Phytoremediation or use of plants to extract soil nutrients is a practice used to ameliorate the impacts of excessive soil nutrients. Pensacola bahiagrass (Paspalum notatum Flügge) and ‘Floralta’ ...limpograss Hemarthria altissima (Poir.) Stapf & Hubb were grown in a P-impacted Immokalee fine sand (Mehlich-1 P 30 mg P kg–1) to evaluate increasing N levels on dry matter yield (DMY), forage P concentration, P removal, and P dynamics in the soil profile. Treatments were four levels of N fertilization (0, 50, 67, and 101 kg N ha–1 harvest–1) replicated four times for each species. Both grasses showed increases in P removal with increasing N fertilizer applications. Phosphorus removed by forages for the highest N application level ranged from 59 (bahiagrass; 2-yr period) to 83 kg ha–1 (limpograss; 3-yr period). The initial soil P content of the Ap horizon of all N > 0 treatments decreased by >or= 85% over the study period. However, more P from the control (N = 0) plots leached to subsurface horizons compared to P lost from the plots receiving N fertilizer. Nitrogen application enhanced P uptake from the soil and consequently reduced off-site P losses from the surface soil. Nitrogen application of 67 kg ha–1 harvest–1 optimized P removal by bahiagrass and limpograss. These data show that well managed, warm-season perennial forage grasses with adequate N fertilization and managed for hay production or greenchop are an option for reducing off-site P losses from P-impacted soils.
Warm-season C4 grasses are capable of removing excess soil nutrients because of their high yield potential and nutrient uptake efficiency. Bahiagrass (Paspalum notatum Flügge), limpograss Hemarthria ...altissima (Poir.) Stapf & Hubb, and stargrass (Cynodon nlemfuensis Vanderyst), three commonly used pasture grasses in South-Central Florida, were grown to examine the effect of increasing N rates on herbage production and soil P removal. Nitrogen was applied at rates of 67, 90, and 134 kg N ha-1 harvest-1, representing 1, 1.3, and 2 times the recommended N fertilizer application rate for hay production. During 3 yr of evaluation, all three grasses showed a positive P-removal potential that increased with increasing N fertilizer application. Phosphorus removed by forages over the 3-yr period for the highest N application rate was 106, 132, and 147 kg ha-1 for limpograss, bahiagrass, and stargrass, respectively. Mehlich 1 extractable P from the Ap horizon of all plots decreased by as much as 80% of the initial P load over the study period; only 15 to 17% of which appeared to leach to subsurface horizons. Nitrogen application enhanced P uptake and consequently reduced P transport to deep (>13 cm) soil depths. These data indicate that stargrass, bahiagrass, and limpograss managed intensively for hay production represent effective options in removing excess soil P from P-impacted sites.
Animal manure application based on crop N requirements often leaves excess P in the soil because of the differences in the N/P ratio in manures and that required by the plants. This experiment was ...designed to evaluate the effects of cattle (Bos taurus) manure applied alone or in combination with ammonium nitrate (AN) on bahiagrass (Paspalum notatum Flügge) dry matter (DM) yield, nutritive value, tissue P concentration and recovery, and soil P concentrations. Treatments consisted of a control, two N rates (200 and 400 kg ha-1), two N sources manure alone or manure plus AN (50/50% combination), and two application frequencies (single vs. split). Bahiagrass was harvested at 28-d intervals and evaluated for DM yield, crude protein concentration (CP), in vitro digestible organic matter (IVDOM), and tissue P concentration. Soil samples were analyzed for Mehlich-1 extractable P. Bahiagrass DM yield, nutritive value, and P recovery were greater for the manure plus AN treatments when compared to the control and manure alone. Although greater N rates increased DM yield and CP, bahiagrass P recovery was reduced as the N rate increased. Approximately 20 and 53% of the applied P was recovered by bahiagrass when manure was applied alone and in combination with AN, respectively. Soil-test P (0-15 cm depth) was greater for the treatments receiving manure alone compared to manure plus AN treatments. Our results demonstrated that applying manure in combination with an inorganic N source can increase forage yield and nutritive value while reducing the risks of soil P accumulation.
Management practices minimizing P application in agricultural catchments ultimately reduce P export to waters. To determine stargrass (Cynodon nlemfuensis Vanderyst var. nlemfuensis) response to P ...and K, eight rates of P and K were applied on experimental units located on Pomona fine sand (sandy, siliceous, hyperthermia Ultic Alaquods) Spodosols, and arranged in a randomized complete block design with four replicates. The forage yield was less from 39:0 (P/K; kg ha(-1) yr(-1)) treatment than the experimental units supplied with 93 kg K ha(-1) yr(-1) and low P (10 and 20 kg ha(-1) yr(-1)) in all years with exception in 1998 (i.e., the year of grass establishment), indicating efficient P utilization due to K applications. No significant differences were obtained in in-vitro organic matter digestibility (IVOMD) from the applications of 10 kg P ha(-1) yr(-1) and 93 kg K ha(-1) yr(-1). The applications of 10 and 93 kg ha(-1) yr(-1) of P and K, respectively, provided efficient P utilization. Phosphorus mass balance showed that stargrass receiving 10 and 93 kg ha(-1) yr(-1) of P and K, respectively, removed maximum P (161% of the applied P) by uptake from soils. This may indicate the capability of stargrass to mine P from subsoils if sufficient K is supplied, and also suggests that stargrass may be useful for crop phytoremediation on P-impacted sites. In general, this study indicates that applications of 10 kg P ha(-1) yr(-1) in combination with 93 kg K ha(-1) yr(-1) will maintain forage nutritive value and quantity, and maximize P removals by stargrass. Moreover, the supply of sufficient K appears to be crucial for efficient P utilization by forages, reducing potential adverse effects of P over-fertilization on water quality.
Amounts of manure generated by concentrated animal operations often exceed the capacity of nearby land, and stricter environmental regulations lead to creation of pockets of highly impacted sites ...within a watershed basin. Linking forage production with manure utilization can be an effective approach for addressing both the problems of manure disposal and impact reductions on water quality. In general, cropping patterns, climate, topography, and fertilization practices affect concentrations of nutrients, including N and P in runoff waters. Forage plants include diverse groups of grasses and legumes adapted to different climatic zones and varying soil fertility. To optimize the P remediation in affected sites, knowledge of P forms and soil properties is crucial. Given the possibility of producing high quality and quantity of herbage from such impacted agricultural areas, it would be worthwhile to utilize existing knowledge of herbage production from differentially manured soils and optimize nutrient uptakes. This review attempts to consolidate the available information on the potentials and limitations of pasture usage for phytoremediation of P in affected soils. Such herbage production systems may not only be environmentally sound for recycling of nutrients and minimizing nutrient loss to water bodies, but they may also help farmers/producers to maintain a profitable business enterprise.
To assess the impact of S fertilization on bahiagrass (Paspalum notatum) quality and Cu metabolism in cattle, two studies were conducted during the summer grazing season (1999 and 2000). Pasture ...replicates (16.2 ha; n = 2/treatment) received the same fertilizer treatment in each growing season, consisting of 1) 67 kg N/ha from ammonium sulfate (AS), 2) 67 kg N/ha from ammonium nitrate (AN), and 3) control (no fertilizer; C). Forage sampling was conducted at 28-d intervals following fertilization by the collection of whole plants (four samples/pasture) in randomly distributed 1-m2 grazing exclusion cages and analyzed for CP, in vitro organic matter digestibility, S, P, Ca, K, Mg, Na, Fe, Al, Mn, Cu, and Zn. To determine the effect of fertilizer treatment on liver trace mineral concentrations in grazing cattle, random liver tissue samples were collected (n = 12; four/treatment) at the start and end of the study period in 2000. Ammonium sulfate fertilization increased (P < 0.001) forage S concentration in both years. Plant tissue N concentrations were increased by N fertilization, regardless of source, in 2000, but not in 1999. Cows grazing AS pastures had lower (P < 0.05) liver Cu concentrations at the end of the study period in 2000 compared to AN and C. In Exp. 2, 37 Cu-deficient heifers grazing AS fertilized pastures were obtained from the same location and allocated to one of two treatments, consisting of supplements providing 123 mg/d of either inorganic (Cu sulfate; n = 12) or organic (Availa-Cu; n = 15) Cu. Treatments were delivered for 83 d. Liver Cu increased over time in all heifers regardless of treatment; however, heifers supplemented with Availa-Cu tended (P = 0.09) to have higher mean liver Cu concentrations than those receiving Cu sulfate. The results of these studies indicate that AS fertilization of bahiagrass increases forage S concentrations. When provided free-choice access to a complete salt-based trace mineral supplement, cows grazing AS-fertilized pastures had lower liver Cu concentrations than cows grazing pastures fertilized with AN; upon removal from high-S pastures, cattle were able to respond to Cu supplementation.
Approximately 70% of Florida's biosolids is land‐applied with little supporting agronomic information. This experiment was conducted on bahiagrass (Paspalum notatum Flugge), on Pomona fine sand soil ...(sandy, siliceous, hyperthermic Ultic Alaquods), to compare the agronomic value of aerobically digested slurry biosolid, lime‐stabilized slurry biosolid, lime‐stabilized cake biosolid, and ammonium nitrate all applied to supply 90 or 180 kg N ha−1 vs. an unfertilized control. Forage production (3–5 Mg ha−1 yr−1) was similar for the ammonium nitrate and the slurries in 1998 and 1999, highest for the lime‐stabilized slurry in 2000, but always 30% lower for the cake biosolid due to the cake's lower N availability. The slurries and ammonium nitrate gave 50% or more forage and higher spring crude protein (CP) concentration (100–170 g kg−1) than the control (75–110 g kg−1). The CP was improved with ammonium nitrate in early spring, after which, there were no consistent differences in CP or in vitro organic matter digestion (460–600 g kg−1) among N sources. Tissue P (2.0–3.5 g kg−1), Ca (3.0–8.0 g kg−1), and Fe (40–250 mg kg−1) were increased by both biosolid slurries in the spring, whereas tissue Cu (6–15 mg kg−1) and Mn (10–100 mg kg−1) were elevated periodically only by the aerobically digested slurry. Forage was deficient in K and Mn in summer across treatments. Lime‐stabilized biosolid could boost bahiagrass production in Florida because it is lower in pathogens, inexpensive, and provides lime and organic matter.
Phosphogypsum (PG), a by‐product in the manufacture of phosphoric acid, is primarily gypsum. The USEPA regulates the removal of PG from stacks because it contains 226Ra. Measures to quantify the ...transfer of radioactivity in PG to the agricultural environment are needed. The objective of the study was to collect data needed for assessment of the radiological impacts of PG applied to two Florida soils. Field experiments using 0, 10, and 20 Mg PG ha−1 were conducted for 2 yr at the University of Florida RCREC, Ona, FL. PG‐attributable levels of 226Ra, 210Pb, and 210Po were observed in the top 5‐cm layer of the soils. Surface 222Rn flux increased by 0.067 to 0.078 mBq m−2 s 1 per Mg PG ha−1. Radionuclide concentrations in regrowth forages increased at one site where the first post‐treatment rainfall did not occur until 20 d after PG application. In mature forages, radionuclide levels generally increased with PG in both soils. No effects on radionuclide levels in subsurface water down to 90 cm and only slight effects on gamma radiation and on airborne 222Rn measured 1 m from the ground were noted. The linear regression slope for a radiological parameter normalized with respect to the pertinent radionuclide applied per m2 per Mg PG ha−1 is proposed as the transfer factor (TF) of that radionuclide in PG to the agricultural medium in terms of that parameter. The TF permits the calculation of the potential effect on certain radiological parameters of PCs containing different radionuclide concentrations from the one used in this study.
The cow-calf (Bos taurus) industry in subtropical United States and other parts of the world depends almost totally on grazed pastures. Establishment of complete, uniform stand of bahiagrass (BG) in ...a short time period is important economically. Failure to obtain a good BG stand early means increased encroachment of weeds and the loss of not only the initial investment costs, but production and its cash value. Forage production often requires significant inputs of lime, N fertilizer, and less frequently of P and K fertilizers. Domestic sewage sludge or biosolids, composted urban plant debris, waste lime, phosphogypsum, and dredged materials are examples of materials that can be used for fertilizing and liming pastures. Perennial grass can be a good choice for repeated applications of sewage sludge. Although sewage sludge supply some essential plant nutrients and provide soil property-enhancing organic matter, land-application programs still generate some concerns because of possible health and environmental risks involved. The objectives of this study were to evaluate the cumulative and residual effects of repeated applications of sewage sludge on (i) bahiagrass (BG, Paspalum notaturn Flügge) production over years with (1997-2000) and without (2001-2002) sewage sludge applications during a 5-yr period, and (ii) on nutrients status of soil that received annual application of sewage sludge from 1997 to 2000 compared with test values of soils in 2002 (with no sewage sludge application) in South Florida.
The field experiment was conducted at the University of Florida Agricultural Research and Education Center, Ona, FL (27 degrees 26'N, 82 degrees 55'W) on a Pomona fine sandy soil. With the exception of the control, BG plots received annual sewage sludge and chemical fertilizers applications to supply 90 or 180 kg total N ha(-1) yr(-1) from 1997 to 2000. Land application of sewage sludge and fertilizer ceased in 2001 season. In early April 1998, 1999, and 2000, plots were mowed to 5-cm stubble and treated with the respective N source amendments. The experimental design was three randomized complete blocks with nine N-source treatments: ammonium nitrate (AMN), slurry biosolids of pH 7 (SBS7), slurry biosolids of pH 11 (SBS11), lime-stabilized cake biosolids (CBS), each applied to supply 90 or 180 kg N ha(-1), and a nonfertilized control (Control). Application rates of sewage sludge were calculated based on the concentration of total solids in materials as determined by the American Public Health Association SM 2540G method and N in solids. The actual amount of sewage sludge applications was based on the amount required to supply 90 and 180 kg N ha(-1). Sewage sludge materials were weighed in buckets and uniformly applied to respective BG plots. Soil samples were collected in June 1997, June 1999, and in June 2002 from 27 treatment plots. In 1997 and 1999, soil samples were collected using a steel bucket type auger from the 0- to 20-, 20- to 40-, 40- to 60-, and 60- to 100-cm soil depths. Forage was harvested on 139, 203, 257, and 307 day of year (DOY) in 1998; 125, 202, 257, and 286 DOY in 1999; 179, 209, 270, and 301 DOY in 2000; and on 156 and 230 DOY in 2002 (no sewage sludge applications) to determine the residual effect of applied sewage sludge following repeated application. Forage yield and soils data were analyzed using analysis of variance (PROC ANOVA) procedures with year and treatment as the main plot and sub-plot, respectively. As a result of significant year effects on forage yield, data were reanalyzed annually (i.e., 1998, 1999, 2000, and 2002).
All sewage sludges used in this study were of class B in terms of USEPA's pathogens and pollutant concentration limit. Pathogen and chemical composition of the class B sewage sludge that were used in the study were all in compliance with the USEPA guidelines. The liquid sludge (SBS11) had the lowest fecal coliform counts (0.2 x 10(6) CFU kg(-1)) while the cake sewage sludge (CBS) had the greatest coliform counts of 178 x 10(6) CFU kg(-1). The fecal coliform counts for SBS7 was about 33 x 10(6) CFU kg(-1). Average soil test values in June 2002 exhibited: i) decrease in TIN (NO3-N + NH4-N), TP, K, Ca, Mg, Mn, and Fe; and ii) slight increase in Zn and Cu when compared with the June 1997 soil test results. The overall decrease in soil test values in 2002 might be associated with nutrient cycling and plant consumption. Although the average BG forage yield in 2002 (2.3 +/- 0.7 Mg ha(-1)) was slightly lower than in 2000 (3.5 +/- 1.2 Mg ha(-1)), yield differences in 2002 between the control (1.2 +/- 0.2 Mg ha(-1)) and treated plots (2.3 +/- 0.5 Mg ha(-1) to 3.3 +/- 0.6 Mg ha(-1)) were indicative of a positive residual effect of applied sewage sludge. This study has shown that excessive build up of plant nutrients may not occur in beef cattle pastures that repeatedly received sewage sludge while favoring long-term increased forage yield of BG. All sources of N (sewage sludge and AMN) gave better forage production than the unfertilized control during years with sewage sludge application (1997-2000) and also during years with no sewage sludge application (2001-2002). The favorable residual effects of applied sewage sludge in 2002 may have had received additional boost from the amount of rainfall in the area.
Repeated applications of sewage sludge indicate no harmful effects on soil quality and forage quality. Our results support our hypothesis that repeated land application of sewage sludge to supply 90 and 180 kg N ha(-1) would not increase soil sorption for nutrients and trace metals. Results have indicated that the concentrations of soil TIN and TP declined by almost 50% in plots with different nitrogen sources from June 1997 to June 2002 suggesting that enrichment of nitrogen and phosphorus is insignificant. The concentrations of soil nitrogen and phosphorus in 2002 following repeated application of sewage sludge were far below the contamination risk in the environment. The residual effect of these sewage sludge over the long term can be especially significant in many areas of Florida where only 50% of the 1 million ha of BG pastures are given inorganic nitrogen yearly.
Successive land application of sewage sludge for at least three years followed by no sewage sludge application for at least two years may well be a good practice economically because it will boost and/or maintain sustainable forage productivity and at the same time minimize probable accumulation of nutrients, especially trace metals. Consecutive applications of sewage sludge may result in build up of some trace metals in some other states with initial high metallic content, but in this study, no detrimental effects on soil chemical properties were detected. The possibilities for economically sound application strategies are encouraging, but more and additional research is required to find optimal timing and rates that minimizes negative impacts on soil quality in particular or the environment in general. For proper utilization of sewage sludge, knowledge of the sewage sludges' composition, the crop receiving it, are absolutely crucial, so that satisfactory types and rates are applied in an environmentally safe manner. There is still much to be learned from this study and this investigation needs to continue to determine whether the agricultural and ecological objectives are satisfied over the longer term.
