The pot experiment was conducted to explore the phytoremediation potential of two different marigold species grown in heavy metals contaminated red, black, alluvial, recent river clay, sewage irrigated, sewage sludge, and garden soil. Different soil types were treated uniformly with lead (20 mg Pb kg⁻¹ soil), cadmium (5 mg Cd kg⁻¹ soil), chromium (30 mg Cr kg⁻¹ soil) and nickel (10 mg Ni kg⁻¹ soil). Completely randomized design (CRD) was used with three replications. African marigold (Tagetes erecta) recorded ∼89.4% more dry matter yield over French marigold (Tagetes patula) when grown under metals treated soils. Both the marigold species were highly effective for removing Cd and Ni from contaminated soils (TF >1) however, Ni (TF ∼14.9) was more efficiently accumulated by T. patula and Cd (TF ∼12.1) by T. erecta. Higher biomass yield in T. erecta resulted higher accumulation of heavy metals (except Cr) compared to T. patula. Assessment of contamination factor (CF) and geo-accumulation index (I_geo) of heavy metals indicates that post-harvest soils had moderate to high degree of contamination by different metals, Cr being the highest. It may be concluded that T. erecta was more efficient in extracting heavy metals from different heavy metals contaminated soils. Novelty statement Contamination of land with heavy metals poses severe environmental threats. Physical and chemical remediation techniques are generally used for remediating metals contaminated sites. These methods are cost-intensive and therefore, commercially non-viable, besides being disruptive in nature and causing deterioration of soil. Alternatively, bio-remediation techniques are cost-effective and environment friendly. Among the various phytoremediation techniques, hyperaccumulator plants are most commonly used for the remediation of the contaminated sites. It has been found that different species of the same plant (marigold) differ in their ability to accumulate metals under various contaminated soils having different properties. Thus, this experiment provided an unique opportunity to investigate the effect of various soil properties on metal accumulation efficacy of marigold under metal-spiked soils. Marigold plants can grow rapidly by developing a robust root system which helps them to survive under contaminated soil environment. Thus, marigold being ornamental plant could be used to decontaminate polluted sites while providing ornamental value and may serve as a source of commercially valuable products extracting metals from biomass by way of incineration. However, meager information is available about the usage of various marigold species for phytoremediation of heavy metals under different metal-polluted soils. In the current experiment, we intend to evaluate the potential use of two different marigold species (Tagetes patula and Tagetes erecta) in remediating heavy metals under nine soils of different nature spiked with metals and assessing heavy metals pollution load indexes in these polluted soils.

Appropriate phosphorus (P) management techniques increase yield and nutritional properties while minimizing environmental concerns. The widespread use of nano-fertilizers (NFs) in agriculture endangers soil and plants. It is vital to research the behavior of nano-phosphors (nano-P) on plant growth and quality, as well as their technique of interaction with soil properties in order to obtain key ecosystem benefits. With this in mind, a field experiment was conducted using wheat as a test crop to explore the impact of nano phosphorus (nano-P) on soil. The study’s goal was to examine how the foliar application of nano-P to wheat affects its growth, yield and nutrient concentration. Treatments consisted of: T₁: 100% NPK (120:137:72 kg N:P₂O₅:K₂O ha⁻¹) by RDF (recommended dose of fertilizer); T₂: 100% NPK by RDF + 2 foliar sprays of nano-P @ 494.21 mL ha⁻¹; T₃: 100% NK + 0% P (no foliar); T₄: 100% NK + 75% P + 2 foliar sprays of nano-P @ 494.21 mL ha⁻¹; T₅: 100% NK + 50% P + 2 foliar sprays of nano-P @ 494.21 mL ha⁻¹;T₆: 100% NK + 0% P + 2 foliar sprays of nano-P @ 494.21 mL ha⁻¹; T₇: 100% NPK by RDF + 1 foliar spray of nano-P @ 494.21 mL ha⁻¹; T₈: 100% NK + 75% P + 1 foliar spray of nano-P @ 494.21 mL ha⁻¹; T₉: 100% NPK + 1 foliar spray of nano-P @ 494.21 mL ha⁻¹; T₁₀-100% NK + 75% P + 1 foliar spray of nano-P @ 494.21 mL ha⁻¹. According to the findings, applying 100% NK + 75% P + 2 foliar applications of nano-P at the tillering and panicle initiation stages increased yield over 100% RDF by 37.1%. Additionally, the highest micronutrient concentration (Zn (36.4 mg kg⁻¹), Cu (21.2 mg kg⁻¹), Mn (22.9 mg kg⁻¹) and Fe (61.1 mg kg⁻¹)) in grain were noticed in T₃ (100% NK + 0% P no foliar spray of nano-P) treatment, which was superior to T₁ (100% NPK). Furthermore, foliar application of nano-P fertilizer in combination with different levels of diammonium phosphate (DAP) slightly increased the amount of N, P and K, as well as micronutrients in post-harvest soil. In summary, the use of 100% NK + 75% + 2 foliar applications of nano-P saved 25% recommendation dose P if supplied as nano-P as a form of phosphorus, and can be a suitable substitute for DAP, especially in smart agriculture, as it possibly reduces P leaching into groundwater, while maintaining or increasing wheat crop yield over the 100% RDF.

A greenhouse experiment was conducted in the Department of Soil Science and Agricultural Chemistry, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi (U.P.), India, during kharif 2013 to find out the effect of biochar and sewage sludge (SS) on growth, yield, and micronutrient uptake in rice crop. Nine treatments were employed using six different doses of biochar (2.5, 5.0, 7.5 10, 15, and 20 t ha⁻¹) amended with a fixed dose of SS (30 t ha⁻¹) and 50% recommended dose of nitrogen (50% RDN), i.e., 60 kg ha⁻¹. Other three treatments were absolute control (no fertilizers), 100% recommended dose of fertilizers (100% RDF) which was 120:60:60 kg ha⁻¹ as nitrogen (N): phosphorus pentoxide (P₂O₅):dipotassium oxide (K₂O), and 30 t ha⁻¹SS + 50% RDN. Experimental results showed a significant increase in yield of rice crop with increasing levels of biochar along with SS. Application of biochar at 20 t ha⁻¹ along with 30 t ha⁻¹SS increased grain yield to the extent of 2.5 times over absolute control (no fertilizers) and 8.5% over control (100% RDF). The uptake of iron (Fe), copper (Cu), zinc (Zn), and manganese (Mn) (micronutrients) increased significantly with graded doses of biochar application from 2.5 to 20 t ha⁻¹ in the soil. The maximum micronutrient uptake and grain yield of rice were found in T₉ where 30 t ha⁻¹SS along with 20 t ha⁻¹ biochar was applied with only 50% RDN. The maximum availability of micronutrients in soil was found with 30 t ha⁻¹ of SS + 50% RDN (T₃) followed by conjoint application of 20 t ha⁻¹ of biochar and 30 t ha⁻¹ SS + 50% RDN (T₉).

A pot experiment was conducted in a glass house on low nickel containing alluvial soil in the Department of Soil Science and Agricultural Chemistry, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, during 2012–13 and 2013–14, to study the response of barley to soil application of nickel (Ni). There were ten treatments of Ni (0, 2.5, 5, 10, 15, 20, 30, 40, 50 and 60 mg kg⁻¹) studied with recommended dose of fertilizers nitrogen, phosphorus, potassium and sulfur (N:P:K:S :: 40:30:30:20 mg kg⁻¹).The results showed a significant increase in plant height, number of tillers, chlorophyll content, straw and grain yield, and 1,000 grains weight with application of 10 mg Ni kg⁻¹ soil during both years of study. The micronutrient concentration and uptake in straw and grain increased with application of <15 mg Ni kg⁻¹ soil and beyond that declined significantly. Diethylenetriaminepentaacetic acid-extractable micronutrient iron, manganese, copper, zinc and nickel (Fe, Mn, Cu, Zn and Ni) content in soil increased with increasing level of Ni. The maximum urease activity in post-harvest soil was noticed with application of 40 mg Ni kg⁻¹ soil. The microbial population viz. bacteria, fungi and actinomycetes were higher with 5, 30 and 10 mg Ni kg⁻¹ soil, respectively.

A pot experiment (Net House) study was conducted in the Department of Soil Science and Agriculture Chemistry, Institute of Agricultural Science, B.H.U. Varanasi to find out the effect of organic amendments in mustard grown in chromium (Cr)-contaminated soil during 2015–16 and 2016–17. There were five levels of Cr (Control, 20, 40, 60 and 80 mg/Kg soil) with and without three organic amendments (viz. Vermicompost (VC), FYM, and Sewage Sludge (Sl)) @ 5 t/ha, 10 t/ha and 20 t/ha, respectively. The maximum number of siliqua/plant (333 and 354), length of siliqua (5.43 and 5.53), number of seeds per siliqua (12.11 and 12.39), dry matter accumulation (50.76 and 54.65g/pot), biological yield (266.51 and 273.34g/pot), seed yield (62.63 and 66.96g/pot), stover yield (203.88 and 206.38g/pot), and harvest index (23.50 and 24.5%) were recorded when Cr-contaminated soil is treated with organic amendments mainly with vermin compost during 2015–16 and 2016–17. It is reported that significant nutrient uptake (N, P, S, K, Fe, Cu, Zn, and Mn) also increased with the application of organic amendments. It is reported that yield attributing characters are improved by the application of VC followed by farm yard manure then sewage Sl.