We investigated the effects of organic amendments (thermophilic compost, vermicompost, and coconut coir) on the bioavailability of trace heavy metals of Zn, Cd, Pb, Co, and Ni from heavy metal-spiked soils under laboratory conditions. To test switchgrass (Panicum virgatum) as a potential crop for phytoremediation of heavy metal from soil, we investigated whether the addition of organic amendments promoted switchgrass growth, and consequently, uptake of metals. Compost is a valuable soil amendment that supplies nutrients for plant establishment and growth, which is beneficial for phytoremediation. However, excess application of compost can result in nutrient leaching, which has adverse effects on water quality. We tested the nutrient leaching potential of the different organic amendments to identify trade-offs between phytoremediation and water quality. Results showed that the amendments decreased the amount of bioavailable metals in the soils. Organic amendments increased soil pH, electrical conductivity (EC), and soil nutrient status. Switchgrass shoot and root biomass was significantly greater in the amended soils compared to the non-amended control. Amended treatments showed detectable levels of heavy metal uptake in switchgrass shoots, while the control treatment did not produce enough switchgrass biomass to measure uptake. Switchgrass uptake of certain heavy metals, and concentrations of some leachate nutrients significantly differed among the amended treatments. By improving soil properties and plant productivity and reducing heavy metal solubility that can otherwise hamper plant survival, organic amendments can greatly enhance phytoremediation in heavy metal-contaminated soils.
The present study was conducted to explore the role of different types of vermicomposts (VCs) prepared from different substrates to improve soil health (physical and chemical properties) and wheat plant growth under field conditions. Different combinations of vermicompost prepared from different substrates (cow dung, paper waste, and rice straw) and inorganic fertilizers were applied in soil using wheat as a test plant. The impact of three different VCs on physico-chemical characteristics and nutrient availability in soil was evaluated to examine their efficacy in combination with chemical fertilizers. Temporal trends in vermicomposting treatments at various stages showed significant improvement in physico-chemical attributes of the VCs substrates. All the plant physiological attributes showed significant response where N:P:K 100:50:50 kg ha −1 + 10 t ha −1 cow dung vermicompost was applied. In addition, post-harvest analysis of soil not only revealed that different combinations of the vermicomposting treatments improved the soil health by improving the physico-chemical attributes of the soil. Conclusively, application of cow dung vermicompost along with recommended NPK not only improved crop yield, soil health, reduced insect (aphid) infestation but also fortified grains with Zn and Fe. Funding acquisition, Z.A., S.B. and M.M.; Investigation, Z.A. and W.H.; Methodology, N.A., N.K.N. and M.I.K.; Resources, M.M.; Supervision, K.B. and Z.C.; Validation, N.A. and N.K.N.; Writing-original draft, S.B.; Writing-review & editing, K.B., Z.C. and M.M.
Turkey has been undergoing positive agricultural transformations since the 2011. Its agricultural sector today is developing new techniques and products. One of the best examples of this is the production of vermicompost and its use in agriculture. Turkey is on both Asian and European continents (Eurasia) with approximately 81 million people. Turkey has 24 million hectares of agriculture land (excluding pastures+ meadows, including total arable land and under permanent crops). However, there is little data available on vermicompost production in Turkey. The production of vermicompost started after 2011. The average solid vermicompost production in 2017 was about 20000 tonnes produced by 15 plants with official production permits by the Republic of Turkey Ministry of Agriculture and Forestry. New legislation in Turkey published in legislative review no 30341 in February 2018 regulates the industry. Turkey aims to be among the top three producers of this fertility amendment by 2023. In addition to the officially sanctioned operations, there are approximately 4200 unauthorized vermicompost producers in Turkey. Interest in and production of vermicompost is likely going to increase. Research showed that there are many positive effects on soil quality and plant growth, although the mechanisms by which it improves the soil-plant systems are not yet fully understood. The use of vermicompost is important for the sustainability of agriculture. The main aim of the paper is to demonstrate and share reasonable causes for the increased interest in vermicompost and earthworms.
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