No abstract

No abstract

Dried aerobically digested sewage sludge applied at seven rates (0, 10, 20, 40, 60, 80, and 120 Mg ha−1) in a field experiment on calcareous bauxite mine spoils significantly increased the available water capacity, concentrations of organic matter, total N, extractable P (Olsen), exchangeable Mg2+, and diethylenetriaminepentaacetic acid (DTPA)‐extractable Cu, Mn, Zn, and Pb of mine spoils. Total N and extractable P concentrations decreased with time after sludge application. The DTPA‐extractable Cu concentration was high 4 yr after application at sludge rates of 80 and 120 Mg ha−1. Extractable Cu and Zn concentrations correlated significantly and positively with Cu and Zn concentrations in burnet (Sanguisorba minor subsp. minor) and fiddleneck (Phacelia tanacetifolia Benth) tissue. Sludge application depressed plant Mn uptake. Plant biomass, plant density, and foliar cover significantly increased with treatment rates in the first and fourth growing seasons but decreased with time. Fiddleneck and burnet were the species favored by the high rates of sludge application.

No abstract

Rooted leafy cuttings of three Greek olive (Olea europaea L.) cultivars (Koroneiki, Kothreiki and Chondrolia Chalkidikis) were grown for six months in three soil types, in an experimental greenhouse, in order to investigate: i) if their root system was colonized by arbuscular mycorrhiza fungus (AMF) genus and, ii) if genotypic differences concerning growth and mineral nutrition of olive plants existed. Gigaspora sp. colonized the root system of the three cultivars studied, while Glomus sp. colonized only the root system of 'Koroneiki'. Furthermore, in most cases root colonization by AMF differed among cultivars and soil types. The maximum root colonization, in all soils, was found in 'Chondrolia Chalkidikis'. In the three soils studied, the ratio shoot dry weight (SDW)/ root dry weight (RDW) was higher in 'Chondrolia Chalkidikis' than in the other two cultivars. Furthermore, root system morphology of the three olive cultivars was completely different, irrespectively of soil type. Leaf Mn, Fe, Zn, Ca, Mg, K and P concentrations, as well as total per plant nutrient content and nutrient use effi ciency, differed among cultivars under the same soil conditions. These differences concerning root morphology, SDW/RDW, as well as nutrient uptake and use effi ciency, could be possibly ascribed to the differential AMF colonization by Glomus sp. and Gigaspora sp.

No abstract

A 2-year study is presented on the impact of arbuscular mycorrhizal fungi (AMF) on plant productivity, uptake of phosphorus (P) and nitrogen (N) and diversity of plant community in a herbaceous, P and N limited grassland consisting exclusively of C 3 species and dominated by two plant species less mycotrophic than the subordinate ones. We hypothesized that AMF suppression will increase the abundance of the dominant species with compensatory decreases of subordinate species and decline of the diversity components. Mycorrhizal colonization was suppressed in field plots through application of the fungicide benomyl as a soil drench every 2 weeks during each growing period. Suppression of mycorrhizae lowered P concentrations of the examined species or species groups and decreased the abundance of the P demanding perennial forbs (the non-legume dicots) and most legumes. Concurrently, there were recorded increases in the abundance of the less P demanding grasses, sedges and the legume Doricnium herbaceum. Many rare forb species were not able to establish in the fungicide-treated plots. As a result, in the fungicide-treated plots there was a decline of the diversity components. In spite of the lower efficiency in soil P use and the lower diversity, primary productivity in the fungicide-treated plots did not differ from that of non-treated plots. It is suggested that AMF are important determinants of plant structure and diversity in P limiting soils, and the direction in which fungicide application affects the diversity of plant communities depends on the mycotrophic status of the dominant and subordinate plant species.

No abstract