旱地农田生态系统氮肥利用率的评价

 在杨凌中等肥力红油土上进行的连续4季大田试验表明,旱地农田生态系统中氮肥不仅在第1季作物产量和吸氮量上表现出突出的效果,而且还有较长的后效,可持续到第4季作物上。当季氮肥利用率平均31.7%,4季叠加利用率63.3%,后者是前者的2倍,施氮量愈高,叠加利用率与当季利用率间的差别更大。这表明仅用当季作物氮肥肥效难以客观可靠评价氮肥利用率,应当把后效考虑在内。     

不同前作对磷肥后效的影响

在小麦、毛苕、豌豆施用磷肥的土壤上,接连种植玉米和小麦,研究前3种作物施磷的后效。结果表明,不同前作施磷均有明显后效,其大小既和前作增产效果、由肥料中吸收的磷素多少有关,也和磷肥用量有关。前作增产效果大,吸磷多,肥料利用率高,后效减少;磷肥用量低而前作利用率较高时,后作利用率显著下降,反之亦然。尽管第二、三料作物的吸磷量和肥料的利用率因前作而异,但三料作物的总利用率却大致接近,以亩施4.5kg P_2O_5者最高。经过三料作物吸收,磷肥用量高者仍有明显后效,但用Olsen法测定,不同处理有效磷含量却无明显差别。     

半干旱地区春小麦氮肥后效的研究

连续4年春小麦氮肥后效的大田试验结果表明:在连续2年(2003~2004年)施用纯氮52.5、105、157.5、210 kg/hm2后再连续2年(2005~2006年)停施氮肥,前2年未被利用的氮素可使后2年籽粒平均增产25.4%;干物质在五叶期及以后时期与对照相比均有明显增加;植株吸氮量在后续第1年(2005年)各处理平均增加22.4%,第2年(2006年)各处理平均增加14.0%;氮肥4年累计利用率比4年连续施用氮肥的处理提高了7.8%~12.9%.     

潮褐土冬小麦-夏玉米轮作体系氮肥后效及去向研究

【目的】在华北平原地区,研究肥料氮在两个轮作季四茬作物中的后效和去向。【方法】采用田间微区15N示踪试验,前茬设置5个氮素水平：0、75、150、225、300 kgN•hm-2（表示为N0、N75、N150、N225、N300）,副处理为小麦品种：科农9204和河农822,共计10个处理。【结果】在该试验条件下,后三茬作物均能吸收利用第一茬冬小麦残留在土壤中的15N标记肥料。第二茬夏玉米、第三茬冬小麦和第四茬夏玉米对残留15N的利用率分别为6.5%-14.1%、0.9%-2.9%和1.2%-1.6%。四茬作物的叠加利用率显著高于氮肥当季利用率,N75、N150、N225和N300处理叠加利用率分别是53.8%、58.7%、58.6%和55.8%（第一茬为河农822小麦品种）;60.0%、61.3%、60.9%和55.2%（第一茬为科农9204小麦品种）。经过四季作物种植后,土壤剖面中仍有22.3-96.2 kgN•hm-2的氮素残留,残留率为22.1%-32.8%,累积总损失量可达9.3-55.3 kgN•hm-2,损失率为8.9%-18.6%。【结论】在小麦当季,高施氮量条件下肥料主要残留在土壤中,后茬作物可以吸收土壤残留氮肥。土壤中15N含量随施氮量的增加而增加,随着茬口的增多有垂直向下运移的趋势,第一茬作物品种间无显著差异。     

稻-麦轮作体系中有机氮与无机氮的去向研究

【目的】在中国多熟制农作生态系统条件下,农田中氮素的低有效度是阻碍作物高产和导致环境问题的重要因素。本项研究旨在跟踪稻麦轮作体系中化学氮肥与有机作物残茬(专指作物地上部秸秆)的氮素去向,为农田氮素的可持续管理提供理论依据。【方法】采用随机区组设计的田间多重复小区内设置15N同位素示踪微区的连续跟踪试验的方法。【结果】在施用化学氮肥的基础上无论作物残茬是取出还是还田,肥料对作物吸氮的贡献率为17.17%(16.55%—17.79%),而施用作物残茬的相应值为12.01%,即作物吸氮有82.83%或87.99%来源于土壤氮库。化学氮肥和作物残茬的作物氮素回收显示截然不同的模式:作物对化肥氮的回收呈现一次性特征,即施肥后第1季的氮回收量占到总回收氮量的92.04%,与之相应单施作物残茬区的第1季作物15N回收率为总回收率的38.03%。表明化肥氮绝大部分在第1季为作物回收,作物残茬氮则有较长的后效;第1季结束时,化学氮肥区和作物残茬区的土壤15N残留率分别为33.46%(两种残茬管理方式的平均值)和85.64%。残茬氮的土壤残留远远高于化肥氮的残留率;在第6季(化学氮肥区)或第5季(作物残茬区)结束时,化肥区与残茬区的作物+土壤的总15N回收率有显著差异(分别为64.38%和79.11%),而在施用化学氮肥的基础上加入或不加作物残茬对肥料氮的作物+土壤回收率则影响很小。【结论】化学肥料氮与作物残茬氮相比,前者对作物吸氮而言更为快速有效。而与之相反,作物残茬氮则对提高土壤供氮能力有更多贡献,因为作物残茬氮进入土壤有机质库的量高于化肥氮。为此,在农业生产中应实行化学氮肥与有机氮源的合理配合使用。     

Fate of Nitrogen from Organic and Inorganic Sources in Rice-Wheat Rotation Cropping System

The lower availability of N is one of the most important limiting factors impeding crop yield enhancement among the various factors that affect crop yield under the multiple-cropping agroecosystem in China.In this study,the recovery of a single application of 15N-labeled fertilizer or residues in rice-wheat cropping system was determined,in order to provide theoretical foundation for the nitrogen management in sustainable agricultural production.A continuous trace experiment was conducted for 15N microplots by using randomized block design with four treatments and four replications（T1 = 15N-labeled fertilizer with crop residue incorporation,T2 = 15N-labeled residues,T3 = 14N fertilizer to generate unlabeled crop residue,and T4 = 15Nlabeled fertilizer without crop residue incorporation）.Our results showed that,on average,17.17 and 12.01% of crop N was derived from N fertilizer and 15N-labeled residues,respectively during the first growing season,suggesting that approximately 82.83 or 87.99% of crop N was derived directly from soil N pool.There was a larger difference in the 15N recovery pattern in crop when N was applied as fertilizer or residues,i.e.,most of crop N derived from N fertilizer was absorbed in the first growing season（92.04%）,and the relevant value was 38.03% when 15N-labeled residues were applied.This implied that most of N fertilizer was recovered in the present cropping season,while a longer residue effect will be found for 15N-labeled residues.Thus,the average recovery of N fertilizer and N residue in the soil after the first growing season was 33.46 and 85.64%,respectively.The recovery of applied N in soil when N was applied as residues was significantly higher than that when N was applied as fertilizer.There was a larger difference in the total 15N recovery in plant and soil when N was applied as fertilizer or residues.By the end of the fifth or sixth cropping season,the total 15N recovery in plant and soil when N was applied as fertilizer or residues were estimated at 64.38 and 79.11%,respectively.On the contrary,there was little difference between the practices of residue incorporation and residue removal following the N fertilizer application.N fertilizer appeared to be more readily available to crops than residue-N,and residue-N replenished soil N pool,especially N in soil organic matter,much more than N fertilizer after six growing seasons.Therefore,residue-N is a better source for sustaining N content of soil organic matter.Thus,one possible management practice is to use both organic and inorganic N sources simultaneously to improve the use efficiency of N while protecting the sustainability of soil.     

甲壳素包裹缓释肥料对农作物生长的作用

[目的]为提高肥料利用率,获得高产高质的农作物打下基础。[方法]考察自制甲壳素包裹缓释肥料对番茄、黄瓜和玉米生长的影响,并对其在农艺性状、产量、肥料利用率和残效方面的作用进行比较。[结果]番茄-黄瓜试验表明甲壳素包裹型缓释肥料的氮素利用率可达58%。[结论]甲壳素包裹型缓释肥料较速效氮肥能够更好地促进农作物植株的稳定生长,实现作物的增产。     

华北平原不同施氮量与施肥模式对作物产量与氮肥利用率的影响

合理施肥是保证作物高产、减少面源污染的重要措施，以华北平原为研究区域，基于7个长期施肥试验，探讨不同施氮量及施肥模式（不施肥CK、化肥NPK、有机肥M、有机无机配施NPKM）对作物产量及氮肥利用率的影响。结果表明，作物产量与施肥量之间整体呈抛物线趋势，作物产量最高值均出现在NPKM处理。不同施肥模式对作物产量有一定影响，NPKM与NPK处理小麦产量无显著差异，且显著高于M、CK处理；NPKM、NPK、M处理玉米产量无显著差异，均显著高于CK处理。氮肥利用率随着施氮量增加呈下降趋势，不同施肥模式对氮肥利用率有一定影响，小麦季NPKM与NPK处理氮肥利用率无显著差异，且高于M处理，玉米季NPKM、NPK、M处理之间氮肥利用率均无显著差异。综合分析施氮量与有机肥替代率两因素对小麦产量的影响，在华北平原，利用有机肥替代化肥潜力可观，且不会显著降低作物产量，甚至增产，但为避免显著减产，在考虑提高有机肥替代率时，需要满足总施氮量的需求。     

Optimizing the phosphate level of soils in agroecosystems of opolie regions of Central Russia

The regularities of the effectiveness of systematic application of phosphorus fertilzer in various types of crop rotations have been studied in long-term permanent field experiments on gray forest soils of opolie regions of Central Russia. The main factors determining the degree of use by crops of freshly applied and residual phosphates—the level of phosphorus fertilizer in agroecosystems, nitrogen supply of crops, and characteristics of phosphorus nutrition of the crops being grown—have been established. Depending on the character of interaction of these factors, crops over the course of 9 to 23 years have utilized 12–88% of applied fertilizer.     

Optimal management of nitrogen fertilizer in the main rice crop and its carrying-over effect on ratoon rice under mechanized cultivation in Southeast China

This study attempted to clarify the carrying-over effect of different nitrogen treatments applied to the main crop on the crop population growth and yield formation of ratoon rice under mechanized cultivation in Southeast China.  Based on the constant total nitrogen application amounts (225.00 kg ha^–1) in the main crop, an experiment with different ratios of basal and topdressing nitrogen fertilizer (the ratio of basal fertilizer:primary tillering fertilizer:secondary tillering fertilizer:booting fertilizer at 3:1:2:4 (N1), 3:2:1:4 (N2), 3:3:0:4 (N3), and 4:3:0:3 (N4), respectively, and a control without nitrogen treatment (N0)) was set up across two consecutive years in field using hybrid rice variety Yongyou 1540 as the test materials.  The results showed that the total tiller number and effective tillering percentage increased in the main crop under the N1 treatment, more nitrogen fertilizer applied in late growth stage of the main crop, and its effective tillering percentage of the main crop was the highest at up to 70.18%, which was 9.15% higher than that of conventional fertilization treatment (N4), more nitrogen fertilizer applied in early growth stage of the main crop.  The same tendency was observed in leaf area index (LAI) value of the main crop and its subsequent ratoon rice, which were 16.52 and 29.87% higher, respectively, in the N1 treatment than that in the N4 treatment at the full heading stage.  The same was true in the case of the transport rates of stem and sheath dry mater and the canopy light interception rates in both the main and its ratoon crops.  The transport rate of stem and sheath in main crop rice under N1 treatment increased by 50.57% compared with N4 treatment.  The canopy light interception rate of N1 treatment increased by 5.07% compared with N4 treatment at the full heading stage of the ratoon crop.  Therefore, the total actual yield was the highest in the main and its ratoon crops under N1 treatment, averaging 17 351.23 kg ha^–1 in two-year trials, which was 23.00% higher than that in the conventional fertilization treatment (N4).  The results showed that appropriate nitrogen treatment was able to produce a good crop stand in the main crop, which was essential for producing a good ratoon crop population and high yield especially under mechanized cultivation with low stubble height of the main crop.  The study suggested that shifting the proper nitrogen application amounts to the late growth stage of the main crop, such as N1 treatment, not only had a higher productive effect on ensuring the yield of the main crop, but also had a positive effect on the axillary bud sprouts from the stubbles for ratoon rice, resulting in an increased percentage of productive panicles and achieving the goal of one planting with two good harvests under the conditions of our study.     

砂壤质潮土定位试验30年的肥效演变

利用建立于1980年的砂壤质潮土肥料长期定位试验,对30年的肥效演变进行了研究与分析.结果表明,长期不同施肥处理,小麦、玉米历年产量顺序基本趋势为NPK＞ NP＞N＞CK;有机肥与化肥配合,作物产量大幅度提高,均高于相对应的化肥,且稳产性好.单施化肥前3年,氮肥养分效率明显,磷、钾肥效果不明显,3年后氮效下降,而磷、钾效上升;磷肥连续施用有明显的残效迭加效应,比一次足量施用具有更好的增产效果,且小麦的磷肥肥效高于玉米;砂壤质潮土增施钾肥有明显和稳定的增产效果,配施有机肥后肥效明显下降.有机肥与化肥配合,有机肥肥效随N、P、K配合比例的增加而降低,有机肥长期施用有明显的后效.养分供应不协调会引起作物缺素而严重影响生长发育,以致减产.     

生物炭对作物氮肥利用率影响的整合分析

为科学施用生物炭、提高氮肥利用率,采用整合分析的方法,收集符合筛选标准的文献33篇,统计了170组包含生物炭配施化肥(BC+NPK)和单施化肥(NPK)处理下作物氮肥利用率的数据,从不同地域、土壤养分、氮肥用量、生物炭特性与施用量、作物种类等方面量化分析生物炭对作物氮肥利用率的影响。结果显示：施用生物炭可以使作物氮肥利用率提高4.76%,其中南方地区生物炭的促进效果最为明显,提高了11.73%。土壤肥力影响生物炭对氮肥利用率的增幅,在土壤pH值、有机质含量、速效氮含量较低的南方地区,施用生物炭对氮肥利用率的提升效果最优,而在有机质含量较高、pH值较高的东北地区,施用生物炭的效果则有所降低;当氮肥施用量≤120 kg/hm2时,生物炭的增效效果最明显,氮肥利用率提高了10.73%。与经济作物相比,粮食作物的氮肥利用率提升效果更为明显,增加了5.71%。生物炭施用量控制在≤1%时,氮肥利用率提高3.43%,木质材料制备的生物炭的提升效果最明显,氮肥利用率提高7.99%;生物炭含氮量>2%时,氮肥利用率提高19.43%;生物炭pH 9~10时氮肥利用率最佳,肥料利用率能够提升5.01%。     

减量施肥模式对稻麦轮作体系作物产量和养分利用效率的影响

为实现化肥高效施用和零增长目标,采用稻麦轮作两季作物大田试验,探讨不同减量施肥模式对轮作体系周年产量及养分利用效率的影响。试验设置不施肥(CK)、常规化肥(CF)以及等养分条件下有机肥与化肥配施(LF1)、有机肥与化肥配施基础上减20%化肥N增施氮肥增效剂(LF2)、有机肥与化肥配施基础上减20%化肥P增施磷素活化剂(LF3)以及有机肥与化肥配施基础上减20%化肥N+减20%化肥P增施氮肥增效剂+磷素活化剂(LF4),共6个处理。结果表明：与常规化肥(CF)相比,LF2处理的稻麦周年产量显著提高了7.6%,LF4处理的稻麦周年产量显著降低了6.2%,LF1和LF3处理对稻麦周年产量影响不显著;LF2处理能够显著增加周年氮、磷、钾素的偏生产力以及氮、磷素的吸收效率,LF4处理显著提高了周年氮、磷素的偏生产力和氮素的吸收效率同时也显著减低了钾素的偏生产力,LF1处理仅显著提高了周年氮素的利用效率,而LF3处理对周年氮、磷、钾素的养分利用效率各指标均无显著影响。综合结果表明,有机肥与化肥配施基础上减少20%化肥N增施氮肥增效剂(LF2)模式有利于协调作物养分吸收和提高产量,可作为长江中下游相似生态区域稻麦轮作种植减肥增效的优选模式。     

水稻-油菜轮作条件下磷肥效应研究

【目的】采用田间裂区试验研究不同磷肥用量对水稻-油菜轮作体系中作物产量、磷素吸收量以及磷肥当季利用率和残留利用率的影响,评估水稻季不同磷肥用量对油菜的后效大小,探讨周年轮作内磷肥的分配,为水稻-油菜周年轮作体系下油菜季磷肥管理提供科学依据。【方法】采用水稻-油菜周年轮作田间试验,前季水稻包含4个不同的磷肥水平,分别为P0（0 kg P2O5•hm-2）、P30（30 kg P2O5•hm-2）、P60（60 kg P2O5•hm-2）和P90（90 kg P2O5•hm-2）,后季油菜在水稻季试验基础上采用裂区试验,每个小区裂区为施磷（60 kg P2O5•hm-2）和不施磷（0 kg P2O5•hm-2）2个副区,研究不同施磷条件下水稻-油菜轮作体系中作物产量、磷素吸收量、磷肥当季利用率和残留利用率,以及水稻季不同磷肥用量对后季油菜产量和磷素吸收量的影响,并引入“后效磷量”的概念评估水稻季磷肥后效。【结果】水稻季施磷60 kg P2O5•hm-2时水稻产量最高,磷肥当季利用率最大,分别为9 694 kg•hm-2和19.2%,施磷不足或者过量均会降低油菜的产量和磷肥当季利用率。与油菜季不施磷处理相比,油菜当季施磷60 kg P2O5•hm-2显著增加油菜干物质量765-1 195 kg•hm-2,其中油菜籽增产427-503 kg•hm-2;油菜产量和磷素吸收量也受到水稻季磷肥用量的影响,水稻季施用磷肥后季油菜干物质量显著增加212-816 kg•hm-2,其中油菜籽粒增产136-409 kg•hm-2,磷素吸收量增加0.4-4.9 kg•hm-2。水稻季残留在土壤中磷肥可以供后季油菜吸收利用,增加油菜当季磷肥的农学效率和磷肥贡献率,具有明显的后效。水稻季磷肥当季利用率16.3%-19.2%,残留利用率为5.4%-7.3%,累积利用率为21.8%-25.6%,磷肥的后效与磷肥用量显著正相关,水稻季磷肥后效相当于油菜当季施磷2-9 kg P2O5•hm-2的增产效果。水稻季磷肥后效也受到油菜季磷肥用量的影响,油菜季施磷处理水稻磷肥对油菜磷素吸收增加作用低于油菜季不施磷处理。【结论】在水稻-油菜轮作体系中,合理的施用磷肥能明显提高两季作物的产量、养分吸收量和肥料利用率,水稻季施用的磷肥残留在土壤中可以被后季作物吸收利用,显著地增加油菜的产量和磷素吸收量,对后季油菜具有明显的后效,其后效的大小与施磷量显著正相关。因此在水旱轮作体系中,在兼顾“重旱轻水”的磷肥管理策略下,油菜季应该充分考虑前茬作物水稻季磷肥后效的基础上进行优化磷肥管理。     

应用15N研究前作施用有机肥对烤烟氮肥效应的影响

为进一步促进烤烟轮作周期内有机肥和氮肥的合理施用,采用田间微区试验和田间小区试验相结合的方法,应用稳定性同位素15N示踪技术,研究了前作施用有机肥(秸杆、油枯、腐熟猪粪)对烤烟氮肥效应的影响。结果显示:与对照相比,前作施用有机肥可以促进烤烟的生长,影响烤烟对氮肥的利用;有机肥的种类不同,对烟株各部位叶片中的氮含量的影响不同;前作施用油枯和腐熟猪粪后,烟株不同部位的氮来自肥料的比例增加,提高了烤烟对氮肥的利用率;有机肥前作施用可以提高上部叶的可用性,对中部叶的品质有利。试验的结果表明:前作施用油枯和腐熟猪粪较好。     

湖南双季稻田氮素去向及残效定量研究

【目的】研究不同施氮量下双季稻田氮素的吸收利用、损失残留和残效特征,定量化揭示湖南双季稻田肥料氮去向和残效规律,为制定科学合理的双季稻田氮肥施用措施提供理论依据。【方法】于2017—2018年在湖南双季稻区开展田间15N微区试验,按氮肥施用量设4个施氮量（以纯N计）处理:N0（不施氮）、N1（早晚稻均为90 kg/ha）、N2（早稻120 kg/ha,晚稻135 kg/ha）、N3（早稻150 kg/ha,晚稻180 kg/ha）。2017年施用15N标记尿素,研究各处理的15N吸收利用、15N在土壤中的残留及15N损失率,明确肥料15N的不同去向及其占比;2018年施用等量未标记尿素,分析各处理残留15N的吸收利用和损失率。【结果】差减法氮肥吸收利用率随施氮量的增加而显著下降（P< 0.05）,2017年早晚稻氮肥吸收利用率分别为42.14%～46.62%和35.45%～43.08%,2018年分别为37.93%～42.56%和37.20%～44.51%。示踪法2017年早稻15N回收率为24.49%～24.53%;晚稻15N回收率为25.32%～26.59%,晚稻略高于早稻;各处理15N回收率相近,无显著差异（P> 0.05）。各处理肥料15N去向基本一致,作物吸收、土壤残留和总损失分别约占25%、23%和52%。肥料15N主要残留在0～20 cm土层中,约占总残留量的77%,20～40 cm土层约占19%,40～60 cm土层约占4%。上一季水稻残留的氮肥,可供下一季水稻吸收利用,是土壤氮库的补充,0～20 cm土层残效最好,2018年两季水稻累积残留15N吸收率为8.13%～9.28%,累积损失率为38.68%～52.97%,最终残留率为38.90%～52.05%。【结论】双季稻田氮肥利用率较低,氮肥损失占比较大,早晚稻均达50%以上;水稻积累的氮素主要来自于土壤,土壤氮贡献率达71.00%以上。双季稻生产中应充分考虑土壤自身的供氮能力以及上季水稻的氮肥残效,适当降低当季水稻的施氮量,实现氮肥的高效利用。     

冬小麦氮素吸收及产量对喷灌施肥均匀性的响应

 为了为喷灌均匀系数设计标准的制订提供更充分的依据，分别于2002~2003和2003~2004年度在北京进行了喷灌施肥均匀系数和施肥量对冬小麦氮素吸收量和产量影响的田间试验。试验中生育期平均喷灌均匀系数变化范围为72%~84%。除了基肥外，其它肥料利用喷灌系统施入，生育期平均喷灌施肥均匀系数变化范围为71%~85%，喷灌施肥量的变化范围为0~180kgN/hm2。试验结果指出，在所研究的均匀系数范围内，均匀系数对氮素吸收量和产量的影响不明显。施肥量对冬小麦产量的影响不明显，但秸秆全氮含量和氮素吸收量均随施肥量的增加呈现出增加趋势。本研究结果表明，对华北平原的冬小麦喷灌来说，目前我国采用的喷灌均匀系数不小于75%的设计标准不会对氮素吸收量和产量造成负面影响。     

缓/控释氮肥对主要粮食作物及环境影响研究进展

本文围绕着近年来缓/控 释氮肥在主要粮食作物（小麦、玉米）上的应用展开综述。从小麦和玉米适用的缓/控 释氮肥类型、缓/控 释氮肥对作物产量和肥料利用率、氮养分平衡的影响、氮损失途径以及缓/控 释氮肥应用前景等方面进行分析,较全面的总结了施用缓/控释氮肥对小麦、玉米作物及土壤环境的影响,并对未来粮食生产的可能影响进行剖析。分析发现不同类型缓/控 释氮肥能不同程度提高小麦和玉米产量或保证稳产;合理施用缓/控 释氮肥能够提高氮肥料利用率、降低土壤氮素累积、减少氮素损失;提高土壤微生物量和酶的活性;减少温室气体排放及降低地下水体的硝酸盐污染。但施用缓/控 释氮肥对根际养分研究相对较少及存在施用方式的不合理性。建立科学合理的简化施肥技术体系,对缓/控 释肥的应用和推广具有重要意义。     

Responses of Nitrogen Uptake and Yield of Winter Wheat to Nonuniformity of Sprinkler Fertigation

Field experiments were conducted to investigate the effects of nonuniformity of sprinkler fertigation and the amount of fertilizers applied through fertigation on nitrogen uptake and crop yield during two growing seasons of winter wheat in 2002-2003 and 2003-2004 at an experimental station in Beijing. In the experiments, the seasonal averaged Christiansen irrigation uniformity coefficient （CU） varied from 72% to 84%. Except for the fertilizer applied before planting, fertilizer was applied with the sprinkler irrigation system with a seasonal averaged CU for fertigation varied from 71% to 85%. Three levels of fertilizer applied varying from 0 to 180 kg N ha^-1 were used in the experiments. The experimental results demonstrated that sprinkler fertigation uniformity had insignificant effects on nitrogen uptake and crop yield for the uniformity range tested. Also, the influence of fertilizer applied through sprinkler fertigation on crop yield was minor, while the total nitrogen content for stem and nitrogen uptake increased with increasing fertilizer applied.     

减量施肥对小白菜连作的产量、品质及生理特性的影响

在大棚种植条件下,以小白菜为试验材料,设置3个施肥水平:225.00kg/hm2(对照)、168.75kg/hm2(减量25%)和146.25kg/hm2(减量35%),研究了施肥水平对三茬小白菜的硝酸盐积累量、产量、营养品质和生理特性的影响。结果表明:每茬小白菜减量施肥处理组产量均低于对照,第三茬减量35%处理减产明显。第三茬减量25%和减量35%小白菜的维生素C和可溶性糖含量较对照下降明显,三茬小白菜的各处理丙二醛(MDA)含量、超氧化物歧化酶(SOD)和过氧化物酶(POD)活性均随着时间的推移呈先升后降的趋势。第一茬和第二茬小白菜过氧化氢酶(CAT)与SOD、POD呈相反变化,对照组均低于处理组水平,第二茬减量35%处理的小白菜硝酸盐含量最低。综合考量本试验土壤肥力、小白菜连作的产量、各品质因素以及食用安全性,减量35%施肥处理至第二茬为宜。