Evaluation and analysis of intraspecific competition in maize: A case study on plant density experiment

Intraspecific competition is a common phenomenon in agricultural production,and maize is one of the most sensitive grass species to intraspecific competition due to its low tillering ability.This study evaluated and analyzed intraspecific competition in maize,and screened competitive indices that could be used to evaluate intraspecific competition in a maize population.A 2-year field experiment was conducted using the maize hybrid Zhongdan 2 at 12 plant densities ranging from 1.5 to 18.0 plants（pl）m-2.The results showed that the response of single-plant grain yield and dry matter at harvest to increased plant density decreased exponentially and that the harvest index decreased linearly.The response of population-level grain yield to plant density was curvilinear,producing a maximum value at the optimum population density.However,the yielddensity equation agreed well with the Steinhart-Hart equation curves,but not with the quadratic equation curves reported by most previous studies.Competitive indices are used to evaluate competition in a plant population or plant species.The present results show that competitive intensity（CI）and absolute severity of competition（ASC）increased with increasing plant density;however,relative yield（RY）and relative reproductive efficiency（RReff）decreased.The different responses of these indices reflect different aspects of competition.According to the analysis of CI,ASC,RY,and RReff,higher CI and ASC values indicate higher intraspecific competition,whereas higher RY and RReff values indirectly reflect lower intraspecific competition.These competitive indices evaluate not only the intraspecific competitive intensity under different plant densities of the same cultivar but also those of different cultivars under the same plant density.However,some overlap exists in the calculations of ASC,CI,and RY,so one could simply select any one of these indices to evaluate intraspecific competition in a maize population.In conclusion,the present study provides a method to evaluate intraspecific competition in maize populations,which may be beneficial for breeding high-yield maize varieties in the future.

Historical trends in maize morphology from the 1950s to the 2010s in China

The morphology of the plant and ear is a preliminary selection characteristic in breeding new varieties of maize.As new maize cultivars were developed from the 1950s through the 2010s in China,most had changes in both plant and ear morphological characteristics that contributed substantially to maize yield gains.Over the seven decades,plant and ear height fluctuated with a small increase from the 1950s to 2000s,and then a decrease in the 2010s,while the ear ratio and internodes length below the ear decreased significantly.Leaf angles became significantly more upright,especially for the leaves above the ear,and the leaf area per plant improved markedly.Leaf orientation increased from the 1950s to the 2000s then decreased in the 2010s.Tassel size and the anthesis-silking interval were both reduced substantially.Ear diameter,kernel number,and kernel weight increased from the 1950 to the 2000s,then decreased in the 2010s under the same cultivation conditions.We found that modern maize hybrids have a lower plant height,ear height and ear ratio which increased lodging resistance,a more erect leaf which increased high-density planting tolerance,and smaller ears and kernels which facilitated rapid dehydration during late grain filling.These morphological selection criteria,which are suitable for mechanized operations,are proposed as the focus for future maize breeding.

不同年代玉米品种籽粒产量形成对种植密度的响应

为了明确不同年代玉米品种的光合和灌浆特性对增加种植密度的响应差异,为玉米合理增密增产提供理论依据。本研究以我国1970s—2010s五个在生产中大面积种植的玉米品种为材料,设置了4.5万株hm^(-2)和10.5万株hm^(-2)两个种植密度,进行3年大田试验。对不同种植密度下,各年代玉米品种的产量及其构成因素、叶片光合性能和籽粒灌浆特性等指标进行对比分析。结果表明,在低种植密度下,2010s品种(登海618,Denghai 618,DH618)吐丝后穗位叶SPAD值、吐丝–吐丝后50 d穗位叶Pn和籽粒平均灌浆速率均较1970s—2000s品种显著提高了2.18~12.05、0.57~4.88μmol CO_(2)m^(-2)s^(-1)和0.02~0.09 g kernel^(-1)d^(-1),活跃灌浆期显著延长了2.62~4.74 d,从而使其粒重和产量显著增加(P<0.05)。增密后,1970s和1980s品种产量降低,1990s品种产量变化不显著,而2000s和2010s品种产量显著增加,且2010s品种产量增加幅度最大,达到2.11 t hm^(-2)。进一步对光合性能、灌浆特性与百粒重和产量等指标的相关分析表明,高种植密度下2010s品种的百粒重对活跃灌浆期依赖程度增大(r=0.70),其在吐丝期、乳熟期和成熟期均较1970s—2000s品种保持相对高的SPAD(提高了6.42%~41.92%),延缓了叶片衰老,使花后玉米叶片仍维持较高的光合势(leaf area duration,LAD)和吐丝后30~50 d的Pn(提高了1.09%~88.95%),从而积累了较多的光合产物,促使活跃灌浆期延长8.73%~15.80%,平均灌浆速率增加了3.39%~24.33%,进而维持了相对稳定的百粒重。

玉米耐高密品种冠层光氮分布及匹配特征研究

在有限氮投入下通过增密种植实现玉米增产增效,需要进一步挖掘耐密品种的光氮匹配利用潜力。揭示不同耐密品种冠层光氮空间分布和匹配特征差异,及其与玉米产量形成及氮效率的关系,对探索玉米产量效率层次差异消减途径具有指导意义。本试验以常规品种KH8和耐高密品种MC670为试验材料,在减氮增密条件下,系统分析了常规和耐密型玉米品种冠层光氮分布及匹配特征的差异。结果表明,耐高密品种MC670穗位以上透光率较常规品种KH8高20.6%。两品种的比叶氮(specific leaf nitrogen,SLN)均表现为上层叶片、中层叶片显著高于下层叶片;MC670上层、中层叶片SLN显著高于KH8,但下层叶片差异不显著。KH8和MC670的光氮匹配系数分别为1.28和0.86,MC670的光氮匹配系数与理想值差异较小,说明MC670的光氮匹配程度优于KH8。综上所述,与常规品种KH8相比,耐高密品种MC670冠层具有较低的消光系数和较高的氮消减系数,使耐高密品种冠层具有较优的光氮匹配程度,同时使其中上部冠层具有更高的光合氮比例、光合氮效率和光合生产力,这是其实现较高的氮肥生理效率、氮肥利用效率及获得高产的重要生理内因。

基于数字图像的马铃薯单株叶面积预测技术研究

本研究的目的是建立马铃薯单株叶面积的预测模型,为马铃薯叶面积无损、快捷测量提供技术支持。通过分时期采集植株数字图像和同步手工测量单株叶面积的方法,获得绿叶图像的总像素、单株实测叶面积。通过像素法计算绿叶的覆盖面积,利用覆盖面积与叶面积间的内在关系,建立基于数字图像的马铃薯单株叶面积预测模型,y=1821.3ln(x)-9567.9 R^2=0.56**(Y指单株马铃薯的叶面积,x表示叶片覆盖面积)。经验证,该模型预测精度较高。

Identification of Wheat Canopy Structure Using Hyperspectral Data

Some winter wheat varieties were selected in this experiment. The results were as follows： 1） Leaf orientation value （LOV） and leaf area index （LAI） of wheat had different contributions to canopy spectral reflectance （CSR）. For example, LOV affected greatly canopy spectra more than LAI did in jointing stage, but LAI had a greater effect on CSR than LOV did after the ground was near to be covered completely. 2） Twenty treatments including different varieties and densities were arranged in this experiment, and the result of cluster analysis showed that all these treatments can be parted into four clusters according to LAI and LOV： varieties with erect leaves and low LAI （denoted as A）, varieties with erect leaves and high LAI （denoted as B）, varieties with horizontal leaves and low LAI （denoted as C）, varieties with horizontal leaves and high LAI （denoted as D）. Their CSR had difference in 400-700 nm and 700-1 150 nm at jointing stage, especially in different plant types. 3） There was obvious distribution difference among different clusters in scatter plot （X=△R890, Y=R890）, △R890 was the reflectance increment from jointing to booting stage. It was seen from the Y-axis direction that R890 of horizontal varieties were higher than the erect ones, and seen from the X-axis direction that the greater △R890 was, the lower LAI one within the same plant type varieties, which indicted that the combination of plant-type and the population magnitude can be initially identified by this method.

新形势下非师范类专业人才培养的思考——以集宁师范学院为例

随着地方经济产业结构的转型升级,对高层次技能人才需求正向应用型转变,高师院校非师范类专业应用型人才培养模式改革势在必行。本文首先对集宁师范学院非师范专业人才培养模式的现状进行分析,指出存在的问题;借鉴欧美国家、国内高校典型应用型人才培养的成功经验,提出集宁师范学院非师范类专业应用型人才培养的建议。

深松对控释肥养分释放及春玉米氮效率的影响

以深松耕作(SS)和浅旋耕作(RT)两种耕作方式为主区,以施用普通化肥(HY)、控释肥(CN)和不施氮肥3种施肥模式为副区,分析控释肥的养分释放率、控释肥和普通化肥氮素积累量及产量、氮效率的变化。结果表明,与浅旋耕作处理相比,深松处理提高0~15 cm土层土壤温度,苗期-吐丝期提高0.36℃~3.79℃,土壤含水量提高0.55%~5.74%;0~40 cm土层土壤容重降低0.69%~7.3%,提高控释肥养分释放率1.5%~13.8%,养分释放率与土壤温度显著相关(r=0.557,p<0.01)。深松处理下,施控释肥氮素积累量显著高于普通化肥,提高幅度为8.46%~125.43%,千粒重平均高6.17%,产量平均高11.96%,氮肥农学利用效率平均高122.76%。深松有利于土壤氮素供应与作物需氮的时空匹配,进而提高作物产量及氮效率。

种植密度对不同年代玉米子粒物质积累的影响

以我国1970~2010年代5个在生产中大面积种植的玉米品种为试验材料,设置4.5万株/hm^(2)和10.5万株/hm^(2)两个种植密度,分析品种更替过程中灌浆特性的演变特征及其对增密的响应情况。结果表明,2010年代品种(DH618)的子粒产量较其余年代品种显著提高10.22%~68.79%(P<0.05),且种植密度越大,产量增加越明显。种植密度增加后,1970~2010年代品种渐增期和快增期灌浆速率均降低,1970、1990、2000年代品种缓增期灌浆速率降低,1980、2010年代品种缓增期灌浆速率增加。2010年代品种渐增期、快增期和缓增期灌浆持续时间较其余年代品种增加了7.68%~51.55%、3.39%~30.22%和3.39%~30.22%,渐增期、快增期和缓增期灌浆速率增加了-16.37%~3.31%、3.65%~14.19%和8.26%~30.18%,百粒重增加了16.99%~34.86%。2010年代品种在高密度种植条件时可有效保障灌浆持续时间并提高缓增期的灌浆速率,缓解百粒重的降低幅度,最终实现了增产。