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2.
Sulphur K-edge X-ray absorption near edge structure (XANES) spectroscopy was used to quantify S species in humic substance extracts from ten soils from the UK, China and New Zealand, which differ in land use and agricultural management. XANES spectroscopy showed the presence of most reduced (sulphides, disulphides, thiols and thiophenes), intermediate (sulphoxides and sulphonates) and highly oxidised S (ester sulphates) forms, with the three groups representing 14-32%, 33-50% and 22-53% of the organic S in the humic substance extracts, respectively. Land use had a profound influence on the relative proportions of S species. Well-drained arable soils generally had a higher proportion of organic S present in the most oxidised form than the grassland soils collected nearby, whereas paddy soils showed a more reduced profile due to episodic flooding. In the Broadbalk Classical Experiment at Rothamsted, reversion of an arable system to grassland or woodland in the 1880s resulted in an increase of the most reduced and intermediate S species at the expense of the most oxidised S species. Long-term applications of farmyard manure to an arable plot also shifted S species from the most oxidised to the intermediate and the most reduced species. Sulphur immobilisation and gross mineralisation were determined in seven soils using the 35S isotope dilution method. Gross mineralisation during a 53-day incubation correlated more closely with the amounts of the most reduced and intermediate S species than with the most oxidised S species, suggesting that the former (C-bonded S) were the main source of organic S for mineralisation in the short-term. 相似文献
3.
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. 相似文献
4.
Summary A study was undertaken to investigate arylsulphatase activity in 15 soils cropped to cocoa (Theobroma cacao) and coffee (Coffea canephora var. robusta) in Ghana. The arylsulphatase activity was correlated positively and significantly with organic C, total N, and cation exchange capacity, and correlated negatively with acetate soluble sulphate. The enzyme was deactivated at an incubation temperature of over 60°C. Preheating and oven-drying of soils decreased arylsulphatase activity. Addition of 1.0 ml toluene during the assay resulted in a sharp decline in arylsuphatase activity. The addition of trace elements at a concentration of 1 ppm caused a reduction in soil arylsulphatase activity compared with that of the untreated samples. 相似文献
5.
《Journal of plant nutrition》2013,36(10-11):2111-2121
Abstract The finding that the methionine is the sole precursor of the mugineic acid family phytosiderophores induced us to evaluate whether sulfur assimilation pathway has a role in plant response to Fe deficiency. Maize plants were grown for 10 days in nutrient solution (NS) containing 80 µM Fe in the presence (+S) or absence (?S) of sulfate. After removing the root extraplasmatic iron pool, half of the plants of each treatment (+S and ?S) were transferred to a new Fe deficient NS (0.1 µM final Fe concentration) (?Fe). The remaining plants of each pre‐culture condition (+S and ?S) were transferred to a new NS containing 80 µM Fe (+Fe). Leaves were collected 4 and 24 hours from the beginning of Fe deprivation period and used for chemical analysis and enzyme assays. Results showed that iron content in the leaves was lower in plants grown in S‐deficiency than in those grown in the presence of the macro‐nutrient. Iron deprivation produced an increase in the level of SH compounds in both nutritive conditions (+S and ?S). These observations are suggestive of some relationship between S nutrition and Fe uptake. For this reason, we next investigated the influence of Fe availability on S metabolism through the evaluation of changes in ATPs and OASs activity, the first and the last enzyme of S assimilation pathway respectively. Results showed that S‐starvation increased the activity of both enzymes, but this effect disappeared in plants upon Fe deficiency suggesting that S metabolism is sensitive to Fe availability. Taken together these evidences suggest that S metabolism is sensitive to soil Fe‐availability for plant nutrition and support the hypothesis of S involvement in plant response to Fe deprivation. 相似文献
6.
在中文WINDOWS98平台上 ,以MAPGIS为基础操作平台 ,利用VisualBasic编程语言和MAPGIS提供的控件和API函数结合Access数据库软件开发了中国农业硫信息系统。根据已有数据材料和生产实践需要 ,系统开发了五个应用模块 ,分为土壤硫状况、作物硫营养、硫肥效应、土壤硫平衡、更新与设置。该系统能为农业技术推广、化肥生产销售部门以及农业科研部门提供一个土壤硫、植物硫营养和硫肥有效使用等信息管理工具 相似文献
7.
8.
The critical S concentration and S requirement of the soil microbial biomass of a granitic regosol was examined. S was applied
at the rate of 0, 5, 10, 20, 30 and 50 μg S as MgSO4·7H2O, together with either 3000 μg glucose-C or 3333 μg cellulose-C, 400 μg N, and 200 μg P g –1 soil and 200 μg K g–1 soil. Microbial biomass, inorganic SO4
2–-S, and CO2 emission were monitored over 30 days during incubation at 25 °C. Both glucose and cellulose decomposition rates responded
positively to the S made available for microbial cell synthesis. The amounts of microbial biomass C and S increased with the
level of applied S up to 10 μg S g–1 soil and 30 μg S g–1 soil in the glucose- and cellulose-amended soil, respectively, and then declined. Incorporated S was found to be concentrated
within the microbial biomass or partially transformed into soil organic matter. The concentration of S in the microbial biomass
was higher in the cellulose- (4.8–14.2 mg g–1) than in the glucose-amended soil (3.7–10.9 mg g–1). The microbial biomass C:S ratio was higher in the glucose- (46–142 : 1) than in the cellulose-amended soil (36–115 : 1).
The critical S concentration in the microbial biomass (defined as that required to achieve 80% of the maximum synthesis of
microbial biomass C) was estimated to be 5.1 mg g–1 in the glucose- and 10.9 mg g–1 in the cellulose-amended soil. The minimum requirement of SO4
2–-S for microbial biomass formation was estimated to be 11 μg S g–1 soil and 21 μg S g–1 soil for glucose- and cellulose-amended soil, respectively. The highest levels of activity of the microbial biomass were
observed at the SO4
2–-S concentrations of 14 μg S g–1 soil and 17 μg S g–1 soil, for the glucose and cellulose amendments, respectively, and were approximately 31–54% higher during glucose than cellulose
decomposition.
Received: 20 October 1999 相似文献
9.
高产夏玉米施用硫肥对矿质元素吸收影响的研究 总被引:4,自引:0,他引:4
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。 相似文献
10.
大田追施硫肥对双低油菜产量与品质的影响 总被引:4,自引:0,他引:4
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。 相似文献