氮肥用量对小麦开花后根际土壤特性和产量的影响

【目的】明确小麦开花后根际土壤特性动态特征及其与产量和籽粒氮素积累量之间的关系,能够为生产上合理施肥、提高氮肥利用效率和减轻环境污染提供理论依据。【方法】2014—2015和2015—2016年在小麦季设置4个氮肥水平(0,CK;150 kg N·hm~(-2),N150;240 kg N·hm~(-2),N240和300 kg N·hm~(-2),N300)并于小麦开花期、灌浆中期和成熟期分层(0—20 cm和20—40 cm)测定小麦根际和非根际土壤铵态氮、硝态氮、蔗糖酶、脲酶,同时测定根、茎、叶和穗生物量及其氮素含量;重点分析根际土壤特性与小麦籽粒产量和氮素积累量之间的关系。【结果】(1)与CK相比,N150、N240和N300处理2年小麦籽粒产量的平均值分别增加99%、130%和107%,且处理之间差异显著。随施氮量的增加小麦根、茎、叶、穗生物量和地上部氮素积累量均呈增加趋势;氮肥回收率呈下降趋势,且处理之间差异显著。(2)从开花到成熟期,0—20 cm和20—40 cm土层小麦根际和非根际土壤铵态氮、硝态氮含量、土壤蔗糖酶和脲酶(0—20 cm除外)活性均呈下降趋势。处理CK、N150、N240和N300根际土壤铵态氮和硝态氮含量显著低于非根际土壤。4个处理2年0—20 cm根际土壤铵态氮含量平均值比非根际土壤降低29%,硝态氮含量降低22%;20—40 cm根际土壤铵态氮含量比非根际土降低34%,硝态氮含量降低14%。而根际土壤蔗糖酶和脲酶活性显著高于非根际土。4个处理2年0—20 cm根际土壤蔗糖酶活性比非根际土壤提高29%,脲酶活性提高15%;20—40 cm根际土壤蔗糖酶活性比非根际土壤提高33%,脲酶活性提高13%。(3)相关分析结果表明,小麦籽粒产量和籽粒氮素积累量均与0—20 cm和20—40 cm根际和非根际土壤无机氮(铵态氮+硝态氮)、脲酶和蔗糖酶(2016年籽粒氮素积累量除外)呈显著正相关。【结论】小麦根际土壤可利用性氮素含量小于非根际土壤,而酶活性高于非根际土;根际和非根际土壤与籽粒产量和籽粒氮素积累量呈显著正相关。根际和非根际土壤特性显著影响小麦籽粒产量。     

不同氮肥水平下玉米根际土壤特性与产量的关系

【目的】明确不同生育时期根际土壤特性与玉米籽粒产量之间的关系,能够为生产上合理施肥、提高氮素利用效率和减轻环境污染提供理论依据。【方法】2012年大田设置5个氮肥梯度固定施肥样地（对照、180 kg·hm^-2、240 kg·hm^-2、300 kg·hm^-2和360 kg·hm^-2,分别简写为CK、N180、N240、N300和N360）,并于2012、2013和2014年连续3年在玉米拔节、吐丝、成熟3个关键生育时期测定玉米根际和非根际土壤铵态氮、硝态氮、脲酶、过氧化氢酶、pH,同时测定玉米根系和地上部生物量及其氮素累积量,重点分析CK、N240和N360 3个处理根际土壤特性以及植株氮素累积量与玉米籽粒产量之间的关系。【结果】与CK相比,4个施肥处理（N180、N240、N300和N360）3年产量的平均值分别增加了23.85%、36.40%、39.87%和34.78%;其地上部不同阶段氮素累积量均显著高于CK（2012年播种-拔节除外）,并随施肥量增加呈先增加后降低趋势。与CK相比,4个施肥处理根际土硝态氮含量分别增加23.38%、57.13%、57.87%和69.74%,非根际土壤硝态氮分别增加59.49%、92.01%、132.08%和179.35%。随施氮量的增加根际土铵态氮含量显著增加;与CK相比,4个施肥处理3年的非根际土壤铵态氮含量分别增加4.27%、3.51%、5.04%和26.26%。根际土壤pH和非根际土壤pH均随着氮肥施用量的增加而降低,其中根际土壤和非根际土壤pH的变化范围分别为4.5-6.7和5.5-7.2。与非根际土pH相比,根际土壤pH平均降低5%。根际土壤脲酶活性随氮肥用量的增加呈先增加后降低趋势。与对照相比,4个施氮处理3年非根际土壤脲酶活性平均值分别增加了4.02%、14.73%、24.55%和19.64%。根际土和非根际土过氧化氢酶活性均随氮肥用量的增加而降低,与CK相比,4个施氮处理3年的非根际土壤过氧化氢酶活性平均值分别降低了3.03%、5.09%、8.24%和12.67%。CK、N240和N360 3个处理不同生育时期玉米根际土壤特性以及植株氮素累积量与籽粒产量之间的相关分析结果表明,拔节期根际土壤硝态氮含量连续3年均与产量呈显著正相关。吐丝期玉米根际和非根际土壤硝态氮、根际土壤铵态氮和非根际土pH均与籽粒产量呈显著正相关;其中2013和2014年根际脲酶活性和根际土壤pH与产量的相关性也达到显著水平。2013和2014年成熟期根际和非根际土硝态氮含量也与玉米产量呈显著相关。主成分分析表明,玉米籽粒产量与拔节期土壤硝态氮含量、根际过氧化氢酶、地上部生物量和氮素累积量相关性较强;与吐丝期根际和非根际土壤硝态氮含量、根际土壤铵态氮含量和土壤pH以及地上部生物量及氮素累积量、根系生物量相关性较强;与成熟期地上部生物量和氮素累积量相关性较强。【结论】根据不同生育时期玉米根际土壤特性与籽粒产量之间的关系,进行合理施肥,能够保证玉米根际养分的有效供应,营造良好的根际土壤环境,提高氮素利用效率、增加玉米籽粒产量。     

Impact of Residual Soil Nitrate on In-Season Nitrogen Applications to Irrigated Corn Based on Remotely Sensed Assessments of Crop Nitrogen Status

Spatial and temporal variability of soil nitrogen (N) supply together with temporal variability of plant N demand make conventional N management difficult. This study was conducted to determine the impact of residual soil nitrate-N (NO₃-N) on ground-based remote sensing management of in-season N fertilizer applications for commercial center-pivot irrigated corn (Zea mays L.) in northeast Colorado. Wedge-shaped areas were established to facilitate fertigation with the center pivot in two areas of the field that had significantly different amounts of residual soil NO₃-N in the soil profile. One in-season fertigation (48 kg N ha⁻¹) was required in the Bijou loamy sand soil with high residual NO₃-N versus three in-season fertigations totaling 102 kg N ha⁻¹ in the Valentine fine sand soil with low residual NO₃-N. The farmer applied five fertigations to the field between the wedges for a total in-season N application of 214 kg N ha⁻¹. Nitrogen input was reduced by 78% and 52%, respectively, in these two areas compared to the farmer’s traditional practice without any reductions in corn yield. The ground-based remote sensing management of in-season applied N increased N use efficiency and significantly reduced residual soil NO₃-N (0–1.5 m depth) in the loamy sand soil area. Applying fertilizer N as needed by the crop and where needed in a field may reduce N inputs compared to traditional farmer accepted practices and improve in-season N management.     

应用于水稻生产的增效减负环保型施肥技术比对——以宁夏引黄灌区为例

过量施肥及盲目灌溉导致宁夏引黄灌区水稻种植中氮素淋失严重,氮肥利用率低下.探索能够在保障水稻产量前提下减少氮素淋失、提高氮素利用率的环保型施肥技术是该区域实现农业可持续发展的现实需求.本研究在前期研究的基础上,就不同施肥技术对灌区水稻生育期内氮素淋失、氮素利用率及水稻产量的影响效果进行比对,旨在为后续工作中技术筛选及推广提供依据.试验共设置4个处理,分别是(1)无肥对照(CK):不施氮肥;(2)常规施肥(FP):施用氮肥300 kg N·hm^-2, 60%作为基肥,分蘖和孕穗期各追肥20%;(3)侧条施肥(SD):施用水稻专用控释肥120 kg N·hm^-2,水稻插秧时将肥料一次性施入;(4)育苗箱全量施肥(NB):施用水稻专用控释肥,用量为120 kg N·hm^-2,育秧时一次性全量施入育秧盘.结果表明,采用SD和NB在氮素用量较FP降低60%的情况下,水稻产量都不会下降.SD可以显着降低稻田氮素淋溶损失,FP水稻生育期内可溶性总氮(TN)、硝态氮(NO₃-N)和铵态氮(NH₄⁺-N)淋失量分别为39.89、26.22 kg·hm^-2和5.49 kg·hm^-2,SD和FP相比,TN、NO₃-N和NH₄⁺-N的淋失量分别减少18.97、11.18 kg·hm^-2和2.27 kg·hm^-2;同时SD可以显着提高宁夏灌区水稻氮素利用率,较FP提高21.4%. NB和FP相比,TN、NO₃-N和NH₄⁺-N淋失量分别减少14.36、10.14 kg·hm^-2和1.84 kg·hm^-2,氮素利用率亦提高15.7%,但是TN、NO₃-N和NH₄⁺-N淋失量较SD处理分别增加4.61、1.04 kg·hm^-2和0.43 kg·hm^-2,同时氮素利用率亦减少5.7%.综合考虑水稻产量和环境效益,SD更适合在宁夏灌区水稻种植中推广应用.     

Effects of nitrogen rate and ratio of base fertilizer and topdressing on uptake, translocation of nitrogen and yield in wheat

Application of nitrogen (N) fertilizer is one of the most important measures to increase grain yield and protein content in winter wheat (Triticum aestivum L.) production. However, misuse of N Tertilizer will not only affect gram yield and quality, but also cause the decline of economic benefits and related negative environmental effects. It is essential to study reasonable N application regimes for profitable yields, efficient N utilization and reduction in possible environmental pollution. The objective of this study was to determine the N uptake and translocation in wheat plants by using ¹⁵N isotope tracers in PVC cylinders (2.05 m long, ϕ 0.2 m, without bottom) in seven treatments: without N fertilizer application (N0); N application rate of 168 kg/hm² (0.527 g/pot), with ratios of base fertilizer to topdressing of 1:1 (N1), 1:2 (N2) and 0:1 (N3); N application rate of 240 kg/hm² (0.753 g/pot), with ratios of base fertilizer to topdressing of 1:1 (N4), 1:2 (N5) and 0:1 (N6). The ¹⁵N tracer experiment showed that the main basal N absorbed by plant from sowing to jointing stage accounted for 78.04%–89.67%; fertilizer N use efficiency (FNUE, N fertilizer accumulation in plant/N supplied) of topdressing was significantly higher than that of basal N; reducing basal N amount and increasing topdressing N amount could appropriately promote the plant’s absorption of more N fertilizer and enhance FNUE, of which treatment N2 had the highest values. Under the high-yield condition, when N fertilizer rate was increased from 168 to 240 kg/hm², there were no significant differences in the amount of N accumulation in plants and in grains between treatments with the same ratio of base fertilizer to topdressing; by reducing basal N amount and increasing topdressing N amount accordingly, the translocation efficiency (TE, accumulation amount from vegetative organs to gram/N accumulation in vegetative organs during anthesis) increased, and the amount of N assimilation to grains after anthesis and its contribution proportion (the amount of N assimilation to grains after anthesis/N accumulation in grain) also increased. In other words, grain N accumulation amount increased with increasing amount of topdressing N at the same N fertilizer rate. There were no significant differences among treatments N2, N3, N5 and N6 in grain N accumulation. Appropriate N fertilizer rate with a reduction in basal N amount and an increase in topdressing N amount such as in N2, N5 and N6 increased grain yield and protein content. In conclusion, under conditions used in this experiment, as far as grain yield, protein content and FNUE are concerned, the recommended appropriate N fertilizer application regime is treatment N2, with a N fertilizer rate of 168 kg/hm² and a ratio of base fertilizer to topdressing of 1:2. Translated from Journal of Acta Agronomica Sinica, 2006, 32(12): 1860–1866 [译自: 作物学报]     

Influences of nitrogen fertilizer application rates on radish yield, nutrition quality, and nitrogen recovery efficiency

Radishes (Raphanus sativus L.) were grown in plastic pots in a screenhouse to investigate the influences of nitrogen fertilizer application rates (NFAR) on yield, nitrate content, nitrate reductase activity (NR), nutrition quality, and nitrogen recovery efficiency (NRE) at commercial mature stage. Five N-rate treatments, 0.644, 0.819, 0.995, 1.170, and 1.346 g·pot⁻¹, were set up in the screenhouse pot experiments, and nitrogen fertilizer (unlabeled N and ¹⁵N-labeled fertilizer) was applied as basal dressing and topdressing, respectively. The results indicated that the fresh and dry weight yields of radish increased with the increase of NFAR at the range of 0.099 to 0.180 g N·kg⁻¹ soil, decreased at 0.207 g N·kg⁻¹ soil, and accordingly there was a significant quadratic relationship between the fresh and dry weight yields of radish and the NFAR. At the high addition of urea-N fertilizer, the nitrate content accumulated in the fleshy roots and leaves due to the decline in NR activity. From 0.644 to 0.819 g N·pot⁻¹ NR increased most rapidly, the highest NR activity occurred at 0.819 g N·pot⁻¹, and the lowest NR activity happened at 1.346 g N·pot⁻¹. Soluble sugar and ascorbic acid initially increased to the highest value and then decreased, and, contrarily, crude fiber rapidly decreased with the increase of NFAR. Total N uptake (TNU), N derived from fertilizer (N_dff), and N derived from soil (N_dfs) in radish increased, except that N_dfs relatively and slightly decreased at the rate of 0.207 g N·kg⁻¹soil. The ratio of Ndff to TNU increased, but the ratio of Ndfs to TNU as well as NRE of N fertilizer decreased with the increase of NFAR. Therefore, the appropriate NFAR should be preferably recommended for improving the yields and nutrition qualities of radish and NRE of N fertilizer. These authors contributed equally to this work     

暗管农田不同类型肥料对向日葵生长及土壤氮素分布的影响

为了探明暗管排水条件下不同肥料对作物生长和土壤氮素环境的影响，明确盐渍化暗管排水农田合理的施肥模式，采用田间试验，设置普通尿素（CK）、控释肥（CF）和有机硅水溶性缓释肥（OF）3个处理，在保证施纯氮量均为225 kg·hm^-2的情况下，对各处理向日葵生育期间的生长状况、产量和氮肥利用效率，以及土壤、排水中的氮素含量进行分析。结果表明：与CK相比，CF和OF处理均可提高向日葵各生育期株高、叶面积指数、光合速率及产量。其中，CF增产效果最为显著，两年内较OF、CK分别提高了14.07%和40.54%。此外，CF处理有利于0~40 cm土层土壤氮素的持续有效供应，可增加植株氮素积累量、氮肥偏生产力和氮收获指数，更好地促进作物对养分的吸收利用。与CK、OF相比，CF可有效减少向日葵收获后期0~160 cm土层NO₃^--N残留量，降幅分别为14.92%和7.87%。两年试验中各处理之间的暗管排水量、排盐量较接近，但NO₃^--N及NH₄⁺-N流失量差异明显，其中OF、CK处理下的NO₃^--N流失量分别是CF的1.25、1.50倍，NH₄⁺-N流失量分别是CF的1.22、1.95倍。研究表明，控释肥可以更好地促进作物对养分的吸收利用，提高氮肥利用率，显著增加作物产量，同时还可以降低土壤中氮素的深层淋洗，减少氮素流失量，是暗管排水条件下较为适宜的肥料品种。     

增效复合肥减氮施用对稻田水氮素流失的影响

通过田间试验研究氨基酸、腐植酸和海藻酸增效复合肥减氮施用对稻田水氮素动态特征和损失的影响,旨在为增效复合肥环境效应评价提供依据。试验设7个处理:不施肥(CK)、不施氮(PK)、常规施肥(CF)、常规施肥减氮20%(CR)、腐植酸复合肥减氮20%(HR)、氨基酸复合肥减氮20%(AR)、海藻酸复合肥减氮20%(SR)。采集水稻生长期不同时间的田面水、径流水和田间渗漏水,分析了不同形态氮素浓度的动态特征和氮素损失。结果表明:增效复合肥减氮处理(AR、HR和SR)明显降低了田面水TN和NH_4~+-N浓度峰值,峰值分别维持在37.1～49.7 mg·L~(-1)和26.0～28.8 mg·L~(-1),以SR处理田面水TN和NH_4~+-N浓度峰值最低,较CR处理分别降低了38.4%和14.3%,其他减肥处理之间未见显著差异;施肥一周后,田面水TN与NH_4~+-N浓度逐渐降低至峰值的15%后趋于稳定;各施肥处理NO_3~--N浓度变幅较小,峰值未见明显差异。SR处理0～20 cm土层渗漏液TN浓度最低为16.5 mg·L~(-1),较CR、HR和AR处理分别降低了60.8%、50.1%和54.0%,氮素形态以NH_4~+-N为主,随土层深度增加,渗漏液TN和NH_4~+-N递减。施氮肥处理的氮素流失率大小顺序依次为CFCRHRARSR,SR处理氮素径流损失量最低为6.22 kg·hm~(-2),较CR处理降低了58.5%;增效复合肥氮素减施均明显降低氮素渗漏损失,施氮肥处理氮素淋失率大小顺序依次为ARCFCRHRSR,SR处理渗漏损失最低为7.70 kg·hm~(-2),较CR处理氮素淋失率降低了18.1%;稻田水氮素损失总量也以SR处理为最低,达13.9 kg·hm~(-2),较CR处理降低了22.8%。研究表明,增效复合肥减氮施用对稻田田面水、土壤渗漏液不同形态氮素浓度有明显影响,可减少稻田水氮素损失风险,以海藻酸增效复合肥减氮处理效果最佳。     

粪肥增施对水稻产量和氮素利用效率的影响

为探究不同用量粪肥增施对水稻生产的影响,在等氮施用化肥的基础上开展盆栽试验,通过系统分析水稻产量、氮素利用效率、水稻收获后土壤理化性质等指标,以及水稻叶片叶绿素相对含量（SPAD值）、田面水无机氮素浓度的动态变化特征,对粪肥增施的最佳用量进行了研究。结果表明：在施用尿素（192.8 kg·hm^-2,以N计）的基础上,增施0.75倍粪肥（相当于增施N 115.1kg·hm^-2）的效果最佳,秸秆产量、籽粒产量、穗数、分蘖数、株高、秸秆吸氮量和籽粒吸氮量等指标均达到最高,与单施尿素相比,分别提高36.2%、46.4%、12.1%、16.1%、0.7%、48.5%和56.3%;氮素利用指标（氮素利用率、氮肥贡献率、氮肥农学效率和土壤氮素依存率）得到显著优化（P<0.05）;追施穗肥后田面水中铵态氮（NH₄⁺-N）和硝态氮（NO₃^--N）的平均浓度分别下降10.4%和10.3%,表明适量增施粪肥会有效降低田面水中氮素的流失风险。另外,增施粪肥对土壤养分含量具有促进作用,其中土壤有机质、全氮、碱解氮、有效磷和铵态氮含量随粪肥增施量的增加而提高。研究表明,在施用化肥基础上增施0.75倍粪肥,可最大程度实现水稻增产和氮素利用效率的提升,同时降低氮素流失风险。研究结果可为水稻生产中有机无机肥配施比例的确定提供参考。     

沼液施用对贵州典型黄壤油菜地氮淋溶的影响

了研究西南喀斯特山区沼液灌溉氮淋溶风险,以及率定沼液还田安全施用量,以该区域典型土壤——黄壤为供试土壤,主栽作物油菜为供试作物,牛场沼液为施用材料,开展大棚盆栽试验模拟沼液灌溉,评估沼液灌溉氮淋溶风险,考察油菜农艺性状响应,率定沼液安全施用量。设置油菜不施肥（CK）、无作物施沼液（NP480,施氮量480 kg·hm^-2）、油菜施化肥（CF,480 kg·hm^-2）、油菜沼液低施用量（R120,120 kg·hm^-2）、油菜沼液中施用量（R240,240 kg·hm^-2）、油菜沼液高施用量（R480,480 kg·hm^-2） 6个处理,将化肥水溶或沼液稀释后按每12 d 1次、每次25 mm连续灌入12次。结果表明：沼液灌溉存在氮淋溶风险,该风险以NO-3-N负荷为主,NO-3-N淋溶风险随施氮量增加而增大,R480处理NO^-₃-N淋溶量分别是CK、R120、R240处理的2、1.8倍和1.4倍;同施氮量下,沼液灌溉氮淋溶风险低于化肥处理,CF处理TN、NH⁺₄-N、NO^-₃-N淋溶量分别是R480处理的3.8、2.3倍和2.9倍; R480处理的氮淋溶风险值得警惕,但油菜氮素吸收能够降低该风险,使TN、NH⁺₄-N、NO^-₃-N淋溶量分别降低34%、30%、32%;适量施用沼液（施氮量120 kg·hm^-2）相对CF处理能改善油菜农艺性状,但过量施用沼液（施氮量480 kg·hm^-2）不利于油菜生长。研究表明,西南喀斯特山区油菜黄壤沼液灌溉存在一定氮淋溶风险,综合考虑氮淋溶风险、油菜农艺性状和沼液消纳需求,沼液还田施氮量控制在240 kg·hm^-2以内为宜。     

施氮、锌对镉污染小麦产量及籽粒锌、镉含量的影响

为了明确氮、锌、镉处理及其互作对小麦产量和籽粒锌、镉含量的影响,本研究设置盆栽裂区试验,以扬麦25为供试材料,主区氮处理设常氮（1.6 g·盆^-1）和减氮（0.8 g·盆^-1）,裂区锌、镉处理设对照、锌处理（150 mg·kg^-1）、镉处理（5 mg·kg^-1）和锌+镉处理,测定小麦产量性状,籽粒不同组分（面粉、次粉和麸皮）氮、锌、镉含量以及籽粒锌、镉有效富集系数。结果表明：与常氮相比,减氮处理使小麦籽粒产量显著降低,这主要与产量构成因子、生物产量和收获指数均显著下降有关;减氮条件下小麦成熟籽粒氮含量（不同组分10%~15%）、镉含量（12%~16%）以及镉有效富集系数亦显著降低。与不施锌相比,土壤施锌对籽粒产量和氮含量均无显著影响,但使籽粒锌含量大幅增加（14%~30%）,使镉含量（18%~28%）以及锌、镉有效富集系数均显著下降。土壤镉处理对籽粒产量和氮含量均无显著影响,使籽粒镉含量（38~42倍）以及锌、镉有效富集系数均显著增加,而使锌含量显著下降（3%~12%）。籽粒组分及其与镉、锌处理的互作对小麦籽粒锌和镉含量影响均达显著。研究表明,5 mg·kg^-1镉污染条件下小麦产量无明显变化,但籽粒各组分镉含量大幅增加,减施氮肥或/和增施锌肥均可显著减少小麦籽粒不同组分镉含量。     

牛粪化肥配施对稻田下渗水氮素流失和水稻氮素积累的影响

采用田间小区试验研究了牛粪与化肥不同比例配施[100%化肥(100%CF)、70%化肥+30%牛粪(70%CF+30%MF)、50%化肥+50%牛粪(50%CF+50%MF)、30%化肥+70%牛粪(30%CF+70%MF)]的稻田土壤中20、40、60 cm处下渗水中总氮(TN)、铵态氮(NH_4~+-N)和硝态氮(NO3--N)的时空变化、氮素下渗流失量和水稻氮素积累特征。结果表明:不同处理的TN、NH_4~+-N和NO3--N流失量以水稻分蘖期较大,氮素流失以NH_4~+-N为主,占TN流失的64.3%～76.7%,后期氮素流失较少;50%CF+50%MF在60 cm处下渗水TN时间间隔加权平均浓度高于上层,其他处理的TN均表现为随土层深度增加而减小。不同处理的氮素流失量中以50%CF+50%MF最高,为23.12 kg·hm-2,显著高于其他处理。水稻产量随牛粪配施量增加而降低,但不同处理之间无显著差异;30%CF+70%MF处理显著降低水稻地上部植株氮素累积量,不利于水稻对氮素的吸收利用。因此,综合考虑水稻产量和氮素流失情况,70%CF+30%MF是值得推荐的最优配比。     

增氮对青藏高原东缘高寒草甸土壤甲烷吸收的早期影响

研究大气氮沉降对青藏高原高寒草甸土壤CH₄吸收的影响,对于揭示氮素调节土壤CH₄吸收的机制和评价氮沉降增加背景下大气CH₄收支平衡至关重要。通过构建多形态、低剂量的增氮控制试验,测定土壤CH₄净交换通量和相关土壤理化性质,分析高寒草甸土壤CH₄通量变化特征及其主要驱动因子。研究结果表明:自然状态下高寒草甸土壤是大气CH₄汇,CH₄平均吸收量为(35.40±1.92)μg·m^-2·h^-1。土壤CH₄吸收主要受水分驱动,其次为土壤NH₄⁺-N和NO₃^--N含量。NH₄⁺-N抑制CH₄吸收,NO₃^--N促进CH₄吸收;不同剂量氮素输入对土壤CH₄吸收影响也不尽相同,低氮处理促进土壤CH₄吸收,而中氮和高氮处理抑制土壤CH₄吸收。结果显示青藏高原高寒草甸土壤是重要的大气CH₄汇,在未来大气氮沉降加倍的情景下CH₄汇功能增强,但当氮沉降量增加两倍以上时CH₄汇功能将会减弱。     

Spring Wheat Response to Fertilizer Nitrogen Following a Sugar Beet Crop Varying in Canopy Color

Experiments were conducted in the Red River Valley (RRV) of Minnesota to determine the responses of hard red spring wheat (Triticum aerstivum L.) to fertilizer N after a sugar beet (Beta vulgaris L.) crop that varied spatially in canopy color and N content. A color aerial photograph was acquired of the sugar beet field just prior to root harvest, and six sites were selected that varied in sugar beet canopy color, three each of green and yellow canopy sites. The three green sugar beet canopies returned 369, 265, and 266 kg N ha^–1 to the soil while the three yellow sugar beet canopies returned 124, 71, and 73 kg N ha^–1 to the soil. Spring wheat response to fall-applied urea-N fertilizer (0, 45, 90, 135, and 180 kg N ha^–1) was determined the following year at each of the above antecedent canopy sites. Soil NO₃-N in the top 0.6 m of soil varied among the locations with a range of 35 to 407 kg NO₃-N ha^–1 at the green canopy sites and 12 to 23 kg NO₃-N ha^–1 at the yellow canopy sites. Application of fertilizer N according to traditional recommendation methods would have resulted in fertilizer applications at all three yellow canopy sites and two of the three green canopy sites. At the antecedent green sugar beet canopy sites, fertilizer N had little or no effect on spring wheat grain yields, grain N concentration, anthesis dry matter, and anthesis N content. In contrast, fertilizer N increased all four parameters at the antecedent yellow sugar beet canopy sites. The data indicate that fertilizer N management can be improved by using remote sensing to delineate management zones according to antecedent sugar beet canopy color.     

干湿交替和模拟氮沉降对巴音布鲁克高寒湿地土壤CO2排放的影响

为探讨干湿交替和模拟氮沉降对高寒湿地土壤CO_2排放的规律,以新疆巴音布鲁克高寒湿地土壤为研究对象,通过室内模拟控制试验,研究水分变化下[100%、70%、50%、40%和25%WFPS(土壤充水孔隙度Water filling soil porosity)]氮添加N0(0 kg·hm~(-2)·a~(-1))、N10(10 kg·hm~(-2)·a~(-1))和N100(100 kg·hm~(-2)·a~(-1))处理对巴音布鲁克高寒湿地土壤CO_2排放的影响。研究结果表明:土壤CO_2排放速率及累积排放量随WFPS值及氮添加量的增大而增加。一个循环,土壤由干到湿的过程中,初期土壤CO_2排放速率最高,随后随着水分减少,土壤CO_2排放速率呈降低趋势;首次干湿循环土壤CO_2累积排放量最大。土壤TN、NO_3~--N、NH_4~+-N、SOC含量均随土壤水分和氮添加量的增加而增加,而土壤SON随土壤水分和氮添加量的增加而减少。水分与土壤CO_2排放速率呈极显著正相关,氮添加与CO_2排放亦呈正相关。除了土壤SON、SOC含量与土壤CO_2排放速率呈负相关关系外,土壤TN、NO_3~--N、NH_4~+-N与CO_2排放都呈现出正相关关系。     

施氮量对冬小麦氮素吸收利用、土壤中硝态氮积累和籽粒产量的影响

为通过控制施氮量来实现高肥力条件下小麦的高产、高效、安全生产提供依据,以冬小麦品种‘藁8901’为材料,研究了高肥力条件下不同施氮水平对小麦氮素吸收利用、籽粒产量和土壤中硝态氮含量的影响。试验结果表明:在高肥力条件下,随着施氮量的增加,冬小麦的籽粒产量和植株吸氮量均是先增加后降低,籽粒产量和植株吸氮量均以N150最高,氮素生产力则以N0最高。在冬小麦的拔节期和成熟期,土壤NO3-N含量均随着施氮量的增加而增加,减少氮肥施入量能降低冬小麦拔节期和成熟期土壤0-100 cm土层中的硝态氮含量。施用氮肥能提高小麦拔节期和成熟期植株全氮积累量和土壤NO3-N积累量,但两者并非同步增加,土壤NO3-N积累量增加的幅度远远大于植株全氮积累量的增长幅度。在施氮量0-180 kg/hm2范围内时,植株全氮积累量有所增加,且土壤中硝态氮的积累量增加较为缓和;而在施氮量180 kg/hm2的基础上继续提高氮素用量,植株全氮积累量下降,而土壤硝态氮积累量却开始大幅度增加。据此综合考虑,冬小麦‘藁8901’的适宜施氮量应控制在150 kg/hm2左右。     

酸性茶园土壤氨挥发及其影响因素研究

氨挥发是土壤氮素损失的主要途径之一。利用大型水泥槽田间试验,采用通气法研究了不同施氮量和施氮时期对茶园土壤氨挥发的影响,同时测定土壤铵态氮和硝态氮含量,结合气象因子进行偏相关分析,探讨了氨挥发的影响因素。设置CK(未施氮)、N1(减量化施氮、225 kg·hm~(-2))和N2(常规施氮,450 kg·hm~(-2))共3个处理,春季追肥、秋季追肥和冬季基肥比例为3∶3∶4。结果表明:茶园土壤氨挥发损失量为13.01~60.85 kg·hm~(-2),氨挥发损失率为10.63%~12.42%;施氮既是氨挥发峰值出现的主要原因,也能显著增加土壤氨挥发量(P0.05),N_1和N_2处理增幅分别为214.78%和367.72%,其增幅效应在冬季基肥期更显著;不同施氮时期对氨挥发量影响很大,冬季基肥期挥发量约占全年氨挥发损失量的50%,与冬季基肥期间土壤铵态氮浓度高且持续时间较长有关。偏相关分析表明,土壤氨挥发与铵态氮含量、地温和空气相对湿度呈显著或极显著正相关,与土壤水分和气温呈极显著负相关,与土壤硝态氮含量相关性不显著。     

Effect of Long-Term Fertilization on Soil Productivity and Nitrate Accumulation in Gansu Oasis

A long-term （1982-2001） field experiment was conducted in a calcareous soil under wheat （Triticum aestivum L.）-wheat （Triticum aestivum L.）-maize （Zea mays L.） rotation system at Zhangye, Gansu Province, China to determine the effects of long-term fertilization on crop yield, nutrients interactions, content and accumulation of nitrate-N in soil profiles. Twenty- four plots in a split-plot factorial with a combination of eight treatments （from nitrogen （N）, phosphorus （P）, potassium （K） and farmyard manure （M） applications） and 3 replications were selected. Main treatments were M and without M, and the sub-treatments were no-fertilizer （CK）, N, NP and NPK. When P and K fertilizers were part of treatments, their ratio to N was 1N：0.22P：0.42K. All M, P and K fertilizers were applied as the basal dressing. The grain yield was harvested each experimental period and straw yield for the period from 1988 to 1997. After crop harvest in 2000, the soil was sampled from the 0-20, 20-60, 60-100, 100-140 and 140-180 cm depths to determine NO3^--N content. Maize yield of CK in 2000 was only 28.2% of that in 1984, and wheat in 2001 was 25.7% of that observed in 1982. Average impact of fertilizers on grain yield decreased in the order of N 〉 M 〉 P 〉 K. Yield response to N and P fertilizers increased with progress of the experiment. The impact of K fertilizer showed no increase in grain yield during the initial 6 years （1982-1987）, moderate increase in the next 5 years （1988-1992）, and considerable increase in the last 9 years （1993-2001）. The straw yield trend was similar to grain yield. Accumulation and distribution of NO3^--N in soil was significantly affected by annual fertilizations. Mineral fertilizers （NP and NPK） led to NO3^- -N accumulation in most subsoil layers, with major impact in the 20-140 cm depth. The combination of mineral fertilizers and farmyard manure （MNP and MNPK） reduced soil NO3^--N accumulation in comparison to mineral fertilizers, It can be argued that long-term fertilization significantly enhanced grain and straw yield in this rotation scheme. The findings of this research suggest that it is important to balance application of mineral fertilizers and farmyard manure in order to protect soil and underground water from potential NO3^--N pollution while sustaining high productivity in the oasis agro-ecosystem.     

减氮适墒对冬小麦土壤硝态氮分布和氮素吸收利用的影响

【目的】针对黄淮冬麦区过量施氮的现象,研究了适量减氮在不同土壤墒情下硝态氮分布以及冬小麦对氮素吸收利用效率和籽粒产量的变化,为该地区小麦生产上科学施用氮肥提供理论依据。【方法】于2014—2015和2015—2016两个小麦生长季,在大田条件下设置3个灌水处理,自然降水(W1)、适墒(W2,70%±5%)、足墒(W3,80%±5%)和3个施氮量处理(不施氮,N1;减氮施肥,N2:195 kg·hm~(-2);常规高量氮肥,N3:270 kg·hm~(-2)),测定了0—100 cm土层硝态氮含量、冬小麦植株氮素吸收转运量和籽粒产量。【结果】0—60 cm土层硝态氮(NO_3-N)的分布随土层加深而减少,随施氮量增加而提高,随土壤墒情的增大而减少;60 cm又出现不同程度的回升,尤其是足墒(W3)加大了NO_3-N的淋溶,N2、N3水平下80—100 cm土层W3平均比W1高出了3.8 mg·kg~(-1)和4.2 mg·kg~(-1);减氮处理(N2)促进了NO_3-N吸收,成熟期0—20 cm土层NO_3-N比开花期平均降幅为2.3 mg·kg~(-1),高氮处理(N3)收获后土层中NO_3-N却有较多的富集。减氮适墒处理(W2N2)显著增加了开花期营养器官氮素积累量(P0.05),并促进氮素向籽粒的有效转运,尤其表现在叶片中;花前氮素转移量和对籽粒的贡献率均达最大,籽粒产量和籽粒中的氮素积累量分别比其他处理平均高出15.4%、27.3%,从而极显著提高了氮素吸收率和生产效率(P0.05)。【结论】本试验条件下,施氮量195 kg·hm~(-2),拔节后土壤相对含水量维持在70%±5%,是兼顾产量、氮肥吸收和生产效率的最佳处理。     

土壤活性氮动态变化及氮素可利用性对紫云英翻压量的响应

通过田间定位试验,研究了减量化肥紫云英不同翻压量下土壤活性氮的含量、动态变化及氮素可利用性,探讨了紫云英鲜草的适宜翻压量和土壤氮素利用效率,为双季稻合理施用氮肥提供理论依据。在稻-稻-紫云英轮作体系典型时期紫云英翻压前、早稻分蘖盛期、早稻成熟期、晚稻分蘖盛期、晚稻成熟期分别采集土壤样品,监测稻田土壤微生物量氮（MBN）、可溶性有机氮（DON）含量动态变化及氮素可利用性,并分析晚稻成熟期土壤铵态氮（NH₄⁺-N）和硝态氮（NO₃^--N）含量。结果表明：与对照（CK）处理相比,各施肥处理均提高了土壤全氮（TN）、NH₄⁺-N和NO₃^--N含量,增幅分别为10.4%~21.2%、10.3%~44.1%和14.7%~52.9%。在翻压紫云英15.0~22.5 t·hm^-2时,土壤TN、NH₄⁺-N和NO₃^--N含量均随紫云英还田量增多而提高,之后则随还田量的增多而降低。与常规施肥处理相比,化肥减施下紫云英各翻压量处理均提高了土壤MBN、DON及活性氮含量,增幅分别为7.0%~28.7%、8.5%~22.5%和5.8%~26.6%,且随紫云英翻压量的增加呈先增加后降低的变化趋势,MBN和活性氮含量均在翻压量22.5 t·hm^-2时最高,DON含量在翻压量30.0 t·hm^-2时最高。MBN/TN在翻压量22.5 t·hm^-2时最高,DON/TN在翻压量30.0 t·hm^-2时最高。各处理不同时期土壤MBN、DON含量及MBN/TN、DON/TN有明显波动,总体来看,土壤MBN含量及MBN/TN在早稻分蘖盛期明显降低,早稻成熟期有所回升,至晚稻成熟期又逐渐降低;土壤DON含量及DON/TN在早稻成熟期降至最低,至晚稻成熟期再次上升。研究表明,减施40%化肥条件下长期翻压紫云英不仅能增加土壤活性氮含量,同时有利于提高土壤氮素可利用性,紫云英翻压量22.5~30.0 t·hm^-2时效果最好。