Early detection of the effects of compaction in forested soils: evidence from selective extraction techniques

Purpose

Soil compaction resulting from mechanisation of forest operations reduces air permeability and hydraulic conductivity of soil and can result in the development of hydromorphic and/or anoxic conditions. These hydromorphic conditions can affect physico-chemical properties of the soils. However, early detection of these effects on mineralogical portion of soils is methodologically difficult.

Materials and methods

To analyse the effects of soil compaction on iron minerals in loamy Luvisol, three compacted and three non-compacted soil profiles up to the depth of 50 cm were collected from an artificially deforested and compacted soils after 2 years of treatment. Soil was compacted with the help of 25 Mg wheeler’s load to increase the dry bulk density of soil from 1.21?±?0.05 to 1.45?±?0.1 g cm^?3. Soil samples were analysed by X-ray diffraction (XRD) and were treated by citrate bicarbonate (CB) and dithionite citrate bicarbonate (DCB) under controlled conditions. Major and minor elements (Fe, Al, Mg, Si and Mn) were analysed by ICP-AES in the CB and DCB extracts.

Results and discussion

It was found that X-ray diffraction is not an enough sensitive method to detect the quick mineralogical changes due to soil compaction. Results obtained from CB-DCB extractions showed that soil compaction resulted in larger CB and smaller DCB extractable elements as compared to non-compacted soil. Labile Fe was found 30 % of total Fe oxides in compacted soil against 10–14 % in non-compacted soils. Compaction thus resulted in Fe transfer from non-labile to labile oxides (s.l.). Results showed that soil compaction leads to the reduction of Fe³⁺ to Fe²⁺. The effects of hydromorphic conditions due to soil compaction were observed up to the depth of 35 cm in forest soil profile. Furthermore, a close association of Al with Fe oxides was observed in the soil samples, while Mn and Si were mainly released from other sources, Mg showing an intermediate behaviour.

Conclusions

Hydromorphic conditions owing to soil compaction affect the mobility and crystallisation process of iron mineral. CB-DCB selective extraction technique, in contrast to XRD technique, can be effectively used to examine the possible effects of soil compaction on iron minerals.

     

Micronutrient composition of field‐grown dry bean and wheat inoculated with Azospirillum and Trichoderma

Micronutrient deficiency and malnutrition in humans are severe problems in many developing countries, particularly in areas with calcareous soils. There is almost no information on whether inoculation with plant growth–promoting Azospirillum and/or Trichoderma can help to reduce this problem by increasing the mineral concentration of the seeds. Field experiments were conducted in Tokat (Turkey) in 2001–2002 to determine whether inoculation with Azospirillum brasilense, Trichoderma harzianum, sole or in combination, and/or the application of P fertilizers can enhance micronutrient concentrations of field‐grown bean (Phaseolus vulgaris) and wheat (Triticum aestivum). In beans, Azospirillum inoculation combined with P fertilization significantly (p < 0.05) increased seed concentrations of Mn, Zn, and Cu, from 8.8, 22.6, and 7.0 mg kg^–1 in the control to 10.3, 28.3, and 11.0 mg kg^–1, respectively. Trichoderma inoculation alone significantly (p < 0.05) reduced the concentrations of Fe, Mn, Zn, and Cu and the cumulative plant uptake of Fe and Zn in 45‐day‐old bean plants. However, it significantly (p < 0.05) increased bean‐seed Cu content and accumulation. The double inoculation resulted in significantly (p < 0.05) higher micronutrient concentrations than Trichoderma inoculation alone in 45‐day‐old plants. In contrast to beans, the effects of microbial inoculations were less in wheat. However, dual inoculation significantly (p < 0.05) increased Zn content by 45% and Zn accumulation by 40% above the uninoculated control. Inoculation with plant growth–promoting microorganisms appears to be a promising strategy to combat micronutrient deficiencies.     

Extraction of Heavy Metals from Manure and their Bioavailability to Spinach (Spinacia Oleracea L.) after Composting

An investigation was carried out on the extractability of heavy metals (HM) from livestock manure during composting and their uptake by spinach (Spinacia oleracea L.) from compost-amended soil. Significant temporal changes were recorded for elements during composting of manure. Higher concentrations of metals were observed during the early stages of composting. Conversely, later stages of composting produced higher amounts of calcium (Ca), magnesium (Mg) and sodium (Na) in the water extract. Total carbon (C) in the samples was inversely related to the length of composting. The application of composted manure increased spinach growth as compared to the fresh manure. Concentrations of HM in spinach varied in the order iron (Fe) > zinc (Zn) > manganese (Mn) > cadmium (Cd) > lead (Pb) > copper (Cu) and their release from post-harvest soil was identical to that in manure samples. The low extractability of HM may suggest that the use of composted manures would lessen environmental pollution problem in the fields.     

In vitro antioxidant properties and phenolic composition of Salvia virgata Jacq. from Turkey

Antioxidant activities and phenolic compositions of the active fractions of Salvia virgata Jacq. (Lamiaceae) from Turkey were examined. The aerial part of S. virgata was extracted with different solvents in an order of increasing polarity such as hexane, ethyl acetate, methanol, and 50% aqueous methanol using a Soxhlet apparatus. Water extract was also prepared from S. virgata by reflux. All solvent fractions were investigated for their total phenolic contents, total flavonoids, flavonols, qualitative-quantitative compositions (by HPLC-PDA analysis), iron(III) reductive activities, free radical scavenging activities (using DPPH*), and effect upon linoleic acid peroxidation activities; also, the peroxidation level was determined by the TBA method. The results of activity tests given as IC50 values were estimated from nonlinear algorithm and compared with standards, viz., butylated hydroxytoluene, ascorbic acid, and gallic acid. Polar fractions were found to be more active for free radical activity whereas nonpolar fractions protected the peroxidation of linoleic acid. Rosmarinic acid was the most abundant component in the extracts, followed by caffeic acid and lutelin-7- O-glycoside.     

Optimal storage temperature and 1-MCP treatment combinations for different marketing times of Korla Xiang pears

Maintenance of green color is the primary indicator of quality in the market evaluation of Korla Xiang pears at present and can generally be achieved through early harvesting and decreasing the storage temperature, but the fruit quality was reduced by early harvesting, and the decreasing storage temperature increased the risk of chilling injury. The objectives of this study were to determine the optimal storage parameters for different storage times and to find ways to preserve the green skin color of pears. Specifically, we analyzed the effects of the ethylene inhibitor, 1-methylcyclopropene(1-MCP), combined with low temperature on quality and maintenance of the green color of Korla Xiang pears during storage. We found that 1-MCP and/or low temperature reduced the loss of green color at 20°C after being removed from cold storage. In addition, 1-MCP significantly inhibited the decline of titratable acid and ascorbic acid but had no significant effect on fruit firmness and total soluble solids. Low temperature with or without 1-MCP inhibited the release of ethylene, inhibited the decline in the stalk preservation index, inhibited the increase in decay rate and weight loss rate during storage, and inhibited the increase in the core browning index after 225 days of storage. Different storage temperatures had different effects on the quality of Korla Xiang pears. Despite inhibiting ethylene release, a storage temperature of –1.5°C increased the respiration rate. Storage at –1.5°C caused core browning early during storage due to chilling injury, whereas at 2°C core browning occurred late during storage due to senescence. In late storage, 1-MCP had no significant effect on the maintenance of Korla Xiang pear quality at 2°C. Based on these results, we determined the optimal combinations of low temperature and 1-MCP treatment to maintain pear quality while avoiding chilling injury. For different marketing times, the optimal conditions for storage until New Year's Day(a storage duration of 90 days) are 2°C or 1-MCP combined with 2°C. For storage until the Spring Festival(a storage duration of 150 days), the optimal conditions are 0°C or 1-MCP combined with 0°C, and for storage until May(a storage duration of 225 days), the best conditions are 1-MCP combined with –1.5°C.