Organic Ameliorants Research Articles

Soil macrofauna in cover crops of figs grown under organic management

Soil fauna plays an important role in organic management through their effects on soil organic decomposition, nutrient mineralization, and amelioration of the soil's physical properties. This work evaluates the density and diversity of the soil macrofauna under types of cover plants in areas cultivated with Ficus carica L. under organic management. The soil macrofauna was collected in 0.25 × 0.25 m areas, down to a soil depth of 0.3 m, and at the surface layer. The treatments consisted of bahiagrass living mulch (Paspalum notatum), siratro living mulch (Macroptilium atropurpureum), and bahiagrass mulch. The highest macrofauna density and the lowest diversity were observed in bahiagrass, of which 80% were represented by ants, thus characterizing the soil under this cover crop as showing the lowest functional diversity and quality.

Rehabilitation of Co-disposed Diamond Tailings: Growth Medium Rectification Procedures and Indigenous Grass Establishment

In the present study tailing dam rehabilitation (revegetation)of De Beers operated diamond mines in South Africa was investigated by doing pot and field trials. Since the reclamation of mine tailings is a challenging task, the type and optimum concentration of organic materials and chemical ameliorants to be applied for the rehabilitation process was evaluated. Further the grass species most effective for rehabilitation was also investigated. In both the pot and field trials Cenchrus ciliaris and Cynodon dactylon were the most successful species, although their densities were low. The field amelioration that has shown the best results was a 60 tons ha-1 vermicompost application with a fertiliser treatment of CaNO3 (25 kg ha-1) and MgNO3 (12.5 kg ha-1). Overall the results indicate that initial vegetation establishment during the first six months on the co-disposed material was slow even under large applications of organic fertilisers, but it is clear that without proper seeding of the plots no vegetation will establish on the co-disposed material.

Soil Physical Conditions and Physiological Performance of Cowpea Following Organic Matter Amelioration of Sandy Substrates

Mulch was added to sand and sandy loam soil in order to simulate repeated additions of organic matter into soils of the tropics where high temperatures cause rapid decomposition. The experiments used pots (0.003 m3) and lysimeters (0.18 m3) to investigate the effect of farmyard manure (FYM) and municipal waste compost (MWC) incorporation on temperature, soil water retention and evaporation, and MWC on transpiration, photosynthetic rate and yield as performance indicators for cowpea [Vigna unguiculata (L)]. Incorporation of FYM and MWC in un-cropped pots increased early stage evaporation compared with surface mulch treatments and compost mulch conserved soil water at depths between 0.05 and 0.6 m. Repeated incorporation of compost in lysimeters increased crop water availability between 7 and 10% and yield increased 3 to 5 times, despite organic matter content remaining below 1%. Results show cowpea performance indicators in light, low fertility soils of the tropics would benefit substantially from repeated incorporations of compost.

Effect of a commercial peat moss-shrimp wastes compost on pucinellia growth in red mud

Revegetation of red mud can be difficult without chemical or organic ameliorant for red mud. A greenhouse experiment was conducted to examine the short-term effect of a commercial peat moss-shrimp wastes compost on the growth of pucinellia (Pucinellia distorts L.) in a bauxite residue (red mud) from the Alcan's Vaudreuil alumina refinery at Jonquière (Québec), Canada. Characterization of the red mud revealed that the residue was strongly alkaline (pHse=11.4) and contained soluble salts (ECse=10.3 dS m−1), soluble Na (2743 mg L−1), soluble Al (275 mg L−1) and low levels of plant-available nutrients. Red mud components included approximately 40.4% Fe, 18.3% Al, 13.4Percnt; Si, 7.5% Ti, 6.7% Na and 3.5% Ca expressed in oxide. Hematite (∝Fe2O3) was the main mineral in the red mud. The results of the revegetation study have shown that compost amendment treatments affected pH values, salinity, organic carbon and DTPA-exlractable Al contents compared to the control. The highest rate (45%) of compost reduced the initial pH to about 9.3. The dry weight yield of pucinellia increased as the percentage of compost in the red mud increased. However, survival and plant growth were very poor when the compost was applied at 18 and 23% rates. The critical substrate pH value for pucinellia growth was between 9.5 and 9.7. In general, the leachates from the compost amended red mud are slightly more concentrated with respect to Al, compared with the unamended red mud (control).

Sewage sludge as organic ameliorant for revegetation of fine bauxite refining residue

The rise in aluminium demand in the world has significantly increased the generation of bauxite residue which occupies huge areas of land worldwide. Direct revegetation of residue storage areas has been unsuccessful because of the high alkalinity and salinity, and poor nutrient contents of the fine residue (red mud). This paper describes glasshouse and field experiments evaluating the potential use of sewage sludge as an organic ameliorant for gypsum amended red mud. The growth of Agropyron elongatum in red mud receiving gypsum (0 and 38.5 t ha −1) and sewage sludge (0, 38.5 and 77 t ha −1) amendment was assessed in a glasshouse study. Leachate and soil analyses revealed that gypsum was effective in reducing the pH, EC and ESP of red mud, while sewage sludge gave additional reductions in EC, Na and ESP. No evidence of any significant increases in heavy metal contents were observed in the leachates following sewage sludge amendment. However, soil Al contents were more available in red mud receiving only sewage sludge treatment. Sewage sludge amendment significantly increased dry weight yield and provided sufficient nutrients for plant growth except K which was marginal. No heavy metal accumulation was observed in Agropyron. Following that, a field experiment was performed having red mud amended with sewage sludge (38.5, 77 and 154 t ha −1) and gypsum (38.5 and 77 t ha −1) to evaluate their effects on soil physical properties of red mud. Sewage sludge significantly reduced soil bulk density (25%) and particle density (9%) and increased the total porosity of red mud (8%). Hydraulic conductivity also increased from 1.5 to 23 × 10 −5 m s −1. Plant cover percentage and dry weight yield of Agropyron increased with an increase in gypsum and sewage sludge amendment. The results confirm that sewage sludge is effective in improving both soil structure and nutrient status of gypsum amended red mud. The use of sewage sludge for red mud revegetation provides not just an option for sludge disposal, but also a cost effective revegetation strategy for bauxite refining industry.