The effect of nitrification inhibitors on nitrous oxide emissions from cattle urine depositions to grassland under summer conditions in the UK.

Nitrous oxide (N2O) has become the prime ozone depleting atmospheric emission and the third most important anthropogenic greenhouse gas, with a global warming potential approximately 300 times higher than CO2. Nitrification and denitrification are processes responsible for N2O emission from the soil after nitrogen input. The application of a nitrification inhibitor can reduce N2O emissions from these processes. The objective of this study was to assess the effect of two different nitrification inhibitors (dicyandiamide (DCD) and a commercial formulation containing two pyrazole derivatives (PD), 1H-1,2,4-triazole and 3-methylpyrazole) on N2O emissions from cattle urine applications for summer grazing conditions in the UK. Experiments were conducted under controlled conditions in a laboratory incubator and under field conditions on a grassland soil. The N2O emissions showed similar temporal dynamics in both experiments. DCD concentration in the soil showed an exponential degradation during the experiment, with a half-life of the order of only 10d (air temperature c. 15 °C). DCD (10 kg ha(-1)) and PD at the highest application rate (3.76 kg ha(-1)) reduced N2O emissions by 13% and 29% in the incubation experiment and by 33% and 6% in the field experiment, respectively, although these reductions were not statistically significant (P>0.05). Under UK summer grazing conditions, these nitrification inhibitors appear to be less effective at reducing N2O emissions than reported for other conditions elsewhere in the literature, presumably due to the higher soil temperature.

Brazilian beef cattle feedlot manure management: a country survey.

No information regarding the management of manure from beef cattle feedlots is available for Brazil. To fill this knowledge gap, a survey of 73 feedlots was conducted in 7 Brazilian states. In this survey, questions were asked regarding animal characteristics, their diets, and manure handling management from generation to disposal. These feedlots finished 831,450 animals in 2010. The predominant breed fed was Nellore, with average feeding periods of 60 to 135 d. Corn was the primary source of grain used in the feedlot diets (76% of surveyed animals) with concentrate inclusion levels ranging from 81 to 90% (38% of surveyed animals). The most representative manure management practice was the removal of manure from pens only at the end of the feeding period. Subsequently, the manure was stored in mounds before being applied to crop and pasture lands. Runoff, mainly from rainwater, was collected in retention ponds and used for agriculture. However, the quantity of runoff was not known. Manure was composted for only 20% of the animals in the survey and was treated in anaerobic digesters for only 1% of the animals. Manure from 59% of the cattle surveyed was used as fertilizer, providing a cost savings over the use of synthetic fertilizers. Overall, chemical analysis of the manure before application to fields was conducted for the manure of 56% of the surveyed animals, but the exact quantity applied (per hectare) was unknown for 48%. Feedlots representing 48% of the surveyed animals noted similar or greater crop and pasture yields when using manure, rather than synthetic fertilizers. In addition, 32% mentioned an increase in soil organic matter. Feedlots representing 88% of the surveyed cattle indicated that information concerning management practices that improve manure use efficiency is lacking. Feedlots representing 93% of the animals in the survey reported having basic information regarding the generation of energy and fertilizer with anaerobic digesters. However, only 1 feedlot implemented this technology. In conclusion, the manure management evaluated in this study represents an important indirect economic benefit that was represented by decreased use of synthetic fertilizers in crops. However, little attention was given to the specific treatments and environmental impacts of handling manure. This survey provides information that should assist in the development of better research practices and broader application of future models.

Carbon-13 variation with depth in soils of Brazil and climate change during the Quaternary.

Paleoecological and geomorphological studies indicate that, during the middle Holocene, there was a predominance of drier conditions with grassy savannahs replacing forests across the South American continent. Modern savannahs are composed mainly of C4 plants and soils developed under this type of vegetation show enrichment in 13C compared to soils under C3 vegetation cover. If soils contain stabilized organic matter formed in the middle Holocene, we hypothesize that former C4 vegetation would be evidenced by a large enrichment of 13C in soil organic matter (SOM). We investigate this possibility examining the depth variation of carbon isotopic composition in 21 soil profiles collected by different researchers at 14 different sites in Brazil. Of these, profiles from only three sites showed a marked increase of 13C with depth (9-10‰ enrichment in δ13C difference between the surface soil and deepest depth); two sites showed intermediate enrichment (4-5‰), and nine sites showed a small enrichment of approximatelly 2.5‰. The majority of sites showing all-C3 derived SOM were in the Amazon region. Possible causes for the absence of a large 13C enrichment with depth are: (1) dominance of C3 rather than C4 grasses in mid-Holocene savannahas, (2) soil profiles did not preserve organic matter derived from mid-Holocene plants, (3) the retreat of forest areas did not occur on a regional scale, but was a much more localized phenomenon.