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991.
华北平原农田生态系统土壤C、N净矿化及尿素转化研究 总被引:4,自引:0,他引:4
以华北平原区4个农田生态系统[京郊蔬菜大棚(GH)和河北栾城(LF)、河北南皮(NF)、山东惠民(HF)3个粮田]为研究对象,采用室内好气、恒温、避光条件下培养30.d,对比研究了不同海拔和不同农业扰动强度下的农田生态系统中耕层(020.cm)土壤的净N矿化、净硝化、净C矿化以及尿素的转化,旨在探索人类农业扰动强度和地理海拔对土壤供N潜力和尿素N转化的影响。结果表明,4个地区的土壤供N潜力分别为:14.4、13.2,17.7和16.5.mg/kg,说明高度熟化的华北区农田土壤供N潜力相对稳定。以施用有机肥为主的蔬菜大棚和以施用化肥为主的粮田对土壤供N没有显著影响。农田土壤净矿化后的供N形式主要是NO3--N。以施用有机肥为主的蔬菜大棚积累了较高的土壤有机质和全N,但是土壤净C矿化以及施用尿素后CO2的排放量均低于以施用化肥为主的粮田。尿素在各区域农田土壤中水解转化后均主要以NO3--N形式存在,NO3--N占尿素水解后无机N增量的98%9~9%;华北平原农田生态系统施入尿素态N.30d后,水解成有效态无机N的转化率为63.4%8~3.2%,即每克尿素态N在京郊蔬菜大棚(GH)、栾城高产农田(LF)、南皮农田(NF)和惠民农田(HF)土壤中转化为NO3--N的量分别为0.69、0.82、0.64和0.63.g/kg,同时可使相应区域农田的CO2排放量分别增加CO21.20、1.360、.67和1.58.g/kg。 相似文献
992.
993.
Xiaoming Zou 《Biology and Fertility of Soils》1993,15(1):35-38
Summary Tree species differ in the quantity and quality of litter produced, and these differences may significantly affect ecosystem structure and function. I examined the importance of tree species in determining earthworm densities in replicated stands of Eucalyptus saligna Sm. and Albizia falcataria (L.) Fosberg, and in mixed stands (25% albizia and 75% eucalyptus). Mean earthworm densities ranged from 92 m-2 in the pure eucalyptus, to 281 m-2 in the mixture, and a maximum of 469 m-2 in the pure albizia stands. Only two earthworm species were present, Pontoscolex corethrurus and Amynthas gracilis. Leaf biomass on the forest floor was highest in the pure eucalyptus and lowest in the pure albizia stands, whereas the annual fine litterfall production was lowest in the pure eucalyptus and highest in the albizia stands. The N content of fine litterfall was correlated positively with earthworm density, and the fine litterfall biomass: N ratio was correlated negatively with earthworm density. Greater leaf biomass on the forest floor under eucalyptus stands despite lower rates of litterfall suggests that litter quality, rather than litter quantity, was primarily responsible for the greater earthworm density in the albizia stands. Some biogeochemical effects of tree species in the tropics may be mediated through effects on earthworm populations. 相似文献
994.
A 28 d N transformation test was developed according to the OECD guideline 216. In the laboratory-based test, a suitable soil was amended with powdered plant meal as an organic N source. Soil samples of 1 kg treated with five concentrations of nitrapyrin (2-chloro-6-(trichloromethyl)-pyridine), in the range 1.0-100 mg kg−1 dry weight were incubated for 28 d at 20±2 °C. A dose response was produced and the N mineralisation EC50 (95% C.I.) for nitrapyrin was 3.1 (1.9-4.3) mg kg−1 dry soil. The determined EC50 was compared with literature figures for similar end points but using different methodology. 相似文献
995.
996.
温室土壤硝态氮积累的温度、水分、施氮量耦合效应 总被引:5,自引:1,他引:5
为了探讨温室作物生产水肥管理和土壤温度对土壤硝态氮累积的影响,本文选取使用5年的温室土壤样品进行培养试验,研究温度、水分、施氮量及其耦合效应对温室土壤硝化作用和硝态氮累积的影响。试验结果表明:温室土壤硝态氮累积量可用“S”曲线进行定量描述,硝化过程中最大硝化速率、延迟期和最大可能累积量是参数土壤温度,含水率和NH4-N含量的函数;通过正交回归分析得出影响最大硝化速率的因素主次顺序依次为温度、含水率、温度与含水率的交互作用、水肥的耦合作用以及施氮量;影响延迟期的因素主次顺序依次为土壤水分、土壤温度、施氮量以及水肥耦合作用;最大可能累积量与温度、含水率及施氮量呈指数关系,其中施氮量影响最大,土壤温度次之,而这3个因素之间的交互作用对最大可能累积量没有明显的影响。利用回归模型,可为不同温度环境及水肥条件下硝态氮累积量及氮利用的有效性预测提供依据。 相似文献
997.
R.R.E. Vernimmen H.A. Verhoef L.A. Bruijnzeel H.R. Zoomer 《Soil biology & biochemistry》2007,39(12):2992-3003
Nitrogen mineralization and denitrification potential in litter were measured during a dry and a wet period in a Bornean Lowland Evergreen Rain Forest (LERF) and two nearby Heath Forests (HF) of contrasting stature. Nitrification was very low or non-existent in all forest types and ammonification was the major constituent of nitrogen (N) mineralization. Rates of net N mineralization in the HFs on infertile sandy soils were lower than in the LERF on a more nutrient-rich clay soil or other LERFs, both during dry and wet conditions. We attribute the differences to the lower litter quality in the HFs compared to LERF. When dissolved organic nitrogen (DON-N) was included, N uptake was the same (15-17 μg g−1 d−1) in all three forest types. We conclude that N availability is the same in all three forest types and that N deficiency is not the reason for the reduced stature of Heath Forests compared to LERF. All three-forest types had denitrifiers present in the ectorganic layers but denitrification will only play a minor role in the N-cycle as nitrification rates were very low. 相似文献
998.
Louisa Wessels Perelo Miguel Jimenez Jean Charles Munch 《Soil biology & biochemistry》2006,38(5):912-922
Microbial biomass N dynamics were studied under field and laboratory conditions in soils of high yield (HY) and low yield (LY) areas in an agricultural field. The objective of the study was to determine the size and activity of soil microbial biomass in the soils of the different yield areas and to compare these data obtained under field and laboratory conditions. Soils were amended with 15N labelled mustard (Sinapis alba) residues (both experiments) and labelled nitrate (laboratory only) at 30 μg N g−1 dry soil. Soil microbial biomass (SMB) N, mineral N (Nmin) and total N content was monitored both in the field and in the laboratory. N2O efflux was additionally measured in laboratory treatments. Isotope ratios were determined for SMB in both experiments, for all other parameters only in the laboratory treatments. In the laboratory less amounts of added substrate N were immobilised by the SMB in HY soils compared to LY soils, whereas in the field immobilisation of added N by SMB was higher in HY soils initially and slightly lower after 40 days of incubation. Calculated turnover times in the laboratory nitrate, laboratory mustard and field mustard amendments were 0.18, 0.27 and 0.74 years (HY) and 0.22, 0.61 and 1.01 years (LY), respectively. The turnover times of added substrate N always showed the trend to be faster in HY soils compared to LY soils. A faster turnover of nutrients in the HY soils may involve a better nutrient supply of the plants, which coincides with the higher agricultural yield observed in these areas. 相似文献
999.
There is now clear evidence for a prolonged increase in atmospheric CO2 concentrations and enrichment of the biosphere with N. Understanding the fate of C in the plant-soil system under different CO2 and N regimes is therefore of considerable importance in predicting the environmental effects of climate change and in predicting the sustainability of ecosystems. Swards of Lolium perenne were grown from seed in a Eutric Cambisol at either ambient (ca. 350 μmol mol−1) or elevated (700 μmol mol−1) atmospheric pCO2 and subjected to two inorganic N fertilizer regimes (no added N and 70 kg N ha−1 month−1). After germination, soil solution concentrations of dissolved organic C (DOC), dissolved inorganic N (DIN), dissolved organic N (DON), phenolics and H+ were measured at five depths down the soil profile over 3 months. The exploration of soil layers down the soil profile by roots caused transient increases in soil solution DOC, DON and phenolic concentrations, which then subsequently returned to lower quasi-stable concentrations. In general, the addition of N tended to increase DOC and DON concentrations while exposure to elevated pCO2 had the opposite effect. These treatment effects, however, gradually diminished over the duration of the experiment from the top of the soil profile downwards. The ambient pCO2 plus added N regime was the only treatment to maintain a notable difference in soil solution solute concentration, relative to other treatments. This effect on soil solution chemistry appeared to be largely indirect resulting from increased plant growth and a decrease in soil moisture content. Our results show that although plant growth responses to elevated pCO2 are critically dependent upon N availability, the organic chemistry of the soil solution is relatively insensitive to changes in plant growth once the plants have become established. 相似文献
1000.
To evaluate the pathways and dynamics of inorganic nitrogen (N) deposition in previously N-limited ecosystems, field additions of 15N tracers were conducted in two mountain ecosystems, a forest dominated by Norway spruce (Picea abies) and a nearby meadow, at the Alptal research site in central Switzerland. This site is moderately impacted by N from agricultural and combustion sources, with a bulk atmospheric deposition of 12 kg N ha−1 y−1 equally divided between NH4+ and NO3−. Pulses of 15NH4+ and 15NO3− were applied separately as tracers on plots of 2.25 m2. Several ecosystem pools were sampled at short to longer-term intervals (from a few hours to 1 year), above and belowground biomass (excluding trees), litter layer, soil LF horizon (approx. 5-0 cm), A horizon (approx. 0-5 cm) and gleyic B horizon (5-20 cm). Furthermore, extractable inorganic N, and microbial N pools were analysed in the LF and A horizons. Tracer recovery patterns were quite similar in both ecosystems, with most of the tracer retained in the soil pool. At the short-term (up to 1 week), up to 16% of both tracers remained extractable or entered the microbial biomass. However, up to 30% of the added 15NO3− was immobilised just after 1 h, and probably chemically bound to soil organic matter. 16% of the NH4+ tracer was also immobilised within hours, but it is not clear how much was bound to soil organic matter or fixed between layers of illite-type clay. While the extractable and microbial pools lost 15N over time, a long-term increase in 15N was measured in the roots. Otherwise, differences in recovery a few hours after labelling and 1 year later were surprisingly small. Overall, more NO3− tracer than NH4+ tracer was recovered in the soil. This was due to a strong aboveground uptake of the deposited NH4+ by the ground vegetation, especially by mosses. 相似文献