Nutrient loss in leachate and surface runoff from surface-broadcast and subsurface-banded broiler litter.

Subsurface band application of poultry litter has been shown to reduce the transport of nutrients from fields in surface runoff compared with conventional surface broadcast application. Little research has been conducted to determine the effects of surface broadcast application and subsurface banding of litter on nutrients in leachate. Therefore, a field experiment was conducted to determine the effects of subsurface band application and surface broadcast application of poultry litter on nutrient losses in leachate. Zero-tension pan and passive capillary fiberglass wick lysimeters were installed in situ 50 cm beneath the soil surface of an established tall fescue ( Schreb.) pasture on a sandy loam soil. The treatments were surface broadcast and subsurface-banded poultry litter at 5 Mg ha and an unfertilized control. Results of the rainfall simulations showed that the concentrations of PO-P and total phosphorus (TP) in leachate were reduced by 96 and 37%, respectively, in subsurface-banded litter treatment compared with the surface-applied litter treatment. There was no significant difference in PO-P concentration between control and subsurface-banded litter treatment in leachate. The trend in the loading of nutrients in leachate was similar to the trend in concentration. Concentration and loading of the nutrients (TP, PO-P, NH-N, and NO-N) in runoff from the subsurface-banded treatment were significantly less than for the surface-applied treatment and were similar to those from control plots. These results show that, compared with conventional surface broadcast application of litter, subsurface band application of litter can greatly reduce loss of P in surface runoff and leachate.

Ammonia emissions from field-simulated cattle defecation and urination.

Atmospheric ammonia (NH(3)) is a concern because of its environmental impact. The greatest contribution to atmospheric NH(3) comes from agricultural sources. This study quantified NH(3) volatilization from cattle defecation and urination on pasture under field conditions in Auburn, Alabama. Treatments consisted of beef feces, dairy feces, dairy urine, and a control. The experiment was conducted during four seasons from June 2003 to April 2004. Fresh feces or urine was applied onto grass swards, and NH(3) volatilization was measured up to 14 d after application using an inverted chamber method. Dairy urine was the only significant source of NH(3). Ammonia nitrogen (N) loss differed among seasons, ranging from 1.8% in winter to 20.9% during the warmer summer months. Cumulative volatilization was best described in this experiment by the equation % NH(3)-N loss = N(max) (1 - e(-ct))(i). The highest rate of NH(3) volatilization generally occurred within 24 h. This study suggests that NH(3) volatilization from cattle urine on pasture is significant and varies with season, whereas NH(3) volatilization from cattle feces is negligible.

Energy content, construction cost and phytomass accumulation of Glycine max (L.) Merr. and Sorghum bicolor (L.) Moench grown in elevated CO2 in the field.

Grain sorghum [Sorghum bicolor (L.) Moench, a C4 crop] and soybean [Glycine max (L.) Merr. cv. Stonewall, a C3 crop] plants were grown in ambient (c. 360µl 1-1 ) and twice-ambient (c. 720 µl 1-1 ) CO2 levels in open-top chambers in soil without root constriction. Plant dry mass, energy content, composition and construction cost (i.e. amount of carbohydrate required to synthesize a unit of plant dry mass) were assessed at the end of the growing season. Elevated CO2 (a) increased phytomass accumulation (kg per plant) in both species, (b) had little affect on energy concentration (MJ kg-1 plant) but caused large increases in the amount of plant energy per ground area (MJ m-2 ground), and (c) did not alter specific growth cost (kg carbohydrate kg-1 plant growth) but greatly increased growth cost per ground area (kg carbohydrate m-2 ground) because growth was enhanced. For soybean, twice-ambient CO2 resulted in a 50 % increase in the amount of nitrogen and energy in grain (seed plus pod) per ground area. This response to elevated CO2 has important implications for agricultural productivity during the next century because the rate of human population growth is exceeding the rate of increase of land used for agriculture so that future food demands can only be met by greater production per ground area.

Ammonia, methane, and nitrous oxide emission from pig slurry applied to a pasture in New Zealand.

Much animal manure is being applied to small land areas close to animal confinements, resulting in environmental degradation. This paper reports a study on the emissions of ammonia (NH3), methane (CH4), and nitrous oxide (N2O) from a pasture during a 90-d period after pig slurry application (60 m3 ha-1) to the soil surface. The pig slurry contained 6.1 kg total N m-3, 4.2 kg of total ammoniacal nitrogen (TAN = NH3 + NH4) m-3, and 22.1 kg C m-3, and had a pH of 8.14. Ammonia was lost at a fast rate immediately after slurry application (4.7 kg N ha-1 h-1), when the pH and TAN concentration of the surface soil were high, but the loss rate declined quickly thereafter. Total NH3 losses from the treated pasture were 57 kg N ha-1 (22.5% of the TAN applied). Methane emission was highest (39.6 g C ha-1 h-1) immediately after application, as dissolved CH4 was released from the slurry. Emissions then continued at a low rate for approximately 7 d, presumably due to metabolism of volatile fatty acids in the anaerobic slurry-treated soil. The net CH4 emission was 1052 g C ha-1 (0.08% of the carbon applied). Nitrous oxide emission was low for the first 14 d after slurry application, then showed emission peaks of 7.5 g N ha-1 h-1 on Day 25 and 15.8 g N ha-1 h-1 on Day 67, and decline depending on rainfall and nitrate (NO3) concentrations. Emission finally reached background levels after approximately 90 d. Nitrous oxide emission was 7.6 kg N ha-1 (2.1% of the N applied). It is apparent that of the two major greenhouse gases measured in this study, N2O is by far the more important tropospheric pollutant.

Role of aquaculture pond sediments in sequestration of annual global carbon emissions.

Aquaculture ponds sequester about 16.6MTyr(-1) of organic carbon worldwide representing around 0.21% of annual, global carbon emissions.