Excessive nitrogen application decreases grain yield and increases nitrogen loss in a wheat–soil system

Abstract

Excessive use of nitrogen (N) fertilizers in wheat fields has led to elevated NO₃-N concentrations in groundwater and reduced N use efficiency. Three-year field and ¹⁵N tracing experiments were conducted to investigate the effects of N application rates on N uptake from basal and topdressing ¹⁵N, N use efficiency, and grain yield in winter wheat plants; and determine the dynamics of N derived from both basal and topdressing ¹⁵N in soil in high-yielding fields. The results showed that 69.5–84.5% of N accumulated in wheat plants derived from soil, while 6.0–12.5%and 9.2–18.1% derived from basal ¹⁵N and top ¹⁵N fertilizer, respectively. The basal N fertilizer recovery averaged 33.9% in plants, residual averaged 59.2% in 0–200 cm depth soil; the topdressing N fertilizer recovery averaged 50.5% in plants, residual averaged 48.2% in 0–200 cm soil. More top ¹⁵N was accumulated in plants and more remained in 0–100 cm soil rather than in 100–200 cm soil at maturity, compared with the basal ¹⁵N. However, during the period from pre-sowing to pre-wintering, the soil nitrate moved down to deeper layers, and most accumulated in the layers below 140 cm. With an increase of N fertilizer rate, the proportion of the N derived from soil in plants decreased, but that derived from basal and topdressing fertilizer increased; the proportion of basal and top ¹⁵N recovery in plants decreased, and that of residual in soil increased. A moderate application rate of 96–168 kg N ha^?1 led to increases in nitrate content in 0–60 cm soil layer, N uptake amount, grain yield and apparent recovery fraction of applied fertilizer N in wheat. Applying above 240 kg N ha^?1 promoted the downward movement of basal and top ¹⁵N and soil nitrate, but had no significant effect on N uptake amount; the excessive N application also obviously decreased the grain yield, N uptake efficiency, apparent recovery fraction of applied fertilizer N, physiological efficiency and internal N use efficiency. It is suggested that the appropriate application rate of nitrogen on a high-yielding wheat field was 96–168 kg N ha^?1.     

毛白杨抗冻性低温诱导过程中糖的效应(英文)

在低温锻炼和结合蔗糖处理的低温锻炼下 ,对毛白杨 (Populustomentosa)幼苗枝条和叶片的可溶性糖含量 ,以及幼苗存活率和抗冻性分别进行了测定 .结果表明 ,低温锻炼明显提高了幼苗枝条和叶片的可溶性糖含量 ,同时也提高了幼苗的存活率和抗冻性 .2 0 %蔗糖处理对上述低温锻炼的作用有加强的效果 .进一步分析发现 ,无论是单纯的低温锻炼还是结合蔗糖预处理的低温锻炼 ,幼苗枝条中可溶性糖含量的提高程度均较叶片明显 ,而且它们的含量增加与幼苗抗冻性的提高密切相关 .这表明低温锻炼所引起的可溶性糖积累可能参与了幼苗抗冻性的诱导     

生物钟基因在绒山羊皮肤中表达模式的比较

文章旨在研究绒山羊皮肤生物钟基因clock、tim、per1和cry1的表达模式,进而分析其在绒山羊皮肤组织中的作用及相互关系。生物钟基因形成一个转录-翻译反馈环,通过钟基因在绒山羊皮肤生长周期进行高表达,激活per1和cry1基因的转录-转化过程,从而在mRNA和蛋白水平的调控下进行有节律的表达。结果表明,这些生物钟基因在绒山羊皮肤中的表达量依次为:clocktimper1cry1;皮肤次级毛囊兴盛期,高振幅clock、per1、tim、cry1的节律表达分别出现在一天中的04∶00、08∶00、08∶00、16∶00;皮肤次级毛囊休止期,这些基因的高振幅节律表达分别出现在一天中的08∶00、04∶00、04∶00、16∶00。另外,cry1、per1基因的表达在生物钟基因正反馈循环中被激活,tim基因的表达在生物钟基因的负反馈循环中被激活。因此,clock、tim、per1和cry1调控下运行的钟基因反馈环是绒毛生长呈周期性现象的基础。     

追氮量对不同粒色小麦籽粒产量、品质及硒吸收的影响

为探究氮肥追施量对不同粒色小麦产量和品质的影响,选用4 个黑粒小麦(‘运黑161’、‘紫优5号’、‘冬黑1号’、‘临黑131’)和7个白粒小麦(‘品育8012’、‘济麦44’、‘济麦23’、‘晋麦95’、‘石农086’、‘邯农1412’、‘中农175’)品种,设置0(N₀)、34.5(N₁)、51.8(N₂)和69.0(N₃)kg/hm² 4个追氮水平(在拔节期追施),测定小麦籽粒产量、品质、氮含量和氮吸收量、硒含量等指标。结果表明:1)与N₀相比,追氮均增加小麦籽粒产量,不同品种达到最高产量的适宜追氮量不同。4个黑粒小麦籽粒产量在N₁处理最高,产量增幅为19.4%~30.8%;白粒小麦‘品育8012’、‘济麦23’、‘晋麦95’、‘济麦44’和‘石农086’籽粒产量在N₂处理最高,产量增幅为20.8%~85.1%,‘邯农1412’和‘中农175’产量随追氮量增加而增加。2)追氮可增加2种粒色小麦籽粒氮含量,黑粒小麦在N₃处理氮含量最高,增幅为4.2%~18.3%,白粒小麦N₂处理最高,增幅为3.9%~18.1%。追氮可使黑粒小麦籽粒硒含量增加11.3%~121.8%,白粒小麦籽粒硒含量降低6.7%~83.0%;追氮使黑粒小麦籽粒蛋白含量增幅为0.7%~16.1%,白粒小麦增幅为0.8%~31.7%。3)综合考虑产量和品质指标,在基施氮肥165.0 kg/hm²基础上,黑粒小麦拔节期追氮34.5 kg/hm²,白粒小麦拔节期追氮51.8 kg/hm²较为适宜。     

砂姜黑土区氮肥基追比对不同小麦品种产量和品质的影响

为了确定豫西南砂姜黑土区小麦的最佳氮肥基追比,以强筋小麦郑麦7698和弱筋小麦偃展4110为试验材料,研究了豫西南砂姜黑土区氮肥基追比(0∶10、2∶8、4∶6、6∶4、8∶2、10∶0)对不同筋度小麦产量和品质的影响.结果表明,在砂姜黑土区,氮肥基追比对不同筋度小麦产量和品质有较大影响,随着氮肥基追比的增加,2个小麦品种的产量及品质总体上均先增加后降低.强筋小麦郑麦7698和弱筋小麦偃展4110分别在基追比4∶6、6∶4时产量最高、品质最优;此时两品种产量分别为7 274.0、7 230.5 kg/hm2,小麦产量的提高主要得益于有效穗数的增加.在豫西南砂姜黑土区,建议强筋小麦以基追比4∶6、弱筋小麦以6∶4施氮方式为优.     

不同变黄时间对烟叶叶绿素及其主要化学成分含量的影响

以云烟87为试材,探讨了在烘烤过程中,不同变黄时间对烟叶叶绿素及其主要化学成分含量的影响。结果表明,延长变黄时间12 h 后,烟叶的总糖、还原糖、总氮、烟碱含量适宜,钾氯比值最高,化学成分最协调,工业可用性较好,综合经济效益最优。     

沼液施用方式和浓度对小白菜生长和品质的影响

以“上海青”小白菜为材料,研究滴灌、喷灌两种施肥方式和沼液浓度对小白菜生长和品质的影响,以更好地将沼液与节水灌溉设施结合应用在叶菜有机基质栽培．结果表明：浇灌适宜浓度的沼液可以改善小白菜的品质,提高产量;滴灌处理中,滴灌沼液比（沼液与水的体积比）以1：5（D4处理）的效果最好,小白菜产量为3．09kg·m-2,V。含量显著高于滴灌营养液的对照,增加25．23％;喷灌处理中,喷灌沼液比以1：4（S3处理）的效果最好,产量为2．B0kg·m-2,Vc含量显著高于喷灌营养液的对照,增加18．98％;D4和％的亚硝酸盐、硝酸盐和重金属含量均低于无公害蔬菜安全标准（GB18406．1—2001）;D4的产量比S3提高10．26％,经济效益更好．     

日光温室番茄的氮素追施与反馈调控

在施用足量有机肥的基础上,以山东寿光当地的常规氮肥追施措施为对照,通过结合硝酸盐速测技术对日光温室秋冬茬番茄不同生育时期的氮素供应进行实时动态调控,以确定合理的追肥数量。结果表明,同当地农民的常规处理相比,采用实时调控处理的氮素投入总量减少了N170kg.hm2,但对番茄的生长(株高、茎粗、果实发育速度等)、产量和品质等指标没有任何影响。根据追肥前根层土壤氮素的供应水平(0—30cm土壤NO3--N含量+氮素追施数量)的监测,可初步确定日光温室秋冬茬番茄在第一穗果膨大期、第二穗果膨大期和第四穗果膨大期时的氮素供应目标值最多为N296kg.hm2、216kg.hm2和191kg.hm2。与此同时,将每个时期所确定的目标值应用在同期生长的其它3个日光温室的番茄氮素追施调控,结果发现与相应的农民常规处理相比,实时调控处理对作物的生长同样没有影响,这表明在日光温室秋冬茬番茄生产过程中,结合植株和土壤硝酸盐速测技术,通过施肥调控满足作物在不同生长时期的氮素供应水平是可行的。     

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]     

Effects of Delayed Nitrogen Topdressing on Grain Yield and Photosynthetic Characteristics of Flag Leaves of Wheat

Four wheat cultivars were used to study the effects of delayed nitrogen topdressing on popula-tion structure, grain yield and photosynthetic characteristics of flag leaves under high-yielding conditions. Theresults showed that the nitrogen topdressing delayed from overwintering-turning green stage (N1) to turninggreen-jointing stage(N2 ) and jointing-booting stage(N3 ) decreased ineffective tiller in spring, retarded the de-cline of green leaf area and chlorophyll content in late life span, promoted photosynthetic ability of flag leavesand significantly increased the grain yield. N3 treatment was suitable for most wheat cultivars except the geno-types with higher single spike productivity and less ears in unit area.