Effects of aggregate size,soil compaction,and bovine urine on N2O emissions from a pasture soil

The dominant N₂O emission source in New Zealand, calculated using the Intergovernmental Panel on Climate Change methodology, is agricultural soils. The largest source of N₂O emissions in New Zealand occurs as a result of excreta deposition onto pasture during grazing. There is a dearth of studies examining the effect of soil compaction and soil aggregate size on N₂O emissions from urine patches in grazed pastures. In this study, we repacked soil cores with four different soil aggregate sizes (<1.0–5.6 mm diameter), applied bovine urine, and then subjected the soil cores to four levels of soil compaction. Fluxes of N₂O were monitored for 37 days after which soil cores were allowed to dry out prior to a rewetting event. There was an interaction between aggregate size and soil compaction with the cumulative loss of N₂O over the first 37 days ranging from 0.3% to 9.6% of the urine-N applied. The highest N₂O emissions occurred from the smallest and most compacted aggregates. Even under the highest levels of compaction the N₂O loss from the large aggregates (4.0–5.6 mm diameter) was <1% of the urine-N applied. Reasons for the observed differences in the N₂O flux from the different-sized aggregates included varying gas diffusivities and higher rates of denitrification in the smallest aggregates, as evidenced by the disappearance of nitrate.     

Comparison of the effectiveness of a nitrification inhibitor, dicyandiamide, in reducing nitrous oxide emissions in four different soils under different climatic and management conditions

Nitrous oxide (N₂O) is a potent greenhouse gas and, in New Zealand, about one‐third of the total greenhouse gas emissions from the agricultural sector are of N₂O, mostly derived from animal excreta in grazed pasture soils. The aim of this study was to determine the effectiveness of a nitrification inhibitor, dicyandiamide (DCD), in reducing N₂O emissions from animal urine patches in four different soils located in different regions of New Zealand with different soil, climatic and management conditions. The four soils are Templeton fine sandy loam and Lismore stony silt loam in Canterbury in the South Island, Horotiu silt loam in the Waikato region and Taupo pumice sand near Lake Taupo, both in the North Island. Results showed that the application of a fine‐particle suspension nitrification inhibitor, DCD, to grazed pasture soils was very effective in reducing N₂O emissions in all four different soils. Total N₂O emissions (over 69–137 days) from animal urine patches ranged from 1 to 20.9 kg N₂O‐N ha^?1 without DCD. These were reduced to 0.31–5.7 kg N₂O‐N ha^?1 by the use of DCD, representing 61–73% reductions (with an average of 70% reduction). The N₂O‐N emission factor from animal urine N, EF₃, was reduced from an average of 0.9 to 0.3% by the use of DCD. These results demonstrate the potential of using nitrification inhibitors to mitigate N₂O emissions in a wide range of grazed pasture soils under different climatic and management conditions.     

Giant larvacean houses: rapid carbon transport to the deep sea floor

An unresolved issue in ocean science is the discrepancy between the food requirements of the animals living on the deep sea floor and their food supply, as measured by sediment traps. A 10-year time-series study of the water column off Monterey Bay, California, revealed that the discarded mucus feeding structures of giant larvaceans carry a substantial portion of the upper ocean's productivity to the deep seabed. These abundant, rapidly sinking, carbon-rich vectors are not detected by conventional sampling methods and thus have not been included in calculations of vertical nutrient flux or in oceanic carbon budgets.     

马家塔露天矿生态复垦区土壤养分状况研究

本文系统研究了神东矿区马家塔露天采坑复垦区土壤养分状况,结果显示:复垦区土壤基本上为原始回填土,剖面层次不发育,成土程度很低;土壤机械组成以砾石、粗沙为主,含量高达90%。有机质、含碱解氮含量略高于未受扰动的原状土壤,但速磷、速钾含量均低于原状土壤,总体评价土壤属于养分贫乏型;成土程度低、养分含量少是农林业生产水平不高的主要原因。研究表明通过改良复垦工艺以及提高复垦区生产管理水平是提高土地生产力的主要措施。     

乳酸菌添加剂对青藏高原燕麦青贮品质的影响

[目的]研究乳酸菌添加剂对青贮燕麦发酵品质的影响,为燕麦的青贮提供技术条件。[方法]按0．005g／kg燕麦的添加量,将乳酸菌粉剂直接加入燕麦,采用捆裹青贮系统进行青贮。处理80d后,观察其感官特征并测定品质,与普通青贮燕麦和青刈燕麦进行比较。[结果]乳酸菌青贮燕麦的气味、色泽和手感均优于普通青贮燕麦,其pH值低于3．8,乳酸与乙酸的比值下降,乳酸占总酸的比例增加,DM、CP和Ash含量增加,NDF、ADF含量降低。[结论]乳酸菌添加剂改善了青贮燕麦的品质,所得燕麦属于优质青贮料。     

糖甜菜定域育种初步研究

试验结果表明，甜菜单粒种采种母根主、侧花枝种子的块根产量、含糖率不同。单粒种根头周边芽所形成的花枝种子比根头中央部芽的花枝种子所产生的块根含糖率高0．79-2．45度，表现趋势较一致；但主、侧花枝种子的块根产量高低表现趋势不一致。为提高含糖率，此方法可在甜菜单粒型品系育种中应用。     

Modeling the Exchanges of Energy, Water, and Carbon Between Continents and the Atmosphere

Atmospheric general circulation models used for climate simulation and weather forecasting require the fluxes of radiation, heat, water vapor, and momentum across the land-atmosphere interface to be specified. These fluxes are calculated by submodels called land surface parameterizations. Over the last 20 years, these parameterizations have evolved from simple, unrealistic schemes into credible representations of the global soil-vegetation-atmosphere transfer system as advances in plant physiological and hydrological research, advances in satellite data interpretation, and the results of large-scale field experiments have been exploited. Some modern schemes incorporate biogeochemical and ecological knowledge and, when coupled with advanced climate and ocean models, will be capable of modeling the biological and physical responses of the Earth system to global change, for example, increasing atmospheric carbon dioxide.     

Efficiencies of ryegrass and white clover herbage utilization in mixtures continuously grazed by sheep

A method for measuring the growth, senescence and defoliation fluxes in a mixture consisting of alternate rows of perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) was used to calculate the actual and potential efficiencies of grass and clover utilization under continuous sheep grazing. White clover contributed relatively more to the growth than to the herbage mass of the mixture and its relative growth rate was usually significantly greater than that of its companion grass. The primary reason for the greater potential efficiency of herbage use of the white clover component was, however, its lower rate of senescence. Greater potential efficiency was not reflected in a greater actual efficiency because the contribution of white clover to the total herbage removed was always smaller than its contribution to the growth flux of the mixture. Despite the commonly assumed sheep preference for white clover, the legume was usually the least defoliated species, presumably because of the lower surface height of white clover compared with grass, which resulted in a lower vertical availability of white clover, thereby restricting its defoliation rate. The positive net herbage accumulation observed with white clover at a constant sward surface height occurred partly through stolon and bud development and partly through the growth of undefoliated leaves from axillary growing points and contributed to a net herbage accumulation per unit dry weight in white clover greater than that in ryegrass. This resulted in an increase in the white clover content of the sward, which was observed independently by destructive measurements.     

In vivo administration of acepromazine or promethazine to horse decreases the reactive oxygen species production response of subsequently isolated neutrophils to stimulation with phorbol myristate acetate

The previous experiments have shown that some phenothiazines have antioxidant and anti-inflammatory properties in vitro . In this study the inhibition of the production of reactive oxygen species (ROS) by neutrophils was studied in two groups of horses, which received a dose of 0.1 mg/kg of either acepromazine or promethazine intravenously. Blood samples were collected before (T0) and 0.5, 1, 3 and 5 h after drug administration. The chemiluminescence (CML) response of neutrophils was measured ex vivo in the presence of luminol for a period of 10 min and the maximum CML value (peak value) recorded. There was a significant inhibition of the ROS production in the acepromazine treated group (49% inhibition) at 5 h after administration and in the promethazine group (24% inhibition) at 3 h after administration ( P  < 0.05 vs. T0). These findings are of therapeutic relevance in the use of phenothiazines in equine patients with inflammatory diseases where neutrophil activation and ROS production are implicated.