Maize harvest index and water use efficiency can be improved by inhibition of gibberellin biosynthesis

Possibilities to improve maize harvest index and nutrient utilization efficiency by application of plant growth regulators were investigated. In container experiments, the effects of different growth regulators on the development of the maize (Zea mays L.) cultivars Pioneer 3906 and Fabregas were tested. Paclobutrazol (PAC) and chlorocholine chloride (CCC), two inhibitors of gibberellin biosynthesis, as well as gibberellic acid (GA₃) were applied at growth stage V5. Three weeks after application of PAC, shoot growth of both maize cultivars was strongly affected with a significant decrease in plant height in the PAC treatment by 44% and 36% for Pioneer 3906 and Fabregas, respectively. The growth‐retarded plants had higher leaf areas and reduced transpiration rates. The higher shoot growth after GA₃ application was accompanied by a reduction in leaf area and an increase in transpiration rate during 1 week before anthesis. CCC treatment showed no significant effects on plant height, leaf area and transpiration rate. The PAC‐treated cultivar Pioneer 3906 produced several cobs per plant, which were mainly barren at maturity. However, PAC application to Fabregas resulted in just one cob per plant with good kernel development and a grain yield, which was not significantly reduced in comparison with the control. With this similar grain yield in combination with a straw yield decrease of 32%, the harvest index was significantly improved by 12%. In addition, with PAC‐treated Fabregas plants, a 19% increased water use efficiency of the grain (WUE_grain) during the critical period of kernel setting was achieved. In this maize cultivar, CCC application also improved harvest index by 5%, but no effect on WUE_grain occurred. GA₃ treatment decreased harvest index of both maize cultivars, and it either reduced WUE_grain (Pioneer 3906) or showed no effect (Fabregas). Utilization efficiencies of N, P and K were not increased with growth regulator application, even in the PAC‐treated Fabregas plants with a significantly improved allocation of assimilates to the grain, mirrored by the higher harvest index. The results indicate that fertilizer applications must be adjusted to the reduced demand of growth‐retarded plants, most likely leading to higher nutrient utilization efficiencies.     

种植密度、氮肥和水分胁迫对玉米产量形成的影响

为阐明种植密度、氮肥和水分胁迫对不同玉米品种产量形成的影响,选用6个玉米品种,在两种密度(45 000株 hm^-2和75 000株 hm^-2)、两种施氮水平(纯氮112.5 kg hm^-2和337.5 kg hm^-2)和两种水分(前期干旱控水和正常灌水)处理下进行大田试验,调查玉米源库性状的主要生理参数和籽粒产量。结果表明,在环境压力较小时(低密度、高氮和正常灌水),玉米品种间籽粒产量、源性状(叶面积指数、穗位叶净光合速率和群体源供应能力)、库性状(群体库容量)、源库协调性状(群体库源比值、籽粒灌浆速率和收获指数)以及成熟期干物质积累量和吐丝期至成熟期干物质积累量差异较小,而逆境胁迫下(高密度、低氮和干旱),差异较大。环境压力较大时(高密度、低氮和干旱),叶面积指数、群体源供应能力、成熟期干物质积累量、吐丝期至成熟期干物质积累量、群体库容量和收获指数与籽粒产量呈显著或极显著正相关。由此说明,在玉米品种产量改良中要强化逆境人工选择,以适应自然选择,改善玉米品种逆境下的群体源库性状,增强吐丝期至成熟期叶片的光合生产效率,强源促库,提高逆境下的生产能力和适应性。     

NDVI-based estimates of evapotranspiration of winter wheat indicate positive effects of N fertilizer application on agronomic water-use efficiency

Yield increases by fertilizer application impose higher crop water use, as biomass production is positively correlated with transpiration. To quantify effects of N fertilizer supply on evapotranspiration (ET) of winter wheat, a field experiment with three nitrogen rates (N0, N120 and N230) under non-water-limited conditions was performed during 2014 and 2015. Normalized difference vegetation index (NDVI) was used to derive crop coefficients which were used to calculate N effects on bare soil evaporation (E), transpiration, evapotranspiration (ET), grain yield and harvest index (HI). E during the early post-winter growth period was measured with micro-lysimeters and compared with model estimates. N fertilizer supply resulted in lower cumulative E, and increases in grain yield were higher than increases in ET, resulting in a higher agronomic water-use efficiency (WUE_Y). HI of treatment N120 was higher than that of treatment N230 indicating that HI was not the main reason of higher WUE_Y of treatment N230. It is concluded that estimates of ET under variable N supply require consideration of N-induced effects on canopy development which could be successfully monitored by NDVI measurements. N supply increases ET and WUE_Y potentially imposing a trade-off between water conservation and efficiency of water use for crop production.     

Agronomic Performance and Nutrient Concentration of Maize (Zea mays L.) as Influenced by Nitrogen Fertilization and Plant Density

A field experiment was conducted at Samaru, Nigeria to study the influence of nitrogen fertilization and plant density on the agronomic performance and nutrient concentration of maize ( Zea mays L.). The treatments were factorial combinations of five nitrogen fertilization rates (0, 50, 100, 150 and 200 kg N/ha) and three plant density levels (25000, 50000 and 75000 plants/ha).
Nitrogen fertilization up to 150 kg N/ha enhanced grain and stover yields and increased kernel number and weight up to 100 kg N/ha. Nitrogen supply also increased maize ear length. Increased N fertilization rates increased concentrations of N, K and Mg but had no effect on P and Ca concentrations. Higher grain yield was closely associated with higher N concentration in ear leaf; with 0.1 % change in N concentration causing 177 kg/ha change in grain yield. Increased plant density increased stover yield up to 50 or 75 thousand plants/ha but depressed kernel number and weight and ear length.     

前茬冬小麦栽培措施对后茬夏玉米光合特性及产量的影响

为了明确前茬冬小麦施氮和种植方式对后茬夏玉米光合特性及产量的影响,于2013-2015年华北平原冬小麦-夏玉米轮作区进行裂区试验。冬小麦施氮112.5 kg/hm2(N1)和225.0 kg/hm2(N2)为主处理,冬小麦等行距(U)改为夏玉米等行距(UR),20+40沟播(F)改为垄作(BP)的种植方式为副处理。结果表明,与UR和N1相比,BP和N2提高夏玉米叶面积指数(LAI)、叶绿素含量指数(CCI)、净光合速率(Pn)及干物质重(DM),且减缓LAI、CCI和Pn后期降低幅度。冬小麦季,与U相比,F种植方式增产3.1%、穗数提高6.9%、穗粒数提高2.4%。与N1相比,N2处理增产5.0%、穗数提高13.8%、穗粒数提高4.9%;夏玉米季,与UR比,夏玉米BP种植方式增产7.1%、穗粒数提高2.4%、收获指数提高5.9%。与N1相比,N2处理增产13.0%、穗粒数提高9.2%、收获指数提高11.9%。在华北冬小麦-夏玉米轮作区,冬小麦季施氮225.0 kg/hm2的条件下,氮肥后效明显,结合沟播冬小麦收获后在垄上直播夏玉米的种植方式是一种全程简化、高效、丰产的栽培措施,在华北平原冬小麦-夏玉米轮作区有很高的实践意义。     

Responses to N Deficiency in Stay Green and Non‐Stay Green Argentinean Hybrids of Maize

Breeding has developed better yielding maize hybrids for low N environments, which also have delayed leaf senescence (‘stay green’ trait, SG). Here, we studied whether the SG trait can further improve yield of modern hybrids under N‐limiting conditions. In two field experiments, four maize hybrids with different senescence behaviour were grown under three N fertilization levels, from 0 to 200 kg N ha^?1 (N0, N100 and N200). After silking, hybrids differed for senescence depending on the canopy layer (P < 0.05): the SG AX878 only delayed senescence at the mid and upper canopy layers while the SG NK880 delayed senescence of all layers. Across N doses, higher yields were achieved by both SG hybrids, AX878 and NK880 (P < 0.05) but yield was not only determined by senescence behaviour. Kernel weight (KW) response to N availability was larger for SGs than for their non‐‘stay green’ counterparts. Delayed senescence in SG hybrids was not related to higher post‐silking N uptake but to higher (P < 0.05) %N in leaves and lower (P < 0.05) %N in kernels at harvest (below the critical 1.1 % under N deficiency). Across N levels, KW positively related to N content per kernel, with a steeper slope (P < 0.05) for the SG hybrids. Taken together, our results suggest that a condition where N limits kernel growth, in a scenario of saturating C availability, may be common to stay green genotypes of maize.     

不同密氮模式下高产玉米品种籽粒产量与氮素利用特性研究

为给玉米高产高效栽培提供科学依据,在大田试验条件下,选用郑单958和先玉335为材料,在每个品种下设置2个种植密度(6.75,8.25万株/hm~2)和4个施氮水平(0,180,240,300 kg/hm~2),研究了种植密度和施氮水平下2个高产玉米品种籽粒产量和氮素吸收利用特性。结果表明:在相同密度水平下,2个玉米品种籽粒产量、氮素积累量和蛋白质产量均随施氮量增加总体呈现增加趋势,氮素利用效率则降低;在相同施氮水平下,2个玉米品种籽粒产量、氮素积累量和蛋白质产量均随密度的增加总体呈现增加趋势,氮素利用效率则降低。在不同密氮组合下,先玉335的籽粒产量、氮素积累量、蛋白质产量及氮素利用效率均高于郑单958。本研究条件下,2个玉米品种在密度为8.25万株/hm~2,施氮量为240 kg/hm~2组合下,均可以同步协调实现籽粒产量、蛋白质产量和氮素利用效率的协调统一。     

Nitrogen Fertilizer and Protein, Lipid, and Non-structural Carbohydrate Concentrations During the Course of Maize Kernel Filling

A field experiment was carried out at four location-years in Southwestern Quebec, Canada in 1990 and 1991, to evaluate the effects of nitrogen (N) application on protein, lipid, non-structural carbohydrate (NSC), and remaining grain components concentrations of maize ( Zea mays L.) grain during kernel development. Three N fertilizers (ammonium nitrate, urea, and calcium ammonium nitrate) were compared for plants receiving pre-plant incorporated N fertilizer at 180 kg ha^-1 as well as a control which received no N fertilizer. The results indicated that between 20 and 30 days after pollination (DAP) protein concentration of maize kernels declined sharply, thereafter only slightly, irrespective of the treatment. At most stages and in all four location-years protein concentration was raised significantly by N-application without clear difference between N-fertilizer sources. At 20 DAP seeds of N-fertilized plants contain 25.5 mg g^-1 more than those without N-application (control); later on, this difference was lower (12.8 mg g^-1) but remained constant over time if averaged over N-sources and location-years. At most growth stages and in most location-years the lipid concentration did not respond to N fertilizer application. Lipid concentration followed an "N" shaped curve over the course of grain development. Non-structural carbohydrate (NSC) concentration increased significantly during grain filling and showed little effect due to N application. However, at most growth stages in the four location-years, the concentration of remaining grain components tended to decline with N application. A significant negative correlation existed between the changes in protein concentration and NSC concentration during kernel development.     

Reduction in kernel weight as a potential indirect selection criterion for wheat grain yield under terminal heat stress

Heat is an important abiotic stress during wheat (Triticum aestivum L.) grain‐filling in South Asia. A study was undertaken to determine effectiveness of selection for reduction in 1000‐kernel weight (TKWR) under heat stress to increase grain yield. Selection was made for low and high TKWR and selected progenies were evaluated in timely and late seeded trials at two locations in Nepal in 2003. One thousand kernel weight (TKW), biomass yield, grain yield, harvest index (HI), grain‐filling duration (GFD) and area under spot blotch progress curve per day (AUDPC/day) were examined. The low and high TKWR groups did not differ significantly for TKW, biomass yield, grain yield, HI, days to heading, GFD and AUDPC/day under timely seeding. However, low TKWR lines showed higher TKW, biomass yield, grain yield, HI, and GFD and lower AUDPC/day than the lines with high TKWR under late seeding. Realized heritability estimates for TKWR ranged from 0.68 to 0.85. The findings show that selection for low TKWR could be used as an indirect selection criterion to identify high grain yielding lines under terminal heat stress.     

Sequential path analysis of grain yield and its components in maize

The efficiency of a breeding programme depends mainly on the direction and magnitude of the association between yield and its components and also the relative importance of each factor involved in contributing to grain yield. The purpose of this research is to describe the application of causal path analysis to grain yield in maize (Zea mays L.) to take into account the sequential development of yield components. Causal-admissible path analysis was performed assuming unidirectional causal relationships among yield components of eight maize populations. Sequential path analysis of the five yield components studied revealed that ears per plant had the highest direct effect on grain yield. However, the indirect effects of component traits via number of grains per ear was maximum. It was concluded that the number of kernels per ear, prolificacy, and grain size serve as potential characters in breeding for superior lines for grain yield in maize.     

Grain yield of wheat (Triticum aestivum L.) under long‐term heat stress is sink‐limited with stronger inhibition of kernel setting than grain filling

The aim of the study was to investigate source‐sink relations of wheat under continuous heat stress and to identify bottle necks of yield formation. A pot experiment was conducted in two climatic chambers exposing wheat plants (Triticum aestivum L. cv. Thasos) either to day/night temperatures of 20/20°C (control conditions) or of 30/25°C (heat stress) during the whole vegetation period in the absence of plant water deficit. Plants were harvested at four phenological stages: three‐node stage (DC 33), start of flowering (DC 61), grain filling (DC 75) and maturity (DC 94). Heat stress shortened the development phases of the plants and caused a significant decrease in total above‐ground biomass between 19% and 41%. At grain filling and at maturity, the reductions in total shoot biomass mainly resulted from grain yield depressions by 77% and 58%, respectively. The ear number per plant was significantly higher under heat stress in comparison with the control, at maturity it was more than doubled. On the contrary, under heat stress, the kernel number per ear was strongly decreased by 83% and 75% during grain filling and at maturity, respectively. The decrease in individual kernel weight was 23% at maturity. Thus, the heat‐stressed plants were able to strongly increase the number of ear‐bearing tillers which were able to set only a small number of kernels, yet these kernels showed good grain filling. The harvest index (HI) of heat‐stressed plants was significantly reduced by 36% (control: HI = 50.1% ± 0.4, heat: HI = 32.2% ± 0.9***). The plants in the stress treatment adapted to the adverse conditions by less biomass production which presumably allowed a higher transpiration without an increase in total water consumption. Nevertheless, under heat stress, the water use efficiency (WUE_grain) was strongly decreased by 62% as a result of a small grain yield. In ears and grains, the sucrose, glucose and fructose concentrations were not significantly different between control and heat stress at start of flowering and during grain filling. Thus, the supply of assimilates was not restricted (no source limitation). Sink capacity was reduced by heat stress, as lesser and smaller kernels were produced than in the control. Concerning sink activity, the sink‐limiting step during kernel set is probably the active transport of hexoses across the plasma membrane into the developing kernels, which could also affect grain filling. This needs to be investigated in more detail in further studies.     

氮肥后移对超高产夏玉米产量及氮素吸收和利用的影响

采用田间试验研究了氮肥后移对超高产夏玉米产量、氮素吸收积累和氮肥效率的影响,旨在了解超高产夏玉米(≥ 12 000 kg hm^-2)的氮素吸收和转运特性,为实现夏玉米超高产合理施肥提供依据。结果表明,夏玉米施氮显著增产,增产幅度为9.62%~15.95%,氮肥后移比习惯施氮增产2.27%~5.33%。超高产夏玉米吐丝后氮素吸收积累量占总积累量的40.30%~47.78%,保证后期氮素养分充足供应对于夏玉米达到超高产水平至关重要;氮肥后移可促进超高产夏玉米后期的氮素吸收积累,降低夏玉米茎和叶片氮素的转运率,显著增强灌浆期夏玉米穗位叶硝酸还原酶活性,提高灌浆期叶片游离氨基酸含量,增加蛋白质产量;氮肥后移比习惯施氮的氮肥利用率提高1.88%~9.70%、农学效率提高0.96~2.21 kg kg^-1,以“30%苗肥+30%大喇叭口肥+40%吐丝肥”方式施用氮肥的产量和氮肥利用效率最佳。     

不同施氮水平对超高产夏玉米氮磷钾积累与分配的影响

为探明不同施氮水平下玉米超高产(≥13 500 kg hm^-2)群体氮磷钾积累及分配规律,通过苏玉20、浚单20两品种3年不同氮肥运筹方案的试验,实现了籽粒最高产量14 753 kg hm^-2的目标。结果表明：(1)随着生育进程,两品种氮磷钾在植株、籽粒中积累逐渐增大,在叶片、茎秆、叶鞘中呈先单峰变化趋势,叶片氮钾峰值在大口期,磷峰值在开花期。增大灌浆期植株氮积累量及叶片氮转移率,促使成熟期籽粒氮磷较大积累量,利于超高产玉米群体的形成。(2)籽粒产量、1 kg氮生产籽粒量、氮肥的农学效率、氮素利用率、植株(及叶片、茎秆、叶鞘、籽粒等器官)氮磷钾含量在450 kg hm^-2施氮水平时达到最大值,其值(苏玉20)分别为14753 kg hm^-2、44.0 kg、19.24%、38.63%、335.4 kg hm^-2、178.2 kg hm^-2、230.7 kg hm^-2,过高过低施氮均使氮磷钾积累量及产量下降。(3)由两品种产量与施氮水平的回归方程,确定了超高产时的最佳施氮量、超高产施氮水平和最佳施氮范围,苏玉20分别为457.0 kg hm^-2、418.3~495.7 kg hm^-2、418.5~495.4 kg hm^-2;浚单20分别为452.7 kg hm^-2(最佳施氮量)、410.8~494.6 kg hm^-2 (最佳施氮范围)。     

施氮量与地膜覆盖对长江中游春玉米产量性能及氮肥利用效率的影响

以宜单629为试验材料,于2012-2013年在湖北武穴通过大田试验,研究施氮量和地膜覆盖对长江中游春玉米产量及其性能参数的调节效应以及氮肥利用效率的影响。结果表明,增施氮肥促进春玉米生长发育,抽雄期和吐丝期提前8~12 d,延长籽粒灌浆期2~6 d,全生育期减少2~7 d;地膜覆盖促进种子萌发和玉米植株发育,种子出苗提前7~8 d,抽雄期和吐丝期提前6~11 d,生理成熟期提前3~6 d。增施氮肥和地膜覆盖优化长江中游春玉米产量性能参数,增施氮肥使平均叶面积指数(MLAI)提高81.18%~112.38%,平均净同化率(MNAR)提高19.20%~25.82%,穗粒数(GN)和千粒重(GW)增加72.61%~95.30%和13.09%~21.26%;同等施氮条件下,地膜覆盖提高MLAI (11.12%~17.12%)、MNAR (0.80%~10.66%)、HI (0.44%~6.50%)、GN (7.02%~16.07%)和GW (5.64%~7.93%);由于产量性能参数间的超补偿作用,增施氮肥和地膜覆盖使春玉米籽粒产量提高6.80%~24.66%和7.16%~22.19%。施氮量增加显著降低春玉米氮肥利用效率,氮肥偏生产力(PFPN)和氮肥农学利用效率(ANUE)分别降低31.34%~51.20%和30.39%~42.12%;地膜覆盖促进春玉米的氮素吸收能力,显著提高春玉米氮肥利用效率,PFPN和ANUE分别提高18.30%~31.67%和25.83%~56.80%。统筹考虑长江中游春玉米产量性能优化补偿增产机制和氮肥利用效率特征,可选用优化施氮量202.5 ~270.0 kg hm^-2和覆膜增温降渍,其产量可达8995~9220 kg hm^-2。     

不同降水状况下旱地玉米生长与产量对施氮量的响应

水分不足是旱地玉米生长主要限制因素,渭北旱塬雨养玉米种植区降水季节波动大,干旱频繁发生,已严重影响春玉米正常生长发育及产量稳定性。于2016—2018年在渭北旱塬合阳县进行旱地玉米施氮量定位试验,设置5个施氮量处理, 2016—2017年包括0、75、150、270、360 kg hm~(–2) (分别以N0、N75、N150、N270、N360表示), 2018年施氮量处理为0、90、180、270、360kgNhm~(–2) (分别以N0、N90、N180、N270、N360表示),供试品种为郑单958(ZD958)和陕单8806(SD8806)。分析了不同降水分布年份施氮量对春玉米生育期土壤水分变化动态、干物质积累动态、产量构成、经济效益及水分利用效率(WUE)的影响。结果表明,试验年份降水分布可分为穗期多雨、粒期干旱型(2016年和2018年)和穗期干旱、粒期多雨型(2017年)。生长季降水量及其分布显著影响土壤蓄水量和玉米地上部干物质积累,从而影响玉米产量及其构成因素,穗期干旱显著降低地上部干物质积累量和穗粒数,粒期干旱会明显降低粒重。不同降水分布年份施氮处理较N0增产6.72%～91.23%不等,施氮量对玉米产量、水分利用效率(WUE)影响呈现二次曲线关系,穗期多雨、粒期干旱型以N270处理籽粒产量和WUE最高,而穗期干旱、粒期多雨型以N150处理产量和WUE最好。籽粒产量与"休闲至抽雄期降水(FP2)"、"播前土壤蓄水量+播种至抽雄期降水(SP2)"相关性较强(FP2:R2=0.839**; SP2:R2=0.837**)。根据产量、水分利用和经济收益综合评价,渭北旱地玉米最适施氮方案为基施氮肥150kghm~(–2),再根据休闲至抽雄期降水量或播前土壤蓄水量与播种至抽雄期降水量之和预测产量,估算并及时追施适宜施氮量。     

夏玉米各器官氮素积累与分配动态及其对氮肥的响应

为探明夏玉米各器官氮素积累与分配动态及其对氮肥的响应,以郑单958为材料,设置5个施氮水平进行了连续2年的大田定位研究。结果表明,除籽粒外各器官的氮素积累进程都呈单峰曲线,茎鞘在吐丝期达到峰值,而叶片、苞叶和穗轴则到吐丝后12 d左右达到峰值,之后逐渐下降;籽粒和整株的氮素积累随生育进程持续增加,成熟期最高。与其他器官相比,叶片对氮素供给更敏感,氮胁迫使叶片氮素积累高峰提前,促进氮素提前向外转运,导致其率先衰老。施氮能提高各器官在各生育时期的氮素积累量和积累速率,但不改变氮素积累变化趋势。总体上,施氮量180 kg N hm^-2可满足夏玉米对氮素的需求,获得较高的产量。以各器官氮素积累最大值与成熟期的差值计算,各处理再转运氮素对籽粒的贡献率均表现为叶片>茎鞘>穗轴>苞叶,各器官再转运氮素对籽粒贡献率之和平均为53.3%,其中苞叶和穗轴占12.3%,也是籽粒中氮素来源的重要组成部分。     

氮肥管理与地膜覆盖对旱地冬小麦产量和氮素利用效率的影响

降雨偏少且季节分布不均,施肥偏多且方式不合理,缺少有效的保水栽培措施是西北旱地小麦生产面临的主要问题。2010年10月至2012年6月连续2个小麦生长季,在陕西渭北旱塬进行田间试验,比较了氮肥追施和总量减少、覆膜、增加种植密度措施较传统施肥和农民习惯施肥种植模式对冬小麦籽粒产量及氮素利用效率的影响。与农户习惯施肥相比,传统施肥不能持续增加产量和氮素利用效率;而减氮追肥、减氮垄覆和减氮垄覆增密处理的增产效果明显,同时提高了氮素利用效率,但减氮垄覆或增加种植密度却使籽粒含氮量降低,主要原因是进入开花期后土壤硝态氮累积量减少,氮素供应不足所致。综合分析,减氮垄覆增产增效更明显,小麦产量、氮肥偏生产力、氮肥生理利用率在第1年分别提高38.6%、49.6%和35.1%,在第2年分别提高7.6%、16.3%和25.7%,说明控氮与覆膜结合是实现旱地冬小麦增产的重要措施,但需注意生长后期土壤氮素供应,在增产的同时保证小麦品质。     

Comparison of Salt and Drought‐Stress Effects on Maize Growth and Yield Formation with Regard to Acid Invertase Activity in the Kernels

The long‐term effects of salt stress (11 dS m^?1) and drought stress (35 % WHC) were investigated for two maize genotypes, focusing on the relation between metabolic changes around the time of pollination and the impact on yield determinants at maturity. The relatively salt‐resistant hybrid Pioneer 3906 and the relatively drought‐resistant hybrid Fabregas were compared. The experiments were conducted in large plastic containers in a vegetation hall in two consecutive years (2011 and 2012). Plant height and leaf area were significantly reduced under both stress conditions. The transpiration rate was only slightly reduced under drought stress; but under salt stress, a significant reduction occurred 40–53 days after sowing. As a significant increase in sucrose concentrations was observed in the salt‐treated maize kernels 2 days after pollination, the availability of assimilates was not limiting and the plants could afford to save water by reduced stomatal opening. Although under both stress conditions the soluble acid invertase activity was reduced 2 days after pollination, concomitantly, an increase in hexose concentrations was observed. Thus, in these experiments, the delivery of hexoses by acid invertase activity did not limit kernel development. Differences in grain yield at maturity between salt and drought stress were most likely caused by salt‐specific effects (Na⁺ toxicity), Fabregas being more affected than Pioneer 3906.     

氮肥后移对玉米间作豌豆耗水特性的调控效应

针对水资源不足严重制约干旱灌区间作发展,间作中以氮调水理论研究的薄弱,生产实践中缺乏氮肥运筹同步提高间作产量和水分利用效率的措施等问题。2012-2013年,以河西走廊规模化应用的玉米间作豌豆为研究对象,在总施氮量相同且基肥和孕穗肥分别占10%和50%条件下,设氮肥后移30% (N₁,拔节肥0+花粒肥40%)、氮肥后移15% (N₂,拔节肥15%+花粒肥25%)、传统制度(N₃,拔节肥30%+花粒肥10%) 3个施氮处理,探讨氮肥后移对间作产量和水分利用效率(WUE)的影响,以期为禾豆间作优化施氮制度、提高产量和水分利用效率提供理论依据。结果表明,氮肥后移对玉米间作豌豆总耗水量(ET)影响不显著,但降低了棵间蒸发量(E)和棵间蒸发量占总耗水量的比例(E/ET);与传统施氮处理相比,氮肥后移15%使玉米间作豌豆的E和E/ET降低6%和4%,氮肥后移30%使玉米间作豌豆的E和E/ET均降低2%。在间作系统中,豌豆带、玉米带的棵间蒸发量分别为329 mm、232 mm,表明豌豆带的无效耗水显著高于玉米带。氮肥后移15%间作的混合籽粒产量、WUE较传统施氮间作分别高出6%、5%,氮肥后移30%间作混合籽粒产量、WUE较传统施氮间作分别提高3%、2%。因此,玉米间作豌豆结合氮肥后移15%,即豌豆开花结荚期(玉米拔节期)追施氮肥67.5 kg hm^-2、玉米大喇叭口期追施氮肥225 kg hm^-2、玉米花后15 d追施氮肥112.5 kg hm^-2,可作为绿洲灌区玉米间作豌豆增产和提高WUE的农艺措施之一。     

施氮方式对玉米-大豆套作体系中作物产量及玉米籽粒灌浆特性的影响

氮肥的过量施用和低效利用, 造成资源浪费和环境污染, 不利于农业的可持续发展。为了减少氮肥的投入量, 发挥氮肥的增产效益, 本研究对玉米-大豆套作模式的施氮量和施肥距离进行优化调整。通过两年田间试验, 探讨了减氮36% (RN36%)、减氮18% (RN18%)和习惯施氮(CN) 3种施氮水平和距离窄行玉米0 cm (D1)、15 cm (D2)、30 cm (D3)、45 cm (D4) 4种施肥距离对作物产量和玉米花后干物质积累与转运、籽粒灌浆特征的影响。结果表明, 与习惯施氮相比, 减氮18%处理的玉米花后干物质转移量、转移率及对籽粒的贡献率分别提高了22.65%、18.75%和15.90%, 籽粒平均灌浆速率和最大灌浆速率提高了9.79%和10.76%; 玉米、大豆产量及系统周年产量提高了4.95%、7.07%和5.35%; 各施肥距离间, 以距离窄行玉米15~30 cm的施肥效果最佳。减氮18%时, D2处理下玉米的平均灌浆速率、最大灌浆速率、穗粒数及百粒重比玉米常规穴施(D1)处理分别提高了10.32%、10.92%、9.08%和4.75%; 玉米、大豆产量和系统总产最高。玉米-大豆套作体系下, 减氮18%和距离窄行玉米15~30 cm施肥有利于增加玉米花后干物质的积累, 促进干物质向籽粒中转运, 增大灌浆速率, 增加百粒重和穗粒数, 提高玉米产量和大豆产量, 以实现系统周年作物增产。