间歇淋洗干湿交替条件下氮肥的氮行为研究

采用土柱淋洗试验方法 ,对包膜尿素、尿素和硝酸铵在石碴土和粘壤质石灰性土壤中氮的行为进行了评价。结果表明 ,包膜尿素、尿素和硝酸铵的回收总氮量 (包括淋洗溶液中各种形态氮 ,土壤吸附的肥料氮和残余的肥料氮 )分别为施入总氮量的 90.5%、74.2 %、93.5%和91.5%、58.5%、91.1%。在 1750mL淋洗溶液中NO3--N分别占淋洗溶液中总氮量的 90%以上。在 7次淋洗干湿交替之后 ,土壤吸附的肥料氮 (NH4+-N和NO3--N)均不超过施氮总量的2.1% ;包膜尿素有62.7%和70.8%的氮以颗粒肥料存在于土壤中。 3种氮肥中包膜尿素较尿素和硝酸铵在土壤中释放持续的时间显著延长 ,尿素的氨挥发损失较高 ,硝酸铵淋失较快     

Soil Inorganic Nitrogen Content and Indices of Red Raspberry Yield,Vigor, and Nitrogen Status as Affected by Rate and Source of Nitrogen Fertilizer

Abstract

The single‐year response of soil inorganic nitrogen (N) content and indices of red raspberry (Rubus ideaus L.) yield, vigor, and N status to rate and source of fertilizer N were determined. Twenty‐nine trials were conducted in commercial plantings from 1994 to 1996. Treatments were 0, 55, or 110 kg N ha^?1 as ammonium nitrate or 55 kg N ha^?1 as a slow‐release fertilizer product containing 60% polycoated sulfur‐coated urea and 40% urea. Soil nitrate (NO₃) content frequently increased during the growing season, indicating that soil N supply was nonlimiting. The plant indices were generally insensitive to fertilizer‐N rate under these high‐N fertility conditions. Soil nitrate content measured after berry harvest was frequently excessive even at the recommended N rate and can be used to identify fields with excess N fertility. The slow‐release N fertilizer provided limited benefits compared with use of ammonium nitrate.     

Phosphate and Nitrate Movement Through Simulated Golf Greens

Phosphorus and nitrogen can leach from porous golf greens potentially causing degradation of ground water quality. Agreenhouse experiment was carried out with 52 cm columns (15 cm diam.) made to USGA green specifications and sodded to `Tifdwarf' bermudagrass to determine the effects of fertilizer sources at various rates on P and N leaching. Fertilizers were balanced soluble and controlled-release (polyand sulfur coated) sources at N rates of 0, 12, 24, and 49 kg N ha^-1 and at P rates of 0, 5, 11, and 21 kg ha^-1 every other week for a total of 6 applications. Controlled-release N was from NH₄ and urea and the soluble source N was from KNO₃, urea, and (NH₄)PO₄. Irrigation rate was 0.63 cm per day initially and increased to 1.25 cm per day at week 7. Weeklyleachate collections for 23 weeks were analyzed for P andNO₃-N. Concentrations of N and P were lower in the leachatefor the controlled-release source than for the soluble source. Leaching of P continued for the entire 23 weeks of theexperiment, whereas N was essentially exhausted by week 15indicating that P leaches at a slower rate than N. For the low Prate (5 kg ha^-1) for the controlled-release source there was no increase in P concentration in the leachate compared to control. Thus, low P rates will not result in degradation of water quality due to increased P. For the controlled-release source at the low rate <10% of the P added leached, whereasthe values for N were in the range of 20 to 45% for all ratesand sources. Control treatments resulted in N concentrations in the leachate as high as 26 mg L^-1. Results show thatP leaching is a potential problem only at high rates of solublesources and high irrigation, whereas N is more readily leached.     

Effects of differences in the nitrogen composition of paste-like fertilizer applied as side dressing on growth and the nitrate concentration of spinach (Spinacia oleracea L. var. crispa)

pp. 849–857

To evaluate the effects of differences in nitrogen composition in paste-like fertilizers applied as side dressing, growth and nitrate concentration of spinach (Spinacia oleracea L. var. crispa) grown in containers were examined and compared to standard fertilization using a compound fertilizer (standard, N, P₂O₅ and K₂O applied to the soil at a rate of 120 mg kg^?1). Three kinds of paste-like fertilizer, which differ in nitrogen source, i.e. urea, a 1:1 mixture of urea and residual liquid with fermented molasses (RLFM) and RLFM, were applied to the soil as side dressing at a rate that was 20% below the standard. Dry matter production and N uptake in spinach treated with paste-like fertilizers was comparable to that treated with standard fertilizer, while the nitrate concentration in spinach treated with paste-like fertilizers was lower than that treated with standard fertilizer. Among the paste-like fertilizers, the nitrate concentration in spinach decreased with the increasing rate of RLFM, in which the major N sources were composed of proteins and amino acids.

To understand the possible explanation for better growth and low nitrate concentration in spinach treated with paste-like fertilizer despite the lower application rate, N concentrations of ammonium, nitrate and organic N were assessed temporally by leaching water from fallow plots. At the initial time of incubation, the nitrate concentration in the leaching water from the standard fertilizer was higher than that from paste-like fertilizer treatments. The paste-like fertilizer composed of urea, however, showed a higher concentration of organic N which was supposed to be urea. The fertilized-N of the standard and paste-like fertilizer composed of urea might be immediately eluviated by irrigation. However, N concentration in the leaching water after treatments with paste-like fertilizer composed of RLFM was lower than that of the former treatments, suggesting that fertilized-N might remain localized. The amount of N eluviated during incubation showed a negative correlation with the viscosity of the paste-like fertilizer. The highest viscosity was observed in the paste-like fertilizer composed of RLFM, followed by a 1:1 mixture of urea and RLFM, and the paste-like fertilizer composed of urea was the lowest in viscosity. Therefore, it was suggested that the paste-like fertilizer composed of RLFM or a 1:1 mixture of urea and RLFM showed limited N leaching due to the high viscosity. Therefore, spinach could take up N efficiently.     

灌溉施用氮肥后氮素在土壤中的转化及淋失状况: 土柱模拟研究

A soil column method was used to compare the effect of drip fertigation (the application of fertilizer through drip irrigation systems, DFI) on the leaching loss and transformation of urea-N in soil with that of surface fertilization combined with flood irrigation (SFI), and to study the leaching loss and transformation of three kinds of nitrogen fertilizers (nitrate fertilizer, ammonium fertilizer, and urea fertilizer) in two contrasting soils after the fertigation. In comparison to SFI, DFI decreased leaching loss of urea-N from the soil and increased the mineral N (NH₄⁺-N + NO₃^--N) in the soil. The N leached from a clay loam soil ranged from 5.7% to 9.6% of the total N added as fertilizer, whereas for a sandy loam soil they ranged between 16.2% and 30.4%. Leaching losses of mineral N were higher when nitrate fertilizer was used compared to urea or ammonium fertilizer. Compared to the control (without urea addition), on the first day when soils were fertigated with urea, there were increases in NH₄⁺-N in the soils. This confirmed the rapid hydrolysis of urea in soil during fertigation. NH₄⁺-N in soils reached a peak about 5 days after fertigation, and due to nitrification it began to decrease at day 10. After applying NH₄⁺-N fertilizer and urea and during the incubation period, the mineral nitrogen in the soil decreased. This may be related to the occurrence of NH₄⁺-N fixation or volatilization in the soil during the fertigation process.     

分根区交替灌溉和氮形态影响土壤硝态氮的迁移利用

采用模拟土柱利用15N标记于土层10~20 cm、40~50 cm的方法,并设置不同形态氮肥供应(铵态氮、硝态氮)、灌溉方式(常规灌溉CI、分根区交替灌溉APRI),研究APRI下土壤中不同层次硝态氮的去向以及不同形态氮肥的影响。结果发现,APRI节水34.31%而不显著影响产量(P0.05)。随着15N标记层次下降,番茄植株对15N吸收利用率以及番茄收获后15N在1 m土层内的残留量显著下降,损失率显著增加。CI对10~20 cm土层的15N淋洗作用强于40~50 cm土层,APRI对10~20 cm的15N淋洗作用相对CI减弱,而促进了40~50 cm土层中61.3%的15N向上层土壤迁移。APRI下15N的损失率显著降低,利用率没有大幅度下降。相对于铵态氮肥料,硝态氮供应由于促进了植株生长及对15N的吸收,造成番茄收获后1m土层内15N累积量减少,而损失率与相应铵态氮供应的处理没有显著差异。因此分根区交替灌溉能够减少土壤中硝态氮的淋洗,并能够促进下层土壤硝态氮向上迁移,减少损失,增加植物吸收利用的机会;不同形态氮肥通过影响植物生长而影响土壤中硝态氮的去向。     

Cotton Response to Source and Timing of Nitrogen Fertilization on a Sandy Coastal Plain Soil

Abstract

A three‐year field study was conducted to evaluate cotton (Gossypium hirsutum L.) response to the source and timing of nitrogen (N) on an irrigated coastal plain soil (Lucy loamy sand; Arenic Kandiudults) in south Alabama. Cotton acreage in this region has increased in the past ten years and there was a need for current data describing cotton response to N fertilization. Treatments included N sources, timing of N application (ammonium nitrate), split applications of N (ammonium nitrate and ammonium sulfate), and a no‐N check. Nitrogen sources applied preplant included: (i) ammonium nitrate (34‐0‐0); (ii) ammonium sulfate (21‐0‐0‐24.2); (iii) urea (46‐0‐0); (iv) urea–ammonium nitrate solution (UAN; 32‐0‐0); (v) UAN + ammonium thiosulfate (28‐0‐0‐5). Non‐sulfur sources were applied with and without additional sulfur (S). Times of application were preplant, first true leaf, first square, and first bloom. Two treatments received split applications of N as a 50:50 mixture of ammonium sulfate with urea or ammonium nitrate. Supplemental applications of potassium (K) were evaluated by applying ammonium sulfate in combination with 56 kg K/ha. Yield data showed some minor differences among sources, but overall the results of this three‐year study show that there were no superior N sources. For ammonium nitrate, preplant applications of N were sufficient in two out of three years. Split applications of ammonium nitrate did not improve yields as compared to preplant N. Applying ammonium sulfate with supplemental K or as a 50:50 mixture with ammonium nitrate or urea did not improve yields as compared to ammonium sulfate or ammonium nitrate applied alone. Lint quality was not affected by N fertility treatments.     

Effects of Slow‐Release Fertilizers on Tomato Growth and Nitrogen Leaching

Tomatoes (Lycopersicon esculentum Mill.) were grown in 9.46‐L plastic pots in a glasshouse for evaluation of their growth and nitrogen (N) losses through leaching. Plants were fertilized with either ammonium nitrate (AN) or one of three slow‐release N fertilizers. The slow‐release N fertilizers were Georgia Pacific liquid 30‐0‐0 (L30), Georgia Pacific granular 42‐0‐0 (N42), and Georgia Pacific granular 24‐0‐0 (N24). Each fertilizer was applied at 112 low N rate (L) and 224 high N rate (H) kg N ha^?1. The pots were filled with either a sandy soil from Florida or a loam soil from Georgia. Increasing the N rate did not influence shoot biomass at 19 days after transplanting (DAT) and increased biomass production at 77 DAT. Shoot biomass differed significantly among fertilizer treatments. The accumulation of N in shoots was significantly influenced by fertilizer source, rate, and soil type. The plants grown in the loam soil accumulated significantly more N than those grown in the sandy soil with the same treatment. In the loam soil, the highest and lowest N accumulations occurred in the N42‐H and N24‐L treatments, respectively; and in the sandy soil the corresponding treatments were AN‐H and N24‐L. The amount of N leached varied with the different fertilizers, soils, and time. The net leaching of N ranged from ?0.4% to 6.3% of the fertilizer N applied for the loam soil and 6.5% to 32.9% for the sand soil. The net amount of N leached from the loam soil at both high and low application rates declined in the following order: AN > N24 > N42 > L30; the corresponding order for the sandy soil was AN‐H > N42‐H > L30‐H > N24‐H. L30 had the least leaching potential, and ammonium nitrate had the most. Slow‐release fertilizers had significantly less leaching N than did ammonia nitrate.     

不同水肥措施下华北露地菜地氮淋溶特征

华北地区典型一年两季露地蔬菜种植系统,蔬菜生长季水热同季、种植管理中水氮供应充足且往往过量,造成大量氮素淋溶到深层土壤,不仅造成水肥资源利用率低,对地下水质也造成威胁。本文以华北潮褐土黄瓜-白菜一年两季典型露地蔬菜为研究对象,利用田间试验研究不同氮肥用量及优化措施(包括抑制剂、生物炭、秸秆还田)以及控制灌溉量对蔬菜产量、土壤氮淋溶及氮平衡的影响。研究结果表明:1)华北典型露地菜地氮肥主要损失去向为深层土壤中积累及氮淋溶。2)农民常规施肥处理[黄瓜季和白菜季各施550 kg(N)·hm~(-2)]淋洗出80cm土壤剖面的总氮占当季氮肥施用量的10.0%,减氮20%和50%分别使总氮淋溶量降低23.8%和45.6%;减氮20%对蔬菜产量没有显著影响,减氮50%对水肥需求量较高的黄瓜产量有显著影响(减产19.6%)。3)减氮20%配合脲酶抑制剂和硝化抑制剂、施用生物炭和添加秸秆还田分别使全年总氮淋溶量比常规水肥处理降低40.7%、43.0%和34.3%,而对蔬菜产量没有显著影响。4)减少灌溉量15%和30%分别使总氮淋溶比常规水肥处理降低43.1%和50.5%,水氮协同调控对降低氮淋溶效果显著;对需水量较高的黄瓜季,灌溉量降低30%黄瓜产量显著降低13.9%。5)高量水肥投入条件下连续种植蔬菜3年6季后,0～80cm土壤剖面硝态氮积累量占0～200 cm土壤剖面积累量的38.2%～50.7%,土壤剖面积累了大量硝态氮而且向深层土壤中移动。因此,合理控制水肥管理,特别是减氮结合脲酶抑制剂和硝化抑制剂配合水分管理,是经济可行的有效阻控土壤氮淋溶的措施。     

Normal and Flush Irrigation Effects On Phosphorus Leaching from Simulated Golf Greens in the Greenhouse

Fertilizer nutrients have the potential to leach from porous golf greens, especially when “flushing” is practiced where 8 or 10 cm of irrigation is applied. A greenhouse experiment was carried out with 52 cm columns (15 cm diameter) made to United States Golf Association green specifications and sodded to ‘Tifdwarf’ bermudagrass to determine the amounts of phosphorus leached for two fertilizer sources (20–20–20 and superphosphate) at three rates (0, 5, and 11 kg ha^?1 added every other week for a total of 6 weeks) and two irrigation schemes (normal irrigation at 6.3 mm day^?1 and the same irrigation with an additional four flushes of 8 cm each). Weekly leachate collections for 29 weeks were analyzed for soluble P. Flushes resulted in higher P concentrations in the leachate where as much as 40% of the added P was recovered in the leachate. In contrast, normal irrigations resulted in less than 10% of the P applied moving through the columns. The two fertilizer sources gave essentially similar results. The higher P rate caused higher concentrations of P in the leachate, but P concentrations for the low rate for normal irrigation were not different than the control. For flushes, the extractable P in the top 15 cm of the rooting media was lower than for normal irrigation and the extractable P in the columns was higher. Results indicate that low rates of P should be applied to golf greens and, if flushing is practiced, it should be done when little P is in the rooting media.     

Effects of polyolefin‐coated fertilizer on nutritional quality of spinach plants

Pot experiments were conducted in order to evaluate the effects of four different urea or ammonium containing polyolefin‐coated fertilizers (POCFs) on the nutritional quality of spinach (Spinacia olèracea L.) and to investigate the mechanisms of these effects in comparison with conventional, rapidly available fertilizer. Compared to the conventional fertilization method yield was decreased in all the four POCF treatments due to less available fertilizer nitrogen (N) and/or realized ammonium nutrition. However, application of POCFs decreased oxalate and nitrate contents and increased ascorbate concent in spinach. Decreased oxalate and nitrate contents were attributed to lower nitrate availability in the soil having caused by the controlled‐released characteristic of POCFs and/or ammonium nutrition. Increased ascorbate content was due to both decreased oxalate and decreased nitrogen contents of the spinach plants. It was concluded that band applications of urea or ammonium containing POCFs improved the nutritional quality of spinach due to realized ammonium nutrition and/or less amount of available fertilizer N.     

Leaching and Recovering of Nitrogen Following N Fertilizers Application to the Soil in a Laboratory Study

Following soil fertilization, nitrogen (N) is partially lost. The objective of this study was to evaluate leaching and recovery of N after addition of fertilizers to the soil. Two experiments were conducted in leaching columns submitted to frequent water percolations. In the leaching experiment, urea, ammonium nitrate, and six coated N fertilizers were utilized; in the N recovery experiment, treatments consisted of urea, potassium nitrate, ammonium sulfate, and ammonium nitrate, combined or not with percolation. Percolations were performed weekly with quantification of ammonium and nitrate in the percolated. The recovered N was obtained by summing total N percolated with N in the soil. Nitrate leaching was highest from amide-N fertilizers, with no differences between them showing that coating urea was not efficient to decrease N leaching. Nitric fertilizers had the lowest recovery of N, probably due to the occurrence of denitrification caused by the frequent water percolation.     

Leaching of nitrogen forms from controlled‐release nitrogen fertilizers

Abstract

Application of soluble forms of nitrogen (N) fertilizers to sandy soils may cause leaching of nitrate N (NO₃‐N) resulting in contamination of groundwater. The leaching loss of N may be reduced to a certain extent by the use of controlled‐release N formulations. A leaching column study was conducted to evaluate the leaching of urea, ammonium N (NH₄‐N), and NO₃‐N forms from selected urea‐based controlled‐release formulations (Meister, Osmocote, and Poly‐S) and uncoated urea under eight cycles of intermittent leaching and dry conditions. Following leaching of 1,760 mL of water (equivalent to 40 cm rainfall) through the soil columns, the recovery of total N (sum of all forms) in the leachate accounted for 28, 12, 6, or 5% of the total N applied as urea, Poly‐S, Meister, and Osmocote, respectively. Loss of urea‐N from all fertilizer sources was pronounced during the initial leaching events (with the exception of Meister). Cumulative leaching of urea‐N was 10% for uncoated urea while <1.7% for the controlled‐release formulations. Cumulative leaching of NH₄‐N was 6.2% for uncoated urea while <0.5% for the controlled‐release formulations. Cumulative leaching loss of NO₃‐N was 3.78% for Osmocote, 4.6% for Meister, 10.4% for urea, and 10.5% for Poly‐S. This study demonstrates a significant reduction in leaching of N forms from controlled‐release formulations as compared to that from the soluble form.     

QUANTITY AND QUALITY OF CITRUS ON A CITROMELO ROOTSTOCK AS AFFECTED BY DIFFERENT TYPES OF N FERTILIZATION (CHEMICAL AND ORGANIC)

With respect to the important effects of nitrogen (N) on plant growth and fruit production, a five-year experiment was performed to evaluate the effects of different sources of N fertilization including chemical and organic on the quantity and quality of citrus fruit. Using five-year old trees, different types of fertilization including ammonium sulfate, urea coated with sulfur, ammonium nitrate and manure were tested using seven treatments in five replicates from 2002 to 2007. Different plant quantitative and qualitative parameters were determined. The most effective strategy on fruit yield production was the use of urea coated with sulfur and manure with 92.46 kg ha^?1 fruit yield followed by ammonium sulfate and manure (87.06 kg ha^?1) and ammonium sulfate (86.43 kg ha^?1). The combination of mineral and organic fertilization may be the most suitable fertilization strategy for citrus production.     

NITRATE LEACHING AND TURF QUALITY IN NEWLY SODDED ST. AUGUSTINEGRASS

There are increasing concerns about the fate of fertilizers applied to lawn grasses. The objectives of this research were to evaluate nitrate leaching and turf response to nitrogen (N) treatment and irrigation in newly sodded St. Augustinegrass. The research was conducted in Citra, FL in 2006 and 2007. Nitrogen was applied at three rates day of sodding and again at 30 days after planting. Analysis of variance indicated there were no differences in nitrate-N (NO₃–N) leached due to N treatment or timing. During the establishment period, NO₃–N loading was greater than reported for established turf and could possibly present a source of nitrate contamination. Turf quality and color were above or just below an acceptable score at all N rates. Due to the potential for high amounts of NO₃–N leaching in new sod, it is not recommended to apply N fertilizer to St. Augustinegrass in the first 30–60 days after planting.     

不同水肥管理模式对太湖地区稻田土壤氮素渗漏淋溶的影响

针对当前我国水稻生产中日益严重的水资源短缺及稻田土壤氮素渗漏淋溶引发的面源污染问题,本研究通过设置2种灌溉方式及4个施氮水平的双因子交互试验,探讨了不同水肥处理对稻田土壤氮素渗漏淋溶的影响.结果表明,稻田20 cm处渗漏水中NH+4-N浓度与施氮量呈正相关关系,减少氮肥施用量,可降低2％～35％的NH+4-N浓度,而80 cm处NH+4-N浓度与施氮量无相关关系;稻田20 cm、80 cm处渗漏水中NO3-N浓度均与施氮量呈正相关关系;控制灌溉显著提高了稻田80 cm处渗漏水中NO-3-N浓度,增幅达31％,但由于其水分渗漏量少,NO3-N淋溶量较常规灌溉仍降低16％～ 49％; NO3-N是稻田中氮素渗漏淋溶的主要形式,占氮素渗漏淋溶总量的77％～92％;减氮施肥条件下,NO3-N渗漏淋溶量降低14％～56％.控灌减氮措施可很好地协调产量效益与水体环境效益,是适宜太湖地区的环境友好型水肥管理模式.     

不同氮肥形态的氨挥发损失比较

利用从德国引进的农田土壤氨挥发风洞法测定系统,对不同N肥形态的肥料进行对比实验。结果表明,在相同施N量条件下,硝酸铵、硝酸铵钙、硫硝酸铵的氨挥发损失分别比尿素减少22.5%、3.2%和8.3%,不同N肥的氨挥发损失差异很大。相同条件下,尿素的氨挥发损失为25.7%,添加DMPP后氨挥发损失为27.6%;硫硝酸铵的氨挥发损失为18.6%,添加DMPP后为20.6%;添加DMPP对尿素和硫硝酸铵的氨挥发影响不显著。     

控释氮肥减量对糜子产量、氮素利用及土壤氮含量的影响

针对黄土高原旱作区糜子生产中氮肥种类单一、肥料利用效率低的问题,本试验以当地习惯施氮尿素N 120kg/hm²(TN)为对照,设置控释氮肥N 120kg/hm²(T1)、108kg/hm²(T2)、96kg/hm²(T3)、84kg/hm²(T4)、72kg/hm²(T5)和不施肥(T0)七个处理,探究不同控释氮肥处理下土壤全氮、微生物量氮、硝态氮和铵态氮含量的变化规律,分析糜子成熟期氮素积累分配、氮素利用效率及产量对控释氮肥的响应,以期为建立旱地糜子控释氮肥一次性基施轻简栽培技术提供支撑。结果表明：与施用尿素相比,等量控释氮肥可以提高糜子抽穗期和成熟期土壤全氮、微生物量氮、硝态氮和铵态氮含量分别达0.38%~5.51%、1.76%~7.63%、5.41%~11.80%和4.04%~14.77%,其中硝态氮和铵态氮含量两年均显著高于TN,随着控释氮肥减量糜子田各形态氮素均呈降低趋势,减氮量达20%以上时土壤硝态氮和铵态氮含量均显著低于TN处理。施用控释氮肥可以提高糜子成熟期氮素积累量1.97%~3.21%,增加糜子氮素向籽粒中的分配比例0.55%~1.18%,控释氮肥减量20%以上时糜子氮素积累量显著低于尿素全量基施处理。与普通尿素相比,控释氮肥提高了糜子氮肥表观利用率、氮肥偏生产力及氮肥农学利用率,增幅分别为3.29%~4.59%、3.88%~4.14%和5.01%~7.63%,其中氮肥偏生产力处理间差异达显著水平,随着控释氮肥减量糜子氮肥表观利用率、氮肥偏生产力及氮肥农学利用率均呈上升趋势。施用控释氮肥通过增加单位面积穗数和穗重显著提高了糜子产量两年分别达3.88%和4.47%,控释氮肥减量20%以下时糜子产量与尿素差异不显著。相关性分析结果表明,糜子氮素积累量与产量呈极显著正相关,氮素利用效率指标与土壤硝态氮含量相关性最强。综上所述,施用控释氮肥较尿素可显著提高糜子生育中后期土壤供氮能力,促进糜子对氮素的吸收利用进而增加产量,且在适量减氮20%时并未显著降低糜子产量,因此控释氮肥在糜子生产中有较大的应用前景及减氮潜力。     

华北平原农田裂缝对硝态氮淋溶的影响

土壤干缩开裂是常见的自然现象。目前关于土壤干缩开裂的研究主要集中于裂缝的最终形态特征,并且以室内试验为主。本研究通过室外大田试验,结合动态计算机图像分析及水氮运移模拟软件WHCNS,研究土壤干缩开裂的动力学过程、特征及其对农田水氮运移的影响。利用原位熔化石蜡浇筑得到了裂缝三维结构形态,借助三维激光扫描仪量化裂缝的几何特征,发现每平米裂缝平均长度为4.58m,裂缝上表面平均宽度为5.72 mm,平均深度为9.06 cm。基于三维扫描仪提取得到的裂缝几何参数,通过WHCNS仿真模拟,发现相较于无裂隙情况,裂隙的存在分别增加了传统施肥和优化施肥情况下97.40%和256.43%的硝态氮淋失量;与优化施肥模式相比,传统施肥模式更容易造成硝态氮的淋失风险。在模拟灌溉模式对硝态氮淋洗情况的影响时,其差异不明显;强降雨的设置同样增加了硝态氮的淋失风险,导致硝态氮的年均淋洗量增加83.61%。裂缝的存在严重影响农田作物对肥料的吸收和利用,通过优化施肥量、更改灌溉模式以及避免强降雨前施肥都可以减少肥料的损失。     

氮肥施用对砖红壤硝态氮和盐基离子淋失特征的影响

氮肥品种的合理选用对作物增产增收、 土壤酸化改良有重要的影响。本文以海南省海口市观澜湖采集的砖红壤为研究对象,采用室内土柱模拟试验,对尿素、 硝酸铵和硫酸铵3种氮肥处理下砖红壤硝态氮及盐基离子（Ca2+、 Mg2+、 K+、 Na+）淋失特征进行了研究。结果表明, 1）硝态氮累积淋溶量表现为硫酸铵硝酸铵尿素N0,且硝态氮的淋溶量与施肥量呈正相关关系,整个淋溶过程中硝态氮累积淋溶量（y kg/hm2）与施肥量（x kg/hm2）之间满足线性方程 y=3.3064x+315.74（R2=0.8848）; 2）尿素、 硝酸铵、 硫酸铵处理整个淋溶过程的盐基离子淋溶量均表现为 Ca2+Mg2+K+Na+,且盐基离子淋溶总量（kg/hm2）表现为硫酸铵（1821.12）硝酸铵（1080.27）尿素（872.24）N0（417.23）; 3）砖红壤盐基离子迁移速率表现为硫酸铵（26.28%）硝酸铵（13.37%）尿素（11.78%）,尿素、 硝酸铵和硫酸铵处理分别以线性方程 y=0.1178x+123.18（R2=0.9121）、 乘幂方程 y=15.634x0.4423（R2=0.9259）和对数方程 y=128.38e0.0007x（R2= 0.9244）的拟合度最高。