太湖地区水稻季氮肥的作物回收和损失研究

在太湖地区水稻土上,采用田间微区15N示踪试验研究了不同氮磷肥配合下水稻季氮肥去向以及残留肥料氮在麦季的吸收利用。结果表明,水稻当季作物对肥料氮的回收率为29%～39%,土壤残留肥料氮的后效很低,后季冬小麦仅利用土壤残留肥料氮的2.4%～5.2%。经过连续两个稻麦轮作,0—60cm土壤中残留肥料氮占施氮量的11%～13%,绝大多数在0—20 cm表层土中。水稻季施用的肥料氮向耕层以下移动很少,20—60 cm土层中累积肥料氮仅占施氮量的0.6%～1.1%,主要发生在小麦季及水稻泡田时期,肥料氮损失占施氮量的47～54%,氨挥发和硝化反硝化气态损失是主要途径。高氮和高磷处理没有增加作物产量和氮肥利用率,过量施氮或施磷无益于作物增产和氮肥吸收利用。     

旱地土壤中残留肥料氮的动向及作物有效性

氮素是作物生长最重要的必需元素之一。合理施用氮肥能促进作物生长并提高产量,但是,过多施用氮肥则抑制作物生长并导致大量的肥料氮残留在土壤中,这部分氮素不但会引起土壤养分不平衡,而且为生态环境带来潜在威胁,因此,研究残留氮的动向及作物有效性可为合理施用化肥氮、高效利用土壤残留氮素和减少残留氮素的损失提供依据。应用~(15)N示踪技术,通过4年定位试验,研究了黄土高原南部旱地冬小麦/夏玉米轮作过程中土壤残留肥料氮的变化及作物吸收利用。在冬小麦和夏玉米轮作的第一个周期,为了制造高肥料氮残留背景,于冬小麦播种前向微区施入240 kg hm~(-2)的~(15)N标记氮素;在夏玉米拔节期,为了研究氮肥施入对残留肥料氮的影响,设置0和120 kg hm~(-2)两个氮水平,以普通尿素施入微区。在第2至第4个轮作周期内,为了分析残留肥料氮的动向及其对作物的有效性,微区内不施任何肥料。结果发现,冬小麦播种前施用的~(15)N标记氮肥于收获期在0~200 cm土壤剖面中均有残留,但大部分累积在0~40 cm土层中,累积总量达到200.9 kg hm~(-2),占当季施入量的83.7%。在随后的夏玉米生长季残留的肥料氮迅速减少,之后随生长季的后移缓慢减少,然后保持相对稳定。经过4年的冬小麦/夏玉米轮作,0~300 cm土壤剖面仍残留大量的~(15)N肥料,后季不追施氮肥和追施氮肥处理的残留量分别为47.1 kg hm~(-2)和54.0 kg hm~(-2)。可见,有一部分肥料氮被固定在土壤有机质中。作物对残留氮的回收量逐年减少,且因后季追施氮肥与否而异,4年中作物对肥料氮的总利用率不追施氮肥和追施氮肥处理的分别为46.9%和50.4%,其中在第1个轮作周期中,小麦和玉米的总利用率分别41.6%和42.0%,后3年利用率分别仅有5.3%和8.4%;4年中残留~(15)N的损失率分别达38.1%和29.7%,其损失主要发生在第1个轮作周期的夏玉米生长季节。说明,在旱地土壤上,氮肥的残留是不可避免的,残留肥料氮的有效性较低,只有少量被作物逐年吸收,一部分以有机形态残留在土壤剖面中,另一部分发生了无效损失。后季追施氮肥可促进作物对土壤残留肥料氮的吸收且增加肥料氮在土壤中的保留,减少残留肥料氮的无效损失,但是以自身的大量损失为代价的。     

不同秸秆还田方式下黑土玉米田肥料氮素去向

探究不同秸秆还田方式下肥料氮在连续两季作物系统中的去向，为黑土地保护下的氮肥管理提供重要依据。于2020—2021年在吉林梨树开展大田微区试验，设置无秸秆还田 (CK)、深翻还田 (DTS)、免耕覆盖还田 (NTS) 3种秸秆还田方式，每种方式下设置2个施氮水平：180 kg?hm-2(N1)和270 kg?hm-2(N2)。结果表明：当季和第二季玉米成熟期植株氮分别有38.0%~46.8%和12.9%~18.6%来源于15N标记氮肥。肥料氮当季平均利用、残留和损失率分别为32.4%~43.9%、32.8%~51.4%和13.2%~32.7%，秸秆覆盖配施适量氮肥 （180 kg?hm-2）处理下肥料氮当季利用率显著提高29.5%，而秸秆深翻还田则使肥料氮在土壤中的残留率显著增加18.2%。当季施用肥料氮仍有8.5%~14.9%被第二季玉米吸收利用，两季累积利用率达40.9%~58.8%，在高氮（270 kg?hm-2）下秸秆深翻还田显著提高肥料氮的第二季利用率及累积利用效率。综上，秸秆覆盖还田配施适量氮肥有利于提高肥料利用效率，而秸秆深翻还田更有利于高施氮量下土壤对肥料氮的保持，增加其被下季作物利用的机会，两者均能显著减少氮的损失。     

太湖和滇池流域保护地蔬菜氮肥去向研究

为了研究化肥氮在保护地土壤-蔬菜系统中的当季利用与损失,在浙江嘉兴和云南昆明15个点位上进行15N田间微区试验。结果表明,保护地莴苣化肥氮当季利用率为8.32%~14.52%,保护地西芹化肥氮当季利用率为6.34%~13.85%,保护地结球生菜化肥氮当季利用率为11.34%。相同土壤、同一种类蔬菜保护地种植中,随着保护地种植年限的增加,蔬菜对化肥氮当季利用率显著降低。莴苣和西芹吸收化肥氮和土壤氮的比例在不同种植年限保护地土壤上差异不显著。当季蔬菜收获后,0～20 cm土层15N丰度和化肥氮残留量显著高于20 cm以下各土层。在保护地莴苣种植系统中,施入土壤中的化肥氮有18.98%～42.5%损失。在保护地西芹种植系统中,有11.7%~18.9%损失。在保护地生菜种植系统中,施入土壤中的化肥氮有16.0%损失。     

化肥氮对冬小麦氮素吸收的贡献和土壤氮库的补偿

  【目的】  小麦对氮素的吸收消耗了土壤氮库，土壤中残留的化肥氮则可补偿土壤氮库的消耗，综合考虑这两方面的影响，核算施氮量和秸秆还田对小麦当季土壤氮库盈亏的影响。  【方法】  收集1980年以来国内报道的小麦15N示踪试验的研究结果，分析化肥氮和土壤氮对小麦当季氮吸收的贡献，小麦当季氮吸收、化肥氮的去向、土壤氮库的盈亏分别与施氮量之间的关系，以及秸秆还田对小麦当季土壤氮库盈亏的影响。  【结果】  施氮量与化肥氮对小麦当季氮吸收的贡献之间呈显著正相关 (P = 0.029)，而与土壤氮的贡献之间呈显著负相关 (P = 0.031)。小麦当季氮素吸收源于土壤的比例约为2/3，源于化肥的比例约为1/3，追施氮对小麦氮吸收的贡献约是基施氮的1.5倍。施氮量与氮肥有效率 (氮肥利用率+氮肥残留率) 之间呈极显著负相关 (P = 0.004)，而与氮肥损失率之间呈极显著正相关 (P < 0.001)。在秸秆不还田和还田条件下，小麦季土壤氮库的盈亏均与施氮量之间呈极显著正相关 (P ≤ 0.001)。  【结论】  在施氮量为N 60～500 kg/hm2时，小麦吸收的氮素1/3来自化肥，2/3来自土壤。冬小麦季化肥氮的3个去向为:地上部吸收、土壤残留和损失，其所占比例分别约为36%、33%和31%。在秸秆不还田和还田条件下，土壤氮库达到平衡的施氮量分别为N 308和233 kg/hm2。     

太湖地区不同轮作模式下的稻田氮素平衡研究

采用田间微区15N示踪,研究了太湖地区稻田不同轮作模式(紫云英-水稻轮作、休闲-水稻轮作、小麦-水稻轮作)和施氮水平(0、120 kg·hm?2、240 kg·hm?2、300 kg·hm?2)下水稻对氮肥的吸收利用效率及土壤氮素残留特征。结果表明,水稻吸收的氮素来自肥料的比例为20.9%~49.6%,休闲-水稻轮作模式下水稻产量的获得更加依赖无机氮肥的大量投入。当季水稻对肥料氮的利用率为25.0%~41.5%,肥料氮的土壤残留率为13.4%~24.6%,其中90%以上的土壤残留肥料氮集中在0~20 cm土层,在土壤剖面中的残留率随土层深度增加而迅速降低,30~40 cm土层的肥料残留量仅占氮肥施用量的0.2%~0.7%。紫云英?水稻轮作和休闲?水稻轮作模式下氮肥利用率和土壤残留率均在施氮240 kg·hm?2时达到最大值,其氮肥利用率显著高于小麦?水稻轮作55.6%和66.0%。稻季施氮240 kg·hm?2时,小麦-水稻轮作模式下的氮肥利用率、土壤残留率以及总回收率显著最低,损失率显著最大;紫云英?水稻轮作模式下的氮肥损失率最小,分别小于休闲?水稻轮作和小麦-水稻轮作13.9%、39.2%。不同轮作模式下,水稻籽粒产量随施氮量的增加而增加,稻季施氮240 kg·hm?2时,紫云英?水稻轮作下水稻籽粒产量显著高于休闲?水稻轮作和小麦?水稻轮作,小麦?水稻轮作籽粒产量虽略高于休闲?水稻轮作,但没有达到显著水平。本研究认为,选择紫云英还田配施氮肥240 kg·hm?2,既可以保证水稻氮肥利用率而获得高产,又能减少氮肥损失而带来的环境风险,是一种值得在当地大力推广的耕作制度。     

稻麦轮作条件下化肥氮素对土壤氮的替换作用

采用盆栽实验，第1季水稻生长期内施入^15N标记硫酸铵，在以后的各季作物生长期内使用非标记硫酸铵，连续5季实施稻麦轮作，在每一季结束后采样测定^15N标记硫酸铵的去向，并利用土壤中^15N残留量数据计算了不同施肥强度下土壤氮被替换的速率，以此反映人们对土壤氮素干预的程度。计算结果是：假设肥料氮一旦进入土壤就看成是土壤氮，那么肥料氮替换50％的土壤氮因施肥量不同需要7～60a（14～121季）；如果将作物成熟以后残留于土壤的肥料氮看成是土壤氮，那么替换20％的土壤氮因施肥量不同需要3～7a（5～15季），替换30％的土壤氮需要无限长时间。     

施入~(15)N标记氮肥在长期不同培肥土壤的残留及其利用

采用盆栽试验和短期矿化培养相结合的方法,研究了施入15N标记氮肥(+N)及其与秸秆配施(+1/2N+1/2S)在3种长期(19年)不同培肥土壤(即:No-F,长期不施肥土壤;NPK,长期施用NPK化肥土壤;MNPK,长期有机无机肥配施土壤)中的残留及其矿化和作物吸收特性。结果表明,第一季小麦收获后,+1/2N+1/2S处理下三供试土壤和+N处理下的NPK和MNPK土壤残留肥料氮(残留15N)中有82.6%~95.1%以有机态存,而+N处理下No-F土壤残留15N有47.7%以矿质态存在。经过28 d矿化培养后,与NPK土壤相比,MNPK土壤氮素净矿化量显著增加,增幅为39%~49%;NPK和MNPK土壤残留肥料氮(残留15N)矿化量为1.23~1.90 mg kg-1,占总残留15N的2.78%~5.53%,均显著高于No-F土壤。与+N处理相比,+1/2N+1/2S处理显著提高了3供试土壤氮素净矿化量,但两施肥处理对NPK和MNPK土壤残留15N矿化量无显著影响。+N处理下No-F土壤残留15N的利用率为20%,显著高于NPK(9%)和MNPK(12%)土壤。两种施肥处理下,MNPK土壤残留15N的利用率均显著高于NPK土壤。短期培养期间土壤氮素矿化量和第二季小麦生育期作物吸氮量呈显著性正相关,而残留15N矿化量和第二季小麦吸收残留15N量间无显著性相关关系。长期有机无机配施可以提高土壤残留肥料氮的矿化量及有效性。     

黄土高原旱地夏季休闲期~(15)N标记硝态氮的去向

夏季休闲是黄土高原旱地小麦常见的蓄纳雨水、恢复地力的措施。随着氮肥用量的增加,一季小麦收获后,旱地土壤剖面累积的硝态氮量不断增加,休闲期间降雨量高,残留硝态氮的去向是值得研究的问题。利用~(15)N标记法研究小麦收获后残留肥料氮在黄土高原旱地(陕西长武)夏季休闲期间的去向,即小麦收获后在微区土壤表层(0~15 cm)施入~(15)N标记的硝态氮肥(30 kg hm~(-2)(以纯氮计),约相当于当地小麦一季作物收获后土壤残留肥料氮量),休闲结束后,采集0~200 cm土壤样品,测定了土壤全氮、硝态氮含量及其~(15)N丰度。结果表明,小麦收获(即休闲开始)时0~200 cm土壤剖面硝态氮累积量在205~268 kg hm-2之间(平均244 kg hm~(-2)),累积量较高。夏季休闲期间降水量为157 mm,属欠水年,但休闲结束后,~(15)N标记肥料氮向下迁移已达80 cm土层,下移深度在45~65cm之间,说明,旱地休闲期间硝态氮的淋溶作用不可忽视。夏季休闲结束后,加入的~(15)N标记肥料氮平均损失率为28%,损失机理值得进一步研究。     

适宜施氮量降低京郊小麦-玉米农田N2O排放系数增加产量

为明确京郊地区小麦-玉米轮作农田的N_2O排放特征,寻求既能减少N_2O排放又保证粮食产量的切实有效措施,以京郊地区冬小麦-夏玉米轮作农田为研究对象,运用静态箱法对8个施氮水平的农田N_2O交换通量进行了连续一年对比研究,每季作物施肥量分别为N0(0 kg/hm~2),N1(50 kg/hm~2),N2(100 kg/hm~2),N3(150 kg/hm~2),N4(200 kg/hm~2),N5(250 kg/hm~2),N6(300 kg/hm~2),和N7(400 kg/hm~2)。在N0-N7施氮量条件下冬小麦季N_2O排放量为0.08~0.52 kg/hm~2;夏玉米季0.26~3.70 kg/hm~2。整个轮作周期,小麦季各处理N_2O排放损失率为0.05%~0.13%;玉米季0.78%~1.02%。在京郊地区冬小麦-夏玉米轮作体系中夏玉米季氮肥施入农田土壤后,土壤N_2O排放通量高于小麦季。京郊农田土壤N_2O排放通量表现出明显的季节性和日变化规律。综合考虑本试验条件下施肥量、N_2O排放量和京郊地区潮土农田小麦-玉米产量,研究认为该轮作体系中每季作物的施肥量为N4(200 kg/hm~2)比较合理,可为合理施肥及估算中国农田温室气体排放量提供参考。     

Decomposition of barley straw in a subarctic soil in the field

Summary The mass loss and N dynamics of barley stems and leaves, placed on the soil surface or buried, were examined over two summers. There was little difference in mass loss or N dynamics in straw placed 7.5 or 15 cm deep. However, the surface straw lost mass much more slowly and immobilized more N for a longer time than the buried straw. Filter paper had a slow rate of mass loss initially, but once started, lost mass much more rapidly than either the barley stems or leaves. Loss of mass was closely correlated with the cellulose loss in straw, whether buried or placed on the soil surface. The sustained rate of mass loss was 6.3 and 7.0% month^-1, respectively, for surface and incorporated leaves compared with 3.5 and 4.3% month^-1, for surface and incorporated stems. The greater loss sustained by the leaves was attributed to a lower lignin content rather than a higher N content, because the addition of N to the straw after 30 days in the field failed to increase CO₂ evolution. Maximum net N immobilization occurred within 30 days for all the barley straw, except for the stems placed on the ground surface, which did not reach maximum N immobilization until the second summer. Immobilization and mineralization of N were estimated for a 3000 kg ha^-1 grain crop. Surface straw immobilized 3.8 kg N ha^-1 in the 1st year and 9 kg N ha^-1 in the 2nd year, whereas incorporated straw immobilixed 3.5 kg N hs^-1 in the 1st year and mineralized 4.5 kg N ha^-1 in the 2nd year. Thus, in Alaska, residue management does not affect N fertilizer requirements in the 1st year, but an additional 13.5 kg N ha^-1 is required for surface residues in the 2nd year.     

Nitrogen addition change soil N pools with litter removal or not in subtropical forest

ABSTRACT

There are many nitrogen (N) pools in soil, so their availability and different status can give information about bulk soil response to N deposition. However, the different size of N pools in forest soils and the relationship between them have not been well studied under N deposition when considering the role of litter. Here soil in an N-deposition experiment carried out for 5 years in a broad-leaved forest was used as an object to study the response of N pools to N deposition by stepwise extraction using water or solutions containing 0.5 M K₂SO₄, 2.5 M H₂SO₄ (LPI), or 13 M H₂SO₄ (LPII), and calculation of recalcitrant (RC) N pool. Under N control (CT), soil with the presence of litter had a higher N of 23.8–106.8% in the first four pools, but lower of 80.6% in recalcitrant N pool compared with soil with the absence of litter. In the absence of litter, N addition increased soil N in labile pool but decreased N in the RC pool compared to CT and these impacts were greater at high added N (HN) than low-added N (LN) rates. However, in the presence of litter, LN increased the amount of N in the K₂SO₄- extracted pool and HN reduced that in the water extracted pool. Additionally, LN and HN increased TN in the RC pool and HN increased the total soluble N (TSN) in the LPI and LPII pool. N changes in the water extraction pool were attributed to inorganic N, whereas they were NH₄ ⁺ and soluble organic N (SON) in the K₂SO₄-extracted, LPI, and LPII pools. In the presence of litter, HN increased the SON concentration in the K₂SO₄, LPI, and LPII extractions; thus, SON may be a potentially important N form for N availability. These results suggested that N additions improve the accumulation of N in RC pool with the presence of litter. The different effects of N additions on soil N pool or N form in each pool depend on litter present or not.     

Effect of Baythroid on nitrogen transformations in soil

Laboratory incubation experiments were conducted in soil to study the influence of the insecticide Baythroid on immobilization-remineralization of added inorganic N, mineralization of organic N, and nitrification of added NH _inf4 ^su+ -N. Baythroid was applied at 0, 0.4, 0.8, 1.6, 3.2, and 6.4 g g^-1 soil (active ingredient basis). The treated soils were incubated at 30°C for different time intervals depending upon the experiment. The immobilization and mineralization of N were significantly increased in the presence of Baythroid, the effect being greater with higher doses of the insecticide. Conversely, nitrification was retarded at lower doses of Baythroid and significantly inhibited at higher doses. The results of these studies suggest that excessive amonts of insecticide residues affect different microbial populations differently, leading to changes in nutrient cycling.     

施用生物炭对农田土壤氮素转化关键过程的影响

生物炭作为一种土壤改良剂,施入土壤后不仅能有效改善土壤结构,提高土壤对营养元素的吸附能力,还可减少温室气体的排放,增强生物固氮能力,因此在农业生产和缓解气候变化方面有着巨大的应用前景。生物炭的输入将直接影响农田土壤氮素的循环和转化,本文结合国内外大量文献,综合分析总结了施用生物炭对土壤氮素转化过程的影响,重点从生物炭对土壤氮素矿化、氮素损失以及硝化、反硝化作用和生物固氮过程的影响过程展开阐述。并在此基础上,提出今后应加强生物炭对氮素转化的作用机理及对环境的长期正负效应研究,特别是对相关微生物群落的多样性、丰度以及土壤酶活性方面的研究,同时提出相关研究应建立在统一的生物炭标准之上,以明确区分生物炭的作用效果及其作用机制。     

Efficiency of nitrogen fertilization in sweet sorghum

Abstract

In spite of a high N requirement, sweet sorghum hasn't shown a consistent response to N fertilization. This research was designed to study the effect of N fertilization on sweet sorghum as affected by rates and time of N application. Five experiments were conducted under field conditions, where 0, 50, 100 and 150 kg N/ha were applied at sowing, and 35, 40, 55, 60 and 80 days after plant emergence. The soil had textures varying from sandy loam to clay, and organic matter contents from 0.67% to 1.9%. The highest yields were observed when N was applied early in the season, showing that for sweet sorghum, sidedressing with N is not necessary. All the N can be applied at planting time, which allows the highest fertilizer use efficiency. On the other hand, late applications of N fertilizer (after 40 days), when the floral primordia is already visible, has little effect on stalk or grain yield. In this situation, a double or triple rate had to be applied to overcome the low efficiency of N utilization. There was no great advantage in splitting the sidedressed N rate. On the other hand, it was impossible to link the response to N to soil analysis as performed in most of Brazilian laboratories.     

Early nitrogen deficiency favors high nitrogen recovery efficiency by improving deeper soil root growth and reducing nitrogen loss in wheat

ABSTRACT

A two-year field and micro-plot ¹⁵N-labelled experiment was conducted under two levels of N application rate (240 and 180 kg N ha^–1) with three basal N application stages [seeding (L0), four-leaf stage (L4), and six-leaf stage (L6)] to investigate the effects of reducing basal N application amount and postponing basal N fertilization period on wheat growth and N use efficiency (NUE). No significant differences were observed in grain yield, root growth and root morphology between the N180L4 and N240L0 treatments, while the root-shoot ratio of N180L4 was significantly improved. Postponing basal N application period increased the residual basal ¹⁵N in soil and reduced basal ¹⁵N loss, and N180L4 treatment favored the highest ¹⁵N recovery efficiency (NRE), mainly due to reduced ¹⁵N loss. Grain yield and basal NRE were significantly positively correlated with root dry weight in deeper soil layers (40–60 cm), and the contribution of root growth to improved grain yield and NRE increased with the downward distribution of the roots. Therefore, postponing the basal N fertilization period under N deficiency promotes deeper root growth during the post-jointing period and increases basal N uptake, as well as reducing basal N loss and increasing grain yield and NUE.     

旱地土壤硝态氮残留淋溶及影响因素研究

在我国北方旱地,施入土壤而未被作物吸收利用的肥料N,主要以NO3--N的形式残留于土壤中。残留的NO3--N如不及时被作物吸收利用,在降水或灌水的作用下,会淋入土壤深层,或随径流进入地表水体,或经反硝化形成N2O进入大气,对土壤、水体和大气环境构成严重威胁。本文分析了旱地农田生态系统中,NO3--N在土壤剖面的残留淋溶与施肥、灌溉/降水、耕作、土壤、植物等因素的关系。提出在今后的研究工作中应特别注意的问题:①建立长期定位试验,确定NO3--N淋溶阈值,评价和预测NO3--N残留和淋失的趋势;②优化作物栽培和养分资源管理措施,提高作物利用土壤NO3--N的能力;③改进N肥施用技术,加强N素管理,防止NO3--N在土壤中大量累积。     

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。     

Interaction Effects of Nitrogen and Phosphorus on Nodulation in Red Clover (Trifolium pratense L.)

Red clover (Trifolium pratense L.) is one of the most important plants in forage production, especially in northern areas. Fertilisation practices are focused on high yield and forage quality but effects of nutrients on nodulation and N₂ fixation are poorly understood. The aim of this work was to study how nitrogen (N) and phosphorus (P) separately as well as in combination affected nodulation. Red clover plants were grown in pots with gravel in a greenhouse for 11 weeks. To resemble field conditions the root temperature was kept lower than the shoot temperature. Plants were given five different combinations of N and P concentrations during growth. The result showed that at high N concentrations P had a counteracting effect on the N inhibition. The N₂-fixation parameters, nodule number, nodule dry matter and specific nitrogenase activity, were six times higher in plants grown with high N and high P than in plants with high N and low P. When the N₂-fixation parameters and the dry matter of roots and shoots were related to total plant dry matter, there was a stronger effect of P on nodulation parameters than on roots and shoots. This indicates that P has a direct effect on the N₂-fixation parameters, rather than an indirect effect via increased plant growth. These results demonstrate the importance to studying the effects of more than one nutrient at a time.     

水氮耦合对苗期葡萄叶片氮素代谢酶活性的影响

为研究水氮耦合对苗期葡萄叶片氮代谢影响及最佳施氮量的制定,以一年生葡萄品种红提为研究试材,利用人工控制环境的方法,在温室内采用水、氮两因素各4水平的全面设计进行实验,水分处理分别为正常灌溉W1（田间最大持水量的70%～80%）、轻度胁迫W2（60%～70%）、中度胁迫W3（50%～60%）和重度胁迫W4（30%～40%）。4个氮素施用水平分别为1.5倍推荐施肥N1（施纯氮25.5g·m⁻²）、正常推荐施肥N2（17g·m⁻²）、0.5倍推荐施肥N3（8.5g·m⁻²）、不施用氮肥N4（不施氮）。处理时间为10、20、30、40d。结果表明,在水分条件适宜时,葡萄叶片硝酸还原酶（NR）、谷氨酰胺合成酶（GS）、谷氨酸合成酶（GOGAT）活性、可溶性蛋白、游离氨基酸含量随施氮量增加而提高;在轻度干旱胁迫时,增施氮肥可缓解干旱胁迫;在重度干旱胁迫时,高氮处理使设施葡萄叶片中氮代谢酶活性、游离氨基酸和可溶性蛋白含量降低。葡萄叶片内氮含量始终随处理时间增加而降低,在轻度水分胁迫下氮的转运率较高,而水分胁迫严重时,高氮处理与无氮处理时氮转运率均偏低。最终得出：在水分条件适宜（W1）和轻度水分胁迫（W2）下,N1处理葡萄叶片的氮代谢能力最高;在中度水分胁迫（W3）和重度水分胁迫（W4）下,N3、N4处理氮代谢能力最高。研究结果可为实际生产中设施葡萄的干旱灾害防控提供理论依据,既能有效缓解水分胁迫带来的危害,又避免生产中肥料的浪费。