广州郊区菜地氮磷养分径流流失特征初步研究

通过对广州市白云区某菜地在天然降雨条件下氮磷养分随地表径流输出的定位动态研究,结果表明：径流量与氮、磷流失量呈显著线性相关。菜地径流流失的氮素以硝态氮为主,雨季期间（4月—7月）其他形态N流失量占总N流失量的比例上升,铵态氮含量一直很低;整个试验期间,TN与NO3--N呈极显著正相关;磷素径流迁移以颗粒态为主。与未施肥对照组相比,菜地常规施肥显著增加N径流流失量,对P未造成显著影响;因而菜地常规施肥对径流水体N富营养化具有较高风险。     

安徽省沿淮地区豆麦轮作农田径流氮、磷流失特征研究

通过淮南市的豆麦轮作试验来观察安徽省沿淮地区豆麦轮作模式下地表径流氮、磷流失的特点。安徽省沿淮地区降水地表径流系数为25％,麦季的氮肥流失率为1．21％,磷肥流失率为0．047％;豆季的氮肥流失率为3．39％,磷肥流失率为0．415％。氮的流失以硝态氮为主,磷的流失以颗粒态磷为主。麦季的氮、磷肥流失量都低于豆季,氮素70％和磷素90％流失在豆季。2008-2010年豆麦轮作的氮肥平均流失率为2．05％,磷肥平均流失率为0．25％。     

春玉米产量、氮肥效率及土壤矿质氮对施氮的响应

为了提高氮肥增产效益,减少对环境的污染,通过田间试验研究了施氮量对春玉米产量、氮肥效率及土壤矿质氮的影响。结果表明,施氮量较低时,春玉米籽粒产量随施氮量增加显著增加,当施氮量高于180kg·hm2时,产量保持不变或有减少趋势。氮肥农学利用率、氮素吸收效率、氮素偏生产力和氮收获指数均随着施氮量增加显著降低,氮肥表观利用率和氮肥生理利用率均先增加后降低。从苗期到收获期,施氮处理0～60cm土层硝态氮含量呈现“上升一下降一上升一下降一稳定”的变化趋势,而60～120cm土层硝态氮在春玉米生长后期有增加的趋势。随着土层加深,土壤硝态氮含量呈波浪式下降,施氮量240kg·hm-2和300kg·hm-2处理在60～100cm土层硝态氮含量均显著高于其他处理。随着施氮量增加,0～120cm土层硝态氮累积量显著增加,当施氮量超过240kg·hm-2时,土层中累积的硝态氮存在着较大的淋溶风险。综合考虑产量、氮肥效率和环境效应,179—209kgN·hm。是本试验条件下春玉米的合理施氮量。     

广西坡耕地主要经济作物施肥与养分径流流失初探

为研究广西坡耕地主要经济作物甘蔗、玉米和花生农民常规施肥及不施肥处理对植株生长情况、经济产量及养分径流流失的影响,探寻提高广西经济作物经济效益、减少成本、减少环境污染的最佳施肥量,在坡耕地,观测降雨过程的养分径流流失,运用SPSS统计分析软件对试验数据进行分析,寻找成本低、效益高的种植方法。结果表明,对照与常规施肥相比,甘蔗、玉米、花生作物的生长情况差异不明显。对照处理的玉米经济产量、生物产量、淀粉含量分别为851．42kg·667m-2 3640．4kg·667m-2．68．40％;比玉米（常规施肥）高100．62kg·667m-2．485．98kg·667m-2 7．5％;花生对照的粗脂肪比其常规施肥高了45g·kg-1;径流养分总氮、总磷、总钾、硝态氮、铵态氮径流流失总量最高的均是花生常规施肥,其次是甘蔗对照,最少的玉米对照。径流量与总氮、总磷、总钾、硝态氮、铵态氮的相关系数,常规施肥处理偏高于对照。玉米对照的养分径流流失总量最少;花生常规施肥养分径流率最大;玉米比花生更适合在广西肥沃的坡耕地中种植。     

我国缓／控释肥发展现状及产业化存在的问题

我国目前所施用的化肥大多是单质速效化肥,肥效期短,养分容易淋失、挥发和固定,利用率很低,造成极大的资源浪费和严重的环境问题,因此开发缓/控释肥就被提到了现代化肥工业生产的日程.从缓/控释肥料的优势出发,并结合我国缓/控释肥料的发展现状,从研发、生产和推广应用等方面说明其实现产业化存在的问题,从而为我国缓/控释肥料的产业化提供参考.     

控释尿素不同施用条件下冬小麦产量和氮素利用效应

采用田间试验方法研究了控释尿素不同施用条件对冬小麦产量、氮素利用和经济效益的影响。试验共设7个处理,即CK （空白处理,不施氮肥）、100%PU10/0（普通尿素全量基施,N 240 kg＆#183;hm-2）、100%PU6/4（60%的普通尿素基施、40%的普通尿素于拔节期追施,N 240 kg＆#183;hm-2）、80%PU6/4（60%的普通尿素基施、40%的普通尿素于拔节期追施,N 192 kg＆#183;hm-2）、100%CRU（全量树脂包膜控释尿素基施,N 240 kg＆#183;hm-2）、80%CRU（80%树脂包膜控释尿素基施,N 192 kg＆#183;hm-2）和40%CRU＋40%PU（40%树脂包膜控释尿素＋40%的普通尿素基施,N 192 kg＆#183;hm-2）。结果表明,无论是产量效应还是氮素利用效应,树脂包膜控释尿素（CRU）处理总体优于普通尿素（PU）处理,尤其树脂包膜控释尿素和普通尿素配施（40%CRU＋40%PU）效果最佳,以7709 kg＆#183;hm-2的产量、36.44%的氮肥吸收利用率、15946元＆#183;hm-2的相对净收入达到处理间最高水平。该处理在减少氮素投入量的情况下,不仅促进了冬小麦增产,而且显著提高了肥料的利用率,拥有较高的产投比。因此,树脂包膜控释尿素和普通尿素的配施处理（40%CRU＋40%PU）是本试验条件下最优的氮肥处理。     

氮素和水分对贝加尔针茅草原土壤酶活性和微生物量碳氮的影响

在内蒙古贝加尔针茅草原,分别设对照（N0）、1.5 g·m^-2（N15）、3.0 g·m^-2（N30）、5.0 g·m^-2（N50）、10.0 g·m^-2（N100）、15.0 g·m^-2（N150）、20.0 g·m^-2（N200）和30 g·m^-2（N300）（不包括大气沉降的氮量）8个氮素（NH4NO3）梯度和模拟夏季增加降水100 mm的水分添加交互试验,研究氮素和水分添加对草原土壤养分、酶活性及微生物量碳氮的影响。结果表明：氮素和水分添加对草原土壤理化性质和生物学特性有显著影响。随施氮量的增加土壤总有机碳、全氮、硝态氮、铵态氮含量呈增加的趋势,相反,土壤pH值呈降低的趋势。土壤脲酶和过氧化氢酶的活性随施氮量的增加而升高,多酚氧化酶则随施氮量的增加呈下降的趋势。氮素和水分添加对草原土壤微生物量碳氮含量有显著影响,高氮处理（N150、N200和N300）显著降低了微生物碳含量,微生物氮含量随施氮量的增加呈上升趋势。水分添加能够减缓氮素添加对微生物的抑制作用,提高微生物量碳、微生物量氮含量。草原土壤养分、土壤酶活性及土壤微生物量碳氮含量间关系密切,过氧化氢酶与全氮、总有机碳、硝态氮呈显著正相关,多酚氧化酶与铵态氮、硝态氮、全氮呈显著负相关。微生物量氮含量与土壤全氮、铵态氮、硝态氮含量以及过氧化氢酶和磷酸酶活性呈显著正相关,与多酚氧化酶呈负相关;微生物量碳与过氧化氢酶呈负相关,与多酚氧化酶活性呈正相关。     

响应面法优化美人蕉净化硝态氮条件的研究

研究旨在优化人工湿地中美人蕉净化硝态氮的最佳组合条件。该研究采用单因素实验考察湿地系统中甲醇浓度(A)、硝酸盐浓度(B)及处理时间(C)对美人蕉吸收硝态氮的影响,在此基础上,利用Design-Expert软件并采用CCD设计三因素五水平的响应面分析法,对美人蕉净化硝态氮条件进行优化。研究表明当甲醇预处理浓度为2.75mM,预处理时间4 h,硝酸根离子浓度为38mg/L时,美人蕉吸收硝酸根离子的效率可达最大,最大吸收效率为0.062mg/(L·g)FW。在实际应用中,可依据试验结果对种植美人蕉的湿地系统施用甲醇,调整系统中硝态氮的浓度,以促进美人蕉对湿地系统中硝态氮的吸收。     

秸秆还田下氮肥用量对玉米产量及土壤无机氮的影响

研究连续2年秸秆还田下氮肥用量对玉米产量、氮肥利用率及土壤硝态氮的影响,结果表明,玉米产量随着施氮量的增加逐渐增加,施氮量达到216 kg·hm^-2时,产量最高,施氮量超过216 kg·hm^-2时产量有降低的趋势。相同施氮处理玉米产量年际变化明显,2010年较2009年产量提高0.69％~4.75％。氮肥利用率、氮肥农学利用率和氮收获指数随着秸秆还田年限的增加,均有不同程度的增加。2年0~100 cm土层土壤硝态氮含量均以施氮240 kg·hm^-2最高,且有向土壤深层迁移的趋势,对浅层地下水构成潜在的威胁。与施氮240 kg·hm^-2相比,施氮168、192 kg·hm^-2和216 kg·hm^-2处理0~100 cm土壤无机氮残留量2年平均减少39.87％、35.84％和29.38％。相同施氮处理,0~100 cm土壤无机氮累积量2010年较2009年略有降低。综合考虑玉米产量、氮肥利用率与生态环境效益,该地区最适施氮量200 kg·hm^-2左右。     

氮磷养分配施对土壤碳氮特征及叶用枸杞生长的影响

通过田间定位试验,探讨水肥一体化技术下不同养分配施措施对土壤碳氮特征及叶用枸杞生长的影响,筛选出适合该区域叶用枸杞高效可持续生产管理模式。结果表明,随着养分浓度的增大,各层次土壤中有机碳含量整体呈现增加趋势,土壤中易氧化态有机碳及土壤碳库管理指数(CPMI)变化趋势与土壤有机碳类似。与对照相比,水肥一体化施肥增加了0～20cm和20～40cm土层硝态氮含量;但随着土层深入,土壤剖面硝态氮含量整体呈现出逐渐降低的趋势,而对照处理硝态氮呈现增加趋势,40～60cm土层硝态氮含量达最大。在水肥一体化N2P3处理下,叶用枸杞叶芽产量最高。研究确定,N2P3处理的"少量多次"水肥一体化灌溉模式,是叶用枸杞生产区最佳的农业高效高产的水肥生产管理模式。     

GENERALIZED WATERSHED LOADING FUNCTIONS FOR STREAM FLOW NUTRIENTS1

ABSTRACT: Loading functions are proposed as a general model for estimating monthly nitrogen and phosphorus fluxes in stream flow. The functions have a simple mathematical structure, describe a wide range of rural and urban nonpoint sources, and couple surface runoff and ground water discharge. Rural runoff loads are computed from daily runoff and erosion and monthly sediment yield calculations. Urban runoff loads are based on daily nutrient accumulation rates and exponential wash off functions. Ground water discharge is determined by lumped parameter unsaturated and saturated zone soil moisture balances. Default values for model chemical parameters were estimated from literature values. Validation studies over a three-year period for an 850 km² watershed showed that the loading functions explained at least 90 percent of the observed monthly variation in dissolved and total nitrogen and phosphorus fluxes in stream flow. Errors in model predictions of mean monthly fluxes were: dissolved phosphorus - 4 percent; total phosphorus - 2 percent; dissolved nitrogen - 18 percent; and total nitrogen - 28 percent. These results were obtained without model calibration.     

Capacity of biochar application to maintain energy crop productivity: soil chemistry, sorghum growth, and runoff water quality effects

Pyrolysis of crop biomass generates a by-product, biochar, which can be recycled to sustain nutrient and organic C concentrations in biomass production fields. We evaluated effects of biochar rate and application method on soil properties, nutrient balance, biomass production, and water quality. Three replications of eight sorghum [ (L.) Moench] treatments were installed in box lysimeters under greenhouse conditions. Treatments comprised increasing rates (0, 1.5, and 3.0 Mg ha) of topdressed or incorporated biochar supplemented with N fertilizer or N, P, and K fertilizer. Simulated rain was applied at 21 and 34 d after planting, and mass runoff loss of N, P, and K was measured. A mass balance of total N, P, and K was performed after 45 d. Returning 3.0 Mg ha of biochar did not affect sorghum biomass, soil total, or Mehlich-3-extractable nutrients compared to control soil. Yet, biochar contributed to increased concentration of dissolved reactive phosphorus (DRP) and mass loss of total phosphorus (TP) in simulated runoff, especially if topdressed. It was estimated that up to 20% of TP in topdressed biochar was lost in surface runoff after two rain events. Poor recovery of nutrients during pyrolysis and excessive runoff loss of nutrients for topdressed biochar, especially K, resulted in negative nutrient balances. Efforts to conserve nutrients during pyrolysis and incorporation of biochar at rates derived from annual biomass yields will be necessary for biochar use in sustainable energy crop production.     

Subsurface application of poultry litter and its influence on nutrient losses in runoff water from permanent pastures

Environmental pressure to reduce nutrient losses from agricultural fields has increased in recent years. To abate this nutrient loss to the environment, better management practices and new technologies need to be developed. Thus, research was conducted to evaluate if subsurface banding poultry litter (PL) would reduce nitrogen (N) and phosphorus (P) loss in surface water runoff using a four-row prototype implement. Rainfall simulations were conducted to create a 40-min runoff event in an established bermudagrass (Cynodon dactylon L.) pasture on soil types common to the Coastal Plain and Piedmont regions. The Coastal Plain soil type was a Marvyn loamy sand (fine-loamy, kaolinitic, thermic Typic Kanhapludults) and the Piedmont soil type was a Hard Labor loamy sand (fine, kaolinitic, thermic Oxyaquic Kanhapludults). Treatments consisted of surface- and subsurface-applied PL at a rate of 9 Mg ha(-1), surface broadcast-applied commercial fertilizer (CF; urea and triple superphosphate blend) at the equivalent N (330 kg N ha(-1)) and P (315 kg N ha(-1)) content of PL, and a nonfertilized control. The greatest loss for inorganic N, total N, dissolved reactive P (DRP), and total P occurred with the surface broadcast treatments, with CF contributing to the greatest loss. Nutrient losses from the subsurface banded treatment reduced N and P in surface water runoff to levels of the control. Subsurface banding of PL reduced concentrations of inorganic N 91%, total N 90%, DRP 86%, and total P 86% in runoff water compared with surface broadcasted PL. These results show that subsurface band-applied PL can greatly reduce the impact of N and P loss to the environment compared with conventional surface-applied PL and CF practices.     

Agroforestry practices,runoff, and nutrient loss: a paired watershed comparison

A paired watershed study consisting of agroforestry (trees plus grass buffer strips), contour strips (grass buffer strips), and control treatments with a corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] rotation was used to examine treatment effects on runoff, sediment, and nutrient losses. During the (1991-1997) calibration and subsequent three-year treatment periods, runoff was measured in 0.91- and 1.37-m H-flumes with bubbler flow meters. Composite samples were analyzed for sediment, total phosphorus (TP), total nitrogen (TN), nitrate, and ammonium. Calibration equations developed to predict runoff, sediment, and nutrients losses explained 66 to 97% of the variability between treatment watersheds. The contour strip and agroforestry treatments reduced runoff by 10 and 1% during the treatment period. In both treatments, most runoff reductions occurred in the second and third years after treatment establishment. The contour strip treatment reduced erosion by 19% in 1999, while erosion in the agroforestry treatment exceeded the predicted loss. Treatments reduced TP loss by 8 and 17% on contour strip and agroforestry watersheds. Treatments did not result in reductions in TN during the first two years of the treatment period. The contour strip and agroforestry treatments reduced TN loss by 21 and 20%, respectively, during a large precipitation event in the third year. During the third year of treatments, nitrate N loss was reduced 24 and 37% by contour strip and agroforestry treatments. Contour strip and agroforestry management practices effectively reduced nonpoint-source pollution in runoff from a corn-soybean rotation in the clay pan soils of northeastern Missouri.     

Using gypsum to reduce phosphorus in runoff from subcatchments in South Australia

Concentrations of phosphorus (P) in runoff from agricultural catchments in southern Australia are high and well above national and international limits. Phosphorus was found to exit two subcatchments of 3.6 and 4.2 ha in the Adelaide hills via both overland flow and interflow. The subcatchments had texture-contrast soils with high inputs of superphosphate and were openly grazed by cattle all year. Interflow at the boundary of the B and C soil horizons accounted for as much as half the total water flow that was measured (overland flow, A-B interflow, and B-C interflow). The average flow-weighted concentration of total P within overland flow was as high as 0.25 mg L(-1), and 0.05 mg L(-1) in B-C interflow. In most years P loss was in the dissolved (<0.45 microm) form. In some years, interflow was the major pathway for P loss off these catchments. The B-C interflow cannot be discounted when searching for management options to reduce P loss from texture-contrast soils to waterways. Preliminary laboratory experiments showed promise that gypsum could modify agricultural soils and reduce the concentrations of P (and dissolved organic C) in runoff before it enters public water supply reservoirs. In this study, gypsum, applied at a rate of 15 Mg ha(-1) to the 4.2-ha subcatchment, substantially modified the soil chemistry, and thereby soil structure. The size and stability of structural aggregates increased markedly and this change affected not only the A but also the upper B horizons, to a profile depth of approximately 50 cm. However, the impact of these physicochemical changes on P concentrations in runoff was not marked. Average profile P concentrations were only slightly lower in the runoff from the subcatchment following treatment. The high subsoil macroporosity of the gypsum-treated subcatchment caused an increase in the proportion of runoff by interflow.     

Nutrient transport within three vegetative treatment areas receiving silage bunker runoff

Silage bunker runoff can be a very polluting substance and is increasingly being treated by vegetative treatment areas (VTAs), but little information exists regarding nutrient removal performance of systems receiving this wastewater. Nutrient transport through the shallow subsurface of three VTAs (i.e. one VTA at Farm WNY and two VTAs at Farm CNY) in glaciated soils containing a restrictive layer (i.e., fragipan) was assessed using a mass balance approach. At Farm WNY, the mass removal of ammonium was 63%, nitrate was 0%, and soluble reactive phosphorus (SRP) was 39%. At Farm CNY, the mass removal of ammonium was 79% in the West VTA, but nitrate and SRP increased by 200% and 533%, respectively. Mass removal of ammonium was 67% in the East VTA at Farm CNY; nitrate removal was 86% and SRP removal was 88%. The East VTA received a much higher nutrient loading, which was attributed to a malfunctioning low-flow collection apparatus within the settling basin. Results demonstrate that nutrient reduction mechanisms other than vegetative uptake can be significant within VTAs. Even though increases in nitrate mass were observed, concentrations in 1.65m deep wells indicated that groundwater impairment from leaching of nitrate was not likely. These results offer one of the first evaluations of VTAs treating silage bunker runoff, and highlight the importance of capturing concentrated low flows in VTA systems.     

Water-quality effects of a mechanized subsurface-banding technique for applying poultry litter to perennial grassland

Poultry litter is known to be an excellent organic fertilizer, but the common practice of spreading litter on the surface of pastures has raised serious water-quality concerns and may limit potential benefits of litter applications. Because surface-applied litter is completely exposed to the atmosphere, runoff can transport nutrients into nearby streams and lakes, and much of the ammonium nitrogen volatilizes before it can enter the soil. Our previous research showed that a manual knifing technique to apply dry litter under a perennial pasture surface effectively prevented about 90% of nutrient loss with runoff from surface-applied litter, and tended to increase forage yield. However, this technique (known as subsurface banding) cannot become a practical management option for producers until it is mechanized. To begin that process, we tested an experimental single-shank, tractor-drawn implement designed to apply poultry litter in subsurface bands. Our objective was to compare this mechanized subsurface-banding method against conventional surface application to determine effects on nutrient loss with runoff from a perennial grassland treated with dry poultry litter. Early in the growing season, broiler litter was applied (6.7 dry-weight Mg ha⁻¹) to each plot (except three control plots) using one of two application methods: surface broadcast manually or subsurface banded using the tractor-drawn implement. Simulated rainfall (5 cm h⁻¹) generated 20 min of runoff from each plot for volume and analytical measurements. Results showed that subsurface-banded litter increased forage yield while decreasing nutrient (e.g. N and P) loss in runoff by at least 90% compared to surface-broadcast litter.     

Effect of surface incorporation of broiler litter applied to no-till cotton on runoff quality

Surface application of broiler litter to no-till cotton could lead to degradation of water quality. Incorporation of broiler litter into the top surface soil (0.05 m) could alleviate this risk. A 2-yr field study was conducted on a silt loam upland soil to determine the effect of incorporation of broiler litter into the soil surface on nutrient and bacterial transport in runoff. The experimental design was a randomized complete block with four treatments and three replications. Treatments were (i) unfertilized control; (ii) surface-appliedbroiler litter at 7.8 Mg ha(-1) without incorporation; (iii) surface-applied broiler litter at 7.8 Mg ha(-1) with immediate incorporation; and (iv) inorganic fertilizer N (urea ammonium nitrate, 32% N) and inorganic fertilizer P (triple superphosphate) at the recommended rate. Phosphorus was surface appliedat 25 kg ha(-1) and N was injected at 101 kg ha(-1) into the soil using a commercial liquid fertilizer applicator. Runoff was collected from small runoff plots (2.4 m by 1.6 m) established at the bottom side of main plots (13.7 m by 6.0 m). Incorporation of broiler litter reduced total N (TN), NO3-N, water soluble P (WSP), and total P (TP) concentrations in runoffby 35, 25, 61, and 64%, respectively, and litter-associated bacteria by two to three orders of magnitude compared with unincorporated treatment. No significant difference in total suspended solids (TSS) in runoffwas obtained between incorporated and unincorporated treatments. Incorporation of broiler litter into the surface soil in the no-till system immediately after application minimized the potential risk for surface nutrient losses and bacteria transport in runoff.     

Nonpoint Source Loading Rates From Selected Land Uses1

ABSTRACT: Loading rates derived from monitoring natural runoff from selected land uses are compared. Land uses selected for evaluation are construction sites, barnyards, and agriculture (dairying). Runoff volumes, sediment, and nutrient fractions were monitored and expressed as areal loadings for comparison purposes. Sediment yield and total phosphorus (total P) loss was directly proportional to runoff (m³/ha). In decreasing order, the loadings for sediment and total P were as follows: construction site > barnyard > general dairying. Runoff from the barnyard area was approximately 10 times higher in soluble phosphorus and ammonium nitrogen than the other land uses under investigation. Areal loss for nitrate nitrogen was highest from the construction site and was attributed to the higher volume of runoff per unit area. Results show that barnyards in a dairying watershed are potentially a major source of sediment and nutrients, especially those dissolved fractions which have the potential for immediate water quality impacts. Relative to general agricultural land, urban construction sites also appear to be a major source of sediment and nutrients. As with barnyard sites, however, the effect of such sites on water quality likely depends on proximity to surface water bodies and other watershed characteristics affecting delivery ratios of contaminants.