Biostimulants induce positive changes in the radish morpho-physiology and yield.

An ever-increasing population has issued an open challenge to the agricultural sector to provide enough food in a sustainable manner. The upsurge in chemical fertilizers to enhance food production had resulted in environmental problems. The objective of the current study is to assess the utilization of biostimulants for sustainable agricultural production as an alternative to chemical fertilization. For this purpose, two pot experiments were conducted to examine the response of radish against individual and combined applications of biostimulants. In the first experiment, the effects of chemical fertilizer (CK), glycine (G), lysine (L), aspartic acid (A), and vitamin B complex (V) were studied. The results demonstrated that V significantly improved the transpiration rate (81.79%), stomatal conductance (179.17%), fresh weight (478.31%), and moisture content (2.50%). In the second experiment, tested treatments included chemical fertilizer (CK), Isabion® (I), glycine + lysine + aspartic acid (GLA), moringa leaf extract + GLA (M1), 25% NPK + M1 (M2). The doses of biostimulants were 5g L-1 glycine, 1g L-1 lysine, 2g L-1 aspartic acid, and 10 ml L-1 moringa leaf extract. The photosynthetic rate improved significantly with GLA (327.01%), M1 (219.60%), and M2 (22.16%), while the transpiration rate was enhanced with GLA (53.14%) and M2 (17.86%) compared to the Ck. In addition, M1 increased the stomatal conductance (54.84%), internal CO2 concentration (0.83%), plant fresh weight (201.81%), and dry weight (101.46%) as compared to CK. This study concludes that biostimulants can effectively contribute to the sustainable cultivation of radish with better growth and yield.

Determining the appropriate level of farmyard manure biochar application in saline soils for three selected farm tree species.

Salinity is a global problem, and almost more than 20% of the total cultivated area of the world is affected by salt stress. Phytoremediation is one of the most suitable practices to combat salinity and recently biochar has showed the tremendous potential to alleviate salt-affected soils and enhance vegetation. Trees improve the soil characteristics by facilitating the leaching of salts and releasing organic acids in soil. Moreover, in the presence of trees, higher transpiration rates and lower evaporation rates are also helpful in ameliorating salt affected soils. This study was designed to check the effect of different levels of biochar on the morph-physiological characteristics of three important agroforestry tree species: Eucalyptus camaldulensis, Vachellia nilotica, and Dalbergia sissoo, in saline soils. Farmyard manure biochar was applied at the rate of 3% (w/w), 6% (w/w), and 9% (w/w) to find appropriate levels of biochar for promoting the early-stage trees growth under saline conditions. Results of the current study revealed that maximum shoot length (104.77 cm), shoot dry weight (23.72 g), leaves dry weight (28.23 g), plant diameter (12.32 mm), root length (20.89 cm), root dry weight (18.90 g), photosynthetic rate (25.33 µ moles CO2 m-2s-1) and stomatal conductance (0.12 mol H2O m-2 s-1) were discovered in the plants of Eucalyptus camaldulensis at the rate of 6% (w/w). All tree species showed better results for growth and physiological characteristics when biochar was applied at the rate of 6% (w/w). In comparison, a decreasing trend in growth parameters was found in the excessive amount of biochar when the application rate was increased from 6% (w/w) to 9% (w/w) for all three species. So, applying an appropriate level of biochar is important for boosting plant growth in saline soils. Among different tree species, Vachellia nilotica and Eucalyptus camaldulensis both showed very promising results to remediate salt affected soils with Vachellia nilotica showing maximum potential to absorb sodium ions.

Role of sugarcane industrial byproducts on soil physicochemical properties and metal accumulation in rice.

Sugar industry produces a variety of organic byproducts causing disposal as well as environmental issues. This study investigated the safe use of these byproducts in assessment of soil physicochemical properties and metal accumulation in rice. A field experiment was performed with following treatments: control only NPK (CF), NPK + sugarcane bagasse (SB), NPK + press mud (PM), NPK + sugarcane vinasse (SV), NPK + SB + PM (SB + PM), NPK + SB + SV (SB + SV), NPK + PM + SV (PM + SV), NPK + SB + PM + SV (SB + PM + SV). Total byproduct input was (1.25 t ha-1) as recommended for organic inputs in the local area. The results indicated that integrated use of these amendments with chemical fertilization improved soil properties and rice yield. Organic matter was significantly improved in SB + SV (191.3%), SB + PM + SV (164.4%), and SB + PM (150.9%). Total N was significantly enhanced in SB + SV (193%), SB + PM + SV (166%), and SB + PM (152.5%); extractable P was high in SB (103%), PM + SV (89.7%), and SB + PM (51%); extractable K was significantly improved in PM (39.6%) and SB (33.4%); extractable Zn was significantly enhanced in SB (1172.8%), SV (829.2%) and PM (819.1%) in soil. Rice grain yield was significantly enhanced in SB (213.1%) and PM (208.8%) while combined application also improved the yield with reference to the CF. The application of SB + PM improved N (58.7%), P (27.4%), K (11.5%), and Zn (166.4%) concentration in grain, while metal accumulation was within the permissible limit. Zn concentration was significantly enhanced in SB + PM (166.4%) whereas the concentration of Cd and Pb was significantly reduced with the application of byproducts. Health assessment results showed no harmful effects for humans. Results conclude that these byproducts are good nutrients source and improve soil physicochemical properties without any health hazards.

Application of K and Zn Influences the Mineral Accumulation More in Hybrid Than Inbred Maize Cultivars.

Maize (Zea mays L.) is an important crop used for feeding humans and cattle globally. Deficiency of potassium (K) and zinc (Zn) adversely impacts the maize crop productivity and quality. However, the application of these nutrients shows variant responses in different maize cultivars. To understand this perspective, the current study aimed at investigating K and Zn's optimal concentration in different hybrid and inbred maize cultivars. The treatments were based on three zinc levels (0, 6, and 12 mg Zn kg-1) and K levels (0, 30, and 60 mg kg-1), and their respective combinations. The experiment results showed that combined fertilization approaches of Zn and K (Zn12K60) improved the plant biometric, and physiological attributes of maize crop. The results revealed a significant increase in plant height (45%), fresh weight (70%), and dry weight (45%). Similarly, physiological attributes significantly improved the relative water content (76.4%), membrane stability index (77.9%), chlorophyll contents (170%), and photosynthetic rate (130%) in both inbred and hybrid genotypes. Furthermore, Zn and K (Zn12K60) increased transpiration rate (E), stomatal conductance (Ci), and internal CO2. In conclusion, maize hybrids (Neelam and DK-6142) were observed best compared with inbred (Afghoi and P-1543) cultivars with the combined application of Zn and K (Zn12K60). Thus, these inbred varieties should be preferred for fodder requirement with optimum fertilizer (Zn12K60) application in Zn deficient soils.

The interactive effect of pH variation and cadmium stress on wheat (Triticum aestivum L.) growth, physiological and biochemical parameters.

Anthropogenic activities such as mining, manufacturing, and application of fertilizers release substantial quantities of cadmium (Cd) into the environment. In the natural environment, varying pH may play an important role in the absorption and accumulation of Cd in plants, which can cause toxicity and increase the risk to humans. We conducted a hydroponic experiment to examine the impact of pH on cadmium (Cd) solubility and bioavailability in winter wheat (Triticum aestivum L.) under controlled environmental conditions. The results showed that Cd concentration was significantly reduced in wheat with an increase in pH from 5 to 7, while it was dramatically increased at pH ranging from 7 to 9. However, in both cases, a significant reduction in physiological traits was observed. The addition of Cd (20, 50, and 200 µmol L-1) at all pH levels caused a substantial decline in wheat growth, chlorophyll and carotenoids contents, nutrient availability, while elevated cell membrane damage was observed in terms of electrolytic leakage (EL), osmoprotectants, and antioxidants activity. In our findings, the negative effects of acidic pH (5) on wheat growth and development were more pronounced in the presence of Cd toxicities. For instance, Cd concentration with 20, 50, and 200 µmol L-1 at acidic pH (5) reduced shoot dry biomass by 45%, 53%, and 79%, total chlorophyll contents by 26%, 41%, 56% while increased CAT activity in shoot by 109%, 175%, and 221%, SOD activity in shoot by 122%, 135%, and 167%, POD activity in shoot by 137%, 250%, and 265%, MDA contents in shoot by 51%, 83%, and 150%, H2O2 contents in shoot by 175%, 219%, and 292%, EL in shoot by 108%, 165%, and 230%, proline contents in shoot by 235%, 280%, and 393%, respectively as compared to neutral pH without Cd toxicities. On the other hand, neutral pH with Cd toxicities alleviated the negative effects of Cd toxicity on wheat plants by limiting Cd uptake, reduced reactive oxygen species (ROS) formation, and increased nutrient availability. In conclusion, neutral pH minimized the adverse effects of Cd stress by minimizing its uptake and accumulation in wheat plants.

Silicon elevated cadmium tolerance in wheat (Triticum aestivum L.) by endorsing nutrients uptake and antioxidative defense mechanisms in the leaves.

Numerous abiotic stressors including heavy metal stresses, specifically cadmium (Cd) stress in agricultural bio-system hinder the plant adequate growth. The present study was aimed to reveal the protective role of silicon (Si) application with two levels and to recognize the optimum level of Si for wheat plants grown hydroponically under three different levels of Cd toxicities. In methodology, we used nine treatments with three levels of Si (0, 1, and 3 mmol L-1; Na2SiO3) against three levels of Cd (0, 50, 200 µmol L-1; CdCl2) with three biological replicates. The results of our study demonstrated that Si incorporation with the advantage of 3 mmol L-1 in cultured media with Cd50 and Cd200 demolished the toxic effects of Cd on the leaves of wheat plants by increasing plant dry biomass by 88% and 262%, leaf area by 48% and 57%, total chlorophyll contents by 120% and 74%, catalase (CAT) activity by 92% and 110%, superoxide dismutase (SOD) activity by 62% and 78%, peroxidase (POD) activity by 66% and 40%, ascorbic acid (AsA) contents by 33% and 34%, glutathione (GHS) contents by 39% and 30% and reduced MDA contents by 56% and 50%, H2O2 contents by 61% and 66%, and EL contents by 56% and 47% as parallel to Cd corresponding levels. In addition, Si incorporation with the advantage of 3 mmol L-1 significantly increased relative water contents (RWC) to maintain the cell turgor pressure and protect the plant from wilting and cells flaccid and enhanced membrane stability index (MSI) to protect the plant from logging under damaging effects of Cd toxicities. Based on the present findings, Si can be considered a quasi-essential element that enhanced wheat tolerance against Cd toxicity by limiting uptake, accumulation, and translocation of Cd and through regulating antioxidative defense mechanisms.

Effect of distillery spentwash fertigation on crop growth, yield, and accumulation of potentially toxic elements in rice.

The safe disposal of industrial effluents always remained a challenging process because of their high level of nutrients, toxic elements, and salts. A pot experiment was conducted to investigate the effects of various concentrations (5%, 10%, 15%, and 20%) of sugar industry effluent spentwash (SW) fertigated with tab water (TW), on soil properties, crop growth, physiological parameters, yield components, and accumulation of potentially toxic elements (PTEs) in rice (Oryza sativa L.) grains and straw. The results showed that soil physico-chemical properties were modified with rise in SW concentration. Application of 5% SW significantly enhanced the plant growth, and yield components. Photosynthesis rate, transpiration rate, and stomatal conductance were significantly higher under 5% SW concentration in comparison with control. However, SW concentrations of > 5% showed inhibitory effects for all growth, physiological, and yield components. Accumulation of PTEs showed increasing trend with rise in SW concentration. However, under 5% SW concentration, all the PTEs in rice grain and straw were within the permissible limits (PLs) recommended by FAO/WHO and no health hazards were detected by health risk assessment. Based on the study results, 5% SW fertigation with TW can be applied as fertilizer for enhancing the growth and productivity of rice. Graphical abstract.

Biochar increased photosynthetic and accessory pigments in tomato (Solanum lycopersicum L.) plants by reducing cadmium concentration under various irrigation waters.

Fresh surface water supplies are gradually becoming insufficient in arid and semi-arid regions of the world. Thus, farmers in these areas are being forced to use poor quality sewage water. Irrigating vegetable crops with sewage water having high metal concentration may affect growth and biochemical processes of plants. Biochar (BC) can sorb these metals and may reduce their toxic effects on plants. Thus, a greenhouse experiment was conducted to study the influence of cotton stalks derived biochar (CSDB) at control (0%) and 1%; ground water (GW; 0.01 ppm Cd); cadmium-contaminated water (CCW; 2 ppm Cd); and sewage water (SW; 0.13 ppm Cd) on growth and biochemical processes of tomato (Solanum lycopersicum) plants. On an average, additions of 1% BC significantly (p ≤ 0.05) enhanced dry weight of roots (36%) and shoots (52%) of plants as compared to without BC application. Biochar (1%) decreased shoot Cd concentration by 33% at SW and 100% at CCW. The Cd uptake was increased by 33% with the BC + CCW treatment. Soil organic matter (SOM) was increased 1.2 times while pH and EC were increased by 5 and 47%, respectively, in 1% BC amended soil. Biochar application alleviated toxic effects of Cd and improved growth as well as productions of photosynthetic and accessory pigments in tomato plants.

Phytoremediation strategies for soils contaminated with heavy metals: Modifications and future perspectives.

Presence of heavy metals in agricultural soils is of major environmental concern and a great threat to life on the earth. A number of human health risks are associated with heavy metals regarding their entry into food chain. Various physical, chemical and biological techniques are being used to remove heavy metals and metalloids from soils. Among them, phytoremediation is a good strategy to harvest heavy metals from soils and have been proven as an effective and economical technique. In present review, we discussed various sources and harmful effects of some important heavy metals and metalloids, traditional phytoremediation strategies, mechanisms involved in phytoremediation of these metals, limitations and some recent advances in phytoremediation approaches. Since traditional phytoremediation approach poses some limitations regarding their applications at large scale, so there is a dire need to modify this strategy using modern chemical, biological and genetic engineering tools. In view of above, the present manuscript brings both traditional and advanced phytoremediation techniques together in order to compare, understand and apply these strategies effectively to exclude heavy metals from soil keeping in view the economics and effectiveness of phytoremediation strategies.