施氮对高淀粉玉米和普通玉米子粒可溶性糖和淀粉积累的影响

采用田间试验、植株生理生化分析和电镜观察等方法,研究了不同氮肥用量对高淀粉玉米吉单535和普通玉米军单8号子粒糖分与淀粉形成的影响。结果表明,在施氮量N 0～200 kg/hm2之间,两品种玉米子粒淀粉含量随着施氮量的增加而增加,过量施氮则淀粉含量降低。灌浆期吉单535子粒蔗糖、果糖、葡萄糖含量高于军单8号,适量施氮使子粒灌浆期保持较高的蔗糖、果糖和葡萄糖含量,有利于淀粉合成。高淀粉玉米在成熟期淀粉粒充满了细胞,大小均匀,排列有序;普通玉米的淀粉粒则没有充满细胞,大小不一,排列混乱。适宜施氮下淀粉粒大小较为均匀,淀粉粒之间挤压轻微,而过量施氮下淀粉粒相互挤压成多面体状。     

高密度直播油菜高产优质和氮肥高效的适宜氮肥施用模式

【目的】探讨高密度直播油菜(36×104plant/hm2)的合理氮肥管理措施。【方法】2011-2012年油菜季选用甘蓝型油菜品种德油6号,在成都平原稻-油轮作区开展了氮肥施用量、施氮方式对油菜产量、品质和氮肥利用率影响的大田试验。氮肥施用量试验在相同施氮方式(底肥+1次苗期追肥)下设置5个施氮水平(N 0、90、180、270和360 kg/hm2);施氮方式试验在同等施氮量(N 225 kg/hm2)条件下,设置3种施氮方式(一次性底施、底肥+1次苗期追肥、底肥+2次苗期追肥)。【结果】直播油菜农艺性状都随施氮量增多而呈增加趋势,而施氮方式对株高、一次分枝数和单株角果数无显著影响。增施氮肥可显著提高油菜籽粒产量和菜油产量,含油率则有所下降。随施氮量增加,油菜籽芥酸含量呈上升趋势,而硫甙含量略呈降低趋势。施氮方式对油菜籽含油率、芥酸和硫甙含量均无显著影响。油菜产量和氮肥贡献率(NCR)都随施氮量(90 270 kg/hm2)加大而提高,当施氮量继续增加(360kg/hm2)时却出现明显下降。但180与270 kg/hm2两施氮量处理间的油菜产量、氮肥贡献率(NCR)和氮肥表观利用率(REN)均无显著差异。随施氮量增加,氮肥农学利用率(AEN)、氮肥偏生产力(PFPN)和氮肥表观利用率(REN)表现出明显降低趋势。当施氮量≥270 kg/hm2时,氮肥农学利用率(AEN)、氮肥偏生产力(PFPN)和氮肥表观利用率(REN)均显著低于90 kg/hm2处理。同等施氮量下,氮肥分期施用可以提高直播油菜籽粒产量和菜油产量,并以底追两次施氮相对较高。底追两次施氮方式的氮肥利用率(AEN、PFPN、NCR、REN)均相对高于其他施氮方式。【结论】在本试验中等肥力条件下,高密度直播油菜(36×104plant/hm2)的合理氮肥施用模式为施氮量180kg/hm2和底追两次施氮方式。     

施氮量和底追比例对小麦氮素吸收利用及子粒产量和蛋白质含量的影响

在大田栽培条件下,运用15N示踪技术研究了不同施氮量和底追肥比例对小麦氮素利用和子粒产量及蛋白质含量的影响。结果表明,施用氮肥提高了小麦植株的氮素积累量、子粒产量、蛋白质含量和蛋白质产量。相同施氮量条件下增加追肥氮的比例,提高了氮肥农学利用率和吸收利用率,增加了植株地上部器官(子粒+营养器官)中追肥氮、土壤氮的积累量,提高了营养器官中氮素的转运量和开花后氮素的同化量,增加了子粒蛋白质含量。相同的氮素底追肥比例条件下,将240.kg/hm2施氮量降至168.kg/hm2的处理,氮肥农学利用率、氮肥吸收利用率、氮肥偏生产力提高,子粒中土壤氮的积累量增加,植株地上部器官中土壤氮的积累量亦增加,开花后氮素同化量提高,子粒蛋白质含量增加。各施氮处理间子粒产量无显著差异。在本试验条件下,施氮量为168.kg/hm2且全部于拔节期追施是兼顾产量、品质和效益的优化处理。     

叶面不同施氮量对大豆氮素吸收与分配的影响

为研究大豆叶面氮素吸收与分配规律,以黑龙江省三江平原大豆主栽品种合丰50为试验材料,采用15N示踪法在大豆R5期进行叶面施氮处理,研究大豆不同器官对氮素同化吸收及积累分配情况。结果表明:当施氮量超过4.5kg·hm-2(N3)条件下,大豆植株各器官干物质量、氮素含量、氮素积累量均不再显著增加。子粒干物重在4个施氮量(N1、N2、N3、N4)条件下分别比无氮处理增加2.51%,5.01%,9.55%和0.51%,在4.5kg·hm-2(N3)条件下最高,为21.8g/株。同一施氮量条件下,大豆不同器官15N积累量为子粒茎叶荚皮叶柄根;在不同施氮量条件下,15N在各器官积累量随施氮量增加而增加,在4.5kg·hm-2(N3)条件下达到最高值,子粒15N积累量为8.17mg/株。从N1到N3处理增加施氮量降低了15N在子粒中的分配比例,但提高了15N在叶片中的分配比例,同时提高了15N在子粒中的积累量。本研究从理论上证明了在大豆R5期进行叶面施氮时,氮素主要积累于子粒中,从而有利于子粒干物质积累,最终获得增产。     

不同施肥处理对油菜产量及品质的影响

通过在姜堰地区的大田试验,研究了不同施肥处理条件下油菜产量及籽粒品质的变化.试验设10个肥料处理:对照(不施肥,CK),缺氮(PKB)、缺磷(NKB)、缺钾(NPB)处理,大量营养元素平衡施肥处理(NPK)、增施微量营养元素处理(NPKB、NPKBZn),不同氮肥施用量处理(1/2N+PKB、3/2N+PKB、2N+PKB).结果表明:①缺失氮、磷、钾中任何一种养分时均能降低油菜产量,且当氮肥施用量为N 18 kg/667m2时,产量最高,而硼和锌肥对油菜增产没有显著效果.②在氮、磷、钾缺素处理中,油菜硫甙含量大小顺序为NKB＞ PKB＞ NPB,芥酸含量大小顺序为PKB＞NKB＞NPB,油菜含油量没有显著变化,油酸含量为NPB＞NKB＞PKB,蛋白质含量在PKB处理下最低.③在NPK处理平衡施肥条件下,施加硼肥能显著降低硫甙和芥酸含量,显著增加油菜含油量、油酸、蛋白质含量;继续增施锌肥对油菜含油量没有显著影响,但能进一步显著降低硫甙和芥酸含量,并显著提高油菜油酸和蛋白质含量;④油菜硫甙对氮肥施用量具有拐点效应.油菜芥酸含量随着氮肥施用量的增加而显著降低.氮肥施用过高(2N+PKB)显著降低含油量.氮肥施用量对蛋白质的影响趋势和油酸一致,即先随施氮量(＜ 12 kg/667m2)的增加而显著增加,而进一步增施氮肥则没显著变化.     

施氮对"双低"油菜吸氮特性及氮素生理效率的影响

采用盆栽试验研究施氮对双低油菜吸氮特性及产量的影响。结果表明，植株氮素累积量，施氮处理从苗期到抽苔末期迅速增加，抽苔末期到开花末期下降，开花末期后有所回升，但仍没有超过抽苔末期的氮素累积量；不施氮处理与施氮处理有类似的变化趋势，但变化幅度明显小于施氮处理，而且开花末期后的氮素累积量超过了抽苔末期。无论施氮与否，营养器官含氮量随生育期的进程持续下降，而生殖器官含氮量施氮时持续下降，不施氮时则呈单峰曲线。干物质累积最大速率出现的日期，不施氮处理明显早于施氮处理。氮素生理效率，施氮处理在角果发育期最高，而不施氮处理在开花末期最高。施氮明显增加植株氮素累积量、植株含氮量、生物量及籽粒产量，但氮素生理效率却降低。     

施氮水平对油菜生育后期氮素吸收积累和分配的影响

以湘油15 为材料,应用15N 示踪技术,在盆栽条件下设置两个施氮水平,通过比较研究油菜初花期、盛花期、终花期、角果发育期、成熟期的干物质积累、氮素积累和分配以及15N 丰度,以揭示油菜生育后期根系对氮肥的吸收特性和氮素的再分配规律,为油菜高效氮肥管理和高产栽培提供理论依据。结果表明:在油菜发育后期,根的氮素累积量变化不大,茎的氮素累积量的变化呈现单峰模式,在盛花期达到最大值。叶片氮素积累量从初花期到终花期显著下降;角果粒氮素积累量呈S 形曲线,终花期之前缓慢增加,终花期至结果发育期快速增加,其后略有增加;茎秆中氮素积累量从盛花期开始缓慢降低;角果皮在终花期积累至最高,其后逐渐下降;角果果瓣在终花期后略有降低,但变幅不大。在低施氮水平(T1 处理)下,油菜生育后期有61.98% 的氮素来自土壤,38.02% 的来自肥料,所有器官中氮素来源于土壤中的比例高于来自肥料中的比例;在高施氮水平(T2 处理)下,油菜生育后期总积累的氮素来自肥料氮的比例为52.69%,高于来自土壤的比例(47.31%),其中角果粒和茎秆中积累的氮素来自肥料的比例显著高于来自土壤的比例,根、角果皮和角果果瓣中积累的氮素来自肥料和土壤的比例相接近。油菜生育后期对氮素仍然有较大的需求量,也具有较强的氮素吸收与累积能力。     

越冬期干旱胁迫对油菜施肥效果的影响

利用田间试验研究了越冬期自然干旱胁迫和适时灌溉条件下,油菜施用氮、磷、钾和硼肥的效果。结果表明,干旱胁迫条件下,油菜的生长发育受到明显抑制,子粒产量比适时灌溉条件显著降低;而且不同施肥处理间的减幅差异较大,其顺序为:不施硼处理(-B)不施钾处理(-K)不施氮处理(-N)≈不施磷处理(-P)NPKB配施处理,表明平衡施肥能够有效提高油菜的抗旱性。试验结果还显示,无论是在干旱胁迫还是适时灌溉条件下,施用肥料均显著促进了油菜的生长发育,表现为增施氮肥效果最好,而磷、钾和硼肥在干旱条件下相对增产效果明显高于灌溉条件;同时施肥与灌溉之间存在着一定的正交互作用。因此,在干旱而缺乏灌溉的情况下,油菜的高产更加依赖于肥料的施用。     

绿肥配施氮肥对双季稻产量和养分吸收的影响

基于2016年的田间定位试验，在冬闲(F)和冬种绿肥(G)2种模式下，探究不同施氮量(N0:不施氮；N50:减氮50%;N100:常规氮；N150:增施氮50%)对双季稻产量、养分吸收特征及氮素利用率的影响，以期为南方稻区绿肥利用和氮肥施用提供科学理论依据。结果表明，与冬闲模式相比，冬种绿肥模式提高4种不同氮水平下的早晚稻产量，其中早、晚稻稻谷产量平均增产8.0%,5.7%。2种模式下的早稻产量随施氮量增加均呈现出先增加后降低的趋势，而晚稻则呈现上升的趋势。冬种绿肥模式同样提高植株地上部氮(N)、磷(P)和钾(K)素积累量和氮肥偏生产力。随施氮量的增加，这2种模式的早晚稻养分收获指数和氮肥利用率大多呈下降趋势，高量氮肥处理(N150)降低早稻地上部K素的积累量。早晚稻稻谷产量与水稻N、P和K素积累量存在显著正相关，2种模式下的高氮处理(N150)K素吸收的降低与其早稻产量下降相关联。结合稻谷产量与施氮量拟合分析、养分吸收利用等多方面效应，综合考量，冬闲模式下，早稻季氮肥适宜施用范围为150.0～170.3 kg/hm²,冬种绿肥模式下，早稻季氮肥适宜施用范围为75...     

配施有机肥条件下油菜化肥氮减施潜力研究

探明湖南省油菜种植区配施有机肥条件下化肥氮减施潜力,为该地区油菜生产中氮肥减施增效提供参考。田间试验在湖南省郴州市进行,供试油菜品种为湘油420,采用裂区设计,研究配施等量(2250 kg/hm²)有机肥条件下不同氮肥用量(0、90、135、180、225、270 kg/hm²)对油菜生长、产量、理论产油量和经济效益的影响。结果表明,所有氮肥水平下配施有机肥均显著提高油菜产量,且在低氮水平下增产效果更加明显,有机肥的增产效果主要通过增加单株角果数和每角果粒数来实现。在不施与施有机肥条件下,施氮量分别为213和199 kg/hm²时油菜籽产量最高,分别为1754和2514 kg/hm²,氮肥减少了6.6%、产量提高了43.3%;施用有机肥条件下达到不施有机肥的最高产量值仅需127 kg/hm²氮肥,减少了44.1%。所有供氮水平下,施用有机肥可显著增加氮素积累量、理论产油量和经济效益,包括有机肥氮的氮肥偏生产力也呈增加趋势,而包括有机肥氮的氮肥农学效率和氮肥表观利用率变化较小;与不施有机肥相比,施有机肥的最高理论产油量施氮量减少了3.0%,最高效益施氮量减少了20.0%,而理论产油量和效益分别增加了41.1%和50.0%。     

双低油菜(Canola)硫营养临界期与最大效率期的研究

利用温室砂培盆栽试验，分别在油菜生长的五个自然生育期严格控制营养液供硫浓度（高S0．75mmol／L或低S0．075mmol／L），研究各生育期供硫水平对油菜生长的影响。结果表明，发芽－莲座期（0～35天）低S处理容易短时间内表现缺硫症状，对子粒产量与含油量有明显的影响；开花期前后充足供硫可明显提高菜籽产量。后期增加供硫浓度不仅可明显增加菜籽的硫浓度、含油量，而且菜籽的硫甙含量也显著提高。比较各生育期供硫不足与菜籽产量的关系，以莲座期与开花期的影响最大。莲座期可作为油菜硫营养的临界期，开花期为最大效率期。硫的两个吸收高峰恰与油菜生长对硫的临界期与最大效率期相吻合。生长前期供硫充足主要促进植株的营养生长，茎枝重量较高但子粒产量很低，而后期供硫充足则显著促进植株的开花结果，增加角果数、角果重及子粒饱满度。前期供硫不足会使作物的花期明显延迟，中后期增加供硫浓度时还会造成植株的再次开花结果而使成熟期显著延迟。     

Dinitrogen fixation and soil n uptake by soybean as affected by phosphorus availability

The effects of phosphorus supply (0, 30, and 90 mg P kg^‐1) on growth, N₂ fixation, and soil N uptake by soybean (Glycine max (L.) Merr.) were studied in a pot experiment using the ¹⁵N isotope technique. Phosphorus supply increased the top dry matter production at flowering and the dry matter production of seeds, straw, pod shells, and roots at late pod filling of inoculated soybeans. Phosphorus supply reduced the N concentration of plant tops at flowering, but increased the amount of N accumulated at both flowering and late pod filling. In inoculated soybeans total N accumulation paralleled the dry matter production. The P concentration in above‐ground plant parts of nodulated soybeans was not affected by P application. At flowering only 18 to 34% of total N was derived from N₂ fixation, whereas as much as 74% was derived from N₂ fixation at late pod filling. Only the addition of 90 mg P kg^‐1 soil significantly increased the amount of N₂ fixed at the late pod filling stage. Phosphorus supply did not influence the uptake of fertilizer or soil N in soybeans, even if the root mass was increased up to 60% by the P supply.     

Ontogenic variation in nitrogen fixation and accumulation of nitrogen in mungbean,blackgram, cowpea,and groundnut

Ontogenic variations in N₂ fixation and accumulation of N by the mungbean (Vigna radiata L. Wilczek), blackgram (Vigna mungo L. Hepper), cowpea (Vigna unguiculata L. Walp.), and groundnut (Arachis hypogaea L.) were studied by a ¹⁵N-dilution technique. Pots filled with 7 kg of red yellow podzolic soil were used. Samples were taken 20, 40, 60, and 80 days after emergence which approximately corresponded to preflowering, flowering, early/mid-pod filling and late pod filling stages, respectively. During early growth (up to 40 days after emergence), the carryover of seed N accounted for a considerable fraction of the total plant N in the legumes, the highest being in the groundnut. With a correction for carryover, the groundnut derived over 45% of its N content from the atmosphere 20 days after emergence whereas the corresponding figures were 33% for the blackgram and about 28% for the cowpea and mungbean. Between flowering and early pod fill, there was a rapid increase in N₂ fixation in all legumes except in groundnut which showed highest fixation from 60 to 80 days after emergence. In the mungbean, N₂ fixation and uptake of soil N were insignificant 60 days after emergence while in other legumes these processes continued beyond this time. All legumes derived about 90% of their N from atmosphere by 80 days after emergence. However, due to considerable interspecific differences in total N yield the final amount of N₂ fixed showed an appreciable variation among legumes. It was highest in the groundnut (443 mg N plant^-1) followed by the cowpea (385), blackgram (273), and mungbean (145), respectively. The groundnut maintained nodules until the late pod filling stage while in other legumes, nodules senesced progressively following the mid-pod filling stage. During pod filling there was a net mobilization of N from vegetative tissues to developing pods in the mungbean, which amounted to about 20% of N in seeds. This mobilization was not evident in other legumes.     

Grain legumes differ in nitrogen accumulation and remobilisation during seed filling

In grain legumes, the N requirements of growing seeds are generally greater than biological nitrogen fixation (BNF) and soil N uptake during seed filling, so that the N previously accumulated in the vegetative tissues needs to be redistributed in order to provide N to the seeds. Chickpea, field bean, pea, and white lupin were harvested at flowering and maturity to compare the relative contribution of BNF, soil N uptake, and N remobilisation to seed N. From flowering to maturity, shoot dry weight increased in all crops by approximately 50%, root did not appreciably change, and nodule decreased by 18%. The amount of plant N increased in all crops, however in field bean (17?g?m^?2) it was about twice that in chickpea, pea, and lupin. The increase was entirely due to seeds, whose N content at maturity was 26?g?m^?2 in field bean and 16?g?m^?2 in chickpea, pea, and lupin. The seed N content at maturity was higher than total N accumulation during grain filling in all crops, and endogenous N previously accumulated in vegetative parts was remobilised to fulfil the N demand of filling seeds. Nitrogen remobilisation ranged from 7?g?m^?2 in chickpea to 9?g?m^?2 in field bean, and was crucial in providing N to the seeds of chickpea, pea, and lupin (half of seed N content) but it was less important in field bean (one-third). All the vegetative organs of the plants underwent N remobilisation: shoots contributed to the N supply of seeds from 58% to 85%, roots from 11% to 37%, and nodules less than 8%. Improving grain legume yield requires either reduced N remobilisation or enhanced N supply, thus, a useful strategy is to select cultivars with high post-anthesis N₂ fixation or add mineral N at flowering.     

Effect of nitrogen fertilization on yield component distribution and assimilate translocation of determinate and indeterminate soybean lines

Studies were conducted to compare the main‐stem and branch yield component distribution of two soybean [Glycine max (L.) Merr.] lines differing in architecture and growth habit, and to relate the partitioning of carbon assimilates during pod filling and seed filling stages. An indeterminate line (MI) and a determinate line (MD) were planted in early May on a fine, mixed mesic Udic Haplustalf soil in southwestern France. For the N treatment, N fertigation was applied at the end of the vegetative phase and the early stages of reproductive growth. Pod production on branches was stimulated in response to N application for the determinate line, and N also enhanced the weight of seeds located on branches for both lines. At different stages during pod setting and seed filling, mid‐canopy‐level leaves were allowed to assimilate ¹⁴CO₂ and 24 h after exposure, radioactivity was measured in different organs and levels of the whole plant. ¹⁴C‐assimilates appeared to be preferentially transferred to the lower level of the main‐stem in MI and to the lower level and branches in the MD line. For N‐treated plants, radiocarbon accumulation was particularly marked in pods located on the lower level and on branches; this was consistent with the yield component distribution patterns seen at harvest.     

PHENOLOGY AND SEED QUALITY RESPONSE OF RAPE (B. NAPUS) VERSUS MUSTARD (B. JUNCEA) TO SULFUR AND POTASSIUM FERTILIZATION IN NORTHWEST PAKISTAN

Inappropriate sulfur and potassium fertilization, particularly with continued soil nutrient mining and yearly fluctuations in rainfall, are major factors contributing to slow growth and low seed quality of canola in northwestern Pakistan. A field experiment was conducted in 2007–2008 on a sulfur (S) and potassium (K) deficient clay loam soil under irrigation at the research farm of NWFP (Northwest Frontier Province) Agricultural University, Peshawar, Pakistan, with an objective to determine response of phenology and seed quality of Brassica oilseed rape versus mustard to S and K fertilizer application. Twenty treatments in a randomized complete block design were consisted of two oilseed genotypes [rape (B. napus canola) and mustard (B. juncea canola)], at three rates each of S (15, 30, and 45 kg S ha^?1) and K (30, 60, and 90 kg K ha^?1), plus control (no K and S applied). Days to flowering, pod formation, seed filling duration and maturity were enhanced with K and S fertilization compared to control plots. The species B. napus took more time to flowering, pod formation, seed filling duration and maturity compared to B. juncea. Both genotypes responded positively for seed quality (oil and protein content) to K and S fertilization, but the magnitude of response varied with level and combination of K and S fertilization. Delay in the phenological stages showed negative relationship with oil and protein content in seed of both genotypes. It is concluded that a combination of 60 kg K ha^?1 + 30 kg S ha^?1 would accelerate phenological development and improve seed quality of rape and mustard in the study area.     

Comparative yield and chemical composition of soybean and fababean grown on chernozemic soils on the Canadian prairies

Abstract

Soybean (Glycine max (L.) Merrill) and fababean (Vicar faba (L.)) were grown under field conditions on six Orthic Black Chernozemic soils over three years at two levels of fertility. At flowering, full pod and maturity the yield and N, P, K and S composition of harvested plant materials were compared. Application of fertilizer (P, K and S) increased dry matter and seed yields of both crops. At all, growth stages fababeans produced more dry matter than soybean, and at maturity produced higher yields of seed, hull and stalk. However, the ratio of seed: hull: stalk for both crops was similar and constant at 3.8: 1: 4.7 on all soils and at both levels of soil fertility. At the high level of soil fertility, at the flowering and full pod stages, the concentration of N, P, and K in fababean was higher than that in soybean, but both crops had a similar concentration of S. At low fertility both crops had similar concentrations of P, K and S. At maturity, soybean seed had the higher concentrations of the four nutrients. The concentration of P in the hull and stalk of both crops was similar, but fababean hull had a higher concentration of K and soybean stalk a higher concentration of S. Soybean seed also had a higher protein content and yielded more protein per hectare than fababean seed.     

Root growth and N‐uptake activity of oilseed rape (Brassica napus L.) cultivars differing in nitrogen efficiency

Nitrate‐N uptake from soil depends on root growth and uptake activity. However, under field conditions N‐uptake activity is difficult to estimate from soil‐N depletion due to different loss pathways. We modified the current mesh‐bag method to estimate nitrate‐N‐uptake activity and root growth of two oilseed‐rape cultivars differing in N‐uptake efficiency. N‐efficient cultivar (cv.) ‘Apex' and N‐inefficient cv. ‘Capitol' were grown in a field experiment on a silty clayey gleyic fluvisol near Göttingen, northern Germany, and fertilized with 0 (N₀) and 227 (N₂₂₇) kg N ha^–1. In February 2002, PVC tubes with a diameter of 50 mm were installed between plant rows at 0–0.3 and 0–0.6 m soil depth with an angle of 45°. At the beginning of shooting, beginning of flowering, and at seed filling, the PVC tubes were substituted by PVC tubes (compartments) of the same diameter, but with an open window at the upper side either at a soil depth of 0–0.3 or 0.3–0.6 m allowing roots to grow into the tubes. Anion‐exchange resin at the bottom of the compartment allowed estimation of nitrate leaching. The compartments were then filled with root‐free soil which was amended with or without 90 mg N (kg soil)^–1. The newly developed roots and nitrate‐N depletion were estimated in the compartments after the installing period (21 d at shooting stage and 16 d both at flowering and grain‐filling stages). Nitrate‐N depletion was estimated from the difference between NO ‐N contents of compartments containing roots and control compartments (windows closed with a membrane) containing no roots. The amount of nitrate leached from the compartments was quantified from the resin and has been taken into consideration in the calculation of the N depletion. The amount of N depleted from the compartments significantly correlated with root‐length density. Suboptimal N application to the crop reduced total biomass and seed‐yield formation substantially (24% and 38% for ‘Apex’ and ‘Capitol’, respectively). At the shooting stage, there were no differences in root production and N depletion from the compartments by the two cultivars between N₀ and N₂₂₇. But at flowering and seed‐filling stages, higher root production and accordingly higher N depletion was observed at N₀ compared to N₂₂₇. Towards later growth stages, the newly developed roots were characterized by a reduction of root diameter and a shift towards the deeper soil layer (0.3–0.6m). At low but not at high N supply, the N‐efficient cv. ‘Apex’ exhibited higher root growth and accordingly depleted nitrate‐N more effectively than the N‐inefficient cv. ‘Capitol’, especially during the reproductive growth phase. The calculated nitrate‐N‐uptake rate per unit root length was maximal at flowering (for the low N supply) but showed no difference between the two cultivars. This indicated that the higher N‐uptake efficiency of cv. ‘Apex’ was due to higher root growth rather than higher uptake per unit of root length.     

Spectral assessments of phenotypic differences in spike development during grain filling affected by varying N supply in wheat

Single plant traits such as green biomass, spike dry weight, biomass, and nitrogen (N) transfer to grains are important traits for final grain yield. However, methods to assess these traits are laborious and expensive. Spectral reflectance measurements allow researchers to assess cultivar differences of yield‐related plant traits and translocation parameters that are affected by varying amounts of available N. In a field experiment, six high‐yielding wheat cultivars were grown with N supplies of 0, 100, 160, and 220 kg N ha^–1. Wheat canopies were observed spectrally throughout the grain‐filling period, and three spectral parameters were calculated. To describe the development of the vegetative plant parts (leaves + culms) and the spikes, plants were sampled four times during grain filling. Dry weights and the relative dry‐matter content were recorded for leaves + culms and spikes. The N status of the plants was assessed by measuring the total N concentration and by calculating the aboveground N uptake. Good correlations were found between spectral indices and single plant traits throughout grain filling but varied with N supply and development stage. The normalized difference vegetation index, NDVI, was strongly affected by the saturation effects of increased N concentration. The red‐edge inflection point, REIP, predicted plant traits with r² values up to 0.98. However, in plants with advanced senescence, the REIP was less efficient in describing plant traits. The NIR‐based index R₇₆₀/R₇₃₀ was closely related to yield‐related plant traits at early grain filling. Compared to the REIP, the R₇₆₀/R₇₃₀ index was resistant to strong chlorophyll decays being able to predict plant traits at late grain filling, with r² values of up to 0.92. Spectral reflectance measurements may represent a promising tool to assess phenotypic differences in yield‐related plant traits during grain filling.     

Use of labeled sulphur‐35 for tracing sulphur transfers in developing pods of field‐grown oilseed rape

Abstract

This study was conducted to better understand the dynamics of sulphur (S) transfer between pod walls and seeds of field‐grown oilseed rape by using sulphur (³⁵S) as an investigative tool. Labeling experiments with ³⁵S were carried out to determine the effects of nitrogen (N) and sulphur fertilization on these transfer mechanisms. Sixty‐four plants from field trials fertilized with 200 kg N ha^‐1 in the forms of ammonium nitrate (AN) or urea (U), with or without 75 kg S ha^‐1 in the forms of ammonium thiosulphate and MgSO₄ were sampled. At 30, 43, 56, and 77 days after flowering (DAF), terminal racemes were cut and labeled with ³⁵S‐SO₄ ^2‐. After labeling, pods and seeds were separated into 3 groups according to their position on stem, and measurements of ³⁵S levels were performed accordingly. This short‐term labeling experiment showed that the pod walls retained from 39 to 61% of labeled ³⁵S, according to the different treatments, whereas seeds accumulated from only 1 to 16% of applied ³⁵S. On average, when S was added, a sharp decrease of ³⁵S in seeds from 2.6 to 1.7%, 9.0 to 5.4%, and 14.8 to 7.7% was observed at 30, 43, and 56 DAF, while progressively the percentage values in pod walls increased from 49.6 to 50.5%, 43.1 to 52.2%, and 41.7 to 63.5%, respectively. The increase of ³⁵S in pod walls was found to be tied to the glucosinolate concentration of seeds. By artificially increasing the ratio values of external N‐NO₃ ^‐ to S‐SO₄ ^2‐, these results demonstrated that the transfer of ³⁵S to seeds was more affected by the higher level of N‐NO₃ ^‐ in plant tissues than S‐SO₄ ^2‐ levels. The N/S ratio value above which the transfer of S was disrupted was around 6.