Soybean Root Research Articles

Bacillus velezensis S141 improves the root growth of soybean under drought conditions.

Bacillus velezensis S141 helps soybean establish specific symbiosis with strains of Bradyrhizobium diazoefficiens to form larger nodules and improve nitrogen fixation efficiency. In this study, we found that the dry weight of soybean roots increased significantly in the presence of S141 alone under drought conditions. Hence, S141 improved the root growth of soybean under limited water supply conditions. S141 can produce some auxin, which might be involved in the improved nodulation. Inactivating IPyAD of S141, which is required for auxin biosynthesis, did not alter the beneficial effects of S141, suggesting that the root growth was independent of auxin produced by S141. Under drought conditions, soybean exhibited some responses to resist osmotic and oxidative stresses; however, S141 was relevant to none of these responses. Although the mechanism remains unclear, S141 might produce some substances that stimulate the root growth of soybean under drought conditions.

Zinc Oxide Nanoparticle-Mediated Root Metabolic Reprogramming for Arsenic Tolerance in Soybean

Arsenate (AsV) is absorbed and accumulated by plants, which can affect their physiological activities, disrupt gene expression, alter metabolite content, and influence growth. Despite the potential of zinc oxide nanoparticles (ZnONPs) to mitigate the adverse effects of arsenic stress in plants, the underlying mechanisms of ZnONPs-mediated detoxification of AsV, as well as the specific metabolites and metabolic pathways involved, remain largely unexplored. In this study, we demonstrated root metabolomic profiling of soybean germinating seedlings subjected to 25 μmol L−1 arsenate (Na2HAsO4) and ZnONPs at concentrations of 25 μmol L−1 (ZnO25) and 50 μmol L−1 (ZnO50). The objective of this study was to examine the effects on soybean root metabolomics under AsV toxicity. Metabolomic analysis indicated that 453, 501, and 460 metabolites were significantly regulated in response to AsV, ZnO25, and ZnO50 treatments, respectively, compared to the control. Pathway analysis of the differentially regulated metabolites (DRMs) revealed that the tricarboxylic acid (TCA) cycle, glutathione metabolism, proline and aldarate metabolism, and arginine and proline metabolism were the most statistically enriched pathways in ZnONPs-supplemented plants. These findings suggest that ZnONPs enhance the tolerance response to AsV. Collectively, our results support the hypothesis that ZnONPs fertilization could be a potential strategy for improving soybean crop resilience under AsV stress.

Phytophthora root and stem rot of soybean: the importance of the disease and host resistance

Phytophthora root and stem rot of soybean: the importance of the disease and host resistance

GmSTOP1-3 Increases Soybean Manganese Accumulation Under Phosphorus Deficiency by Regulating GmMATE2/13 and GmZIP6/GmIREG3.

Mineral nutrient deficiencies and metal ion toxicities coexist on acid soils. Phosphorus (P) deficiency in plants is generally accompanied with significant levels of leaf manganese (Mn) accumulation. However, the molecular regulatory mechanisms underpinning remain unclear. The present study found that P-deficient soybean plants accumulated more Mn compared to P-sufficient ones on acid soils in both field and greenhouse experiments. Meanwhile, both P deficiency and Mn toxicity enhanced the expression of GmSTOP1-3. Over-expressing GmSTOP1-3 enhanced Mn accumulation in transgenic soybean hairy roots, but RNA-interference did not show obvious differences. Moreover, transgenic soybeans with GmSTOP1-3-overexpression showed enhanced root citrate exudation and augmented Mn accumulation. RNA-sequence identified four downstream genes of GmSTOP1-3, including multidrug and toxic compound extrusion (GmMATE2/13) and metal transporter genes (GmZIP6/GmIREG3), which encode plasma membrane proteins. GmSTOP1-3 activated the transcription of these four genes by directly binding to their promoter regions. In addition, both GmZIP6 and GmIREG3 functioned in Mn uptake as manifested by the higher Mn concentration and decreased growth of soybean hairy roots with their overexpression. Taken together, it is suggested that upregulation of GmSTOP1-3 by low P stress on acid soils activates transcripts of GmMATE2/13 and GmZIP6/GmIREG3, which consequently result in enhanced Mn accumulation in soybean.

GmTRAB1, a Basic Leucine Zipper Transcription Factor, Positively Regulates Drought Tolerance in Soybean (Glycine max. L).

The basic leucine zipper (bZIP) transcription factors play crucial roles in plant resistance to environmental challenges, but the biological functions of soybean bZIP members are still unclear. In this study, a drought-related soybean bZIP gene, GmTRAB1, was analyzed. The transcript of GmTRAB1 was upregulated under drought, ABA, and oxidative stresses. Overexpression of GmTRAB1 improved the osmotic stress tolerance of transgenic Arabidopsis and soybean hairy roots associated with increased proline content and activity of antioxidant enzymes and reduced accumulations of malonaldehyde and reactive oxide species. However, RNA interference silencing of GmTRAB1 in the soybean hairy roots improved drought sensitivity. Furthermore, GmTRAB1 increased the sensitivity of transgenic plants to ABA and participated in modulating ABA-regulated stomatal closure upon drought stress. In addition, GmTRAB1 stimulated the transcript accumulation of drought-, ABA-, and antioxidant-related genes to respond to drought. Collectively, this research will contribute to understanding the molecular mechanisms of bZIP transcription factors in soybean's resistance to drought.

Preinoculation with Bradyrhizobium japonicum enhances the salt tolerance of Glycine max seedlings by regulating polyamine metabolism in roots

Rhizobia are common symbiotic microorganisms in the root system of leguminous plants that can usually provide nitrogen to the host through nitrogen fixation. Studies have shown that rhizobium-preinoculated soybean plants usually exhibit improved salt tolerance, but the underlying mechanism is not fully understood. In this paper, transcriptome sequencing (RNA-seq) revealed that preinoculation with rhizobia affected polyamine (PA) metabolism in soybean roots. The assay of PA contents showed that preinoculation with rhizobia significantly increased the putrescine (Put) content in roots and leaves during short-term salt treatment (0-5d). Long-term salt treatment (5-7d) resulted in a high Put content and significantly increased Spm and Spd contents, resulting in a rapid increase in the Put/(Spd+Spm) ratio (0-5d) and subsequent decrease. Moreover, rhizobium preinoculation of soybean plants resulted in increased contents of conjugated and bound PAs under salt stress. Further transcriptome sequencing, PA contents, PA synthase expression and activity analysis revealed that GmADC may be a key gene related to salt tolerance in rhizobium-preinoculated soybean plants, and the GmADC-overexpressing soybean hairy-root composite plants exhibited less ROS damage, lower Cl-/NO3- ratios and Na+/K+ ratios, and stabilized ion homeostasis. Taken together, preinoculation with rhizobia increased the expression level and enzyme activity of arginine decarboxylase (ADC) in soybean roots, increased the content of Put in roots and leaves, and increased the content of conjugated and bound PAs in soybean plants, thereby alleviating the oxidative and ionic injuries of soybean plants and enhancing the salt tolerance.

The WRKY Family Transcription Factor GmWRKY72 Represses Glyceollin Phytoalexin Biosynthesis in Soybean.

Phytoalexins are plant defense metabolites that are biosynthesized transiently in response to pathogens. Despite that their biosynthesis is highly restricted in plant tissues, the transcription factors that negatively regulate phytoalexin biosynthesis remain largely unknown. Glyceollins are isoflavonoid-derived phytoalexins that have critical roles in protecting soybean crops from the oomycete pathogen Phytophthora sojae. To identify regulators of glyceollin biosynthesis, we used a transcriptomics approach to search for transcription factors that are co-expressed with glyceollin biosynthesis in soybean and stilbene synthase phytoalexin genes in grapevine. We identified and functionally characterized the WRKY family protein GmWRKY72, which is one of four WRKY72-type transcription factors of soybean. Overexpressing and RNA interference silencing of GmWRKY72 in the soybean hairy root system decreased and increased expression of glyceollin biosynthetic genes and metabolites, respectively, in response to wall glucan elicitor from P. sojae. A translational fusion with green fluorescent protein demonstrated that GFP-GmWRKY72 localizes mainly to the nucleus of soybean cells. The GmWRKY72 protein directly interacts with several glyceollin biosynthetic gene promoters and the glyceollin transcription factor proteins GmNAC42-1 and GmMYB29A1 in yeast hybrid systems. The results show that GmWRKY72 is a negative regulator of glyceollin biosynthesis that may repress biosynthetic gene expression by interacting with transcription factor proteins and the DNA of glyceollin biosynthetic genes.

Dynamic Landscapes of Long Noncoding RNAs During Early Root Development and Differentiation in Glycine max and Glycine soja.

Soybean (Glycine max) is an important crop for its nutritional value. Its wild relative, Glycine soja, provides a valuable genetic resource for improving soybean productivity. Root development and differentiation are essential for soybean plants to take up water and nutrients, store energy and anchor themselves. Long noncoding RNAs (lncRNAs) have been reported to play critical roles in various biological processes. However, the spatiotemporal landscape of lncRNAs during early root development and differentiation in soybeans is scarcely characterized. Using RNA sequencing and transcriptome assembly, we identified 1578 lncRNAs in G. max and 1454 in G. soja, spanning various root portions and time points. Differential expression analysis revealed 82 and 69 lncRNAs exhibiting spatiotemporally differential expression patterns in G. max and G. soja, respectively, indicating their involvement in the early stage of root architecture formation. By elucidating multiple competitive endogenous RNA (ceRNA) networks involving lncRNAs, microRNAs and protein-coding RNAs, we unveiled intricate regulatory mechanisms of lncRNA in early root development and differentiation. Our efforts significantly expand the transcriptome annotations of soybeans, unravel the dynamic landscapes of lncRNAs during early root development and differentiation, and provide valuable resources into the field of soybean root research.

Prokaryotic expression, purification, and activity of the inositol polyphosphate 5-phosphatase Gs5PTase8 from wild soybean

Inositol polyphosphate-5-phosphatase (5PTase) is a key enzyme in the inositol signaling pathway. It hydrolyzes the 5-phosphate on the inositol ring of inositol phosphate (IP) or phosphatidylinositol phosphate (PIP). However, there is limited reports on the homologous genes in soybean. This study cloned the salt tolerant gene Gs5PTase8 from wild soybean (Glycine soja S. & Z.) and explored its substrate. Gs5PTase8 encodes 493 amino acid residues. The sequence alignment and phylogenetic tree showed that this gene was conserved in plants. RT-qPCR was employed to determine the expression of Gs5PTase8 in different tissues of soybean and the results showed that Gs5PTase8 was mainly expressed in soybean roots. To investigate the hydrolytic substrates, we constructed pET28a-Gs5PTase8 and pGEX4T1-Gs5PTase8 for the Escherichia coli expression system and only obtained the recombinant protein GST-Gs5PTase8. The induction conditions for the protein expression including the isopropyl beta-d-thiogalactopyranoside (IPTG) concentration and temperature (16 ℃, 30 ℃, and 37 ℃) were optimized. The expression level was highest when the expression was induced overnight with 0.2 mmol/L IPTG at 16 ℃. The SDS-PAGE results showed that the recombinant protein had a relative molecular weight of 75 kDa and presented a single band after purification, with the purity reaching over 95%. The yield of the recombinant protein determined by the BCA method was 4.9 mg/L LB. The hydrolytic substrates of this enzyme in vitro included IP3 [inositol(1, 4, 5)trisphosphate], IP4 [inositol(1, 3, 4, 5)tetrakisphosphate], PI(4, 5)P2 [phosphatidylinositol(4, 5) bisphosphate] and PI(3, 4, 5)P3 [phosphatidylinositol(3, 4, 5)trisphosphate]. This study provides a scientific basis for further research on the molecular mechanism of Gs5PTase8 involved in salt tolerance.

Proteomic Analysis to Understand the Promotive Effect of Ethanol on Soybean Growth Under Salt Stress

Finding solutions to mitigate the impact of salinity on crops is important for global food security because soil salinity significantly reduces plant growth and grain yield. Ethanol may play an important role in mitigating the negative salt-induced effects on crops. Soybean root growth was significantly reduced under salt stress; however, it was restored and comparable to control values by ethanol application even under stress. To study the positive mechanism of ethanol on soybean growth, a proteomic approach was carried out. The categories with the greatest changes in protein numbers were protein metabolism, transport, and cell organization in biological processes, nucleus and cytosol in cellular components, and nucleic acid binding activity in molecular functions. Proteomic data were confirmed using immunoblot analysis. Reactive oxygen species enzymes increased under salt stress; among them, mitochondrial ascorbate peroxidase was further accumulated by ethanol application. Among the cell wall and membrane-associated proteins, xyloglucan xyloglucosyl transferase and H+-ATPase increased and decreased, respectively, under salt stress; however, they were restored to control levels by ethanol application. These results suggest that soybeans were adversely affected by salt stress and recovered with ethanol application via the regulation of cell wall and membrane functions through the detoxification of reactive oxygen species.

Impact of Sulfur Deficiency and Excess on the Growth and Development of Soybean Seedlings.

Sulfur is a critical element for plant growth and development, serving as a component of amino acids (cysteine and methionine), iron-sulfur clusters, proteins, glutathione, coenzymes, and auxin precursors. Deficiency or low concentrations of sulfur in the soil can lead to significant growth retardation in plants. The objective of our study was to examine the effects of sulfur (S) deficiency and excess on morphological symptoms, sulfur and nitrogen (N) metabolism, as well as antioxidant activity in soybean. We found that S starvation decreased the fine root length, biomass, and activity, and the chlorophyll content was reduced, while excess sulfur promotes lateral root growth. In contrast to sulfur excess, sulfur deficiency inhibits N and S metabolism levels in both subsurface and above-ground parts, and induced the expression of some sulfur transporters (SULTRs). In this study, we created soybean hairy root lines overexpressing the SULTR gene (GmSULTR2;1a) to observe metabolic changes following sulfur deficiency treatment. The results showed that GmSULTR2;1a saved the sulfur-deficient phenotype, and the antioxidant enzyme activity was much higher than that of the wildtype in the absence of sulfur. Our study revealed the important role of sulfur element in soybean growth and development and the regulation of sulfur deficiency by GmSULTR2;1a.

Metabolic pathways regulated by strigolactones foliar spraying enhance osmoregulation and antioxidant defense in drought-prone soybean

BackgroundDrought stress is a significant abiotic stressor that hinders growth, development, and crop yield in soybeans. Strigolactones (SLs) positively regulate plant resistance to drought stress. However, the impact of foliar application of SLs having different concentrations on soybean growth and metabolic pathways related to osmoregulation remains unknown. Therefore, to clarify the impact of SLs on soybean root growth and cellular osmoregulation under drought stress, we initially identified optimal concentrations and assessed key leaf and root indices. Furthermore, we conducted transcriptomic and metabolic analyses to identify differential metabolites and up-regulated genes.ResultsThe results demonstrated that drought stress had a significant impact on soybean biomass, root length, root surface area, water content and photosynthetic parameters. However, when SLs were applied through foliar application at appropriate concentrations, the accumulation of ABA and soluble protein increased, which enhanced drought tolerance of soybean seedlings by regulating osmotic balance, protecting membrane integrity, photosynthesis and activating ROS scavenging system. This also led to an increase in soybean root length, lateral root number and root surface area. Furthermore, the effects of different concentrations of SLs on soybean leaves and roots were found to be time-sensitive. However, the application of 0.5 µM SLs had the greatest beneficial impact on soybean growth and root morphogenesis under drought stress. A total of 368 differential metabolites were screened in drought and drought plus SLs treatments. The up-regulated genes were mainly involved in nitrogen compound utilization, and the down-regulated metabolic pathways were mainly involved in maintaining cellular osmoregulation and antioxidant defenses.ConclusionsSLs enhance osmoregulation in soybean plants under drought stress by regulating key metabolic pathways including Arachidonic acid metabolism, Glycerophospholipid metabolism, Linoleic acid metabolism, and Flavone and flavonol biosynthesis. This study contributes to the theoretical understanding of improving soybean adaptability and survival in response to drought stress.

Transcriptomes of soybean roots and nodules inoculated with Sinorhizobium fredii with NopP and NopI variants.

The major crop, soybean, forms root nodules with symbiotic rhizobia, providing energy and carbon to the bacteria in exchange for bioavailable nitrogen. The relationship is host-specific and highly host-regulated to maximize energy efficiency. Symbiotic nitrogen fixation (SNF) is greener than synthetic fertilizer for replenishing soil fertility, contributing to yield increase. Nodulation Outer Protein P (NopP) and NopI of the type 3 secretion system (T3SS) of the rhizobium determine host specificity. Sinorhizobium fredii CCBAU25509 (R2) and CCBAU45436 (R4) have different NopP and NopI variants, affecting their respective symbiotic compatibilities with the cultivated soybean C08 and the wild soybean W05. Swapping the NopP variants between R2 and R4 has been shown to switch their compatibility with C08 with the rj2/Rfg1 genotype. To understand the effects of Nops on host compatibility, analyses on the transcriptomic data of W05 roots and nodules inoculated with S. fredii strains containing Nop variants uncovered many differentially expressed genes related to nodulation and nodule functions, providing important information on the effects of Nops on hosts and nodules.

Enhanced biochemical properties of soybean root nodule asparaginase through plant molecular farming compared to bacterial enzyme for cancer treatment

Asparaginase is a therapeutic enzyme used as an anticancer agent and is typically produced through microbial fermentation using organisms such as Escherichia coli and Erwinia chrysanthemi. However, this method faces challenges, including potential enzyme contamination during production, allergic reactions to the enzyme, and stability issues requiring stringent control measures. An innovative solution is the application of plant molecular farming, utilizing Rhizobium root symbiosis for asparaginase production. The objective is to optimize nodule development for asparaginase yield, characterize the enzyme's properties, and evaluate its anticancer efficacy against microbial enzyme. In our study, we established soybean root cultures and inoculated them with Bradyrhizobium japonicum to form root nodules. We evaluated eukaryotic asparaginase production at different incubation times. We purified asparaginase from the root nodule cultures and compared its physicochemical properties and anticancer activity with microbial asparaginase. Results showed that asparaginase reached maximum activity in root nodule cultures 10 days after rhizobium inoculation in the culture media. The root nodule asparaginase exhibited a high content of alpha helices and beta sheets and a low random coil. It demonstrated higher stability and activity across different pH levels and temperatures than Escherichia coli asparaginase. Additionally, root nodule asparaginase displayed better catalytic parameters and stability over time than E. coli asparaginase. Thus, root nodule asparaginase is superior to E. coli asparaginase as an anticancer agent. This ensures the root nodule asparaginase can effectively target cancer cells, enhancing the overall therapeutic outcome. This provides a renewable, cost-effective, and environmentally friendly alternative to traditional enzyme production methods.

Structure-based virtual screening of novel chitin synthase inhibitors for the control of Phytophthora sojae.

Chitin synthase (CHS) is an important target for pesticide development as chitin biosynthesis is essential for the survival and reproduction of various organisms, such as oomycetes, fungi and insects. Small-molecule inhibitors of CHS have potential applications for the control of agricultural pests and diseases. In this study, exploiting the cryo-EM structures of PsChs1, the CHS indispensable to the sporangial production and virulence of soybean root rot pathogenic oomycete Phytophthora sojae, a virtual screening method combining by molecular docking, inhibitory activity measurement and biological activity determination was conducted, to identify novel small-molecule inhibitors of CHS. A chemical library containing ≈1.8 million compounds was screened, and four potent inhibitors (HS-20, HS-24, HS-36 and HS-40) were identified. Amongst these compounds, HS-20 showed the most potent inhibitory activity with a Ki value of 4.2 ± 0.2 μM. Besides inhibitory activities towards PsChs1, these compounds were effective in decreasing sporangial production and preventing zoospore infection. When inoculated with zoospores, HS-20 and HS-24 completely inhibited the growth of P. sojae, suggesting their potential in its prevention and control. This study identified four new compounds with potent chitin synthase (CHS) inhibitory activity, all of which significantly reduce sporangia production and zoospore infection. It also presents promising in silico techniques and small molecule candidates for the design and development of novel CHS inhibitors. © 2024 Society of Chemical Industry. Published by John Wiley & Sons Ltd.

Bacillus amyloliquefaciens strain BaNCT02: An antagonist with multiple mechanisms of action against Meloidogyne incognita

AbstractBacillus species are among the most studied and commercially exploited biocontrol agents of plant‐parasitic nematodes. These antagonists may control nematodes by producing toxic or repellent substances, inducing systemic resistance in plants and disrupting nematode chemotaxis. Understanding the mechanism of action of antagonists increases the likelihood of success for microbiological nematicides under field conditions. Therefore, the objective of this work was to elucidate the mechanisms of action of Bacillus amyloliquefaciens strain BaNCT02 against Meloidogyne incognita. We assessed the potential of this strain for forming biofilm in roots and producing volatile and non‐volatile toxic substances. BaNCT02 did not induce systemic resistance in tomato plants against M. incognita. Scanning electron microscopy and chemotaxis analyses revealed that the bacteria form a biofilm on soybean roots and 67% of second‐stage juveniles of M. incognita are repelled by common bean roots treated with the antagonist. Additionally, BaNCT02 produces substances with toxic effects against eggs and juveniles of M. incognita, including volatile organic compounds such as 2‐undecanone and 2‐heptanone, as well as non‐volatile metabolites like proteases and chitinases. The suppressive effect of these substances on hatching and mortality of juveniles varied from approximately 70% to more than 90%. We concluded that B. amyloliquefaciens BaNCT02 forms a biofilm on root surfaces and produces volatile and non‐volatile metabolites with nematicidal and repellent effects against M. incognita.

Crystal structure and function of a phosphate starvation responsive protein phosphatase, GmHAD1-2 regulating soybean root development and flavonoid metabolism.

Phosphate (Pi) availability is well known to regulate plant root growth. However, it remains largely unknown how flavonoid synthesis participates in affecting plant root growth in response to Pi starvation. In the study, the crystal structure of a plant protein phosphatase, GmHAD1-2, was dissected using X-ray crystallography for the first time. It was revealed that GmHAD1-2 contained a modified Rossmannoid class of α/β folds with three layered α/β sandwich. Transcripts of GmHAD1-2 were increased by Pi starvation in soybean roots, especially in lateral root tips. GmHAD1-2 suppression or overexpression significantly influenced soybean lateral root length and number, as well as phosphorus (P) content. Furthermore, GmHAD1-2 was found to interact with a chalcone reductase, GmCHR1. Suppression of GmHAD1-2 significantly changed the flavonoid biosynthesis pathway in soybean roots. Taken together, the results highlight that GmHAD1-2 can regulate soybean root growth by influencing flavonoid metabolism.

YIELD AND QUALITY RESPONSES OF SOYBEAN (Glycine max. L. Merr.) VARIETIES INOCULATED WITH RHIZOBIA STRAINS UNDER DROUGHT STRESS

The aim of this study was to investigate the effects of nodule formation and nodulation performance of Rhizobia bacteria on yield and quality in soybean roots under limited water application conditions in soybean varieties depending on climate change. In this study, 4 different irrigation applications (limited vs irrigated: 25%, 50%, 75%, 100%), 2 soybean varieties (Cinsoy and Altınay) and 3 different Rhizobia inoculants (Control, AZOTEK-2, USDA-110) were applied for two years (2020-2021) in order to determine the yield and quality characteristics of soybean. The experiment was established according to randomized complete block split-split plots experimental design with 3 replications. In the experiment, the main factor was Rhizobia inoculant treatments, the first sub-factor was soybean varieties, and the second sub-factor was irrigation applications. Within the scope of the study, yield and quality parameters such as plant height (cm), first pod height (cm), number of pods plant-1, number of seeds pod-1, seed yield (kg ha-1), 1000 seed weight (g), leaf area (cm2 plant-1), seed crude protein (%) and oil content (%) were examined. It was concluded that irrigation and inoculant applications and combinations of these factors had significant effects on yield parameters of soybean varieties. The study revealed that there was no discernible nodulation development observed in soybean roots under both irrigated and limited irrigation conditions. It was determined that under conditions of limited irrigation combined with high temperature conditions, the growth of the soybean was significantly impacted, resulting in a notable reduction in yield and leaf area but this was not observed in the quality characteristics.

Surface liming combined with the use of monoammonium phosphate and elemental sulphur in a no‐till wheat–soybean cropping system

AbstractTropical and subtropical soils typically have high acidity and limited nutrient availability. Surface liming under no‐till systems ameliorates topsoil acidity in the short term, but it is generally slow to neutralize subsoil acidity. A field experiment was conducted in the period from 2016 to 2021 in Parana State, Brazil, on a loamy, kaolinitic, thermic Typic Hapludox to evaluate the effects of surface application of lime combined with the use of monoammonium phosphate (MAP) and elemental S on soil acidity, root growth, plant nutrition and grain yields of wheat (Triticum aestivum L.) and soybean (Glycine max. [L.] Merr.) under no‐till. Treatments consisted of a control (no amendments), surface lime (SL), SL + MAP and SL + MAP + elemental S. Applying lime to the soil surface increased soil pH, exchangeable Ca2+ and Mg2+ contents and base saturation, as well as reducing Al3+ content and Al3+ saturation throughout the soil profile. Such effects were more pronounced in the 0–10 cm layer and occurred to a lesser extent in the 10–100 cm layers. The addition of MAP or MAP + elemental S did not improve the effectiveness of surface liming in alleviating soil acidity throughout the soil profile. The root length per soil surface area to a depth of 100 cm exhibited a strong correlation with wheat yield, but not with soybean yield. Surface liming increased wheat yield by 40% and when lime application was combined with MAP + elemental S, the increase in wheat yield reached 74%. Surface liming resulted in a 36% increase in soybean yield, regardless of the use of MAP and elemental S. Thus, surface application of lime was effective in reducing soil acidity to a 100‐cm depth, regardless of fertilizer application with MAP and MAP + elemental S. The improving effects of surface liming had a more favourable impact on wheat root growth than on soybean root growth, probably because wheat was more affected than soybean by insufficient rainfall during the crop development cycle. Wheat showed a greater yield response to P and S fertilizer application than soybean.

Effects of the combination of biochar and organic fertilizer on soil properties and agronomic attributes of soybean (Glycine max L.)

This research aimed to investigate the impacts of a combination of rice husk biochar and organic fertilizer on the physical and chemical properties of soil, the population of soil bacteria, the relative chlorophyll content of leaves, the development of soybean root nodules, and yield components under strongly acid soil conditions. A greenhouse and pot experiment was designed using a randomize complete block design with factorial 2 × 3 treatments and three replications. The experimental treatments comprised two rates of biochar (35 and 70 g/pot) and three rates of organic fertilizer (70, 105, and 140 g/pot). After 100 days of amendment of strongly acidic soils, the results showed that application of treatments B35F70 and B70F140 increased soil pH by 16.80% compared to the control group (CK). On the other hand, treatments B35F140 and B70F105 resulted in an increase of soil electrical conductivity by 66.67% compared to CK. In addition, after 100 days of amendment with treatments B35F105, B35F105, B35F140, B70F105, B70F70, B70F70, and B35F140, organic matter, available phosphorous (P), potassium (K), calcium (Ca), magnesium (Mg), copper (Cu), and zinc (Zn), organic matter, available phosphorous (P), potassium (K), calcium (Ca), magnesium (Mg), copper (Cu), and zinc (Zn), significantly increased when compared to the control group (CK). Treatment B35F140 increased relative leaf chlorophyll content and soybean seed weight per plant by 60.76% and 100.56%, respectively when compared to the CK. Furthermore, treatment B35F70 produced 125% more root nodules than CK. Moreover, each amended strongly acid soil resulted with a significant upsurge in total soil bacteria compared to the CK. Overall, statistics proved that a combination of biochar and organic fertilizer improved soil properties and soybean agronomic attributes.