Response of peanut (Arachis hypogaea L.) plant to bio-fertilizer and plant residues in sandy soil.

Nitrogen (N) fertilizer has been intensively used to improve peanut productivity. However, the high cost of N fertilizer, and the need for sustainable alternative fertilizer sources have increased the strategic importance of nitrogen fixation (NF). Thus, field experiments were conducted in an experimental farm with a drip irrigation system, at the Atomic Energy Authority, Inshas, Egypt, in order to measure the impact of efficiency symbiotic Bradyrhizobium sp. and asymbiotic Azotobacter sp. on NF, from air and soil, in the presence or absence of plant residues on the growth and yield of peanut plant. All treatments received nitrogen fertilizer at a rate of 72 kg N per hectare. Nitrogen dose was applied using ammonium sulphate 15N labeled of 10% atom excess from the peanut. Results indicated that the application of Bradyrhizobium sp. with plant residues significantly increased fresh and dry weight/m2, pod and seed weight/plant-1,100- seed weight, and biological yield kg ha-1, where the highest mean values of seed yield (4648 and 4529 kg ha-1), oil % (52.29 and 52.21%), seed protein percentage (16.09 and 15.89%), as well as nitrogen derived from air (63.14 and 66.20%) in the first and second seasons were recorded under the application of Bradyrhizobium sp, respectively. Bradyrhizobium sp. inoculation showed nearly close portions of Ndfa to those recorded with Azotobacter sp., in both the presence and absence of plant residue application through the two seasons. The investigated yield signs and their properties were significantly enhanced by bacterial inoculation with plant residue application. The present study shows that both possibility of NF of peanut, and nitrogen uptake in the soil are enhanced by field inoculation with effective Bradyrhizobium sp. with plant residue application. In practice, inoculation is a great strategy to improve soil fertility for subsequent planting, since it helps boost the import of nitrogen from plant biomass into the soil.

Exogenous melatonin mitigates chromium toxicity in maize seedlings by modulating antioxidant system and suppresses chromium uptake and oxidative stress.

Melatonin, being an endogenous signaling molecule plays important role in plant growth and stress alleviation. The present study was conducted to evaluate the ameliorative role of melatonin against Cr toxicity in maize seedlings. The Cr toxicity (50, 100 and 200 µM) severely affected hydroponically grown seedlings growth in a dose-dependent manner; however, the melatonin (0.5 and 1.0 µM) application markedly restored toxicity-induced growth retardation. Higher dose of melatonin (1.0 µM) was more effective in case of lower Cr toxicity (50 and 100 µM). Exposure of 200 µM Cr caused 45% and 43% reduction in shoot and root lengths and more than 80% reduction in biomass. In case of 200 µM Cr toxicity, application of 1.0 µM MT effectively restored shoot and root lengths reduction (from 45 to 30%) and biomass decline (from 80 to around 60%). Biomass restoration by 1.0 µM melatonin under 50 and 100 µM Cr was even more pronounced bringing it near to control plants having no Cr exposure. Further, both melatonin levels also improved root tips, root diameter, root volume and root surface area that had been damaged by Cr exposure. The melatonin also alleviated Cr-induced chlorophyll and carotenoids inhibition, improved relative water content, and markedly lowered proline and MDA content in shoots. Lower accumulation of MDA and proline, and greater membrane stability indices indicate that the melatonin conferred better plant growth by playing the role of antioxidant and detoxifying oxidative stress creating substances. Although antioxidant enzymes viz. SOD, POD, CAT and APX activities were also elevated by MT, this increase was not significantly different in the most of cases. No significant difference in NPK contents of shoot was observed by Cr and melatonin application indicating the growth retardation being caused directly by Cr intrinsic toxicity and not by nutrients deficiency. The melatonin-based amelioration of Cr toxicity in maize seedlings seems as the result of its nature as antioxidant, and not by activation/elevation of antioxidative enzymatic system.

Diazotrophic Community Variation Underlies Differences in Nitrogen Fixation Potential in Paddy Soils Across a Climatic Gradient in China.

Biological nitrogen (N2) fixation as a source of new N input into the soil by free-living diazotrophs is important for achieving sustainable rice agriculture. However, the dominant environmental drivers or factors influencing N2 fixation and the functional significance of the diazotroph community structure in paddy soil across a climatic gradient are not yet well understood. Thus, we characterized the diazotroph community and identified the ecological predictors of N2 fixation potential in four different climate zones (mid-temperate, warm-temperate, subtropical, and tropical paddy soils) in eastern China. Comprehensive nifH gene sequencing, functional activity detection, and correlation analysis with environmental factors were estimated. The potential nitrogenase activity (PNA) was highest in warm-temperate regions, where it was 6.2-, 2.9-, and 2.2-fold greater than in the tropical, subtropical, and mid-temperate regions, respectively; nifH gene abundance was significantly higher in warm-temperate and subtropical zones than in the tropical or mid-temperate zones. Diazotroph diversity was significantly higher in the tropical climate zone and significantly lower in the mid-temperate zone. Non-metric multidimensional scaling and canonical correlation analysis indicated that paddy soil diazotroph populations differed significantly among the four climate zones, mainly owing to differences in climate and soil pH. Structural equation models and automatic linear models revealed that climate and nutrients indirectly affected PNA by affecting soil pH and diazotroph community, respectively, while diazotroph community, C/P, and nifH gene abundance directly affected PNA. And C/P ratio, pH, and the diazotroph community structure were the main predictors of PNA in paddy soils. Collectively, the differences in diazotroph community structure have ecological significance, with important implications for the prediction of soil N2-fixing functions under climate change scenarios.

Effect of urea fertilization on growth of broad bean (Vicia faba L.) under various nickel (Ni) levels with or without acetic acid addition, using 15N-labeled fertilizer.

Although nickel (Ni) has direct relationship with nitrogen metabolism of plants, the high dose of Ni fertilizer in broad bean plants may affect the nitrogen use efficiency (NUE), impair plant development and even cause Ni pollution in soil. Thus, a pot experiment was set up to study the effect of urea fertilization on N-uptake, root and shoots' Ni content as well as growth of broad bean plants under different levels of Ni, using 15N tracer technique. 15N-labeled urea (5% 15N atom excess) was added at three doses (0, 30 and 60 mg N kg-1 soil). Nickel sulfate (NiSO4) was also applied at three levels (0, 50 and 100 mg Ni kg-1 soil). The experiment was laid out with or without acetic acid in randomized complete block design in three replicates. Treatment with the addition of 60 mg N + 50 mg Ni showed the highest values in dry weights of root and shoots, N-uptake by shoots, nitrogen derived from fertilizer (Ndff %) and NUE % by shoots in both with or without acetic acid solution. Higher rate of Ni addition can decrease shoot and root biomass by inhibiting the ability of the plant to uptake the nitrogen efficiently. However, addition of acetic acid solution induced the improvement of NUE % and Ndff % by shoot and root of broad bean plants. This study provides insight into how to improve plant yield without damaging the soil health and will be helpful to create a better world with sustainable agriculture.

Effect of intercropping and biochar amendments on lead removal capacity by Corchorus olitorius and Zea mays.

Intercropping is a sustainable strategy recognized for boosting crop production and mitigating heavy metal toxicity in contaminated soils. This study investigates the effects of biochar amendments on Pb-contaminated soil, utilizing monocropping and intercropping techniques with C. olitorius and Z. mays. The research assesses Pb removal capacity, nutrient uptake, antioxidant enzymes, and soil Pb fractionation. In monocropping, the phytoremediation ratio for C. olitorius increased from 16.67 to 27.33%, while in intercropping, it rose from 19.00 to 28.33% with biochar amendments. Similarly, Z. mays exhibited an increased phytoremediation ratio from 53.33 to 74.67% in monocropping and from 63.00 to 78.67% in intercropping with biochar amendments. Intercropping significantly increased the peroxidase (POD) activity in Z. mays roots by 22.53%, and there were notable increases in shoot POD of C. olitorius (11.54%) and Z. mays (16.20%) with biochar application. CAT showed consistent improvements, increasing by 37.52% in C. olitorius roots and 74.49% in Z. mays roots with biochar. Biochar amendments significantly increased N content in soil under sole cropping of Z. mays and intercropping systems. In contrast, Cu content increased by 56.34%, 59.05%, and 79.80% in monocropping (C. olitorius and Z. mays) and intercropping systems, respectively. This suggests that biochar enhances nutrient availability, improving phytoremediation efficacy in Pb-contaminated soil. Phyto availability of trace metals (Zn, Mn, Cu, and Fe) exhibited higher levels with biochar amendments than those without. The findings indicate that intercropping and biochar amendments elevate antioxidant enzyme levels, reducing reactive oxygen species and mitigating Pb toxicity effects. This approach improves phytoremediation efficiency and holds promise for soil pollution remediation while enhancing nutrient content and crop quality in Pb-contaminated soil.

Effect of land use on soil properties, microbial abundance and diversity of four different crop lands in central Myanmar.

Changing land use systems impact on local edaphic factors and microbial abundance and diversity, however, the information on it in central Myanmar's soils is still lacking. Therefore, soils with four different land uses were analyzed; WAP (soil from perennial tree orchard), PNON (soil from crop rotation of peanut and onion), SESA (soil from mono-crop of sesame) and CHON (soil from mono-crop of onion for 3 years consecutively). Soil organic carbon (SOC), total nitrogen (TN), dissolved organic carbon (DOC), ammonium nitrogen (NH4 +-N) and pH showed the highest in PNON soil, which suggested crop rotation with high fertilizer input and irrigation had positive effect on the edaphic factors of soil. CHON soil showed the lowest in most soil properties and microbial abundance as a result of intensive use of fertilizer and irrigation, no crop rotation and no input of manures. Microbial community composition showed differences among tested soils and relative abundance of Chloroflexi was the highest in CHON soil whereas that of Basidiomycota was the highest in WAP soil. The abundances of bacteria and fungi were significantly affected by Olsen P, whereas the abundances of archaea were influenced by SOC. Our results suggested crop rotation and manure fertilization (PNON soil) enhanced soil properties and microbial abundance although long-time onion mono-crop (CHON soil) reduced soil fertility. This study can provide information to improve soil quality and sustainability of agro-ecosystems using appropriate agricultural management. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13205-021-02705-y.

Improved immobilization of soil cadmium by regulating soil characteristics and microbial community through reductive soil disinfestation.

Cadmium (Cd) contamination arising from industrialization has attracted increasing attention in recent years. Reductive soil disinfestation (RSD) as an effective agricultural practice has been widely applied for soil sterilization. However, there is little research regarding RSD affecting Cd immobilization. Here, five treatments, namely untreated soil (CK), flooding-treated soil (FL), RSD with 2% ethyl alcohol (EA), 2% sugarcane bagasse (SB), and 2% bean dregs (BD) were designed to detect their performance for Cd immobilization in contaminated soils, and the change of soil properties and microbial communities were monitored. The results revealed that pH significantly increased in FL and RSD-treated soils, but was negatively correlated with the exchangeable fraction of Cd (EX-Cd), while Oxidation-Reduction Potential (Eh) significantly decreased in FL and RSD-treated soils, and was positively correlated with EX-Cd. BD treatment might contribute to the increase of CaCO3 as shown by X-Ray Diffractomer analysis and strongly decreased the EX-Cd in the soil, but increased the relative abundances of Firmicutes, Planctomycetes, Acidobacteria, and Gemmatimonadetes, which may promote Fe (III) reduction or induce resistance to Cd. Bacterial communities at the phylum and genus levels were closely related to Cd fraction. The FL and RSD treatments moderately altered bacterial specific functions, including iron respiration, which may contribute to remediation of Cd-polluted soil by Fe (III) reduction. Field experiments were conducted to confirm that BD treatment resulted in a significant increase in pH whereas the content of total available Cd was reduced in soils. Compared to the control, concentration of total available Cd of red amaranth, sweet potato, towel gourd, and cowpeas were reduced by approximately 46%, 74%, 72%, and 76% in a BD-treated field, respectively. Our study highlights the potential of RSD as an effective method for Cd immobilization in contaminated soils by improving soil characteristics and altering the composition of the microbial community.