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

FERTILIZER MANAGEMENT EFFECTS ON FORAGE AND SEED YIELD OF TROPICAL GRASSES IN THE U.S VIRGIN ISLANDS

Guineagrass (Panicum maximum Jacq.), an important tropical forage in the eastern Caribbean Islands is established from seed. Low seed availability due to seed shattering losses and low germination percentages limits pasture development in the U.S. Virgin Islands. Recent introduction of Atra paspalum cv. Suerte (Paspalum atratum Swallen) exhibited potential as stand-over forage, but more information is needed on dry matter yield (DMY) and seed yield. A field experiment was conducted on a mildly alkaline Fredensborg clay (fine carbonatic, isohyperthermic, Typic Rendols, Mollisols) in 2000 to determine the effect of three N rates (0, 56, and 112 kg ha'1) on DMY and seed yield of guineagrass, Bluegrass, and Suerte. Ammonium sulfate as N source was broadcast applied on cut grass stands (15-cm stubble height) on 15th August 2000 and harvested in November 2000(12 wk). Guineagrass and Suerte differed in DMY (P0.05). Seed yield of guineagrass was 242 kg ha"1 and Suerte was 278 kg ha'. There was a trend for seed increase with increasing N rates for guineagrass (P=0.10) and a quadratic response (P<0.05) for Suerte. Results of the study indicate a strong response of guineagrass to N applications. During seed maturity, strong easterly winds may have affected yields of both grasses. Multiple harvests may be needed for these grasses to get a better estimate of seed yield and quality

Effect of cattle manure application rate and strategy on bahiagrass yield and nutritive value

We evaluated the effects of Ν rate and two strategies of cattle manure (CM) application on dry matter yield (DMY) and nutritive value of bahiagrass (Paspalum notatum L. Fluege). The Ν rate treatments were 200 and 400 kg Ν ha"1 from CM or 50/50 CM plus ammonium nitrate (AN) combination, applied either in a single or split dosage. Bahiagrass was clipped at 28-d intervals for DMY, crude protein concentration (CP) and in vitro organic matter digestibility (IVOMD). First year results showed significant effects of application strategies and Ν rate. The combination of CM+AN performed better than treatments with CM alone. Dry matter yields of 6.67, 6.46, 5.73 and 6.27 Mg ha"1 were recorded for the 400 kg Ν ha"1 as CM+AN in single and split, and for the 200 kg Ν ha"1 as CM+AN in single and split applications, respectively. Comparatively, DMY of 6.38, 5.35, 5.98 and 4.82 Mg ha"1 were recorded for the 400 kg Ν ha"1 of CM in single and split, and for the 200 kg Ν ha"1 of CM in single and split applications, respectively. The 400 kg Ν ha"1 of CM+AN had the greatest IVOMD values of 547 and 543 g kg"1 for the single and split applications. Treatments receiving split application of CM had the lowest DMY, IVOMD and CP values. Phosphorus uptake and percentage recovery were also greatest for treatments that received CM+AN combination. Between 23 to 26% of the applied Ρ was recovered in the CM+AN treatments compared to 10 to 21% in the treatments that had CM alone. The results show that applying CM in combination with an inorganic nitrogen source can provide high forage yield of high quality and also reduce Ρ risk to the environment