Application of Municipal Biosolids to Bahiagrass Pasture: Trace Metals in Harvested Forage

Municipal biosolids (sewage sludge) are the by-products of wastewater treatment plants and their production, worldwide, has steadily increased over the past years. Florida is one of the fastest growing states in the USA. Biosolids are readily and increasingly available throughout the state. Pasture fertilization has been shown to increase biomass and quality of bahiagrass (Paspalum notatum Flugge) dramatically in Florida sandy soils. Nevertheless, with low cattle prices, ranchers are forced to reduce fertilizers inputs. Biosolids contain considerable amounts of nutrients, especially nitrogen (N), phosphorus (P), sulphur (S), calcium (Ca), and micronutrients, and are inexpensive when compared with commercial fertilizers. Nevertheless, the concern remains that metals contained in these residuals accumulate in the tissues, in levels that would result be harmful to animals consuming the forage. This study investigated effects of seven rates of municipal biosolids applied to bahiagrass pasture on trace metal concentration in the forage. Iron (Fe), copper (Cu), cadmium (Cd), lead (Pb), and nickel (Ni) concentrations were determined in the tissue sampled at various dates after initial biosolids application. Metal concentrations were increased with increasing rates of biosolids, especially with the highest rate, in the first harvest date, but decreased with successive harvests. By the fourth harvest, Cd, Pb and Ni were hardly detected in forage. The increases verified in plant metal contents were not substantial enough to yield concerns regarding animal consumption, even with the higher rates of biosolids

Sewage Sludge as an Alternative Fertilizer for Tropical Pasture Grasses

This study was conducted to determine the effects of source (Liquid sludge at pH 7 (LS7) or pH 11 (LS11), cake biosolid (CB) or ammonium nitrate (AM)) by rate (0, 80 or 160 kg ha-1) of N application on bahiagrass forage yield, quality and tissue composition. Same plots were fertilized in March 1998 and 1999. Forage yield was measured at 30 d intervals from May through November and subsamples were dried and ground for quality analyses. The 2-year mean forage yield was similar for AM, LS7 and LS 11 fertilizer applications. Forage yield from CB application was 30% lower than yield from other N sources at comparable N rates. Forage crude protein content was highest for the AM treatment only during the initial harvest. Tissue concentrations of plant nutrients were increased by organic sources of fertilizer. These results, in conjunction with data from soil and groundwater analyses, suggest that processed domestic septage could be a safe and inexpensive substitute to inorganic fertilizer for tropical pasture grasses

Quantitative trait loci and candidate gene mapping of aluminum tolerance in diploid alfalfa

Aluminum (Al) toxicity in acid soils is a major limitation to the production of alfalfa (Medicago sativa subsp. sativa L.) in the USA. Developing Al-tolerant alfalfa cultivars is one approach to overcome this constraint. Accessions of wild diploid alfalfa (M. sativa subsp. coerulea) have been found to be a source of useful genes for Al tolerance. Previously, two genomic regions associated with Al tolerance were identified in this diploid species using restriction fragment length polymorphism (RFLP) markers and single marker analysis. This study was conducted to identify additional Al-tolerance quantitative trait loci (QTLs); to identify simple sequence repeat (SSR) markers that flank the previously identified QTLs; to map candidate genes associated with Al tolerance from other plant species; and to test for co-localization with mapped QTLs. A genetic linkage map was constructed using EST-SSR markers in a population of 130 BC(1)F(1) plants derived from the cross between Al-sensitive and Al-tolerant genotypes. Three putative QTLs on linkage groups LG I, LG II and LG III, explaining 38, 16 and 27% of the phenotypic variation, respectively, were identified. Six candidate gene markers designed from Medicago truncatula ESTs that showed homology to known Al-tolerance genes identified in other plant species were placed on the QTL map. A marker designed from a candidate gene involved in malic acid release mapped near a marginally significant QTL (LOD 2.83) on LG I. The SSR markers flanking these QTLs will be useful for transferring them to cultivated alfalfa via marker-assisted selection and for pyramiding Al tolerance QTLs

Biological and Biotehnological Control of Insect Pests

374 hal,;ill,;21 c