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Revegetation of Mine Sites
Published in Bruno Bussière, Marie Guittonny, Hard Rock Mine Reclamation, 2020
Some substrates characterized by fine grain size (silts and clays), such as mine tailings, can provide enough water, but their slow drainage can induce lack of oxygen availability to plant roots. Oxygen and water are essential resources for plant development (see Table 12.2). Mineral substrates can also be chemically unstable due to weathering of the minerals exposed to water and air in surface conditions. This weathering can induce salt excess in the substrate, which decreases water absorption of plants and causes a pH change (see Chapter 1). Weathered cations may be rapidly leached and unavailable for plant nutrition due to low cation exchange capacity associated with a lack of OM. Finally, mineral substrates are often characterized by nutrient deficiencies, especially nitrogen, while phosphorus availability is less problematic since the weathering of minerals often provides phosphorus in available forms (Chapin et al. 2011). Nitrogen and phosphorus are the main macronutrients needed by plants (see Table 12.2). Nitrogen deficiency in plants directly results in a decrease in productivity since photosynthetic enzymes represent a major sink of leaves’ N.
Stability, Maturity, and Phytotoxicity
Published in Epstein Eliot, The Science of Composting, 2017
A stable product, on the other hand, does not produce odors in storage. If the product is bagged at the proper moisture content, opening the bag should not release putrescible odors. Further, when incorporated into the soil, a stable product does not decompose rapidly and utilize nitrogen required for plant growth. When a compost that has a high C/N ratio is added to soil, the microbial population competes with plants for soil nitrogen. In this case, plants typically exhibit chlorosis, yellowing of the leaves, indicating nitrogen deficiency. If organic materials with low C/N ratios are added to soil, ammonia can be released, which can cause phytotoxicity (Dowdy et al., 1976). Ammonia in refuse extracts has been shown to reduce germination and root elongation (Wong, 1985).
Influence of biochar and compost on phytoremediation of oil-contaminated soil
Published in International Journal of Phytoremediation, 2018
Lindsey Saum, Macario Bacilio Jiménez, David Crowley
Biochar and compost amendments in conjunction with phytoremediation are of interest for facilitating cleanup of petroleum-contaminated soils. However, there are complex interactions between these variables that control the bioavailability of both metal and hydrocarbon contaminants as well as the bioavailability of nitrogen and other nutrients that are required for growth and activity of a hydrocarbon degrader community (Anyika et al.2015). This affects not only the rate of degradation, but also the demand for nitrogen, which must be recycled within the community or added to the system in order to drive biodegradation of oil, which has a high carbon-to-nitrogen ratio. In the present study, biochar additions were shown to reduce both tree seedling shoot growth and the rate of oil degradation. This likely reflects the effects of nitrogen deficiency whereby the mesquite seedlings altered their root:shoot ratio to increase their nutrient uptake capacity. Nitrogen deficiencies are common in petroleum-contaminated soils and are associated with the high carbon-to-nitrogen ratio of oil, resulting in demand for additional nitrogen to support plant and microbial growth. Plants typically respond to nitrogen deficiency by diverting carbon from above ground growth and allocating more carbon to expand the root system for better nutrient acquisition (Mardanov et al.1998).