Short-term biodegradation of petroleum in planted and unplanted sandy soil.

A greenhouse experiment was conducted to determine the effect of microbial populations and biodegradation of petroleum hydrocarbons in Lam. 'Passerel Plus' planted and unplanted contaminated sandy soil. Plant adaptation, growth, photosynthesis, rhizosphere microbial population, and total petroleum hydrocarbon (TPH) degradation were determined. Petroleum contamination resulted in reduced plant growth, photosynthesis, and macro- and micronutrient content. Filamentous fungi populations were stimulated by the petroleum concentrations, especially when plants were exposed to intermediate to high petroleum contamination. In general, unplanted containers had lower bacterial colony forming units compared with planted containers. Thus, bacterial populations were stimulated by the rhizosphere effect of when compared with fungal populations. Degradation of TPH was greater in the lower petroleum concentration when compared with the higher petroleum concentrations in the soil and was not affected by plant presence. Nevertheless, the TPH biodegradation occurred at greater rates: 48 mg kg d for concentration of 3000 mg kg and 66 and 165 mg kg d for concentrations of 6000 and 15,000 mg kg, respectively, which concurs with the high fungal and bacterial populations with increasing petroleum concentrations regardless of plant presence.

Supplementary calcium ameliorates ammonium toxicity by improving water status in agriculturally important species.

Fertilization of agricultural plants with ammonium [Formula: see text] is often desirable because it is less susceptible to leaching than nitrate [Formula: see text] reducing environmental pollution, risk to human health and economic loss. However, a number of important agricultural species exhibit a reduction in growth when fertilized with [Formula: see text] and increasing the tolerance to [Formula: see text] may be of importance for the establishment of sustainable agricultural systems. The present study explored the feasibility of using calcium (Ca) to increase the tolerance of bell pepper (Capsicum annuum) to [Formula: see text] fertilization. Although [Formula: see text] at proportions ≥25 % of total nitrogen (N) decreased leaf dry mass (DM), supplementary Ca ameliorated this decrease. Increasing [Formula: see text] resulted in decreased root hydraulic conductance (Lo) and root water content (RWC), suggesting that water uptake by roots was impaired. The [Formula: see text]-induced reductions in Lo and RWC were mitigated by supplementary Ca. Ammonium induced increased damage to the cell membranes through lipid peroxidation, causing increased electrolyte leakage; Ca did not reduce lipid peroxidation and resulted in increased electrolyte leakage, suggesting that the beneficial effects of Ca on the tolerance to [Formula: see text] may be more of a reflection on its effect on the water status of the plant. Bell pepper plants that received [Formula: see text] had a low concentration of [Formula: see text] in the roots but a high concentration in the leaves, probably due to the high nitrate reductase activity observed. Ammonium nutrition depressed the uptake of potassium, Ca and magnesium, while increasing that of phosphorus. The results obtained in the present study indicate that [Formula: see text] caused growth reduction, nutrient imbalance, membrane integrity impairment, increased activity of antioxidant enzymes and affected water relations. Supplementary Ca partially restored growth of leaves by improving root Lo and water relations, and our results suggest that it may be used as a tool to increase the tolerance to [Formula: see text] fertilization.

Controlled release fertilizer increased phytoremediation of petroleum-contaminated sandy soil.

A greenhouse experiment was conducted to determine the effect of the application of controlled release fertilizer [(CRF) 0, 4,6, or 8 kg m(-3)] on Lolium multiflorum Lam. survival and potential biodegradation of petroleum hydrocarbons (0, 3000, 6000, or 15000 mg kg(-1)) in sandy soil. Plant adaptation, growth, photosynthesis, total chlorophyll, and proline content as well as rhizosphere microbial population (culturable heterotrophic fungal and bacterial populations) and total petroleum hydrocarbon (TPH)-degradation were determined. Petroleum induced-toxicity resulted in reduced plant growth, photosynthesis, and nutrient status. Plant adaptation, growth, photosynthesis, and chlorophyll content were enhanced by the application of CRF in contaminated soil. Proline content showed limited use as a physiological indicator of petroleum induced-stress in plants. Bacterial and filamentous fungi populations were stimulated by the petroleum concentrations. Bacterial populations were stimulated by CRF application. At low petroleum contamination, CRF did not enhance TPH-degradation. However, petroleum degradation in the rhizosphere was enhanced by the application of medium rates of CRF, especially when plants were exposed to intermediate and high petroleum contamination. Application of CRF allowed plants to overcome the growth impairment induced by the presence of petroleum hydrocarbons in soils.