Estimation of Nutrient Atmospheric Deposition to Long Island Sound

Anthropogenic nutrient sources (especially nitrogen and phosphorus) released into the Long Island Sound (LIS) causes excessive phytoplankton growth resulting in hypoxic conditions. Atmospheric deposition (both wet and dry deposition) has significant effect on aquatic and terrestrial ecosystems. Two dry deposition monitoring sites were established along the north shore of LIS in February 1991. Wet and dry deposition samples were collected since then. A dry deposition velocity model, based on the characteristics of the water surface, was used to estimate the loading as well as the seasonal variability (dynamics) of nutrients in atmospheric deposition to LIS. The average nitrogen flux from each site was 6.64 kg (as-N) ha-yr^-1. The total atmospheric nitrogen loading was estimated to be 2240 metric tons yr^-1 which correcponds to 2.5% of the estimated total nitrogen loading to the Sound from all sources. The average phosphorus flux was 37.44 g (as-P) ha-yr^-1. The total atmospheric phosphorus loading to the Sound was estimated to be 12.62 metric tons yr^-1. The results show that wet deposition was the predominant source of atmospheric contribution to the Sound.     

A lysimeter study of the fate of fertilizer nitrogen in spring barley crops grown on shallow soil overlying Chalk: crop uptake and leaching losses

The objective of this work was to determine the fate of fertilizer nitrogen (labelled with nitrogen-15) applied to an undisturbed shallow soil overlying Chalk contained in 10 lysimeters (80 cm diameter, 135 cm deep). Measurements are reported of the nitrogen uptake by four spring barley crops and the rate and extent of leaching of nitrate beyond the roots. The crops were fertilized with 0, 80 or 120 kg N ha^?1 in each of four years, but only the first application in 1977 was labelled with nitrogen ?15. Rainfall and irrigation approximated to the long-term average, but in two treatments dry or wet spring conditions were imposed for the 10 weeks after sowing the first crop in 1977. The dry matter and grain yields of the spring barley crops varied from year to year in the ranges 8.7–14.0 t ha^?1 and 3.5–6.1 t ha^?1 respectively. The total nitrogen harvested in the crop approximated to the amount of nitrogen applied in each year with an apparent recovery of fertilizer in the range 38–76%. The recovery of nitrogen derived from fertilizer (labelled with nitrogen-15) was 46–54% in the first crop and after 2 years rapidly declined to below 1%. The total amount of nitrogen-15 labelled fertilizer recovered in four barley crops was 49–57% of that applied. Mean annual nitrate concentrations in water draining from the base of the lysimeters were in the range 11.8–26.7 mg N 1^?1 and did not differ significantly between nitrogen fertilizer treatments (0, 80 and 120 kg N ha^?1 a^?1). In all treatments nitrate concentrations varied considerably within each growing season, with a cycle of peaks and troughs. Annual losses of nitrate were in the range 39–128 kg N ha^?1, and the mean annual losses over the 4 years varied between lysimeters from 65 to 83 kg N ha^?1. Nitrogen-15 labelled nitrate was detected in the first drainage water collected in autumn following its spring application, 5 months earlier. Recovery of fertilizer-derived nitrogen in drainage water was greatest during the winter following the second barley crop, and was 3.4–3.7% of the nitrogen-15 applied. Over the 4 years of the experiment 6.3–6.6% of labelled fertilizer was accounted for in drainage water, representing 2–3% of the total nitrogen lost by leaching.     

Dry and wet atmospheric deposition of nitrogen, phosphorus and silicon in an agricultural region

We measured atmospheric nutrient deposition as wet deposition and dry deposition to dry and wet surfaces. Our analyses offer estimates of atmospheric transport of nitrogen (N), phosphorus (P) and silicon (Si) in an agricultural region. Annual dry and wet deposition (ha^?1 year^?1) was 0.3 kg of P, 7.7 kg of N, and 6.1 kg of Si; lower than or similar to values seen in other landscapes. N:P and Si:N imply that atmospheric deposition enhances P and Si limitation. Most P and soluble reactive P (SRP) deposition occurred as dryfall and most dry-deposited P was SRP so would be more readily assimilable by plant life than rainfall P. Dry deposition of N to wet surfaces was several times greater than to dry surfaces, suggesting that ammonia (NH _x ) gas absorbtion by water associated with wet surfaces is an important N transport mechanism. Deposition of all nutrients peaked when agricultural planting and fertilization were active; ratios of NH _x :nitrate (NO _x ) hbox{reflected} the predominant use of NH _x fertilizer. Wet deposition estimates were consistent over hundreds of km, but dry deposition estimates were influenced by animal confinements and construction. Precipitation wash-out of atmospheric nutrients was substantial but larger rain events yielded higher rates of wet deposition. Methodological results showed that local dust contaminated wet deposition more than dry; insects, bird droppings and leaves may have biased past deposition estimates; and estimating dry deposition to dry plastic buckets may underestimate annual deposition of N, especially NH _x .     

Nitrate leaching from grazed grassland lysimeters: effects of fertilizer input, field drainage, age of sward and patterns of weather

Drained and undrained grassland lysimeter plots were established in 1982 on a clay loam of the Hallsworth series at a long-term experimental site in south-west England. The plots were continuously grazed by beef cattle, and received fertilizer at either 200 or 400 kg N ha^-1 per annum to the existing permanent sward, or at 400 kg N ha^-1 to a new sward, reseeded to perennial ryegrass following cultivation. Drainage water was monitored at V-notch weirs and sampled daily for the analysis of nitrate-N. Seven years of data are presented (five years for the reseeded swards). On the drained plots a large proportion of the rainfall was routed preferentially down large pores to the mole drains, whilst on the undrained plots, drainage was mainly by surface runoff. The average quantities of nitrate N leached per year were 38.5, 133.8 and 55.7 kg ha^-1 from the old sward that received 200 and 400 kg N ha^-1, and from the reseed that received 400 kg N ha^-1 fertilizer, respectively. Ploughing and reseeding resulted in a two-fold reduction in leaching, except during the first winter after ploughing, and twice as much leaching occurred after a hot, dry summer as after a cool, wet one. Nitrate concentrations in drainage from either drained or undrained plots were rather insensitive to rainfall intensity, such that concentration was a good predictor of nitrate load for a given drainage volume. The drainage volume determined the proportion of the leachable N that remained in the soil after the winter drainage period. Initial (peak) concentrations of nitrate N ranged, on average, from 55 mg dm^-3 for the drained old sward that received 400 kg N ha^-1 fertilizer, to 12 mg dm^-3 for the undrained sward at 200 kg N ha^-1 fertilizer input. Concentrations of nitrate N in drainage from similar, unfertilized plots rarely exceeded 1 mg dm^-3. The results suggest that manipulating the nitrate supply can lessen leaching and that the route of water through soil to the watercourse determines the maximum nitrate concentration for a given load.     

SUSCEPTIBILITY OF THOMPSON SEEDLESS GRAPEVINES RAISED ON DIFFERENT ROOTSTOCKS TO LEAF BLACKENING AND NECROSIS UNDER SALINE IRRIGATION

Saline irrigation water having high sodium (Na⁺) content leads to the development of black leaf disorder in the vines resulting in reduced productivity and death of permanent vine parts. The response of the vines raised on different rootstocks differs under such conditions. Investigation was carried out to study the susceptibility of grafted and own-rooted Thompson Seedless (Vitis vinifera L.) vines to black leaf disorder. Grapevines grafted on four different rootstocks viz. Dog Ridge (Vitis champini), Salt Creek (Vitis champini), B2-56 (Vitis berlandieri x Vitis rupestris) and 1613C [Vitis longii x (Vitis labrusca x Vitis riparia) x Vitis vinifera] were studied. The variations in nutrient content of various vine parts under saline irrigation in relation to leaf blackening and necrosis symptoms were also studied. Thompson Seedless vines grafted on Dog Ridge, Salt Creek and own rooted vines started developing leaf blackening and necrosis symptoms during the ripening stage. Vines exhibiting these symptoms contained significantly lower potassium (K⁺) and higher Na⁺ content in the leaf blades as compared to healthy vines. Vines grafted on Salt Creek showed most severe leaf blackening and necrosis symptoms and had the lowest K⁺ content in blades and petioles. Amongst the rootstocks, vines raised on B2-56 had the lowest Na⁺ concentration in leaf blades whereas those on Dog Ridge and Salt Creek accumulated Na⁺ in leaf blades to a toxic level. Significantly higher K⁺ content was found in vines raised on B2-56 and 1613C rootstocks in all the vine parts compared to other stock-scion combinations. Vines grafted on B2-56 and 1613C could maintain higher K⁺: Na⁺ ratio and tolerated saline irrigation better than other stock-scion combinations. All the rootstocks reduced chloride concentration significantly in the vine parts (petioles, blade and canes) compared to own rooted vines. Vines raised on their own roots and on B2-56 rootstock had significantly higher phosphorus (P) concentration in petiole, blade and canes compared to vines grafted on Dog Ridge and Salt Creek. Total biomass (petiole + blade + cane on dry weight basis) and yield was the highest in B2-56 rootstock and least in 1613C.     

耕作方式和氮肥用量对旱地小麦产量、水分利用效率和种植效益的影响

为探索旱地小麦增产增效增收协同的耕作方式及其配套施氮技术。2016—2017(欠水年)和2017—2018(丰水年)年度,在豫西典型旱区洛宁县设置夏闲期深松(ST,麦收后2周左右隔年进行)和翻耕(PT,传统的7月或底8月初连年进行)2种耕作方式为主区,设置4个氮肥用量为副区(播前基施纯氮0(N0),120(N120),180(N180),240 (N240) kg/hm~2)的田间定位试验,分析了土壤水分以及小麦产量、水分利用效率和种植效益。结果表明:与翻耕相比,深松提高了休闲效率,播前、开花期和成熟期0—200 cm土壤蓄水量分别提高6.5%～11.7%,5.0%～8.5%,4.7%～8.2%,使欠水年的千粒重、丰水年的穗数和穗粒数显著提高(P0.05),从而使欠水年的产量和经济效益分别提高7.1%～17.8%和5.5%～30.2%,丰水年施氮处理的产量、水分利用效率和经济效益分别提高10.2%～22.0%,3.0%～13.0%,16.1%～35.1%。增加氮肥用量有利于提高休闲效率,使播前土壤蓄水量翻耕下得到恢复、深松下显著提高(P0.05),小麦产量、水分利用效率和经济效益翻耕下N180最优,较其他处理分别提高6.5%～43.9%,8.1%～36.1%,12.4%～61.3%;深松下欠水年以N180较优,丰水年以N240最优,且较其他处理分别提高3.9%～67.9%,1.0%～54.1%,3.6%～95.8%。因此,麦收后2周左右隔年深松有利于提高土壤含水量,进而提高产量、水分利用效率和种植效益,且在欠水年配施纯氮180 kg/hm~2、丰水年配施纯氮240 kg/hm~2效果最优。研究结果可为提高旱地小麦产量、效率和效益提供理论依据和技术参考。     

Italian ryegrass and nitrogen source fertilization in western Oregon in two contrasting climatic years. II. Plant nitrogen accumulation and soil nitrogen status

To develop optimum nitrogen (N) fertilization practices with the least impact on environmental quality and with the greatest economic return, it is imperative that a greater understanding of crop and soil N dynamics be sought. This paper reports on research conducted with these objectives: (i) to determine the relationship between plant N and dry matter accumulation and soil N status as affected by N‐source fertilization as a function of accumulated growing degree days (GDD), and (ii) to determine if western Oregon soil conditions favor ammonium (NH₄) over nitrate (NO₃) nutrition during the period of grass seed crop growth. In a companion paper, plant growth and seed yield component data were discussed in relation to N‐source treatments and climatic year effects. Western Oregon field plots of Italian ryegrass (Lolium multiflorum Lam.) were fertilized with calcium nitrate, ammonium nitrate, ammonium sulfate, ammonium chloride, and urea‐dicyandiamide (DCD) to manipulate soil NH₄ and NO₃ ratios. Italian ryegrass accumulated the greatest portion of plant N and dry mass between tiller elongation and mid‐heading. Reduced growth and seed yield in 1991, compared to 1992, were associated with lodging and low soil pH. Higher soil NH₄ levels in 1991 was most likely responsible for a greater reduction in soil pH for that year. Declines in soil pH due to elevated NH₄ levels during climate years normal to western Oregon, wet and cool, may have an additive effect to other factors limiting seed yield. When cool wet soil conditions exist NH₄ was the predominate mineral N‐form. Information reported here and in the companion paper is valuable to farm managers and consultants in the context of N fertilization of ryegrass grown for seed in western Oregon. It begins to establish criteria for the future development of site specific nutrient management plans and adds knowledge that will aid in improving N‐use efficiency through improving N fertilizer timing and N source use.     

THE USE OF BULK COLLECTORS IN MONITORING WET DEPOSITION AT HIGH-ALTITUDE SITES IN WINTER

Concentrations of dissolved ions from samples collected by wet/dry collectors were compared to those collected by bulk collectors at Halfmoon Creek and Ned Wilson Lake in western Colorado to determine if bulk collectors can be used to monitor wet deposition chemistry in remote, high-altitude regions in winter. Hydrogen-ion concentration was significantly lower (p <0.05) in the bulk collectors. All other ion concentrations were significantly higher (p <0.05) in the bulk collectors except for ammonium (p >0.05) at Halfmoon Creek. Wet deposition concentrations were predicated from bulk deposition concentrations through linear regression analysis. Results indicate that anions (chloride, nitrate and sulfate) can be predicted with a high degree of confidence. Lack of significant differences between seasonal (winter and summer) ratios of bulk to wet deposition concentrations indicates that at sites where operation of a wet/dry collector during the winter is not practical, wet deposition concentrations can be predicted from bulk collector samples through regression analysis of wet and bulk deposition data collected during the summer.     

Nitrate leaching from the Broadbalk Wheat Experiment, Rothamsted, UK, as influenced by fertilizer and manure inputs and the weather

Abstract. Nitrate leaching was measured over the eight drainage seasons spanning the nine years from 1990–1998 on the 157‐year old Broadbalk Experiment at Rothamsted, UK. The weather pattern of two dry, three wet and three dry years was the dominant factor controlling nitrogen (N) loss. Both the concentration of nitrate in the drainage waters and the amount of N leached increased with the amount of N applied, mostly because of long‐term, differential increases in soil organic matter and mineralization. On average, losses of N by leaching were 30 kg ha^?1yr^?1 when no more than the optimum N application was applied and were typical of amounts leached from arable land in the UK. Losses increased significantly in both amounts and as the percentage of N applied for supra‐optimal applications of N and from autumn‐applied farmyard manure (FYM). Extra spring‐applied fertilizer was very effective at increasing yields on plots given FYM in the autumn but at the expense of leaching losses three times those from optimum fertilizer N applications. Losses increased after potatoes because they left significant amounts of mineral N in the soil, and decreased after forage maize because it used applied N more effectively. Losses measured 120 years ago from identical treatments were 74% greater than current losses because of today's larger yields and more efficient varieties and management practices. Average concentrations of nitrate in drainage waters did not exceed the EU limit of 11.3 mg NO₃‐N l^?1 until supra‐optimal amounts of N fertilizer (>150–200 kg ha^?1yr^?1) were applied in spring or FYM was applied in autumn. However some drainage waters from all plots, even those that have not received fertilizer for >150 years, exceeded the limit when rain followed a dry summer and autumn. Nitrate leaching into waters will remain a problem for profitable arable farming in the drier parts of Eastern England and Europe despite increased N use efficiency.     

Evaluation of leaching and runoff losses of selenium from seleniferous soils through simulated rainfall

Experiments were conducted to study drainage and runoff losses of selenium (Se) from two seleniferous soils (from Simbly containing total Se 850 μg [kg soil]^–1 and from Barwa containing 1310 μg [kg soil]^–1) under simulated rainfall (250–260 mm in three rainstorms) conditions. Rainfall intensities ranged from 56 to 120 mm h^–1 with uniformity coefficients ranging from 70.6% to 84.2%. Selenium lost through drainage (sum of drainage from initially saturated soil for 24 h and through dry and wet runs) was 0.15% and 0.11% of total Se content in the two soils. In soils having similar pH and organic‐C content, losses of Se through drainage as well as runoff were defined by total Se, water‐soluble Se, CaCO₃ content, and texture of the soils. The amount of runoff water was almost two times in the soil with fine texture and less infiltration rate than in the other and that same trend was observed with respect to loss of sediment. The soil with higher CaCO₃ content and water‐soluble Se lost more Se with moving water both through leaching and runoff, whereas the other soil with fine texture lost greater amount of Se with the sediment. Total Se lost through drainage as well as runoff was 0.29% of the native Se present in both the soils suggesting that significant amount of Se could be lost from seleniferous soils during irrigation and rainfall events.     

窟野河水沙变化发展趋势预测

窟野河是黄河河龙区间水土流失严重的一条多沙粗沙支流,流域内人类活动频繁,神府东胜煤田正在开发,其水沙变化发展趋势令人关注。经分析预测,神府东胜矿区一、二期工程排弃的土石数量为6.3亿t,1987～2000年平均每年增沙1130～1350万t;2000年前规划治理减沙效益为37.1％,减水效益为37.8％;一次洪水垮坝冲失的泥沙,将增加该次洪水泥沙量的13.3％～36.5％;河道淤积会加重防洪困难,其泥沙还可能集中排入黄河;丰水年份洪水泥沙有可能剧增,枯水年份水量进一步减少,甚至会出现水资源危机。     

Midwest (U.S.A.) reservoir water quality modification I. Particulate parameters

Both qualitative and quantitative approaches were used to evaluate the impact of a flood control, low flow augmentation reservoir on seven water quality parameters: Suspended solids and total phosphate (particulate parameters); BOD, COD, and ammonia (O₂-demanding parameters); and orthophosphate and nitrite plus nitrate N (soluble nutrients). Fourteen years of weekly sampling data above, in, and downstream of the reservoir both before and after the reservoir became operational were analyzed. This paper considers the effects of the reservoir on the particulate parameters. There was a dramatic decrease in both suspended solids and total phosphate concentrations in the reservoir discharges, particularly during periods of high river flows and high reservoir inflow parameter concentrations. At all sampling stations, the annual parameter loading rates (kg ha^?1 yr^?1) correlated linearly with annual runoff (cm yr^?1). The suspended solids removal efficiency of the reservoir was dependent on annual runoff and averaged about 90%. Non-point source contributions of suspended solids were well over 99% when annual runoff exceeded 6.57 cm y^?1 and over 95% even when annual runoff was as low as 1.63 cm yr^?1     

Losses of nitrate-nitrogen in water draining from under autumn-sown crops established by direct drilling or mouldboard ploughing

The leaching of nitrate-N under autumn-sown arable crops was measured using hydro-logically isolated plots, about 0.24 ha in area, from 1984–1988. Fluxes of water and nitrate moving over the soil surface (surface runoff), at the interface between topsoil and subsoil (interflow), and in the subsoil (drainflow) were monitored in plots with mole-and-pipe drain systems (drained plots); surface runoff and interflow only were monitored in ‘undrained’ plots. Half the drained and undrained plots were direct-drilled, and on the other half seedbeds were prepared by tillage to 200 mm. Tillage increased the total leaching loss of nitrate by 21 % compared with direct drilling in drained plots. About 95% or the nitrate moving from the soil was present in the water intercepted by the subsoil drains in these plots. In undrained plots less water and nitrate were collected in total; more of the nitrate was present in interflow on ploughed plots and in surface runoff in direct-drilled land. Losses of nitrate for the whole experiment from 1978-1988 were analysed. This showed that, between the harvest of one crop and the spring application of fertilizer to the next, loss of nitrate-N from ploughed land (L_p) was approximated by L_p=22+Fkg N ha^?1, where F was the autumn fertilizer-N applied. After fertilizer was applied in spring, loss of nitrate-N depended on rainfall such that for 100 mm rainfall about 30% of the fertilizer-N was lost by leaching. About 18% more nitrate-N was lost from direct-drilled land than from ploughed land in spring, but the total loss was generally small compared to that over winter. The apparent net mineralization of organic-N was measured in 1988. In autumn and winter there was little effect of tillage treatment (26 and 31 kg N ha^?1 on direct drilled and tilled plots respectively). However, over the year 83 kg N ha^?1 were mineralized in tilled plots, and 67 kg N ha^?1 in direct-drilled plots. Five factors governing the leaching of nitrate are assessed and this identified that fertilizer nitrogen application to the seedbed of winter sown crops and the mineralization of nitrogen from the residues of the previous crop are the most significant factors for nitrogen leaching in the UK.     

近50年半干旱典型草原区域不同时间尺度上的降水、径流研究

以内蒙古锡林河流域典型草原区域为研究区,采用1963—2015年气温、相对湿度、降水量、风速、日照时数、蒸发量、径流日数据,应用统计分析、趋势检验和Spearman相关分析等方法对研究区区域7项水文气象要素的平均最高值、平均值、平均最低值突变前后变化及突变后停滞特征进行了分析,结果表明;（1）内蒙古锡林河流域典型草原区域的降水量最大月（7月）与径流量最大月（4月）不同,降水天数明显小于径流天数,且降水量远大于径流深,多年丰水季降水总量近似于枯水季的3倍,而多年枯水季径流总量是丰水季的2倍;（2）径流量多年来呈现显著减少的趋势,而降水的整体变化趋势不太明显,存在1998—2011年处于由丰变枯阶段,2011年后有由枯转丰的迹象;（3）年、丰水季、枯水季径流发生突变年份均为2004,同一时期发生突变,年、枯水季径流天数发生突变年份为2007年、2004年,丰水季在此期间未发生突变;（4）该区年径流天数枯水季所占比例居多,径流量年、丰、枯水季突变年限一致,造成突变的驱动因数接近,枯水季径流天数相对于年径流天数突变年份较早,枯水季对引起突变的驱动因数更为敏感;（5）影响该区降水大小的主要气象因素依次为日照时数 > 相对湿度 > 平均风速 > 平均气温 > 降水量=蒸发,影响该区径流大小的主要气象因素依次为蒸发 > 相对湿度 > 平均风速 > 平均气温=降水量 > 日照时数。     

黄土高原泾河流域梯田对河道径流及生态基流影响

[目的]定量分析泾河流域梯田建设对河道径流、生态基流的影响程度,为流域梯田建设提供一定理论支撑。[方法]采用合作开发的嵌入梯田模块的SWAT(soil and water assessment tool)模型模拟河道径流量。[结果]嵌入梯田模块的SWAT模型在模拟河道径流时可满足模型模拟精度的要求;随着梯田面积增加,河道年径流量减少,生态基流保障程度提高,年、月生态基流不满足天数降低;梯田的年平均减流量为4.25×104 m3/(km2·a);梯田具有蓄洪补枯作用,且对丰水期的调控效果高于枯水期,对河道生态基流的影响为:枯水期平水期丰水期。[结论]嵌入梯田模块的SWAT模型在该流域具有较好的适用性,提高流域内梯田面积是滞洪补枯的有效手段之一,在一定程度上保障了河道生态基流。     

东北典型稻区不同种植模式下稻田氮素径流损失特征研究

为了降低东北稻区稻田氮素径流损失,选择东北典型水稻种植区盘锦市,开展了不同栽培模式下水稻生长季田间氮素径流监测试验,试验设5个处理:对照(CK)、常规模式(TR)、稻蟹共生(CR)、有机水稻(OR)和减量施肥(RR),利用集水池收集各处理的地表径流,并测定径流的硝态氮、铵态氮、总氮含量,计算氮素流失量。研究结果显示:稻田地表径流损失的铵态氮远高于硝态氮;稻蟹共生和常规模式处理田间排水铵态氮的损失量相差不大,减量施肥处理比常规模式处理低26%,有机水稻处理比常规模式低73%。稻蟹共生处理比常规模式处理排水中硝态氮的排放量少23%,减量施肥处理比常规模式处理减少34%,有机水稻处理比常规模式处理低67%。稻蟹共生和常规模式处理排水总氮排放量无显著差异,分别为6.15 kg.hm 2和5.89 kg.hm 2;减量施肥处理显著低于常规模式处理,总氮排放量为4.76 kg.hm 2,比常规模式处理低19%;有机水稻处理在各水稻模式中总氮排放量最低,仅为1.93 kg.hm 2,并且显著低于常规模式处理,比常规模式处理低67%。     

灌木式屋顶绿化设计及对屋面初期雨水的净化

[目的]探讨灌木式屋顶绿化屋面承载力及对屋面初期雨水径流污染物的净化效果,为屋顶绿化设计及雨水资源化利用提供一定的理论指导。[方法]根据屋面所能承受承载力大小及屋面雨水径流的特点设计灌木式屋顶绿化结构,采用蛭石、珍珠岩作为吸水剂,与红壤土、腐殖土按一定比例复配为屋顶灌木绿化的种植基质。通过将收集到的屋面雨水模拟降雨,淋洒屋顶灌木,对其干、湿重荷载和对雨水去除效果进行研究。[结果]1m3复配的人工土壤的饱和吸水量为0.65m^3,种植基质湿容重为1 190kg/m^3,灌木式屋顶绿化的干、湿重荷载分别为261,529kg/m^2。对屋面初期雨水中的SS,COD,TN,TP的削减量分别在60.1%~71.3%,50.0%~61.8%,49.2%~53.2%和55.6%~67.7%之间。[结论]灌木式屋顶绿化能满足一般建筑物屋顶的荷载要求,同时对初期雨水径流具有较好的净化效果。     

Nitrogen and Potassium Fertilization Responses of Potato (Solanum tuberosum) cv. Spunta

A potato field experiment was conducted for 2 consecutive years to determine the effects of nitrogen (N) and potassium (K) fertilization rates on the yield and quality of potato cv. Spunta cultivated on soil low in N and K. A 3?×?4 complete factorial experiment was used with three rates of nitrogen (330, 495, and 660 kg N ha^–1) and four rates of potassium (112, 225, 450, and 675 kg K₂Ο ha^–1). An additional treatment without fertilization was used as the control. On soils low in N and K, potatoes showed low yield response to K fertilizer. The greatest tuber yields for both years were achieved at 495 kg N ha^–1 and 112 kg K₂O ha^–1 (29.81 t ha^–1) and 225 kg ha^–1 (27.13 t ha^–1), respectively. Differences in mean fresh weight due to treatment application were not significant. Application of 495 kg N ha^–1 significantly reduced harvest index (the ratio of tuber dry weight to the total dry weight at harvest) compared to 330 kg N ha^–1, but at 660 kg N ha^–1 harvest index achieved the greatest significant value. Potassium fertilization had no significant influence on harvest index. Nitrogen rates positively influenced the number of tubers. The addition of 450 kg K₂O ha^–1 significantly enhanced the number of tubers compared to the lower K rates, and the number was significantly decreased by the application of 675 kg K₂O ha^–1. Tuber dry-matter concentration was significantly promoted by N fertilization in both cultivation years, but it was negatively affected by K fertilization in the first year of cultivation. There was no change in tuber N with N application, but N application strongly increased nitrate (NO₃) concentration, which fluctuated between 360 and 1382 mg kg^–1 wet mass. Tuber NO₃ was negatively correlated with tuber yield, indicating that high levels of NO₃ in tubers can adversely affect yield. Tuber response to K fertilization was not in accordance with the rate of applied nutrient.     

THE ERODIBILITY OF TWO SOILS FROM KENYA

A portable rainfall simulator was used to measure the runoff rates and soil losses from a freshly ploughed luvisol at Katumani, and a nitosol at Kabete, on a 6° slope at varying rainfall intensities. The soil losses from storms of 50 and 100 mm/h intensities, in which a total of SO mm rain was applied to plots in the wet moisture state, varied from 0.8 to 1.4 metric tons/ha at Kabete and 8.5 to 13.9 metric tons/ha at Katumani. The percentage runoff from these storms was 15 to 17 per cent at Kabete and 67 to 71 per cent at Katumani. The much greater runoff rates from the Katumani soils were shown to be due to surface capping caused by degradation of the surface structure. It has been proposed that soil credibility K factors of 0.4 and 0.04 could be used for the Katumani and Kabete soils respectively in the Universal Soil Loss Equation     

Urban Influences on Stream Chemistry and Biology in the Big Brushy Creek Watershed, South Carolina

Naturally high total dissolved solids and upstream agricultural runoff often mask the influence of urban land cover on stream chemistry and biology. We examined the influence of headwater urbanization on the water chemistry, microbiology, and fish communities of the Big Brushy Creek watershed, a 96 km² drainage basin in the piedmont of South Carolina, USA. Concentrations of most major anions and cations (especially nitrate, sulfate, chloride, sodium, potassium, and calcium) were highest in the urban headwaters and decreased downstream. Generally, the highest concentrations of suspended coliform bacteria occurred in the urban headwaters. In contrast, stream habitat quality and the abundance, species richness, and species diversity of fishes did not differ significantly between urban and rural sites. Discharge of wastewater treatment plant effluent at one rural location caused an increase in concentrations of many solutes and possibly the abundance of benthic algae. We hypothesize that atmospheric dry deposition and domestic animal wastes are important sources of stream solutes and of coliform bacteria, respectively, in the urban headwaters. The lack of significant differences in fish abundance and diversity between urban and rural sites may indicate that urban development in the Big Brushy Creek watershed has not yet degraded habitat conditions greatly for stream fishes. Alternatively, agriculture or other land uses may have degraded stream habitat quality throughout the watershed prior to urbanization.