In modern agricultural practice, heavy metal (HM) contamination is one of the main abiotic stress threatening sustainable agriculture, crop productivity, and disturb natural soil microbiota. Different reclamation techniques are used to restore the contaminated site; however, they are either costly or unable to remove contaminant when concentration is very low. In such circumstances, bioremediation is used as a novel technique involving microbes for soil restoration. In the current project, Aspergillus welwitschiae(Bk) efficiently endure metal stress (i.e., Cr-VI and As-V in the form of K₂Cr₂O₇ and Na₃AsO₄) up to 1200 μg/mL and enhanced the production of phytohormones, i.e., 54.83 μg/mL of indole acetic acid (IAA) compared to control 15.56 μg/mL, solubilized inorganic phosphate, and produced stress-related metabolites. The isolate Bk was able to enhance growth of soybean by showing higher root shoot length and fresh/dry weight under stress (p<0.05). Besides, the strain strengthened the antioxidant system of the host increasing enzymatic antioxidants, i.e., catalases (CAT) by 1.58 and 1.11 fold, ascorbic acid oxidase (AAO) by 6.75 and 7.94 fold, peroxidase activity (POD) by 1.12 and 1.37 fold, and 1,1-diphenyl-2-picrylhydrazyl (DPPH) by 1.42 and 1.25 fold at 50 μg/mL of chromate and arsenate. Thus, actively scavenging the reactive oxygen species (ROS) produced results in lower ROS accumulation and high ROS scavenging. On the other hand, the isolates cut down Cr and As uptake by approximately 50% at 50 μg/mL from the medium while bio-transforming it, thereby stabilizing it and assisting the host to resume normal growth, thus avoiding phytotoxicity. It is evident from the current study that A. welwitschiae may potentially be used as a bioremediating agent for reclamation of Cr- and As-contaminated soil.

Row crop agriculture systems are a significant contributor to non-point source nutrient loading into water bodies. One approach to reduce phosphorus (P) losses through surface runoff is applying flue gas desulfurization (FGD) gypsum as a soil amendment. This research was conducted to examine the effects of different rates of FGD gypsum application to corn (Zea mays L.)–soybean (Glycine max) plots on water quality parameters including dissolved reactive phosphate (DRP), total phosphorus (TP), and total suspended solids (TSS). The study was conducted on a high P level (>30 mg P kg⁻¹) soil in a completely randomized design with four treatments each replicated three times. The four treatments were no FGD gypsum (control), FGD gypsum at a rate of 2.2 Mg ha⁻¹, FGD gypsum at 4.5 Mg ha⁻¹, and FGD gypsum at 13.5 Mg ha⁻¹. Gypsum applications were effective in reducing P loads in surface runoff water, with a significant (P < 0.1) reduction in DRP and TP from all the treatments compared to the control during the initial post-gypsum application period (December 2018–May 2019). Results suggest application rates of 4.5 Mg ha⁻¹ and 13.5 Mg ha⁻¹ were most suitable to reduce P loads in surface runoff water from Hosmer silt loam soil with high soil test P (STP) prior to P fertilizer application. However, following P fertilizer application (May 2019–January 2020), gypsum was not effective in reducing P in surface runoff. Overall, FGD gypsum appeared to be an effective phosphorus abatement tool for southern Illinois soils to improve water quality. Though, how long it remains effective appears to be in question given our results in the post P fertilization period.

Disadvantages associated with chemical coagulants and goal of sustainable development have shifted the focus to natural plant-based coagulants. Raw and defatted soybean (Glycine max L.) seed powder, as innovative and eco-friendly coagulant, was appraised in detail for turbid water treatment and compared with alum in this study. Design of experiments was conducted by employing response surface method which lacks in past studies pertaining to plant-based coagulants. Experiments were conducted with lab prepared turbid water with initial turbidity of 200 NTU and wide range of pH (2–10) and dose (20–100 mg/L). Results revealed that raw and defatted soybean gave residual turbidities of 4 and 3 NTU at optimum conditions which were comparable to alum. Analysis of variance (ANOVA) identified that pH was more significant parameter as compared with dose for soybean and alum, while interaction of pH and dose was most significant in case of defatted soybean. Characterization of the coagulants and flocs, by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscope (SEM), revealed that postulated mechanism of coagulation for plant-based coagulants is adsorption and charge neutralization. Cost of treating 1000 m³ of water by raw and defatted soybean is lower (US$12 and US$3.9 respectively) compared with alum (US$31.2).

Heavy metal accumulation in crop grains due to hazardous metal contamination is considered a great concern. However, phytobeneficial fungi are reported to have important abilities for the biosafety of crops grown in contaminated soil. Therefore, the current study was undertaken to explore the mutualistic association of plant growth-promoting endophytic fungi in reducing heavy metal concentration in the seeds of soybean plants subsequently grown in contaminated soil, without comprising seed quality and biochemical profile. The results revealed that endophytic Paecilomyces formosus LHL10 and Penicillium funiculosum LHL06 synergistically produced higher amounts of GAs and IAA in a co-cultured medium. Moreover, the co-inoculation of LHL06 and LHL10 to soybean plants grown under multi-metal toxic conditions significantly mitigated the adverse effects of heavy metal toxicity and increased the seed production (number of pods per plants, number of seeds per pod, and 100 seed weight) of soybean plants grown under control and multi-metal toxic conditions. Moreover, the levels of carbohydrates (glucose, sucrose, and fructose), minerals (iron, calcium, magnesium, and potassium), amino acids (serine, glutamic acids, glycine, methionine, lysine, arginine, and proline), and antioxidants (superoxide dismutase, catalase, and peroxidase) were significantly enhanced in sole and co-inoculated plants under control and stress conditions. Whereas organic acids (citric acid, tartaric acid, malic acid, and succinic acid), lipid peroxidation (MDA) products, multi-metal accumulation (nickel, cadmium, copper, lead, chromium, and aluminum), and stress-responsive endogenous abscisic acid levels were significantly decreased in seeds of soybean plants grown under control and multi-metal toxic conditions upon LHL06 and LHL10 sole and co-inoculation. The current results suggested the positive biochemical regulation in seeds for improving the nutritional status and making it safe for human consumption.

Two cultivars of soybean (Pusa 9814 and Pusa 9712) were investigated to evaluate the impact of ambient and elevated concentrations of ozone (O3) in a suburban site of India with and without application of 400 ppm ethylenediurea (EDU) in open top chambers having filtered air (FCs), non-filtered air (NFCs), and non-filtered plus 20 ppb O3 (NFCs + 20 ppb). Significant reductions were observed in various growth parameters, biomass accumulation, and yield attributes of soybean cultivars due to ambient O3 in NFCs and elevated concentration of O3 in NFCs + 20 ppb. Reductions in all parameters were of lower magnitude in plants treated with EDU as compared to non-EDU treated plants. Yield (weight of seeds plant−1) increased by 29.8% and 33% in Pusa 9712 and by 28.2% and 29.0% in Pusa 9814 due to EDU treatment in plants grown at ambient and elevated levels of O3, respectively. The results clearly showed that (a) EDU can be effectively used to assess phytotoxicity of O3 by providing protection against its deleterious effects, (b) EDU can be used for biomonitoring of O3 in areas experiencing its higher concentrations, and (3) EDU is more effective against higher concentrations of O3.

Diverting the infiltrating water away from the zone of N application can reduce nitrate-nitrogen (NO₃-N) leaching losses to groundwater from agricultural fields. This study was conducted from 2001 through 2005 to determine the effects of N-application methods using a localized compaction and doming (LCD) applicator and spoke injector on NO₃-N leaching losses to subsurface drainage water and corn (Zea mays L.)-soybean (Glycine max L.) yields. The field experiments were conducted at the Iowa State University's northeastern research center near Nashua, Iowa, on corn-soybean rotation plots under chisel plow system having subsurface drainage ‘tile' system installed in 1979. The soils at the site are glacial till derived soils. The N-application rates of 168 kg-N ha⁻¹ were applied to corn only for both the treatments each replicated three times in a randomized complete block design. For combined 5 years, the LCD N-applicator in comparison with spoke injector showed lower flow weighted NO₃-N concentrations in tile water (16.8 vs. 20.1 mg L⁻¹) from corn plots, greater tile flow (66 vs. 49 mm), almost equivalent NO₃-N leaching loss with tile water (11.5 vs. 11.3 kg-N ha⁻¹) and similar corn grain yields (11.17 vs. 11.37 Mg ha⁻¹), respectively, although treatments effects were found to be non-significant (p = 0.05) statistically. The analysis, however, revealed that amount and temporal distribution of the growing season precipitation also affected the tile flow, NO₃-N leaching loss to subsurface drain water, and corn-soybean yields. Moreover, the spatial variability effects from plot to plot in some cases, resulted in differences of tile flow and NO₃-N leaching losses in the range of three to four times despite being treated with the same management practices. These results indicate that the LCD N-applicator in comparison with spoke injector resulted in lower flow weighted NO₃-N concentrations in subsurface drain water of corn plots; however, strategies need to be developed to reduce the offsite transport of nitrate leaching losses during early spring period from March through June.

Changes in land-use or management practices may affect water outflow, sediment, nutrients and pesticides loads. Thus, there is an increasing demand for quantitative information at the watershed scale that would help decision makers or planners to take appropriate decisions. This paper evaluates by a modeling approach the impact of farming practices and land-use changes on water discharge, sediment and NO3-N loads at the outlet of a 51.29 km2 watershed of central Iowa (Walnut Creek watershed). This intensively farmed (corn-soybean rotation) watershed is characterized by a flat topography with tiles and potholes. Nine scenarios of management practices (nitrogen application rates: increase of current rate by 20, 40%, decrease of current rate by 20, 40 and 60%; no tillage) and land-use changes (from corn-soybean rotation to winter wheat and pasture) were tested over a 30 yr simulated period. The selected model (Soil and Water Assessment Tool, SWAT) was first validated using observed flow, sediment and nutrient loads from 1991 to 1998. Scenarios of N application rates did not affect water and sediment annual budgets but did so for NO3-N loads. Lessening the N rate by 20, 40 and 60% in corn-soybean fields decreased mean NO3-N annual loads by 22, 50 and 95%, respectively, with greatest differences during late spring. On the other hand, increasing input N by 20 and 40% enhanced NO3-N loads by 25 and 49%, respectively. When replacing corn-soybean rotation by winter wheat, NO3-N loads increased in early fall, immediately after harvest. Pasture installation with or without fertilization lessened flow discharge, NO3-N and sediment delivery by 58, 97 and 50%, respectively. No-tillage practices did not significantly affect the water resource and sediment loads. Finally, such realistic predictions of the impact of farming systems scenarios over a long period are discussed regarding environmental processes involved.

The scope of this study is to analyze the climatic potential productivity of soybean [Glycine max (L.) Merr.] and explore the impact of climate change on soybean in the frigid region in China by using daily climatic variables from 144 meteorological stations for the period 1971‒2019. The gradually descending model is used to estimate photosynthesis, light-temperature, and climatic potential productivity of soybean. The results show that climate potential productivity of soybean in the frigid region ranges from large to small: Liaoning > Jilin > Heilongjiang > East Four Leagues (four cities in eastern Inner Mongolia), with Heilongjiang and East Four Leagues showing a significant upward trend. Spatially, the climate potential productivity is larger on plains than that on mountains. The Northeast Plain and Sanjiang Plain are areas with high climate potential productivity. Changes in climatic factors have different impacts on the climate potential productivity of soybean. The influence of temperature changes on the climate potential productivity shows a positive effect, and climate warming compensates for the lack of heat in the frigid region. Furthermore, radiation and precipitation are the main climatic factors leading to spatial differences in the climate potential productivity of soybean in the frigid region. Radiation changes have a positive effect on soybean climate potential productivity in plain areas and a negative effect on the mountains. However, precipitation reduction negatively affects most of the frigid region, while it has a positive effect on the two plains of Heilongjiang. Precipitation responses the needs of soybean growth. Our findings recommend that a transition of soybean planting from the mountainous region to plain, that is, from low potential productivity areas to high potential productivity areas, could be an effective strategy for regional optimization for planting structure and rational utilization of irrigation technology.