品种对三七根系构型的影响及其与品质的关系

【目的】分析不同品种三七的根系形态指标及主根皂苷含量差异,探究根系形态特征与三七生物量及皂苷含量和累积量的关系,为基于三七根系形态特征的高品质三七品种选育提供理论依据。【方法】以苗乡三七1号(M1)、苗乡7号(M7)、苗乡8号(M8)和文院紫七1号(Z1)4个三七品种的2年生植株为研究对象,利用根系扫描仪测定三七的根系形态指标,通过高效液相色谱法测定三七主根中主要皂苷的含量,同时测定三七的地上部和地下部生物量,并分析根系形态指标与三七生物量、根冠比及皂苷含量和累积量的相关性。【结果】不同三七品种的地上部、地下部生物量及根冠比存在一定差异,其中Z1的地上部鲜重最高,M1的地下部鲜重和干重最高,而M8的根冠比最大;不同三七品种的根系形态特征也存在差异,M7、M8和Z1的总根长、总根尖数和分枝数均显著大于M1(P<0.05,下同),M7和Z1的总根表面积显著大于M1;不同三七品种主根中的皂苷含量及累积量,以Z1主根中三七皂苷R1、人参皂苷(Rg_(1)、Rb_(1)和Rd)及总皂苷含量最高,以M1主根中各单体皂苷累积量及总皂苷累积量最高。相关分析结果表明,总根表面积、根平均直径、总根体积等根系形态指标与三七地上部和地下部生物量及皂苷累积量均呈正相关,且粗根(根直径>2mm)根表面积、根体积与三七地上部和地下部生物量及皂苷累积量的相关性大于细根(根直径≤2 mm)。【结论】不同三七品种的根系形态特征、生物量、皂苷含量及累积量存在一定差异,且三七的总根表面积、根平均直径、总根体积等根系形态指标与三七的生物量和皂苷累积量关系密切,良好的根系形态特征对三七生长和品质形成至关重要。

果树种植土壤N2O排放研究:认识与挑战

果树种植土壤因其较高的施氮量,很可能是温室气体氧化亚氮(N2O)的重要排放源。本文重点阐述了果园系统土壤N2O排放监测的复杂性,在此基础上探讨了如何形成有效的监测系统,揭示了利用现有技术测定N2O的排放规律和减排技术效果,并对今后的研究工作提出了展望。今后应重点开展以下几方面的工作:制定不同种类果树种植下土壤N2O排放监测标准;研发果树种植系统不同施肥模式、不同灌溉模式、不同土壤管理制度下土壤N2O减排技术;加强与N2O排放相关联的土壤氮素转化过程及其关联微生物机制的研究;构建果树种植系统土壤氮素平衡和N2O排放模型。

基于DPSIR模型的曲周县氮素资源可持续利用评价与预测

我国北方地区由于氮素利用效率低导致的环境问题日益凸显。以驱动力-压力-状态-影响-响应(DPSIR)模型为基础,选取38项指标构建河北省曲周县氮素资源可持续利用评价指标体系,结合1997—2017年曲周县统计资料,对研究区氮素资源可持续利用进行评价,并利用灰色预测模型分析研究区氮素资源可持续发展趋势。结果表明,1997—2017年曲周县氮素利用驱动力、状态、影响因素评价值均呈上升趋势,而压力因素评价值呈下降趋势,响应因素评价值呈先下降后上升趋势。曲周县氮素资源在多重因素共同影响下由弱可持续水平向基本可持续水平发展。灰色预测模型预测结果显示2018—2030年研究区氮素资源可持续利用呈上升趋势。情景模拟结果表明研究区城镇化率、人均GDP、农民人均纯收入和城镇人均可支配收入提高10%,均可以使曲周县氮素资源可持续利用综合评价值提高。在曲周县经济发展和城市化进程中,增加经济作物种植面积,加大废弃物处理设施的投入以促进家庭消费系统中氮的资源化,可以提高曲周县氮素资源可持续利用水平。

Effects of Long-Term Application of Inorganic Fertilizers on Biochemical Properties of a Rice-Planting Red Soil

A long-term experiment was set up in Yingtan of Jiangxi Province to investigate the effects of long-term application of inorganic fertilizers on the biochemical properties of a rice-planting soil derived from Quaternary red earth. Noncultivated soils are extremely eroded and characterized by a low pH and deficiencies in available nutrients, in particular P and N. After 13 years of inorganic fertilization in cultivation for double-cropped rice, the biochemical properties of the soil were changed. The nitrification potential and urease activity were higher in the treatments with N application than those without N application, Acid phosphatase activity and dehydrogenase activity were also higher in the treatments with P application than in those without P application. The dehydrogenase activity correlated well with the concentrations of both total P and hydrolysable N and with rice crop yield, suggesting that dehydrogenase activity might be a suitable indicator for improvement in soil fertility.

Effects of long-term amendment of organic manure and nitrogen fertilizer on nitrous oxide emission in a sandy loam soil

To understand the effects of long-term amendment of organic manure and N fertilizer on N2O emission in the North China Plain, a laboratory incubation at different temperatures and soil moistures were carried out using soils treated with organic manure （OM）, half organic manure plus half fertilizer N （HOM）, fertilizer NPK （NPK）, fertilizer NP （NP）, fertilizer NK （NK）, fertilizer PK （NK） and control （CK） since 1989. Cumulative N2O emission in OM soil during the 17 d incubation period was slightly higher than in NPK soil under optimum nitrification conditions （25℃ and 60% water-filled pore space, WFPS）, but more than twice under the optimum denitrification conditions （35℃ and 90% WFPS）. N2O produced by denitrification was 2.1-2.3 times greater than that by nitrification in OM and HOM soils, but only 1.5 times greater in NPK and NP soils. These results implied that the long-term amendment of organic manure could significantly increase the N2O emission via denitrification in OM soil as compared to NPK soil. This is quite different from field measurement between OM soil and NPK soil. Substantial inhibition of the formation of anaerobic environment for denitrification in field might result in no marked difference in N2O emission between OM and NPK soils. This is due in part to more rapid oxygen diffusion in coarse textured soils than consumption by aerobic microbes until WFPS was 75% and to low easily decomposed organic C of organic manure. This finding suggested that addition of organic manure in the tested sandy loam might be a good management option since it seldom caused a burst of N2O emission but sequestered atmospheric C and maintained efficiently applied N in soil.

Estimate of Methane Emission from Rice Paddy Fieldsin Taihn Region, China

Methane fluxes from late rice and single cropping rice fields in Taihu region were measured using closedchamber method in 1992 and 1993 and CH_4 emission from this region (total area of paddy soils was about1.88 million hectares, of which 0.63 million hectares are distributed in the south of Jiangsu Province) wasestimated on the basis of the mean CH_4 fluxes observed. The results showed that the mean CH_4 flaxes fromlate rice and single cropping rice field were quite similar under the prevailing cultivation practices in theregion, being around 5 mg CH_4/m￣2/h (4.31-5.31 mg CH_4/m￣2/h for various cultivars of the late rice and3.20-6.22 mg CH_4/m￣2/h for various treatments of the single cropping rice). Total CH_4 emission from paddysoils in the region was estimated to be 0.185-0.359 Tg CH_4 per year. Continuously flooding the soil witha water layer till ripening caused higher mean CH_4 flux; and addition of nitrification inhibitor (thiourea)stimulated CH_4 emission. There was no simple relationship between CH_4 flux and either soil temperature orsoil Eh.

Soil Respiration During a Soy bean-Growing Season

Soil respiration induced by soybean cultivation over its entire growing season and the factors influencing soil respiration were investigated to examine the seasonal pattern of soil respiration induced by soybean cultivation, explore soybean growth and photosynthesis on soil respiration, and determine the temperature dependence on soil respiration. Soil respiration in a pot experiment with and without soybean plants was sampled using the static chamber method and measured using gas chromatograph. Air temperature was a dominant factor controlling soil respiration rate in unplanted soil. Additionally, rhizosphere respiration comprised 62% to 98% of the soil respiration rate in the soybean-planted soil varying with the soybean growth stages. Harvesting aerial parts of soybean plant caused an immediate drop in the soil respiration rate at that stage. After harvesting the aerial parts of the soybean plant, a highly significant correlation between soil respiration rate and air temperature was found at the flowering stage （P 〈 0.01）, the pod stage （P 〈 0.01）, and the seed-filling stage （P 〈 0.05）. Thus, rhizosphere respiration during the soybean-growing period not only made a great contribution to soil respiration, but also determined the seasonal variation pattern of the soll respiration rate.

Decomposition and Products of Wheat and Rice Straw from a FACE Experiment Under Flooded Conditions

Winter wheat and rice straw produced under ambient and elevated CO2 in a China rice-wheat rotation free-air CO2 enrichment （FACE） experiment was mixed with a paddy soil at a rate of 10 g kg^-1 （air-dried）, and the mixture was incubated under flooded conditions at 25℃ to examine the differences in decomposition as well as the products of crop residues produced under elevated CO2. Results showed that the C/N ratio and the amount of soluble fraction in the amended rice straw grown under elevated CO2 （FR） were 9.8% and 73.1% greater, and the cellulose and lignin were 16.0% and 9.9% lesser than those of the amended rice straw grown under ambient CO2 （AR）, respectively. Compared with those of the AR treatment, the CO2-C and CH4-C emissions in the FR treatment for 25 d were increased by 7.9% and 25.0%, respectively; a higher ratio of CH4 to CO2 emissions induced by straw in the FR treatment was also observed. In contrast, in the treatments with winter wheat straw, the CO2-C and CH4-C emissions, the ratio of straw-induced CH4 to CO2 emissions, and the straw composition were not significantly affected by elevated CO2, except for an 8.0% decrease in total N and a 9.7% increase in C/N ratio in the wheat straw grown under elevated CO2. Correlation analysis showed that the net CO2-C and CH4-C emission from straw and the ratio of straw-induced CH4 to CO2 emissions were all exponentially related to the amount of soluble fraction in the amended straw （P 〈0.05）. These indicated that under flooded conditions, the turnover and CH4 emission from crop straw incorporated into soil were dependent on the effect of elevated CO2 on straw composition, and varied with crop species. Incorporation of rice straw grown under elevated CO2 would stimulate CH4 emission from flooded rice fields, whereas winter wheat straw grown under elevated CO2 had no effect on CH4 emission.

Effects of long-term fertilization on soil gross N transformation rates and their implications

Application of fertilizer has been found to significantly affect soil N cycling. However, a comprehensive understanding of the effects of long-term fertilization on soil gross N transformation rates is still lacking. We compiled data of observations from 10 long-term fertilization experiments and conducted a meta-analysis of the effects of long-term fertilization on soil gross N transformation rates. The results showed that if chemical fertilizers of N, P and K were applied in balance, soil p H decreased very slightly. There was a significantly positive effect of long-term fertilization, either chemical or organic fertilizers or their combinations, on gross N mineralization rate compared to the control treatment（the mean effect size ranged from 1.21 to 1.25 at 95% confidence intervals（CI） with a mean of 1.23）, mainly due to the increasing soil total N content. The long-term application of organic fertilizer alone and combining organic and chemical fertilizer could increase the mineralization-immobilization turnover, thus enhance available N for plant while reduce N losses potential compared to the control treatment. However, long-term chemical fertilizer application did not significantly affect the gross NH4＋ immobilization rate, but accelerated gross nitrification rate（1.19; 95% CI： 1.08 to 1.31）. Thus, long-term chemical fertilizer alone would probably induce higher N losses potential through NO3– leaching and runoff than organic fertilizer application compared to the control treatment. Therefore, in the view of the effects of long-term fertilization on gross N transformation rates, it also supports that organic fertilizer alone or combination of organic and chemical fertilizer could not only improve crop yield, but also increase soil fertility and reduce the N losses potential.

Relationship between light and heavy fractions of organic matter for several agricultural soils in China

Although numerous studies about the nature and turnover of soil organic matter（SOM） in light and heavy fractions（ LFOM and HFQM, respectively） have been made, little information is available in relation to the relationship between LFQM and HFOM, and no attempts have been made to quantify a general relationship between LFQM and HFQM for agricultural soils under field condition. Qur hypothesis is there may be an inherent relationship between LFQM and HFQM for agricultural soils under certain unaltered management practices for a long period, to this end, we therefore studied typically soils taken from different parts in China by using a simple density fractionation procedure. The results indicated that LFQM was positively correlated with LFOM/HFOM ratio for three typical soils. This information will be of particular use not only in deepening our understanding of the dynamics of SQM fractions but also in evaluating the potential of agricultural soils to sequestrate C under different management practices in a long term.

福建省戴云山乡镇尺度农田生态系统氮素流动及其效率

氮素在农业生产中至关重要,农业生产及农产品消费等过程中存在氮素利用率低、损失率高的现象,由此引发一系列氮的生态环境污染问题。全面认识农业生产过程中氮素的利用效率及其环境负荷特征,有助于寻找削减氮排放的途径。采用物质流分析法构建农业生态系统氮素平衡模型,分析了福建省德化县戴云山地区赤水镇、南埕镇和上涌镇农业生产系统氮素流动特征。结果表明,2002—2016年,3个镇农田生产氮素流动通量呈下降趋势,其中赤水镇氮素输入量由2002年的86.40 kg·hm^(-2)下降至2016年的37.19 kg·hm^(-2)。农田生产的单位面积施氮量总体高于全国平均水平,化肥氮的过量输入是农业生产环境负荷产生的主要原因。3个镇化肥氮平均投入量占总氮输入量的45.56%~72.26%。上涌镇氮素利用率在27.05%~35.05%之间波动,氮素环境平均损失率最低。尽管调查期间化肥过量使用状况有明显改善,但是氮素利用率低、损失率高依然是当地面临的主要问题。发展可持续农业对改善当地环境效益至关重要,建议调整肥料施用配比,提升农业废弃物的资源化利用率,提高氮素循环利用率,以减少资源浪费和环境污染。

Progress in Significant Soil Science Fields of China over the Last Three Decades: A Review

Due to continuous decreases in arable land area and continuous population increases,Chinese soil scientists face great challenges in meeting food demands,mitigating adverse environmental impacts,and sustaining or enhancing soil productivity under intensive agriculture.With the aim of promoting the application of soil science knowledge,this paper reviews the achievements of Chinese scientists in soil resource use and management,soil fertility,global change mitigation and soil biology over the last 30 years.During this period,soil resource science has provided essential support for the use and exploitation of Chinese soil resources,and has itself developed through introduction of new theories such as Soil Taxonomy and new technologies such as remote sensing.Soil fertility science has contributed to the alleviation and elimination of impeding physical and chemical factors that constrain availability of essential nutrients and water in soils,the understanding of nutrient cycling in agroecosystems,and the increase in nutrient use efficiency for sustainable crop production.Chinese soil scientists have contributed to the understanding of the cropland's role in global change,particularly to the understanding of methane and nitrous oxide emission from rice fields and the effect of elevated carbon dioxide and ozone on rice-wheat system.Soil biology research has progressed in biological N fixation,distribution of fauna in Chinese soils,and bioremediation of polluted soils.A new generation of soil scientists has arisen in the last three decades.The gaps between research and application in these soil science fields are also discussed.

Straw Application Altered CH_4 Emission,Concentration and ^(13)C-Isotopic Signature of Dissolved CH_4 in a Rice Field

CH4 emission and the concentration of dissolved CH4 in soil solution and floodwater in a rice field and their stable carbon isotopic signatures as affected by straw application were investigated in 2009 in a field experiment at Jurong, Jiangsu Province, China. Straw application increased CH4 emission and CH4 concentration in the soil solution and floodwater. A positive seasonal correlation was also observed in the variation between CH4 flux and CH4 concentration in soil solution. The seasonal total CH4 emission （51.6 g CH4 m^-2） in Treatment WS （straw applied） was about 168% higher than that in Treatment CK （without straw）. The emitted CH4 and CH4 in soil solution were initially relatively enriched, then depleted and finally enriched again in 13C in both treatments, while CH4 in floodwater became isotopically heavier. The carbon isotopic signature of emitted CH4 and CH4 in floodwater averaged around -62%o and -45%0 for both treatments, respectively, and was not significantly influenced by the application of straw. However, straw application caused the CH4 in soil solution to be significantly depleted in lac during the middle of the rice season, and the mean δ13C value was lower in WS （-57.5‰） than in CK （-49.9‰）. Calculation from the isotopic data showed that straw application increased the fraction of CH4 oxidized, causing no significant difference in the δ13C value of the emitted CH4 between the two treatments.

Influence of Agricultural Activity on Nitrogen Budget in Chinese and Japanese Watersheds

To analyze the effect of agricultural activity on nitrogen(N) budget at the watershed scale,a comparative study was conducted at two Japanese watersheds,the Shibetsu River watershed(SRW) and Upper-Naka River watershed(UNRW),and one Chinese watershed,the Jurong Reservoir watershed(JRW).The total area and the proportion of agricultural area(in parentheses) of the watersheds were 685(51%),1 299(21%),and 46 km 2(55%) for SRW,UNRW,and JRW,respectively.The main agricultural land use in SRW was forage grassland,while paddy fields occupied the highest proportion of cropland in UNRW(11% of total area) and JRW(31% of total area).The farmland surplus N was 61,48,and 205 kg N ha 1 year 1 for SRW,UNRW,and JRW,respectively.The total input and output for the whole watershed were 89 and 76,83 and 61,and 353 and 176 kg N ha 1 year 1 for SRW,UNRW,and JRW,respectively.The proportion of discharged N to net anthropogenic N input was 31%,37%,and 1.7% for SRW,UNRW,and JRW,respectively.The two watersheds in Japan showed similar proportions of discharged N to those of previous reports,while the watershed in China(JRW) showed a totally different characteristic compared to previous studies.The high N input in JRW did not increase the amount of discharged N at the outlet of the watershed due to high proportions of paddy fields and water bodies,which was an underestimated N sink at the landscape scale.