NPK Treatment Research Articles

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.

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.

The Crop Phosphorus Uptake, Use Efficiency, and Budget under Long-Term Manure and Fertilizer Application in a Rice–Wheat Planting System

Little is known about the effect of the long-term application of organic and inorganic fertilizers on P-use efficiency, P budget, and the residual effect of P fertilizer. To clarify the effect of different fertilization on soil P balance in a rice (Oryza sativa L.)–wheat (Triticum aestivum L.) rotation system is helpful to promote the sustainable development of agriculture. Thus, a thirty-five-year fertilizer experiment was conducted with eight treatments, including an unfertilized control (CK); chemical nitrogen (N), phosphorus (P), and potassium (K) fertilizers; and organic manure (M) either alone or in combination treatments (N, NP, NPK, M, MN, MNP, and MNPK). The results indicated that crop yields and P uptake were higher in the combined application of manure and chemical fertilizer treatments than in the manure or chemical fertilizer alone treatments. Soil P budget indicated a 23.4–55.4 kg P ha−1 yr−1 surplus in the organic combined with or without mineral fertilizer treatments, but the soil P budget indicated a 20.0 and 21.9 kg P ha−1 yr−1 deficit in the control and N treatments. The proportion of residual fertilizer P converted to soil available P in NP, NPK, M, MN, MNP, and MNPK treatments was 4.5%, 4.8%, 19.1%, 19.0%, 11.5%, and 13.3%, respectively, over a 35-year period. Furthermore, according to the higher P content and crop uptake in organic manure treatment compared with chemical P fertilizer alone, an organic addition could effectively reduce the use of chemical fertilizer and become an effective way of sustainable development in practice. Therefore, the combined application of organic and inorganic fertilizer will be a practical method to increase crop yields and soil P status in a rice–wheat planting system.

Nitrogen fertilization and soil nitrogen cycling: Unraveling the links among multiple environmental factors, functional genes, and transformation rates

Anthropogenic nitrogen (N) inputs substantially influence the N cycle in agricultural ecosystems. However, the potential links among various environmental factors, nitrogen functional genes, and transformation rates under N fertilization remain poorly understood. Here, we conducted a five-year field experiment and collected 54 soil samples from three 0–4 m boreholes across different treatments: control, N-addition (nitrogen fertilizer) and NPK-addition (combined application of nitrogen, phosphorus and potassium fertilizers) treatments. Our results revealed pronounced variations in soil physiochemical parameters, metal concentrations and antibiotic levels under both N and NPK treatments. These alternations induced significant shifts in bacterial and fungal communities, altered NFG abundance and composition, and greatly enhanced rates of nitrate reduction processes. Notably, nutrients, antibiotics and bacteria exerted a more pronounced influence on NFGs and nitrate reduction under N treatment, whereas nutrients, metals, bacteria and fungi had a significant impact under NPK treatment. Furthermore, we established multidimensional correlations between nitrate reduction gene profiles and the activity rates under N and NPK treatments, contrasting with the absence of significant relationships in the control treatment. These findings shed light on the intricate relationships between microbial genetics and ecosystem functions in agricultural ecosystem, which is of significance for predicting and managing metabolic processes effectively.

Comparison of Organic and Inorganic Fertilization in Fenugreek Cultivation Using Nitrogen Indicators

Nitrogen indices could be used to evaluate organic and inorganic fertilization because they provide quantitative measures of nitrogen availability in the soil, allowing for a more accurate assessment of nutrient-management practices and optimization of crop yields. This study investigates the impact of different fertilization types and salinity on various soil parameters in fenugreek (Trigonella foenum-graecum L.) cultivation and nitrogen indices. A field experiment was established at the Agricultural University of Athens during the cropping period of 2018–2019 (CP I), 2019–2020 (CP II), and 2020–2021 (CP III) in a split-plot design with two main salinity treatments (high salinity, HS, and conventional salinity, CS) and five fertilization treatments (biocyclic–vegan humus soil (BHS), manure (FYM), compost (COMP), inorganic fertilization (11–15–15), and the control (C). The Nitrogen Balance Intensity (NBI) was statistically significantly affected by the factors of fertilization (p ≤ 0.01) and salinity (p ≤ 0.001) for CP I. The maximum NUEcrop value was recorded in the FYM treatment (0.83 ± 0.04) and the minimum in the COMP treatment (0.64 ± 0.04). Physiological efficiency (PE) was not significantly affected by any treatment for CP III. The fertilization factor significantly affected the NUEsoil index (p ≤ 0.001) for all three CPs. For CP I, the highest Nitrogen Uptake Efficiency (NUpE) value was recorded in the BHS treatment (27.08 ± 7.31) and the lowest in the C treatment (13.22 ± 7.31). There were no significant differences in CP I and CP II NUEbalance values among the NPK, BHS, and FYM treatments. These findings underscore the potential of organic fertilizers in addressing the global nitrogen challenge and promoting environmentally sustainable farming practices.

Soil organic carbon regulation by pH in acidic red soil subjected to long-term liming and straw incorporation

The manipulation of soil pH through liming and straw incorporation plays a pivotal role in influencing soil organic carbon (SOC) dynamics in acidic red soil. This study aimed to assess the impact of these practices on SOC and elucidate the relationship between SOC and pH. Over a 31-year field experiment, seven different fertilization treatments were implemented: unfertilized (CK), nitrogen and potassium fertilizers (NK), NK with lime (NKCa), nitrogen, phosphorous, and potassium fertilizers (NPK), NPK with lime (NPKCa), NPK with straw (NPKS), and NPKS with lime (NPKSCa). Results revealed that liming and straw incorporation significantly elevated soil pH by 0.13–0.73 units. Lime application boosted SOC and mineral-associated organic carbon (MAOC) by 20.2% and 28.7%, respectively, in NK treatment, whereas its impact on SOC in NPK and NPKS treatments were negligible. SOC witnessed a 17.1% increase with NPKS and a 15.2% increase with NPKSCa compared to NPK alone. Notably, NPKS and NPKSCa led to a significant surge in particulate organic carbon (POC) by 19.7% and 37.7%, respectively, albeit NPKSCa reduced MAOC by 14.9% relative to NPK. Linear regression analysis unveiled a positive correlation between POC and soil pH, while SOC and MAOC exhibited an initial rise at lower pH levels followed by stabilization as pH continuously increasing. A partial least squares path model showed two pathways through which pH influenced SOC: firstly, by positively affecting SOC through increasing Fe and Al oxides contents and enhanced aggregate stability, and secondly, by negatively influencing SOC through altered ratios of fungi/bacteria and Gram-positive bacteria/Gram-negative bacteria. In conclusion, the long-term effects of lime and straw application on SOC and MAOC were contingent upon soil pH, with more pronounced positive effects observed at lower pH levels. These findings underscore the importance of considering soil pH when implementing lime and straw strategies to mitigate acidification and regulate SOC in acidic red soil.

Response of comammox Nitrospira clades A and B communities to long-term fertilization and rhizosphere effects and their relative contribution to nitrification in a subtropical paddy field of China

The recently discovered complete ammonia oxidation (comammox Nitrospira) containing clade A and clade B has further complemented our understanding of nitrification process. Nevertheless, understanding the community feature of comammox Nitrospira clades A and B and their relative contribution to nitrification in paddy rhizosphere are still in its infancy. In this study, we assessed the community diversity and structure of comammox Nitrospira clades A and B in paddy rhizosphere and bulk soils under thirty years of different fertilization strategies, i.e., non-fertilization control (CK), chemical fertilizers application (NPK), and NPK plus swine manure (NPKM), respectively. NPKM significantly increased the a-diversity (Chao1 and Shannon indices) of comammox Nitrospira clade A and altered the community structure (P < 0.05) but had little effect on clade B. A two-way analysis of variance (ANOVA) showed that the effect of long-term fertilization on soil comammox Nitrospira community and nitrification potential rate (PNR) was much greater than that of rhizosphere. Compared with NPK, soil PNR was greatly increased by 51.0% under the NPKM treatment in the rhizosphere (P < 0.05). Phylogenetic analysis showed that NPKM improved the relative abundances of sub-clade A.2.1 and sub-clade A.3.2 of the comammox clade A community, with an average increase of 212.2 and 210.4% in both rhizosphere and bulk soils relative to the NPK treatment. Soil organic matter, NH4+-N, and pH were significant soil drivers of comammox Nitrospira clades A and B community. Furthermore, linear regression and structural equation modeling clearly showed that comammox Nitrospira clade A a-diversity were significantly associated with soil PNR (P < 0.05). Our results suggest (i) that comammox Nitrospira clade A are sensitive to the organic fertilization; and (ii) that comammox Nitrospira clade A contribute more to nitrification than clade B under the long-term organic fertilized paddy soil.

Differences in Soil Fertility and Bacterial Community Structure Between Carbon Inputs such as Biochar and Organic Fertilizer and Their Relationship

The potato planting area of Guizhou Province ranks second in China. However, due to factors such as climatic conditions and unbalanced fertilization, soil organic matter in potato fields is consumed rapidly and has a large deficit, which affects soil biological function and soil fertility. Biochar and organic fertilizer are effective ways to supplement foreign aid organic matter to improve soil quality. However, the differences in soil fertility and microbial community structure and their relationships under the conditions of organic fertilizer or biochar combined with chemical fertilizer are not clear. In this study, three treatments of conventional fertilization （NPK）, increased application of biochar （NPKB）, and increased application of organic fertilizer （NPKO） were set up to investigate the characteristics of potato rhizosphere soil, bacterial community composition, and diversity； to analyze the effects of these factors on the soil integrated fertility index； and to explore the direct and indirect effects of IFI on soil fertility and bacterial community structure differences between treatments and their driving factors. The results showed that soil pH, available phosphorus （AP）, available potassium （AK）, total nitrogen （TN）, organic carbon （SOC）, and C/N ratio were significantly higher in the NPKB and NPKO treatments than in the NPK treatment （P<0.05）. Soil IFI was greatest for NPKO, followed by NPKB and least for the NPK treatment. A total of 8 214 ASVs were obtained from all the soil samples, belonging to 26 phyla, 75 classes, 165 orders, 176 families, and 251 genera （excluding unidentified fungi）. Proteobacteria, Actinobacteria, and Chloroflexi were the dominant phyla, accounting for 54.85% of all ASVs. Compared to that in the NPK and NPKB treatments, the NPKO treatment had the highest bacterial diversity and number of significantly different taxa, and soil AN, AP, AK, SOC, TN, and IFI were significant correlates of bacterial diversity index （P<0.05）. Additionally, pH, TN, and SOC were significant influencers of bacterial taxa differences （P<0.05）, with importance ranked as TN （70.59%） &gt; SOC （49.42%） &gt; pH （27.08%）. Structural equations suggested that pH-related soil properties and bacterial community diversity were the direct pathways influencing IFI, and soil pH-related soil characteristics could also indirectly affect IFI by affecting bacterial Shannon diversity. These results indicate that soil fertility and bacterial community structure were significantly different and correlated between the biochar and organic fertilizer addition treatments and that pH and bacterial community diversity were the key factors influencing IFI, with the NPKO treatment in particular having the best effect on improving IFI. Considering the effect of soil fertilization and the functional group of bacteria, NPKO is the recommended combination for the best synergistic effect of soil fertilization, that is, N 150 kg·hm-2+P2O5 135 kg·hm-2+K2O 135 kg·hm-2+organic fertilizer 6.6 t·hm-2.

Compost as an Alternative to Inorganic Fertilizers in Cowpea [Vigna unguiculata (L.) Walp.] Production

ABSTRACTSoil fertility management is essential to sustain agricultural production in smallholder farming systems. An experiment was carried out to assess the viability of the combined use of compost and inorganic fertilizers as an alternative to conventional inorganic fertilization under greenhouse conditions. The 10 treatments, arranged in a randomized complete block design (RCBD) with six replications, consisted of a control, conventional mineral fertilization (150 kg NPK ha−1), composts added to the soil alone (2.5, 5, 7.5, and 10 t ha−1), and their combination with 50% of recommended rate of inorganic fertilizers (75 kg NPK ha−1). Application of 7.5 t ha−1 of compost and 50% of the recommended dose of inorganic fertilizer (75 kg NPK ha−1) gave the significantly highest seed yield, corresponding to a 30% increase over NPK‐fertilized plants. The combined application of 2.5 or 10 t ha−1 compost with 75 kg NPK ha−1 increased plant height by 38% compared with the NPK treatment. Additionally, stem diameter increased by 53% when 5 t ha−1 of compost and 75 kg NPK ha−1 were mixed. As expected, control plants produced the most nodules (108), 85% more than inorganic fertilization. Plants fertilized with 7.5 or 10 t ha−1 of compost and 75 kg NPK ha−1 produced 17% more pods, seeds per pod, and seeds per plant than NPK treatments. However, fertilization treatments had no significant effects on cowpea fresh and dry biomass or SPAD values. The results reveal that combining compost with inorganic fertilizer reduced synthetic fertilization by 50%, while producing growth and yields comparable to, or even higher than, recommended inorganic fertilization. This experiment demonstrated that integrated soil fertility management can be used as an alternative to the use of inorganic fertilizers in cowpea cultivation.

Soil Test Crop Response Concerning Soil Properties and Yield Attributes of Mustard (Brassica juncea L.) var. Krishna

We experimented in the field at the central research farm of the Department of Soil Science and Agricultural Chemistry, Sam Higginbottom University of Agriculture, Technology and Sciences, Prayagraj during Rabi season of 2022-23. The soil in the experimental area was characterized by a sandy loam texture. There were 27unit plots in total, with each plot sized at 2 X 2 m. We used a randomized block design, incorporating different levels of NPK (80:40:40), vermicompost, and two levels of sulfur (50% and 100%). The T9 (STCR+ 5t ha-1 Vermicompost+ 100% S) demonstrated that although there was a slight decrease in pH, bulk density, and particle density, there was a significant (P&lt;0.05) increase in pore space, water holding capacity, electrical conductivity (EC), organic carbon, and the availability of nitrogen, phosphorus, and potassium. Improvements were observed in plant growth and yield attributes, which showed the best results in terms of plant height, number of siliquae per plant, and total mustard yield compared to the control conditions. However, the use of organic manures and their combination with a full NPK treatment significantly enhanced the growth and overall yield attributes of mustard.