有机无机肥料配合施用对滨海盐土土壤生物量态氮及土壤供氮特征的影响

采用盆栽试验研究滨海盐演化土上蚕粪与无机氮肥（碳铵和尿素）的施用对土壤生物量态氮和土壤供氮特征的影响，指出（１）施肥均能明显地提高土壤生物量态碳和生物量态氮的含量，蚕粪与无机氮肥配合施用比化肥单施或蚕粪单施更能增加土壤生物量态氮含量；（２）土壤生物量态氮是土壤氮素转化的重要环节，也是土壤有效氮的重要组成部分；（３）土壤生物量态氮的消长与土壤的供氮特征关系极为密切，只要前期有强烈的微生物固持无机氮肥过程，则中、后期势必会发生无机氮的释放过程，这一点对麦类作物生长发育极为重要；（４）蚕粪能有效地提高无机氮肥的利用率，尤其是碳铵，由于在滨海盐渍化土壤上氨的挥发很严重，因此，寻求与无机氮肥相配施的合适的有机肥料种类是提高滨海盐渍化土上氮肥利用率的最有效途径。

红壤添加有机质后生物量态氮和矿质氮的消长动态

本文报道实验室培养条件下红壤添加黑麦草后生物量态氮和矿质氮的消长动态及其相互关系。结果表明：（１）添加黑麦草后，红砂土和黄筋泥中的生物量态氮分别在８、２１、６０天和８、２１、４８天时出现高峰；而经７２天培养后，生物量态氮含量基本不变，并维持较低水平。（２）除黑麦草加入后３０～６０天外，其余培养时间里生物量态氮的消长趋势红砂土与黄筋泥相似。（３）加入黑麦草５天后，两种红壤中的矿质氮含量均开始明显增加。红砂土中的矿质氮含量在培养２０天时达到最大值，随后矿质氮含量呈下降趋势。黄筋泥中的矿质氮含量在培养３０天时达到最大值，在随后的３０～９０天内基本不变，９０天后矿质氮略有下降。（４）在两种红壤中添加黑麦草后，其矿质氮含量的变化存在差异。（５）培养初期的１８天内，生物量态氮的消长与有机氮的矿化关系密切。

秸秆、有机肥及氮肥配合使用对水稻土微生物和有机质含量的影响

通过大田试验,研究了秸秆还田、施用有机肥和氮肥对水稻土微生物和土壤有机质含量的影响。试验结果表明:(1)在秸秆还田的情况下,增施氮肥(0-330kg/hm2范围内)可促进秸秆的的腐解;(2)秸秆还田、施用有机肥和氮肥中的单一措施均能不同程度地增加水稻土壤细菌、真菌、放线菌的数量;(3)综合运用秸秆还田、施用有机肥和氮肥措施能协同增加土壤微生物数量,提高土壤生物量态氮和有机质含量,以秸秆还田量为6000kg/hm2、施用有机肥量为4500kg/hm2、施用氮肥量为240kg/hm2效果较佳。

非腐解有机物培肥对水田土壤生物量态碳、氮的影响

两种水田土壤的盆栽试验结果表明，在水稻的生长季节内，三种非腐解有机物料的施入，大幅度地提高了土壤的微生物量，但不同的有机物料以及不同的水田土壤之间，对土壤微生物量的影响存在着差异。

Vertical variation and storage of nitrogen in an aquic brown soil under different land uses

The vertical variation and storage of nitrogen in the depth of 0-150 cm of an aquic brown soil were studied under 14 years of four land use patterns, i.e., paddy field, maize field, fallow field and woodland in Shenyang Experimental Station of Ecology, Chinese Academy of Sciences in November of 2003. The results showed that different land uses had different profile distributions of soil total nitrogen (STN), alkali N, ammonium (NH4+-N) and nitrate (NO3--N). The sequence of STN storage was woodland >maize field > fallow field > paddy field, while that of NO3--N content was maize field > paddy field > woodland > fallow field, suggesting the different root biomass and biological N cycling under various land uses. The STN storage in the depth of 0-100 cm of woodland averaged to 11.41 thm-1, being 1.65 and 1.25 times as much as that in paddy and maize fields, respec-tively, while there was no significant difference between maize and fallow fields. The comparatively higher amount of NO3--N in maize and paddy fields may be due to nitrogen fertilization and anthropogenic disturbance. Soil alkali N was significantly related with STN, and the correlation could be expressed by a linear regression model under each land use (R20.929, p<0.001). Such a correlation was slightly closer in nature (woodland and fallow field) than in agro ecosystems (paddy and maize fields). Heavy N fertilization induced an excess of crop need, and led to a comparatively higher amount of soil NO3--N in cultivated fields than in fallow field and woodland. It is suggested that agroforestry practices have the potential to make a significant contribution to both crop production and environment protection.

Effects of Nitrogen Addition on Plant Functional Traits in Freshwater Wetland of Sanjiang Plain,Northeast China

To clarify the responses of plant functional traits to nitrogen(N) enrichment, we investigated the whole-plant traits(plant height and aboveground biomass), leaf morphological(specific leaf area(SLA) and leaf dry mass content(LDMC)) and chemical traits(leaf N concentration(LNC) and leaf phosphorus(P) concentration(LPC)) of Deyeuxia angustifolia and Glyceria spiculosa following seven consecutive years of N addition at four rates(0 g N/(m2·yr), 6 g N/(m2·yr), 12 g N/(m2·yr) and 24 g N/(m2·yr)) in a freshwater marsh in the Sanjiang Plain, Northeast China. The results showed that, for both D. angustifolia and G. spiculosa, N addition generally increased plant height, leaf, stem and total aboveground biomass, but did not cause changes in SLA and LDMC. Moreover, increased N availability caused an increase in LNC, and did not affect LPC. Thus, N addition decreased leaf C∶N ratio, but caused an increase in leaf N∶P ratio, and did not affect leaf C∶P ratio. Our results suggest that, in the mid-term, elevated N loading does not alter leaf morphological traits, but causes substantial changes in whole-plant traits and leaf chemical traits in temperate freshwater wetlands. These may help to better understand the effects of N enrichment on plant functional traits and thus ecosystem structure and functioning in freshwater wetlands.

Microbial Biomass C,N and P in Disturbed Dry Tropical Forest Soils,India

Variations in microbial biomass C (MB-C),N (MB-N) and P (MB-P) along a gradient of different dominant vegeta- tion covers (natural forest,mixed deciduous forest,disturbed savanna and grassland ecosystems) in dry tropical soils of Vindhyan Plateau,India were studied from January 2005 to December 2005.The water holding capacity,organic C,total N,total P and soil moisture content were comparatively higher in forest soils than in the savanna and grassland sites.Across different study sites the mean annual MB-C,MB-N and MB-P at 0-15 cm soil depth varied from 312.05 ± 4.22 to 653.40 ± 3.17,32.16 ± 6.25 to 75.66 ± 7.21 and 18.94 ± 2.94 to 30.83 ± 23.08 μg g ?1 dry soil,respectively.At all the investigated sites,the maximum MB-C,MB-N and MB-P occurred during the dry period (summer season) and the minimum in wet period (rainy season).In the present study,soil MB-C,MB-N and MB-P were higher at the forest sites compared to savanna and grassland sites.The differences in MB-C,MB-N and MB-P were significant (P < 0.001) among sites and seasons.The MB-C (P < 0.0001),MB-N (P < 0.001) and MB-P (P < 0.0001) were positively correlated with organic C,while the relationship between soil moisture and MB-C,MB-N and MB-P (P < 0.001,P < 0.01 and P < 0.0001,respectively) was negative.The decreasing order of MB-C,MB-N and MB-P along study ecosystems was natural forest > mixed deciduous forest > savanna > grassland.The results suggested that deforestation and land use practices (conversion of forest into savanna and grassland) caused the alterations in soil properties,which as a consequence,led to reduction in soil nutrients and MB-C,MB-N and MB-P in the soil of disturbed sites (grassland and savanna) compared to undisturbed forest ecosystems.

Soil Carbon and Nitrogen in Response to Perennial Bioenergy Grass, Cover Crop and Nitrogen Fertilization

Cover crop and nitrogen （N） fertilization may maintain soil organic matter under bioenergy perennial grass where removal of aboveground biomass for feedstock to produce cellulosic ethanol can reduce soil quality. We evaluated the effects of cover crops and N fertilization rates on soil organic carbon （C） （SOC）, total N （STN）, ammonium N （NH4-N）, and nitrate N （NO3-N） contents at the 0-5, 5-15, and 15-30 cm depths under perennial bioenergy grass from 2010 to 2014 in the southeastern USA. Treatments included unbalanced combinations of perennial bioenergy grass, energy cane （Saccharum spontaneum L.） or elephant grass （Pennisetum pur- pureum Schumazh.）, cover crop, crimson clover （Trifolium incarnatum L.）, and N fertilization rates （0, 100, and 200 kg N ha-l）. Cover crop biomass and C and N contents were greater in the treatment of energy cane with cover crop and 100 kg N ha-1 than in the treatment of energy cane and elephant grass. The SOC and STN contents at 0-5 and 5-15 cm were 9%-20% greater in the treatments of elephant grass with cover crop and with or without 100 kg N ha-1 than in most of the other treatments. The soil NO3-N content at 0--5 cm was 31%-45% greater in the treatment of energy cane with cover crop and 100 kg N ha-1 than in most of the other treatments. The SOC sequestration increased from 0.1 to 1.0 Mg C ha-1 year-1 and the STN sequestration from 0.03 to 0.11 Mg N ha-1 year-1 from 2010 to 2014 for various treatments and depths. In contrast, the soil NH4-N and NO3-N contents varied among treatments, depths, and years. Soil C and N storages can be enriched and residual NO3-N content can be reduced by using elephant grass with cover crop and with or without N fertilization at a moderate rate.