Diffusion of N-labelled N2O into soil columns: a promising method to examine the fate of N2O in subsoils

Nitrous oxide research has generally focused directly on measuring fluxes of N₂O from the soil surface. The fate of N₂O in the subsoil has often been placed in the ‘too hard’ basket. However, determining the production, fate and movement of N₂O in the subsoil is vital in fully understanding the sources of surface fluxes and in compiling accurate inventories for N₂O emissions. The aim of this study was to generate and introduce into soil columns ¹⁵N labelled N₂O, and to try and determine the consumption of the ¹⁵N₂O and production of ambient N₂O. Columns, 100 cm long by 15 cm diameter, were repacked with sieved soil (sampled from 0 to 5 cm depth) and instrumented with silicone rubber gas sampling ports. Nitrous oxide enriched with ¹⁵N was generated using a thermal decomposition process at 300 °C and then transferred to 2 l flasks. After equilibrating with SF₆ tracer gas the ¹⁵N₂O was introduced into the soil columns via passive diffusion. Gas samples from the soil profile and headspace flux were taken over a 12-day period. A watering event was simulated to perturb the ¹⁵N₂O gas composition in the soil profile. Using the measured ¹⁵N enriched fluxes and the rate of decline in ¹⁵N in the N₂O reservoir, from which the N₂O diffused into the soil, we calculated an N₂O sink (consumption plus absorption by water) equal to 0.48 ng N₂O g⁻¹ soil h⁻¹. The decrease in the ¹⁵N enrichment between successive soil depths indicated N₂O production in the soil profile and we calculated a net N₂O production rate of 0.88 ng N₂O g⁻¹ soil h⁻¹. This pilot study demonstrated the potential for simultaneously measuring both N₂O consumption and production rates, using the ¹⁵N enrichment of the N₂O measured. Further potential refinements of the methodology are discussed.     

高产夏玉米施用硫肥对矿质元素吸收影响的研究

每公顷基施:0(CK)、36.3(S₁)、413.85(S₂)kg硫时,玉米每公顷产量分别为9 784.5、10 639.5、11 322 kg,处理分别比对照增产8.73%和15.71%,并提高了果穗长度,增加了穗行数、行粒数,对千粒重影响不大.单株对氮、磷、钾、锰、锌、镁的吸收量表现为S₂>S₁>CK.施入(NH₄)₂SO₄后,0～20 cm、21～40 cm、41～60 cm土层的pH值降低,收获后有所回升,各处理各土层的pH值均表现为CK>S₁>S₂.施入硫肥后,0～60 cm土层全氮含量降低,速效钾的含量提高,0～20 cm土层中的速效磷含量有所提高,21～40 cm土层变化不大,41～60 cm土层中的速效磷含量降低。     

青海藏羊羊毛纤维长度与含硫量的分布

通过对终年放牧的青海藏羊毛纤维长度5cm区段含硫量的测定，结果表明青海藏羊毛纤维不同长度区段的含硫量不同，含硫量顶峰值前，随着长度增加含硫量逐步增加，但成年公羊顶峰值后随机度增加，含硫量逐渐减少。青海藏羊毛长5cm各区段各硫量差异不显著（P＞0．05），毛长与含硫量除成年公羊为强的负相关（r=-0.56964)，其余各性能年龄组内均为弱的正相关关系，相关系数r=-0.116182-0.354898.     

狗舌草中毒猪血液中吡咯代谢物的测定

用含 10 %狗舌草的饲料喂猪 144d ,进行了血液S—吡咯测定。染毒后第 8～ 96d ,试验猪血液S—吡咯TLC呈现较为明显的淡紫色斑 ,Rf值在 0 5 6～ 0 78之间 ;在试验的第 8d ,试验猪血液S—吡咯光密度值达 0 0 89± 0 0 0 7OD单位 ,此后一直呈上升趋势     

Re-creation of heathland on improved pasture using top soil removal and sulphur amendments: Edaphic drivers and impacts on ericoid mycorrhizas

Understanding the factors that drive successful re-creation and restoration of lowland heaths is crucially important for achieving the long-term conservation of this threatened habitat type. In this study we investigated the changes in soil chemistry, plant community and interactions between Calluna vulgaris and symbiotic ericoid mycorrhizas (ERM) that occurred when improved pasture was subjected to one of three treatments (i) acidification with elemental sulphur (ii) acidification with ferrous sulphur (iii) removal of the topsoil. We found that the soil stripping treatment produced the greatest reduction in available phosphate but did not decrease soil pH. Conversely, acidification with elemental sulphur decreased pH but increased availability of phosphate and potentially toxic cations. The elemental sulphur treatment produced plant communities that most closely resembled those on surrounding heaths and acid grasslands. The most important driver was low pH and concomitant increased availability of potentially toxic cations. Plant community development was found to be little related to levels of available soil phosphate, particularly at low pH. The elemental sulphur treatment also produced the best germination and growth of C. vulgaris over 4-5 years. However, this treatment was found to inhibit the development of symbiotic relationships between C. vulgaris and ERM. This may affect the long-term persistence of re-created vegetation and its interactions with other components of heathland communities.     

Soil sulphur status following long-term annual application of animal manure and mineral fertilizers

 In agricultural systems with low S inputs, crops rely on the release of S from organic forms in the soil. In the Askov long-term experiments, started in 1894 on both sandy and loamy soils, soil S status following long-term application of animal manure and mineral fertilizers was investigated in the growing season of 1995. In a field trial with oil-seed rape (Brassica napus, L.) soil analysis, leaf tissue analysis, yield and S removal in plant material was used to characterize differences in availability of soil S. One half of all plots received 63 kg S ha^–1 as gypsum. Long-term fertilization with animal manure or NPK fertilizer increased the content of soil organic C in both soils and of organic S in the sandy soil compared with unfertilized plots. Although dry matter yields were unaffected, the S uptake in harvested crop parts increased considerably after S application. The amounts of N and S in harvested seeds and straw were closely related, but the N : S ratio decreased when S was applied. Soil and plant analyses both indicated that critical levels of S concentrations were reached, and that S application was capable of raising S concentrations well above the critical level. Because no additional mineralization from residual organic S took place, it was concluded that the residual S effect from long-term annual applications of animal manure or mineral fertilizers did not significantly increase the level of soil S available for crops with a short growing season, such as oil-seed rape. Received: 9 January 1998     

拟南芥莲座叶芥子油苷组成和含量对缺硫胁迫的响应

[目的]探讨缺硫胁迫下拟南芥(Arabidopsis thaliana)生长到12片莲座叶时芥子油苷组成和含量的变化规律。[方法]以模式植物拟南芥为原材料,通过水培方法进行缺硫胁迫处理,采用高效液相色谱-质谱联用(HLPC-MS)法分析芥子油苷的组成和含量。[结果]缺硫胁迫处理48 h,拟南芥莲座叶中检测出7种脂肪族芥子油苷、4种吲哚族芥子油苷。缺硫胁迫对吲哚族芥子油苷含量影响不显著,对脂肪族芥子油苷含量影响显著。[结论]试验结果为探索缺硫胁迫下芥子油苷的代谢途径提供了理论依据。     

大田追施硫肥对双低油菜产量与品质的影响

硫酸盐肥料以S10或40kg／hm2分别在油菜的出苗期、莲座期、现蕾期、抽薹期及初花期施入缺硫土壤，并在出苗期结合施用氮肥N80或160kg／hm2。结果表明，对照区植株在抽薹期表现出严重的缺硫症状，特别是单施N160kg／hm2的小区。追施S10kg／hm2可显著提高油菜产量及含油量，但追施时期间差异未达到显著性水准，这一施用量明显不足，油菜籽产量远低于施S40kg／hm2处理。迟于花期追施S40kg／hm2，籽粒产量较前期减少约20％。此外，施S40kg／hm2还可明显提高籽粒的蛋白质含量。对缺硫植株，籽粒N：S比大于10，而供硫适宜植株为7．5。总硫代葡萄糖甙含量随施硫量的增加而提高，且后期追施明显高于前期。     

Effects of sulphur on yield and malting quality of barley

Eight field experiments were conducted at four sites in the UK in 2003 and 2004 to investigate the effects of sulphur (S) application on yield and malting quality of barley. Significant yield responses to S additions were obtained in five out of the eight experiments, with yield increases ranging from 0.2 to 1.2 t/ha (4.7–22.5%). At the two most S-deficient sites, S application significantly increased malt diastatic power, alpha-amylase activity, friability and homogeneity, and decreased (1→3,1→4)-β-glucan concentration in the wort, indicating an improved endosperm modification during malting. Sulphur applications also significantly increased the concentration of S-methylmethionine (the precursor of dimethylsulphide) in kilned malt, which could impact on beer flavour. When the supply of N was limiting, S applications decreased grain N concentration due to a dilution effect as a result of increased grain yield. In some cases, S applications resulted in decreased grain size. At sites non-deficient or marginally deficient in S, applications of S had little effect on grain or malting quality parameters. The need to maintain an adequate S supply to barley for both yield and malting quality was demonstrated.     

蒜苔挥发油化学成分的研究

用色质联机分析蒜苔挥发油，鉴定出２４个有机硫化物，其中１，２，３－三噻环己烷１，２，３，４－四噻环庚烷，甲基烯丙基四硫化物以及二烯丙基四硫化物为首次在蒜中发现。