大气CO2浓度升高对黄花蒿生长和氮磷钾养分吸收的影响（英文）

Annual wormwood(Artemisia annua L.) is the only viable source of artemisinin,an antimalarial drug.There is a pressing need to optimize production per cultivated area of this important medicinal plant;however,the effect of increasing atmospheric carbon dioxide(CO_2) concentration on its growth is still unclear.Therefore,a pot experiment was conducted in a free-air CO2 enrichment(FACE) facility in Yangzhou City,China.Two A.annua varieties,one wild and one cultivated,were grown under ambient(374μmol mol~(-1)) and elevated(577 μmol mol~(-1)) CO_2 levels to determine the dry matter accumulation and macronutrient uptake of aerial parts.The results showed that stem and leaf yields of both A.annua varieties increased significantly under elevated CO_2 due to the enhanced photosynthesis rate.Although nitrogen(N),phosphorus(P),and potassium(K) concentrations in leaves and stems of both varieties decreased under elevated CO_2,total shoot N,P,and K uptake of the two varieties were enhanced and the ratios among the concentrations of these nutrients(N:P,N:K,and P:K) were not affected by elevated CO_2.Overall,our results provided the evidence that elevated CO_2 increased biomass and shoot macronutrient uptake of two A.annua varieties.     

硝态氮促进水稻生长和氮素吸收的生理机制

Rice is being increasingly cultivated in intermittently irrigated regious and also in aerobic soil in which Nitrate (NO₃^-) plays important role in nutrition of plant. However, there is no information regarding the influence of nitrate on the overall growth and uptake of nitrogen (N) in rice plant. Solution culture experiments were carried out to study the effects of NO₃^- on the plant growth, uptake of N, and uptake kinetics of NH₄⁺ in four typical rice (Oryza sativa L.) cultivars (conveutioual indica, conventional japonica, hybrid indica, and hybrid japonica), and on plasma membrane potential in roots of two conventional rice cultivars (indica and japonica) at the seedling stage. The results obtained indicated that a ratio of 50/50 NH₄⁺-N/NO₃^--N increased the average biomass of rice shoots and roots by 20% when compared with that of 100/0 NH₄⁺-N/NO₃^--N. In case of the 50/50 ratio, as compared with the 100/0 ratio, total N accumulated in shoots and roots of rice increased on an average by 42% and 57%, respectively. Conventional indica responds to NO₃^- more than any other cultivars that were tested. The NO₃^- supply increased the maximum uptake rate (V_max) of NH₄⁺ by rice but did not show any effect on the apparent Michaelis-Menten constant (K_m) value, with the average value of V_max for NH₄⁺ among the four cultivars being increased by 31.5% in comparison with those in the absence of NO₃^-. This suggested that NO₃^- significantly increased the numbers of the ammonium transporters. However, the lack of effect on the K_m value also suggested that the presence of NO₃^- had no effect on the affinity of the transporters for NH₄⁺. The plasma membrane potential in the roots of conventional indica and japonica were greatly increased by the addition of NO₃^-, suggesting that NO₃^- could improve the uptake of N by roots of the rice plant. In conclusion, the mechanisms by which NO₃^- enhances the growth and N uptake of rice plant was found by the increased value of V_max of NH₄⁺ and increased plasma membrane potential. Thus promotion of nitrification in paddy soil is of great significance for improving the production of rice.     

盐胁迫下硝态氮对囊果碱蓬根系发育和氮吸收的影响

The effiects of NaCl salinity and NO₃^- on growth, root morphology, and nitrogen uptake of a halophyte Suaeda physophora were evaluated in a factorial experiment with four concentrations of NaCl (1, 150, 300, and 450 mmol L^-1) and three NO₃^- levels (0.05, 5, and 10 mmol L^-1) in solution culture for 30 d. Addition of NO₃^- at 10 mmol L^-1 significantly improved the shoot (P < 0.001) and root (P < 0.001) growth and the promotive effect of NO₃^- was more pronounced on root dry weight despite the high NaCl concentration in the culture solution, leading to a significant increase in the root:shoot ratio (P < 0.01). Lateral root length, but not primary root length, considerably increased with increasing NaCl salinity and NO₃^- levels (P < 0.001), implying that Na⁺ and NO₃^- in the culture solution simultaneously stimulated lateral root growth. Concentrations of Na⁺ in plant tissues were also significantly increased by higher NaCl treatments (P < 0.001). At 10 mmol L^-1 NO₃^- , the concentrations of NO₃^- and total nitrogen and nitrate reductase activities in the roots were remarkably reduced by increasing salinity (P < 0.001), but were unaffected in the shoots. The results indicated that the fine lateral root development and effective nitrogen uptake of the shoots might contribute to high salt tolerance of S. physophora under adequate NO₃^- supply.     

Net ecosystem carbon exchange for Bermuda grass growing in mesocosms as affected by irrigation frequency

Intensification of grazed grasslands following conversion from dryland to irrigated farming has the potential to alter ecosystem carbon (C) cycling and affect components of carbon dioxide (CO₂) exchange that could lead to either net accumulation or loss of soil C. While there are many studies on the effect of water availability on biomass production and soil C stocks, much less is known about the effect of the frequency of water inputs on the components of CO₂ exchange. We grew Bermuda grass (Cynodon dactylon L.) in mesocosms under irrigation frequencies of every day (I₁ treatment, 30 d), every two days (I₂ treatment, 12 d), every three days (I₃ treatment, 30 d), and every six days (I₆ treatment, 18 d, after I₂ treatment). Rates of CO₂ exchange for estimating net ecosystem CO₂ exchange (F_N), ecosystem respiration (R_E), and soil respiration (R_S) were measured, and gross C uptake by plants (F_G) and respiration from leaves (R_L) were calculated during two periods, 1–12 and 13–30 d, of the 30-d experiment. During the first 12 d, there were no significant differences in cumulative F_N (mean ±standard deviation, 61 ±30 g C m^-2, n = 4). During the subsequent 18 d, cumulative F_N decreased with decreasing irrigation frequency and increasing cumulative soil water deficit (W), with values of 70 ±22, 60 ±16, and 18 ±12 g C m^-2 for the I₁, I₃, and I₆ treatments, respectively. There were similar decreases in F_G, R_E, and R_L with increasing W, but differences in R_S were not significant. Use of the C₄ grass growing in a C₃-derived soil enabled partitioning of R_S into its autotrophic (R_A) and heterotrophic (R_H) components using a ¹³C natural abundance isotopic technique at the end of the experiment when differences in cumulative W between the treatments were the greatest. The values of R_H and its percentage contributions to R_S (43% ±8%, 42% ±8%, and 8% ±5% for the I₁, I₃, and I₆ treatments, respectively) suggested that R_H remained unaffected across a wide range of W and then decreased under extreme W. There were no significant differences in aboveground biomass between the treatments. Nitrous oxide (N₂O) emission was measured to determine if there was a trade-off effect between irrigation frequency and increasing W on net greenhouse gas emission, but no significant differences were found between the treatments. These findings suggest that over short periods in well-drained soil, irrigation frequency could be managed to manipulate soil water deficit in order to reduce net belowground respiratory C losses, particularly those from the microbial decomposition of soil organic matter, with no significant effect on biomass production and N₂O emission.     

水培和土培条件下氮素供应对燕麦生长和磷素吸收的影响

Plants show different growth responses to N sources supplied with either NH₄⁺ or NO₃^-. The uptake of different N sources also affects the rhizosphere pH and therefore the bioavailability of soil phosphorus, particularly in alkaline soils. The plant growth, P uptake, and P availability in the rhizosphere of oat (Avena nuda L.) grown in hydroponics and in soil culture were investigated under supply with sole NH₄⁺-N, sole NO₃^--N, or a combination. Sole NO₃^--fed oat plants accumulated more biomass than sole NH₄⁺-fed ones. The highest biomass accumulation was observed when N was suppliedw ith both NH₄⁺-N and NO₃^--N. Growth of the plant root increased with the proportion of NO₃^- in the cultural medium. Better root growth and higher root/shoot ratio were consistently observed in NO₃^--fed plants. However, root vigor was the highest when N was supplied with NO₃^-+NH₄⁺. NH₄⁺ supply reduced the rhizosphere pH but did not affect P uptake by plants grown in soils with CaHPO₄ added as P source. No P deficiency was observed, and plant P concentrations were generally above 2 g kg^-1. P uptake was increased when N was supplied partly or solely as NO₃^--N, similarly as biomass accumulation. The results suggested that oat was an NO₃^--preferring plant, and NO₃^--N was essential for plant growth and the maintenance of root absorption capacity. N supply with NH₄⁺-N did not improve P nutrition, which was most likely due to the absence of P deficiency.     

Carbon mineralization in subtropical alluvial arable soils amended with sugarcane bagasse and rice husk biochars

Subtropical recent alluvial soils are low in organic carbon (C). Thus, increasing organic C is a major challenge to sustain soil fertility. Biochar amendment could be an option as biochar is a C-rich pyrolyzed material, which is slowly decomposed in soil. We investigated C mineralization (CO₂-C evolution) in two types of soils (recent and old alluvial soils) amended with two feedstocks (sugarcane bagasse and rice husk) (1%, weight/weight), as well as their biochars and aged biochars under a controlled environment (25 ±2 ℃) over 85 d. For the recent alluvial soil (charland soil), the highest absolute cumulative CO₂-C evolution was observed in the sugarcane bagasse treatment (1 140 mg CO₂-C kg^-1 soil) followed by the rice husk treatment (1 090 mg CO₂-C kg^-1 soil); the lowest amount (150 mg CO₂-C kg^-1 soil) was observed in the aged rice husk biochar treatment. Similarly, for the old alluvial soil (farmland soil), the highest absolute cumulative CO₂-C evolution (1 290 mg CO₂-C kg^-1 soil) was observed in the sugarcane bagasse treatment and then in the rice husk treatment (1 270 mg CO₂-C kg^-1 soil); the lowest amount (200 mg CO₂-C kg^-1 soil) was in the aged rice husk biochar treatment. Aged sugarcane bagasse and rice husk biochar treatments reduced absolute cumulative CO₂-C evolution by 10% and 36%, respectively, compared with unamended recent alluvial soil, and by 10% and 18%, respectively, compared with unamended old alluvial soil. Both absolute and normalized C mineralization were similar between the sugarcane bagasse and rice husk treatments, between the biochar treatments, and between the aged biochar treatments. In both soils, the feedstock treatments resulted in the highest cumulative CO₂-C evolution, followed by the biochar treatments and then the aged biochar treatments. The absolute and normalized CO₂-C evolution and the mineralization rate constant of the stable C pool (K_s) were lower in the recent alluvial soil compared with those in the old alluvial soil. The biochars and aged biochars had a negative priming effect in both soils, but the effect was more prominent in the recent alluvial soil. These results would have good implications for improving organic matter content in organic C-poor alluvial soils.     

中国陕西省施有机肥黄土NH4+固定的热力学性质

Some thermodynamic properties of NH₄⁺ fixation by loess soil in plowing and clay layers are discussed. The results indicate that the four ion adsorption equations commonly used can describe the properties of NH₄⁺ fixation in these soils under constant temperature. Among the four adsorption equations, the single-surface Langmuir equation is the best. When the concentration of NH₄Cl solution is 10^-1 mol below, the Freundlich equation can be used. The changes of apparent standard free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) illustrate that NH₄⁺ fixation in soil is an endothermic adsorption and spontaneous reaction, and the process can be enhanced by a higher temperature and clay content in soil. The "proper value of NH₄⁺ fixation by soil (K₁ × q_m) increased with increasing clay content and temperature. The heat of NH₄⁺ fixation in soil (Q_m) confirms the conclusions made in this paper.     

Sensitivity analysis of the SWAP (Soil-Water-Atmosphere-Plant) model under different nitrogen applications and root distributions in saline soils

Sensitivity analysis is important for determining the parameters in the model calibration process. In our study, a variance-based global sensitivity analysis (extended Fourier amplitude sensitivity test, EFAST) was applied to an agro-hydrological model (the SWAP (Soil-Water-Atmosphere-Plant model) model). The sensitivities of 20 parameters belonging to 4 categories (soil hydraulics, solute transport, root water uptake, and environmental stresses) for the simulated accumulated transpiration, dry matter (DM), and yield of sunflowers were analyzed under three nitrogen application rates (N1, N2, and N3), four salinity levels (S1, S2, S3, and S4), and three root distributions (R1, R2, and R3). The results indicated that for predominantly loamy soils, the high-impact parameters for accumulated transpiration, DM, and yield were the soil hydraulic parameters (α and n), critical stress index for compensatory root water uptake (ω_c), the salt level at which salt stress starts (Pi), the decline of root water uptake above Pi (SSF), residual water content (θ_r), saturated water content (θ_s), and relative uptake of solutes by roots (TSCF). We also found that nitrogen application did not change the order of the parameter impacts on accumulated transpiration, DM, and yield. However, TSCF replaced α as the highest-impact parameter for the accumulated transpiration, DM, and yield at high salinity levels (S2 and S3). Furthermore, α was also the highest-impact parameter for DM and yield under different root distributions, but the highest-impact parameters for transpiration were ω_c, α, and θ_s under R1, R2, and R3, respectively. Nitrogen application could be neglected when considering the interactive effects of nitrogen application, salinity level, and root distribution on the transpiration, DM, and yield. Additionally, the mean values and uncertainties of the transpiration, DM, and yield were similar in all scenarios, except S3, which showed a sharp decrease in the mean values. We suggest determining the above eight parameters (α, n, ω_c, Pi, SSF, θ_r, θ_s, and TSCF) and the saturated vertical hydraulic conductivity (K_s) based on rigorous calibrations with direct or indirect local measurements using economical methods (e.g., a literature review), with limited observations for other parameters when using the SWAP model and other similar agro-hydrological models.     

红三叶草丛枝菌根对有机磷的吸收

The capacities of two arbuscular mycorrhizal (AM) fungi, Glomus mosseae and Glomus versderme, tomineralize added organic P were studied in a sterilized calcareous soil. Mycorrhizal (inoculated with either of the AM fungi) and non-mycorrhizal red clover (Trghlium pmtense L.) plants were grown for eight weeksin pots with upper root, central hyphal and lower soil compartments. The hyphal and soil compartmentsreceived either organic P (as Na-phytate) or inorganic P (as KH₂PO₄) at tbe rate of 50 mg P kg^-1. No P wasadded to the root compartments. Control pots received no added P. Yields were higher in mycorrhizal than innon-mycorrhizal clover. Mycorrhizal inoculation doubled shoot P concentration and more than doubled total P uptake of plaflts in P-amended soil, irrespective of the form of applied P. The mycorrhizal contributionto inorganic P uptake was 80% or 76% in plants inoculated with G. mosseae or G. verefforme, respectively. Corresponding values were 74% and 82% when Na-phytate was applied. In the root compartments of the mycorrhizal treatments, the proportion of root length infected, hyphal length density and phosphatase activity were all higher when organic P was applied than when inorganic P was added.     

Relationship between granitic soil particle-size distribution and shrinkage properties based on multifractal method

The mechanical properties of granitic residual soils vary with depth due to changes in soil type and heterogeneity caused by weathering. The purpose of this study was to relate the spatial variation of particle-size distribution (PSD) of granitic soils with soil shrinkage parameters using multifractal theory. The heterogeneity of PSD and pedogenic processes were depicted in detail by multifractal dimensions. The PSD generally increased with the increase of profile depth in accordance with the variation of single fractal dimension (D) ranging from 2.45 to 2.65. The shrinkage limit was greatly influenced by the multifractal dimension parameters, including information dimension (D₁) and capacity dimension (D₀) (Adjusted R²=0.998, P < 0.01), and the maximum linear extensibility (κ_v) was determined by spectral width (△α) and bulk density, with the latter explaining 89% of the total variance of κ_v (P < 0.01). Soil shrinkage characteristic curve was fitted by the modified logistic model (R² > 0.97, root sum of squares < 0.1), and the water variation corresponding to the maximum change rate of linear extensibility was determined by the silt content (R²=0.81, P < 0.01). Overall, the shrinkage of granitic soils was primarily influenced by PSD and soil compactness.     

施氮、供水对菠菜(Spinacia oleracea L.)的生长和土壤残留矿质氮的影响

Effects of conventional and optimized water and nitrogen managements on spinach (Spinacia oleracea L.) growth and soil mineral N (N_min) residues were compared in an open field experiment in which water balancemethod and N recommendation with the KNS-system were included. It was shown that the conventionalwater treatment (seasonal irrigated amount: 175 mm) reduced spinach growth compared to the water balancetreatments (seasonal irrigated amount: 80 and 85 mm) at the same N supply level due to N loss through leaching caused by excessive water supply. Although 309 kg N ha^-1 was applied in the conventional N treatment, compared to 82 and 66 kg N ha^-1 in the optimum N treatments, no significant difference in cropyield was investigated between the N treatments with the same irrigation practice. N uptake in spinach andsoil residual Nmin contents were also significantly affected by the irrigation practices. The conventional water supply not only decreased water use efficiency, but also resulted in excessive NO₃^--N being leached below the root zone. In order to meet the same target value of N requirement for the next crop, cauliflower, based on the KNS-system, at least extra 50 kg N ha^-1 was needed in the conventional water treatments in comparison to the water balance treatment.     

液面上部气体的置换对土壤厌氧培养下的N2O和CO2排放的影响

To study effect of C2H2 and change of headspace gas on N2O emission,denitrification,as well as CO2 emission,slurries of an agricultural soil were anaerobically incubated for 7 days at 25℃.Both N2O reduction and CO2 emissions were inhibited by the addition of 100 mL L^-1 of C2H2.However,the inhibition to CO2 emission was alleviated by the replacement of headspace gas,and the N2O emission was enhanced by the replacement.Acetylene disappeared evidently from the soil slurries during the incubation.Consequently results obtained from the traditional C2H2 blocking technique for determination of denitrifcation rate,especially in a long-time incubation,should be explained with care because of its side effect exsting in the incubation environments without change of headspace gas.To reduce the possible side effect on the processes other than denitrification ,it is suggested that headspace gas should be replaced several times during a long-time incubation.     

农田改为农林(草)复合系统对红壤CO2和N2O排放的影响

以鄂南玉米地、紫穗槐/玉米地、香根草/玉米地、紫穗槐林地、香根草草地与撂荒地6种土地利用类型为研究对象,利用静态箱法,对夏玉米生长期间土壤CO2和N2O通量及影响因子进行了测定,研究我国北亚热带丘陵红壤区农田改变为林(草)地和农林(草)复合系统后土壤CO2和N2O排放特征。研究结果表明:(1)土地利用方式改变后,撂荒地土壤CO2排放量明显低于其他5种土地利用类型,但紫穗槐/玉米地、单作玉米地、香根草/玉米地、紫穗槐林地、香根草草地5种土地利用类型之间土壤CO2排放量差异不显著。(2)玉米生长期间,6种不同土地利用方式下,土壤N2O排放总量从高到低依次为紫穗槐/玉米地(508 g·hm-2·a-1)、紫穗槐林地(470 g·hm-2·a-1)、撂荒地(390 g·hm-2·a-1)、香根草/玉米地(373 g·hm-2·a-1)、香根草草地(372 g·hm-2·a-1)、单作玉米地(285 g·hm-2·a-1)。(3)土壤CO2通量与土壤有机碳、土壤微生物生物量碳和土壤含水量无显著相关关系;土壤N2O通量与土壤氮素净矿化率呈显著线性相关,但与土壤无机氮和土壤含水量无显著相关关系。农田改变为农林(草)复合系统可能潜在地增加土壤CO2和N2O排放;农田改变为林(草)地可能潜在地减少土壤CO2排放,增加土壤N2O排放。     

浮萍对福州平原稻田CH4和N2O排放的影响分析

浮萍是稻田中常见的漂浮在水面的水生植物,具有固氮作用,但是,浮萍对稻田温室气体排放的影响尚不明确.以位于湿润亚热带的福州平原稻田为研究对象,探讨浮萍对该区域稻田CH4和N2O排放的影响,为科学评价、准确编制我国水稻田温室气体排放清单提供基础数据.研究结果表明,观测期内,有萍小区和无萍小区CH4排放范围分别为0.19～26.50 mg·m-2·h-1和1.02～28.02 mg·m-2·h-1,平均值分别为9.28 mg·m-2·h-1和11.66 mg·m-2·h-1,有萍小区CH4排放低于无萍小区(P＜0.01),有萍小区CH4排放高峰比无萍小区约提前1周,高峰期后排放迅速降低;有萍小区和无萍小区N2O排放范围分别为-50.11～201.82 μg·m-2·h-1和-28.93～54.42μg·m-2·h-1,平均值分别为40.29 μg·m-2·h-1和11.93 μg·m-2·h-1,有萍小区N2O排放高于无萍小区(P＜0.05).稻田排干后,N2O排放迅速上升,2个小区N2O排放呈现出相似的规律.有萍小区和无萍小区的CH4与N2O排放的影响因子有所不同.综合考虑CH4和N2O两种温室气体,CH4仍是稻田温室效应产生的主要贡献者,浮萍可降低位于沿海区域的福州平原稻田综合温室效应的17.3％.     

不同氮素水平下冬小麦叶片酚酸类物质代谢对FACE的响应

利用开放式空气CO2浓度升高(Free Air Carbon-dioxide Enrichment, FACE)平台, 研究了低氮(LN)和常氮(NN)水平下, 大气CO2浓度升高对冬小麦叶片酚酸类物质代谢的影响.结果表明, CO2浓度升高对小麦叶片水杨酸、对羟基苯甲酸、肉桂酸、阿魏酸和香草酸含量的影响随供氮水平的不同而有所差异.低氮下小麦通过提高叶片苯丙氨酸解氨酶(PAL)活性(30.1%)而使其含量均显著增加, 增幅分别达33.7%、119.6%、26.7%、39.9%和28.6%; 而常氮下PAL活性和酚酸类含量变化均未达显著水平.可见, 大气CO2浓度升高对冬小麦酚酸类物质代谢的影响受氮水平的调控, 在未来CO2浓度升高条件下, 选择适宜的施肥水平将显得更为重要.此外, 总酚含量与水杨酸、对羟基苯甲酸、肉桂酸、阿魏酸和香草酸等含量变化趋势基本一致, 且总酚含量变化的79.6%～151.4%是由这几种酚酸含量变化引起的, 说明CO2浓度升高使水杨酸、对羟基苯甲酸、肉桂酸、阿魏酸和香草酸等含量增加是总酚含量增加的直接原因.低氮条件下大气CO2浓度升高将通过改变酚酸类物质代谢而间接影响小麦与伴生杂草的关系.     

定期淹水强碱性盐渍土中14C标记葡萄糖和NH4+的动态

Flooding an extremely alkaline（pH 10.6） saline soil of the former Lake Texcoco to reduce salinity will affect the soil carbon（C）and nitrogen（N） dynamics.A laboratory incubation experiment was done to investigate how decreasing soil salt content affected dynamics of C and N in an extremely alkaline saline soil.Sieved soil with electrical conductivity（EC） of 59.2 dS m^-1 was packed in columns,and then flooded with tap water,drained freely and conditioned aerobically at 50%water holding capacity for a month.This process of flooding-drainage-conditioning was repeated eight times.The original soil and the soil that had undergone one,two,four and eight flooding-drainage-conditioning cycles were amended with 1000 mg glucose-¹⁴C kg^-1 soil and 200 mg NH₄⁺-N kg^-1soil,and then incubated for 28 d.The CO₂ emissions,soil microbial biomass,and soil ammonium（NE₄⁺）,nitrite（NO₂^-） and nitrate（NO₃^-） were monitored in the aerobic incubation of 28 d.The soil EC decreased from 59.2 to 1.0 dS m_¹ after eight floodings,and soil pH decreased from 10.6 to 9.6.Of the added ¹⁴C-labelled glucose,only 8%was mineralized in the original soil,while 24%in the soil flooded eight times during the 28-d incubation.The priming effect was on average 278 mg C kg^-1 soil after the 28-d incubation.Soil microbial biomass C(mean 66 mg C kg^-1 soil) did not change with flooding times in the unamended soil,and increased 1.4 times in the glucose-NH₄⁺-amended soil.Ammonium immobilization and NO₂^- concentration in the aerobically incubated soil decreased with increasing flooding times,while NO₃^- concentration increased.It was found that flooding the Texcoco soil decreased the EC sharply,increased mineralization of glucose,stimulated nitrification,and reduced immobilization of inorganic N,but did not affect soil microbial biomass C.     

铁铝氢氧化物对两种土壤和高岭石表面K+和NH4+解吸的影响

Potassium (K) and nitrogen (N) are essential nutrients for plants. Adsorption and desorption in soils affect K+ and NH + 4 availabilities to plants and can be affected by the interaction between the electrical double layers on oppositely charged particles because the interaction can decrease the surface charge density of the particles by neutralization of positive and negative charges. We studied the effect of iron (Fe)/aluminum (Al) hydroxides on desorption of K+ and NH + 4 from soils and kaolinite and proposed desorption mechanisms based on the overlapping of diffuse layers between negatively charged soils and mineral particles and the positively charged Fe/Al hydroxide particles. Our results indicated that the overlapping of diffuse layers of electrical double layers between positively charged Fe/Al hydroxides, as amorphous Al(OH) 3 or Fe(OH) 3 , and negatively charged surfaces from an Ultisol, an Alfisol, and a kaolinite standard caused the effective negative surface charge density on the soils and kaolinite to become less negative. Thus the adsorption affinity of these negatively charged surfaces for K+ and NH + 4 declined as a result of the incorporation of the Fe/Al hydroxides. Consequently, the release of exchangeable K+ and NH +4 from the surfaces of the soils and kaolinite increased with the amount of the Fe/Al hydroxides added. The greater the positive charge on the surfaces of Fe/Al hydroxides, the stronger was the interactive effect between the hydroxides and soils or kaolinite, and thus the more release of K+ and NH + 4 . A decrease in pH led to increased positive surface charge on the Fe/Al hydroxides and enhanced interactive effects between the hydroxides and soils/kaolinite. As a result, more K+ and NH + 4 were desorbed from the soils and kaolinite. This study suggests that the interaction between oppositely charged particles of variable charge soils can enhance the mobility of K+ and NH + 4 in the soils and thus increase their leaching loss.     

2个马铃薯杂交组合F1的SSR鉴定

杂交育种是马铃薯新品种选育的重要方法, 其杂种F₁真实性鉴定是获得目标性状单株的关键环节。为选育优质、高产、抗病性及抗旱性强的马铃薯新品种, 用马铃薯品种"费乌瑞它"(Favorita)分别与"J07-6"和"陇薯3号"杂交, 获得了杂种F1代。本试验利用SSR标记技术对"Favorita"×"J07-6"、"Favorita"×"陇薯3号"2个杂交组合F1共86个单株的真实性进行了鉴定。试验从43对SSR引物中筛选出2对适宜引物STM1049和S7。利用这2对引物进行PCR扩增, 将"Favorita"×"J07-6"杂交种F1和"Favorita"×"陇薯3号"杂交种F1的SSR带型划分为双亲互补型、缺失型、父本型和母本型4种类型。依据SSR带型特征, 从"Favorita"×"J07-6"和"Favorita"×"陇薯3号"2个杂交组合F₁单株中分别鉴定出真杂种34个和27个, SSR分子标记技术用于马铃薯杂交种真实性鉴定是可靠的。该研究结果可为马铃薯杂交种优良株系选育提供依据。     

Impacts of nitrogen fertilization on biomass production of switchgrass (Panicum Virgatum L.) and changes in soil organic carbon in Ohio

Growing switchgrass (Panicum virgatum, L.), a promising bioenergy crop, needs finely-tuned nitrogen (N) fertilization to improve biomass yields depending on soil types and site characteristics. N fertilization can also affect the soil organic carbon (SOC) pool. Therefore, this study was conducted to assess the effects of N fertilization on switchgrass biomass production and the SOC stock in Ohio. Switchgrass was established at three research stations (Northwest, Jackson, and Western sites) of the Ohio Agricultural Research and Development Center (OARDC) in spring 2004. N fertilizer was applied at four different rates (0, 50, 100, and 200 kg N ha⁻¹) in 2008 and 2009. Aboveground and root biomass and the carbon (C) and N concentrations in plant tissues, SOC concentrations up to 30 cm depth were measured at the end of the growing season in 2009. Aboveground biomass at the Western site was the highest as 26 Mg ha⁻¹ with 200 kg N ha⁻¹ application, but there were no significant effects of N fertilization on aboveground biomass at two other sites and on root biomass across all sites. The amount of N export due to harvesting aboveground biomass increased with increase in N rates but did not vary among sites. With increasing N rates, the SOC stock linearly increased from 102 to 123 and from 55 to 70 Mg C ha⁻¹ at the Northwest and the Jackson sites, respectively. However, this positive correlation was not observed for the Western site (a range of 59 to 67 Mg C ha⁻¹). This study showed a potential of growing switchgrass as a bioenergy crop in Ohio and positive responses of the SOC stock to N fertilization.     

日本氮素的循环和流向以及减少N2O散发和NO3-污染的对策

To feed an increasing population, large amounts of chemical nitrogen fertilizer have been used to produce much of our food, feed and fiber thereby increasing nitrogen levels in soils, natural waters, crop residues, livestock wastes, and municipal and agricultural wastes, with national and international concern about its potential adverse effects on environmental quality and public health. To understand these phenomena and problems, first the nitrogen cycle and the environment are described. Then recent trends for nitrogen cycling through the food and feed system, N₂O emissions from fertilized upland and paddy soils, and NO₃^- pollution in ground water in Japan are reported. Finally, mitigation strategies in Japan for reducing N₂O emission and NO₃^- pollution are proposed, including nitrification inhibitors, controlled release fertilizers, utilization of plant species that could suppress nitrification, utilizing the toposequence, government policy, and appropriate agricultural practices. Of all the technologies presented, use of nitrification inhibitors and controlled release fertilizers are deemed the most important with further development of these aspects of technologies being expected. These practices, if employed worldwide, could help reduce the load, or environmental deterioration, on the Earth''s biosphere.