Nitrogen flux in broad-leaved Korean pine forest land in Changbai Mountain

IntrotIuctionBroad-leavedKoreanpineforestistI1ezonalvegetationinNortheastChina.Theforms,transfdrmationandtransfer-enceofNintheforestlandarenotonlyimportantpartSofmaterialcyclingintheforestecosystem,butalsocon-cernedwithhoPOrtantenvironmentalquestions.InordertoinquireintoNflux,Nmineraliration,plantuptakeandleachinglossesinthetop2ocmoftheforestfloorwerestudiedwiththeinsitUsequentialcoringtechniquefromMaytoSeptemberofl994.MatcriaIsandmethodsSitcconditionThesampleplotstUdiedissituatedinErd…     

多孔高分子载体固定化微生物厌氧流化床处理低浓度废水的研究

本文报道用厌氧流化床反应器处理低浓度有机废水的可行性研究结果。采用多孔高分子载体固定厌氧微生物和流态化技术强化传质过程,可克服低浓度有机废水甲烷化能力低的障碍。实验表明,在３５±１℃条件下,处理ＣＯＤ浓度为１６００ｍｇ／Ｌ的人工葡萄糖废水,床层最优膨胀率为５０％,容积有机负荷率为１９．２ｇＣＯＤ／（Ｌ·ｄ）,ＣＯＤ去除率达７０％;处理ＣＯＤ浓度为２２０～２５０ｍｇ／Ｌ的城市污水,容积有机负荷率为２．４～２．６ｇＣＯＤ／（Ｌ·ｄ）,ＣＯＤ去除率为５４％～５６％。     

Soil N dynamics in a natural calcareous grassland under a changing climate

 This paper reports the results from a medium-term field scale investigation into the effects of simulated climate change on soil N mineralisation in a semi-natural calcareous grassland in southern England. The experiment utilised soil warming cables, automatic rainshelters and a watering system to examine two climate change scenarios: warmer winters with summer drought and warmer winters with enhanced summer rainfall. Gross N mineralisation rates in treated plots were determined, using ¹⁵N pool dilution techniques, at 6-weekly intervals over a 3-year period. Results from control plots showed a strong seasonality of mineralisation with highest rates in autumn and winter and lowest rates in summer. They suggest that water availability is the main constraint on microbial processes and plant growth. Unexpectedly, additional summer rainfall had no direct effect on N mineralisation at the time of application (summer). The treatment did, however, significantly (<0.05%) reduce rates in subsequent autumn and winter months. In contrast, summer drought significantly increased N mineralisation rates in autumn and winter. Winter warming similarly had no direct effect on N mineralisation in winter but decreased rates in spring. We hypothesise that the observed treatment effects result from changes in organic C and N input, in plant litter, resulting from the direct impact of climatic manipulation on perennial plant growth, death and senescence. This paper compares and contrasts the response to climate manipulation in the grassland system with results from other ecosystem types such as northern forests. Received: 1 December 1997     

Comparison of the difference method and 15N technique for studying the fate of nitrogen from plant residues in soil

We compared the dynamics of net mineralization of nitrogen (N) derived from white clover material (Ndfc) as measured by the difference and the ¹⁵N methods in a pot experiment with a sandy loam (15°C and pF 2.4) planted with Italian ryegrass. On day 22, mineralized Ndfc (soil mineral N plus plant N uptake) was 5.8% and 1.3% of added N for the ¹⁵N and the difference methods, respectively. The discrepancy was reduced on day 43. On day 64, the relationship was reversed, and on day 98 the values given by the two methods were 22.8% and 29.5%, respectively. The results obtained by the two methods were linearly correlated (r = 0.987) and, on average, did not differ significantly. Nevertheless, the different temporal patterns led to appreciably different parameter values as estimated by fitting of a reparameterized Richards model. On day 22, clover amendment reduced mineralized N derived from soil (Ndfs) by 3.4 mg N pot^–1. The reason for this was that the clover amendment led to a reduction in plant growth and uptake of Ndfs, most likely because of allelopathy, while mineral Ndfs did not increase correspondingly. Clover-induced Ndfs in the microbial biomass of 5.1 mg N pot^–1 suggested that the mineral Ndfs not taken up by plants had been reimmobilized. Towards the end of the experiment, clover-induced Ndfs in the biomass declined to 1.5 mg N pot^–1, while mineralized Ndfs due to clover amendment increased to 5.1 mg N pot^–1. The results strongly suggested that this increase was caused by a real stimulation of humus N mineralization by clover amendment rather than by isotope displacement or pool substitution. Received: 5 May 1997     

Control of nitrate leaching from a Nitrate Vulnerable Zone using paper mill waste

Abstract. The effects on nitrate leaching of incorporation of paper mill waste at three cultivation depths in fields previously cropped to iceberg lettuce and calabrese are reported. In the lettuce experiment, incorporation of 40 t DM paper mill waste/ha resulted in a decrease in N leaching (measured with suction cups) from 177 to 94 kg/ha (S.E._d= 23). Deep ploughing with and without paper waste increased N leaching from 105 kg/ha (normal ploughing or surface incorporation) to 172 kg/ha (S. E. _d= 27). Measurements of nitrate leaching using deep soil cores showed a less clear cut effect. Nitrous oxide (N₂O) emissions were very high immediately after paper waste was ploughed in to a depth of 35 cm. Non–significant increases in biomass N content were measured in the spring following paper waste application. There was no significant reduction in plant N uptake in subsequent crops. Removal of above–ground crop residues did not have a significant effect on nitrate leaching or N₂O losses. In the calabrese experiment, application of 40 t DM paper mill waste/ha followed by summer cropping with iceberg lettuce caused a decrease in N leaching (measured using deep soil cores) from 227 to 152 kg/ha (S. E._d= 22, mean of all cultivation treatments).     

Soil microbial biomass and nitrogen supply in an irrigated lowland rice soil as affected by crop rotation and residue management

 Processes that govern the soil nitrogen (N) supply in irrigated lowland rice systems are poorly understood. The objectives of this paper were to investigate the effects of crop rotation and management on soil N dynamics, microbial biomass C (C_BIO) and microbial biomass N (N_BIO) in relation to rice N uptake and yield. A maize-rice (M-R) rotation was compared with a rice-rice (R-R) double-cropping system over a 2-year period with four cropping seasons. In the M-R system, maize (Zea mays L.) was grown in aerated soil during the dry season (DS) followed by rice (Oryza sativa L.) grown in flooded soil during the wet season (WS). In the R-R system, rice was grown in flooded soil in both the DS and WS. Three fertilizer N rates (0, 50 or 100 kg urea-N ha^–1 in WS) were assigned to subplots within the cropping system main plots. Early versus late crop residue incorporation following DS maize or rice were established as additional treatments in sub-subplots in the second year. In the R-R system, the time of residue incorporation had a large effect on NO₃ ^–-N accumulation during the fallow period and also on extractable NH₄ ⁺-N, rice N uptake and yield in the subsequent cropping period. In contrast, time of residue incorporation had little influence on extractable N in both the fallow and rice-cropping periods of the M-R system, and no detectable effects on rice N uptake or yield. In both cropping systems, C_BIO and N_BIO were not sensitive to residue incorporation despite differences of 2- to 3-fold increase in the amount of incorporated residue C and N, and were relatively insensitive to N fertilizer application. Extractable organic N was consistently greater after mid-tillering in M-R compared to the R-R system across N rate and residue incorporation treatments, and much of this organic N was α-amino N. We conclude that N mineralization-immobilization dynamics in lowland rice systems are sensitive to soil aeration as influenced by residue management in the fallow period and crop rotation, and that these factors have agronomically significant effects on rice N uptake and yield. Microbial biomass measurements, however, were a poor indicator of these dynamics. Received: 31 October 1997     

施用氮肥对温州蜜柑产量和品质的影响

红壤丘岗坡地桔园,在施用有机肥和磷钾肥的基础上,施用不同量的氮肥后,土壤ｐＨ值随着施氮量的增加而下降,呈线性负相关。不同施氮量对柑桔产量的影响具有极显著的差异。施氮后,土壤速效氮,磷,钾和叶片氮,磷,钾含量与产量呈显著或极显著线性相关。     

应用~(15)N稀释法筛选高固氮能力的大豆品种

应用＾１５Ｎ稀释法筛选出了具有高固氮能力的大豆品种和品系,大豆品系１００５,８５０２,２０９６,１４５４,９４用东农４２是高固氮品系,它们的固氮效率高达７０％,大豆品系１４５４和１５５５即高产又高固氮。根据方差分析,不同大豆品种或品系固氮效率差异显,固氮效率与产量无相关关系,与成熟期呈正相关,成熟期越长,固氮效率越高。有１０年品种或品系在１９９２和１９９４年两次进行试验,尽管两年的降雨情况有较大     

关于不同籼稻品种和施肥时期稻株对15N的吸收及其分配的研究

氮肥吸收率随不同水稻品种产量水平的提高而提高。稻株对氮肥的吸收率在分蘖期各品种之间差异不显著,而在灌浆成熟期表现其显著差异,即矮秆水稻品种和杂交稻对氮肥的吸收利用率高于高秆水稻品种。杂交稻汕优63,稻株对穗肥15N的吸收收率明显高于基肥15N和分蘖肥15N。杂交稻汕优63在抽穗后20天,有50%或50%以上被吸收的15N转     

水稻的氮磷等产量线及氮磷可替代性的研究

根据１９９６年有关水稻合理施肥研究的结果,于１９９７年选择６个氮磷施肥点,采用随机区组设计证实了等产量线的客观存在性及在一定范围内存在的氮磷肥相互可替代性,并用产量构成因素的变化来对此进行了初步探讨．氮磷等产量线及氮磷可替代性的客观存在,为合理施肥及以此来抑制或控制病虫害等领域提供了可靠的理论依据