materials (manure and straw) on SON fractions in NPK (mineral fertilizer addition) and NPKM (NPK combined with composted pig manure) treatments. Our findings indicate that long-term incorporation of manure substantially elevates soil fertility compared to the exclusive use of mineral fertilizers. Notably, exogenous N primarily boosts soil N availability by enhancing acid-soluble organic N fractions, particularly ammonium nitrogen (AN) and amino acid nitrogen (AAN). Organic materials, particularly straw, significantly enhanced the retention of mineral fertilizer N in both NPK and NPKM treatments (9.54 % vs 10.70 %). Moreover, over 70 % of the N from straw or manure remained in the soil as stable SON fractions. While straw rapidly improves low-fertility soils, manure contributes to enhanced soil N reserves and increased crop yields. Therefore, incorporating organic matter may bolster soil N sequestration in Northeast China, which is contingent upon soil fertility and tailored fertilizer management strategies. This research elucidates the distribution and conversion of exogenous N within SON pools, facilitating optimized N management, sustaining yields, reducing farmland N pollution, and promoting agricultural sustainability.

Evaluation of nitrogen use efficiency and N-supplying capacity on pomelo (Citrus grandis L. Osbeck) grown on alluvial soil in the Cuu Long Delta

The study was conducted to determine the nitrogen use efficiency (NUE) and the ability to provide nitrogen from alluvial soil for growing pomelo (Citrus grandis L. Osbeck) in the Mekong Delta. The experiment was arranged in a randomized complete block design including two treatments (NPK treatment: 673 N - 385 P2O5 -192 K2O g/plant and PK treatment: 0 N - 385 P2O5 - 192 K2O g/plant) and three replicates (3 plants for each replicate). The results showed that fruit yield was highest (39.1 kg/plant, N recovery efficiency of 53.8%) in the full NPK fertilization treatment and lowest in the PK fertilization treatment (18.5 kg/plant). Calculation results of the ability to supply nitrogen to pomelo trees in Chau Thanh, Hau Giang showed that alluvial soil had the ability to provide 49.6% of N and the remaining 50.4% from additional fertilizer sources for maximizing fruit yield.

Enhancing the sustainability of cowpea production through the integrated use of fish effluents and animal manure

AbstractThe integration of aquaculture and agriculture in arid and semi‐arid environments is crucial for maximizing water and land productivity, especially considering the increasing global water scarcity and the simultaneous use of water for crop and fish production. A greenhouse study was conducted to determine the effects of fish effluent on the growth, yield parameters, and yield of cowpea (Vigna unguiculata). The experiment involved 13 fertilization treatments, including three types of irrigation water (river water—control, Nile tilapia (Oreochromis niloticus), African sharp‐toothed catfish (Clarias gariepinus), four fertilizers (poultry, cattle, and sheep manures at 10 t ha−1), recommended rate of inorganic fertilizer (150 kg ha−1 of NPK 6‐20‐10), and six mixed treatments with fish effluent and 50% of the applied rate of manure alone (5 t ha−1). The combined use of C. gariepinus effluent + 50% poultry manure significantly increased stem diameter, nodules per plant, pods per plant, and seed yield compared to NPK treatments. The shortest days to reach 50% flowering were obtained with the effluent of O. niloticus + 50% sheep manure, C. gariepinus/O. niloticus + 50% poultry manure, and 10 t ha−1 poultry manure. However, fertilization treatments did not significantly influence the number of branches, pod and root length, number of pods per plant, 100‐seed weight, and leaf chlorophyll concentrations. This study suggests that fish effluents, when combined with manure, can improve plant growth and seed yield, providing a cost‐effective alternative to inorganic fertilizers for smallholder farmers.

Impacts of nitrogen (N), phosphorus (P), and potassium (K) fertilizers on maize yields, nutrient use efficiency, and soil nutrient balance: Insights from a long-term diverse NPK omission experiment in the North China Plain

Context or problemSoil nutrient deficiency is one of the significant challenges in grain production, particularly nitrogen (N), phosphorus (P), and potassium (K). These deficiencies not only reduce crop yields but also cause associated environmental issues, such as soil structure deterioration and ecosystem services diminution. ObjectivesThis research aimed to investigate the long-term effects of NPK fertilizers on soil nutrient properties and maize phenology, further on the grain yield, and to evaluate the nutrient use efficiency and soil nutrient balance under different fertilization managements. MethodsA long-term field experiment was initiated in 1990 in a summer maize field in the North China Plain, including five fertilizer treatments: CK (control), NP, NK, PK, and NPK. The soil nutrient properties, maize yields, crop nutrient uptake amount, nutrient recovery efficiency (NRE), nutrient harvest index (NHI), and soil nutrient balance were annually evaluated from 2005 to 2022. ResultsSignificant improvements in maize yields were found under NPK (9081 kg ha−1), NP (6426 kg ha−1), and PK (2668 kg ha−1) compared with CK (1809 kg ha−1) and NK (1656 kg ha−1). The yield increase was mainly attributed to: (1) enhancing in soil nutrient properties, such as soil organic carbon, soil total N (TN), available N (AN), total P (TP), available P (AP), and available K (AK), and (2) the shortened vegetative period, leading to greater sunshine hours (SH) and accumulative growing degree days (GDD) during the reproductive period. Furthermore, a random forest analysis quantified their importance to grain yield, showing that the edaphic factors (mainly SOC, TN, AK, AN, TP, AP, C:N, and N:P) explained a much greater proportion of yield variation compared with phenological factors (mainly GDD during tasseling and physiological maturity stages, and SH during tasseling stage). Additionally, the significantly higher response ratio of both N and P to NRE and NHI implied that N and P fertilizers having a more pronounced impact on improving nutrient use efficiency than K fertilizer. In terms of soil nutrient balance, a most relative soil nutrient balance was detected under NPK treatment, avoiding either substantial nutrient depletion or accumulation under any nutrient deficiency conditions. ConclusionsSoil deficiencies in N and P had more severe impacts on maize yields and nutrient use efficiency compared with K deficiency. Additionally, a balanced NPK fertilizer regime effectively managed soil nutrient balance. Implications or significanceThese findings elucidate the roles of N, P, and K fertilizers in maize production and soil nutrient conditions from a long-term field experiment, which could provide valuable insights for optimizing fertilization management strategies.

Long‐term application of mineral fertilizer weakens the stability of microbial N‐transforming functions via the decrease of soil microbial diversity

AbstractIntroductionEnsuring functional stability is crucial for the sustainable development and soil health of agroecosystems amidst escalating climate changes. Although mineral fertilization is known to enhance the strength of soil N‐transforming functions, its effects on functional stability remain unclear.Materials & MethodsThis study evaluated three stability components (resistance, resilience, and recovery), along with the dimensionality of soil microbial N‐transforming functions during drought‐rewetting process. We investigated enzymatic activity and functional gene abundances after 10 years of fertilization under three strategies, mineral fertilization (NPK), mineral fertilization plus organic amendments (OMN), and no fertilization (CK).ResultsThe resistance was 0.60, 0.66 and 0.56; the resilience was 0.46, 0.28 and 0.46; and the recovery was 0.83, 0.73 and 0.82, respectively in the CK, NPK and OMN treatments. Soils with long‐term mineral fertilization exhibited the highest resistance but the lowest resilience and recovery during drought‐rewetting. Furthermore, mineral fertilization demonstrated the lowest dimensionality of stability, with smallest ellipsoid volume and most negative correlations. Soil microbial alpha diversity was identified as a key predictor of functional stability, positively correlating with stability across fertilization strategies.ConclusionMineral fertilization, which decreased alpha diversity, posed challenges for sustainable development of agroecosystems under drought conditions. Mineral fertilization plus organic amendments provided strong N‐transforming functions and moderate stability, making it as an optimal fertilization strategy. These results offer valuable insights for optimizing agroecosystem management and advancing soil sustainability.

Organic–Inorganic Fertilization Shifts Dissolved Organic Matter Chemodiversity in Runoff From Tropical Cropland: Roles of Soil Nutrient Stoichiometry

ABSTRACTDissolved organic matter (DOM) is a crucial quality indicator for water health. However, it remains unknown how organic–inorganic fertilization differently shifts the DOM chemodiversity in cropland‐impacted runoff, especially the roles of terrestrial nutrient stoichiometry. Here, a field experiment subjected to 7‐year history of four fertilization regimes, that is, unfertilized (CK), chemical fertilization (NPK), straw return (SR), and NPK + SR, was conducted to examine the quantity and chemodiversity of runoff DOM in tropical China. Moreover, the ecological relationships between runoff DOM properties and soil C:N:P stoichiometry were evaluated. Relative to the control treatment, the carbon content (DOC) of runoff DOM increased by 29.20% and 48.82% under SR and NPK + SR treatments, but remained unchanged in NPK treatment. Conversely, the DOM nitrogen content (TDN) only elevated in NPK treatment (262.58%). For DOM chemodiversity, SR treatment was rich in methyl carbon and protein‐like substances, but lacked fulvic‐/humic‐like compounds. NPK treatment increased the hydrophilic compounds like amino acids and polysaccharides, while reducing aromaticity. NPK + SR treatment enhanced DOM's aromaticity, molecular weight and humification due to the enrichment of quinone, ketone and fulvic‐like substances, possibly shaping an oligotrophic aquatic microbial community. Further study revealed that the occurrence of aromatic DOM was positively correlated with soil moisture content, TK (total potassium), total organic carbon and stoichiometric N:P ratio, indicating the contribution of terrestrial straw‐decomposed products. Inversely, the accumulation of hydrophilic substances (e.g., TDN) correlated positively with soil NO3‐N and C:P ratio, indicating the contribution of endogenous DOM.

Impact of Long-term Application of Fertilizers and FYM on Nutrient Uptake by Soybean Crop and Properties of Black Soil

Long Term Fertilizer Experiment (LTFE) play an important role in understanding the complex interactions involving plant, soil, climate, management practices and their effect on soil productivity over a long period of time. The present investigation is a part of ongoing All India Coordinated Research Project on Long Term Fertilizer Experiment with Soybean-Wheat Cropping Sequence, which was initiated since 1972. The experiment was carried out in a randomized block design consisting of eight treatments, viz. 50% NPK, 100% NPK, 150% NPK, 100% NP, 100% N, FYM (100% NPK+FYM), 100% NPK (-S) and Control. The significant nutrient content with nutrient uptake by soybean was noted in 100% NPK+FYM treatment over the control plot. It was also observed that nutrient content with nutrient uptake increased significantly with consecutive doses of fertilizers. On the other hand, 100% N and in the control group had the lowest value. However, adding fertilizer P in addition to N (100% NP) increased nutrient content and nutrient uptake by soybean crop. The highest. Soil organic carbon content was recorded with 100% NPK dose+FYM followed by 150% NPK treatment combination which could apparently due to the synergistic contribution of integration of fertilizer and FYM application. Similarly, the available N,P, K and S content in soil were found highest with 100% NPK + FYM followed by 150% NPK fertilizer dose. However, the lowest content was noted in control where crop was grown without fertilizers. Available sulphur was significantly higher over control in all the treatments receiving single super phosphate.

Long-Term Manuring Enhanced Compositional Stability of Glomalin-Related Soil Proteins through Arbuscular Mycorrhizal Fungi Regulation

Glomalin-related soil proteins (GRSP) play a crucial role in strengthening soil structure and increasing carbon (C) storage. However, the chemical stability of GRSP and related arbuscular mycorrhizal fungi (AMF) community response to fertilization remains unclear. This study investigated C and nitrogen (N) contents, three-dimensional fluorescence characteristics in GRSP, and AMF properties based on a field experiment that was subjected to 29 years of various fertilizations. The experiment included treatments with no fertilizer (CK), chemical fertilizer (NPK), manure (M), and manure combined with NPK (NPKM) treatments. Results showed that GRSP contained 37–49% C and 6–9% N, respectively. Compared with CK and NPK, the C and N proportions in GRSP significantly increased under M and NPKM. Using the parallel factor model, four fluorescent components of GRSP were identified: one fulvic acid-like component (C2), one tyrosine-like component (C4), and two humic acid-like components (C1, C3). Under M and NPKM, the fluorescent intensity of C2 and C4 decreased, while the humification index (HIX) increased relative to CK and NPK, indicating that organic fertilization could enhance the stability of GRSP. The C and N proportion in GRSP positively associated with soil organic C (SOC), total N (TN), available phosphorus (AP), AMF biomass, and diversity, while C2 and C4 showed negative associations. Structural equation modeling further revealed that manure-induced changes in pH, SOC, TN, and AP increased AMF biomass and diversity, thereby altering GRSP composition and stability. This study provides valuable insights into the compositional traits of GRSP, contributing to sustainable soil management and C sequestration in agroecosystems.

Comprehensive Effect of Zinc Boron with NPK and Salicylic Acid Foliar Application Treatments on Rice Yield and Grain Quality Under Salty Soil Conditions

Comprehensive Effect of Zinc Boron with NPK and Salicylic Acid Foliar Application Treatments on Rice Yield and Grain Quality Under Salty Soil Conditions

Hybrid Modeling and Management of Lodging in Subtropical Fiber Flax: Optimizing Plant Nutrition for Sustainable Cultivation

ABSTRACT Subtropical fiber flax faces significant challenges due to crop lodging, exacerbated by the high N regimes needed for increased fiber production. This study examines impact of balanced P and K applications under varied N regimes on lodging resistance, fiber yield, and quality of flax. Field experiments with 12 NPK treatments revealed that while 120:19:38 kg N, P, K ha−1 achieved highest plant height, stem-diameter, and fresh-weight while increased lodging percentage and reduced fiber quality when P and K were not balanced. Conversely, balanced P and K applications mitigated negative effects of high N, significantly reducing lodging and enhancing fiber yield, quality. Optimal fiber quality, including fiber length and bundle tenacity, was observed with 90:19:38 kg N, P, K ha−1. The novelty of this study lies in integration of stochastic and ML approaches to develop hybrid models for lodging. By combining LASSO with ANN, NLSVR, and RF techniques, hybrid models outperformed individual models in lodging prediction. Specifically, LASSO-NLSVR provided most accurate predictions due to its nonlinear mapping capabilities. Key predictive factors included fiber content, linear density, and tensile strength at 60 days post-sowing, offering valuable insights for breeders and agronomists to improve flax lodging resistance and fiber quality in subtropical climates.

EFFET COMPARE DES FERTILISATIONS ORGANIQUES ET MINERALES SUR LA PRODUCTION ET LA CONSERVATION DE LA TOMATE FRAICHE (Solanum lycopersicumL.) DANS LA PREFECTURE DE LA KOZAH AU TOGO

The tomato (Solanum lycopersicum) is a crucial vegetable for human nutrition and an important source of income for farmers. In response to increasing demand, producers increasingly use chemical inputs, raising serious health and environmental concerns. As a perishable fruit, the tomato rapidly deteriorates after ripening, making preservation a major challenge. To promote sustainable production and conservation, a study was conducted at the agriculturalexperimental station of the University of Lome, located atTchitchao, in the Kara region of Togo. The study assessed the effects of four types of fertilizers on agronomic parameters and the shelf life of two tomato varieties - ANAYAand MONA. A randomized block design was employed, with five treatments: SR1 GOLD, poultry manure, compost, NPK, and a control. The results indicate that poultry manure significantly enhances the growth, yield, and conservation of tomatoes compared to the other treatments. The application of 20 t/ha of poultry manure increased production by 86.67% for the MONAvariety and 65.11% for the ANAYAvariety compared to the control. Additionally, the manure extended the shelf life by two weeks for MONA and one week for ANAYA, compared to the NPK treatment, under ambient conditions. Under refrigerated storage, tomatoes treated with poultry manure exhibited the lowest rate of spoilage up to the tenth week, suggesting that poultry manure is a viable alternative for improving both the production and preservation of tomatoes.

Contrasting effects of iron oxides on soil organic carbon accumulation in paddy and upland fields under long-term fertilization

Active iron oxides, especially poorly crystalline forms, benefit soil organic carbon (SOC) accumulation via directly bounding and indirectly promoting aggregation. However, it remains unclear on the impacts of active iron oxides on SOC accumulation in paddy and upland soils under long-term fertilization regimes. Here, we attempted to clarify the underlying mechanisms of amorphous (FeO) and organically complexed (FeP) iron oxides mediating SOC accumulation in paddy and upland soils based on two long-term fertilization experiments (both including no fertilization [CK]; chemical nitrogen, phosphorus and potassium [NPK] and NPK plus manure [NPKM] treatments). Results showed that compared to upland soil, Fe-bound organic carbon (Fe-bound OC) content in paddy soil, occupying 21–30% of SOC, was 77% higher on average, due to larger amounts of FeO (+31%) and FeP (+224%). The FeO and FeP were positively related to mean weight diameter (MWD) of soil aggregates across paddy and upland soils. Compared to NPK treatment, NPKM treatment strongly increased FeO (+41%), FeP (+60%) and associated Fe-bound OC (+19%) in paddy soil, and increased FeO (+17%) and FeP (+25%) while decreasing Fe-bound OC (−9%) in upland soil. These combined findings indicated the importance of poorly crystalline iron oxides facilitating Fe-bound OC formation and its contribution to SOC accumulation in paddy soil rather than upland soil. Moreover, long-term manure amendment could enhance SOC accumulation by increasing Fe-bound OC and aggregation stability in paddy soil and enhancing physical protection in upland soil, largely attributed to increased poorly crystalline iron oxides. Overall, these results highlight the potential mechanisms through which active iron oxides regulate SOC accumulation and guide fertilization management in paddy and upland soils.

A 44-year balanced fertilizer application affected rill erosion resistance by changing humus, aggregates, and polyvalent cation

Fertilizer application can affect the physicochemical properties of soil, such as the contents of large aggregates, humus, and exchangeable cations, thereby influencing soil erosion resistance. However, the rill erosion resistance and its key influencing factors of soil following long-term balanced fertilizer application remains unclear. This study aimed to analyze the change in rill erosion resistance following 44 years of balanced fertilizer application (No changes in the type of fertilizer) to non-calcareous soils and establish a Partial Least Squares Regression (PLSR) model of rill erodibility (kd) and soil critical shear stress (τc) to changes in the physical and chemical properties of the soil. Five treatments were designed: (1) CK (no fertilizer applied), (2) N (nitrogen), (3) NP (nitrogen plus phosphorus), (4) NK (nitrogen plus potassium), and (5) NPK (nitrogen, phosphorus, and potassium). Compared to CK, the N, NP, NK, and NPK application significantly increased τc by 49.6, 96.7, 73.6, and 36.2 %, respectively. Whereas, kd increased significantly only in the NPK treatment group. The optimal partial least squares regression model showed that mean weight diameter (MWD) had the greatest positive influence on soil critical shear stress, followed by fulvic acid (FA) content, whereas water-dissolved substances had a negative influence. Long-term balanced fertilizer application can increase MWD and τc by combining micro-aggregates and humus into large aggregates. Ca2+ content had the greatest positive effect on kd. Compared with that of CK, exchangeable Ca2+ content increased significantly with NP and NPK application (7.9 and 34.3 %, respectively). Ca2+ can increase kd by binding to the polar functional groups in FA to promote the shedding of hydration shells in large aggregates. Among all treatments, the NP treatment showed the best performance for reducing kd and increasing τc. This study could contribute to the understanding of the rill erosion process and modeling in non-calcareous soils and offer a reference for agricultural erosion control treatments.

Nitrous oxide emissions and soil profile responses to manure substitution in the North China Plain drylands

Substituting synthetic fertilizers with manures in agriculture enhances soil properties and crop yield. However, the impact on nitrous oxide (N2O) emissions, especially from the soil profile, remains poorly understood. This study examined emissions from 2017 to 2019 on a well-established (>10-year) maize field site in the North China Plain. Three treatments were compared: 100 % synthetic nitrogen (NPK), 50 % synthetic fertilizer N + 50 % manure N substitution (50%MNS), and 100 % manure N substitution (100%MNS). N2O emissions were monitored for three years, and in 2019, N2O concentrations at 20 cm and 40 cm soil depths were analyzed in relation to surface N2O fluxes and environmental factors. The results showed manure substitution resulted in about 13.8 %–25.2 % (50%MNS) and 40.3 %–72.2 % (100%MNS) reduction in N2O emissions over the 3-year period compared with the NPK treatment. Throughout the maize growing season, the top-dressing accompanied by rainfall was responsible for the N2O emissions. The difference in N2O concentrations between all the treatments at 20 cm depth was insignificant, but at 40 cm depth the N2O concentrations were significantly higher for the 50%MNS treatment than the other treatments. The N2O fluxes and N2O concentration were not synchronized especially in NPK. The decoupled relationship between the N2O fluxes and the N2O concentration in the soil profile depth suggested the contribution of N2O produced in the soil profile to the surface N2O fluxes is limited. This study highlights that manure substitution is an efficient measure to reduce N2O emissions.

Nanoagrochemicals versus Conventional Fertilizers: A Field Case Study with Tailor-Made Nanofertilizers for Sustainable Crop Efficiency of Brassica oleracea L. convar. Capitata var. Sabauda

Excessive use of conventional fertilizers in agricultural soils can lead to environmental contamination, particularly affecting aquifers and surface waters. Nanofertilizers, with smaller particles and greater nutrient efficiency, offer a promising alternative. This study evaluates the application of nanofertilizers by reducing NPK-doses compared to conventional fertilizers in the cultivation of Brassica oleracea L. convar. capitata var. sabauda (Savoy cabbage). Field assays were conducted in experimental plots with different NPK doses and treatments using urea-hydroxyapatite and potassium sulfate nanoparticles (optimum dose: 80 N, 100 P2O5, 250 K2O kg ha−1; and half optimum dosage). The assay was monitored throughout the crop cycle, and cabbages were harvested to determine biometric parameters, yield, and nutrient contents. The results indicated that nanofertilizers at half the recommended dosage yielded similar results to conventional fertilization in terms of cabbage growth and yield. Specifically, soil pH and available P increased by the end of the crop cycle, while total N, C, CEC, and soil texture remained unchanged, regardless of the fertilizer dose applied. Cabbage plants treated with nanofertilizers showed no significant differences in nutrient content compared to those treated with conventional fertilizers. This study supports the potential of nanofertilizers as an environmentally sustainable alternative that can reduce nutrient inputs in agriculture without compromising crop yield and quality.