Competition between Imperata cylindrica and maize in the forest savannah transition zone of Nigeria

Imperata cylindrica is a noxious weed that infests annual and perennial crops in most tropical regions. High crop densities may offer opportunities to reduce I. cylindrica competition in small‐scale farming systems. The competitive ability of maize relative to I. cylindrica was evaluated in an addition series experiment in the forest savannah transition zone in 2006 and 2007 at Ibadan, Nigeria. Maize and I. cylindrica were planted in eight monoculture densities (4, 8, 12, 16, 20, 32, 48 and 64 plants m^?2) and in a 1:1 mixture at eight total densities (2:2, 4:4, 6:6, 8:8, 10:10, 16:16, 24:24 and 32:32 maize: I. cylindrica plants m^?2) as in monoculture. Non‐linear regression models were used to relate crop and weed shoot biomass to their densities and total grain yield to maize density. In maize, intraspecific competition was more than interspecific competition; in I. cylindrica, interspecific competition was higher than intraspecific. As expected, total grain yield was lower in the mixture than in maize monoculture at all total densities. Average maize grain yield in maize monoculture differed from that in mixtures by 0.77 t ha^?1 in 2006 and 0.57 t ha^?1 in 2007. Niche differentiation indices were <1 in 2006 and >1 in 2007, indicating that both species competed for similar resources in 2006, but not in 2007. The greater competitive ability of maize over I. cylindrica may be associated with rapid growth and canopy development observed in the field.     

西藏麦类作物对恶性杂草白茅抑制作用分析

以西藏青稞‘藏青2000’和小麦品种‘高原437’为研究对象, 研究了不同种植密度对西藏恶性杂草白茅的抑制作用。结果表明, 供试的青稞和小麦品种对恶性杂草白茅种群数量有显著抑制作用。不同密度的青稞对白茅种群数量和干重的抑制作用没有显著差异。随着小麦种植密度增大, 白茅种群数量差异显著, 而干重差异不显著; 当小麦种植密度达到15 kg/667m2时, 抑制白茅的作用最佳。在青稞与小麦种植密度相同时, 对白茅种群数量和干重的抑制差异极显著, 小麦的抑草效果更佳。     

Development of chloroplast DNA markers in Japanese Imperata cylindrica

Imperata cylindrica (cogongrass) is one of the most invasive grass weeds found worldwide. In Japan, this grass grows as three climate types: cool temperate (CT), common (CM) and subtropical (ST). An early flowering (E) type has been also reported. Among them, the CM type is large and most invasive. Recent global warming may cause the extension of distribution of the CM type to northern parts of Japan and may allow hybrids to form between the CM and CT or E types. The hybrids sometimes show heterosis and this leads to new weed problems. Distinguishing between the hybrids and parents on a morphological basis is difficult. We investigated polymorphisms of eight cpDNAs to enable distinction between the ecotypes and the hybrids. Fourteen haplotypes were detected in 33 Japanese clones, based on variations in eight cpDNA regions. Based on three substitutions in the psbA–matK spacer, the ORF170 intron1, the trnL(UAA) intron–trnF(GAA) spacer and indels in the trnL(UAA) intron–trnF(GAA) spacer, the haplotypes were clustered into three phylogenetic groups: I, IIa and IIb, which corresponded with the CM and ST, E and CT types, respectively. The polymorphism in the cpDNA therefore enables us to distinguish among the ecotypes and is useful for prediction of the range expansion of the CM type.     

氮磷营养对覆膜春玉米产量和品质的影响

对不同品种玉米在春覆膜及不同氮磷肥施用量条件下产量和籽粒主要品质变化的研究结果表明:氮肥和品种是影响玉米产量和籽粒品质的主要因素;在覆膜和露地栽培方式下,增施氮肥,玉米籽粒中蛋白质分别含量增加0.63%~0.87%、0.71%~0.75%,淀粉含量分别减少0.78%~1.74%、0.54%~1.02%;覆膜可增大不同品种玉米籽粒容重5.8~24.5g/L,增加籽粒淀粉含量0.32%~2.69%,降低籽粒中蛋白质含量0.29%~1.63%;施肥和覆膜对玉米籽粒脂肪和赖氨酸含量的影响较小。增施氮磷肥,能够明显提高玉米单产;春季覆膜栽培提高玉米单产777.00~2851.50kg/hm2。     

水肥一体膜下滴灌对玉米产量与氮素利用的影响

为探讨水肥一体滴灌对玉米产量与氮素利用的影响,以玉米杂交种‘桂单688’为材料,列区设计,设4个灌水量(A1,A2,A3,A4)和4个施肥水平(B1,B2,B3,B4)进行田间试验。结果表明,灌水量由A4(1237.5 m3·hm-2)提高到A1(2 250 m3·hm-2)时,玉米产量由7 682.2 kg·hm-2提高到8 640.7 kg·hm-2,A1灌水量(2 250m3·hm-2)与B2施肥水平(纯N 191.25 kg·hm-2、P2O576.5 kg·hm-2和K2O 153.0 kg·hm-2)组合可获玉米产量9016.9 kg·hm-2,是最优水、肥配合选择。随着灌水量由A4提高到A1,玉米籽粒蛋白质由9.01%提高到9.92%;同一灌水量下,玉米籽粒蛋白质含量B1B2B3B4;随灌水量增加,氮素利用率、氮素农学效率、氮素生理效率均有所增加,随施氮量增加氮素利用率、氮素农学效率、氮素生理效率均有所降低,同一施肥水平随密度增加氮吸收利用率、氮农学效率、氮生理效率均有所提高。合理的水肥协同优化组合可以提高水分、养分利用效率,是提高产量的关键。     

休闲期深翻覆盖对旱地小麦土壤水分运行及产量与品质形成的影响

为充分利用休闲期自然降水,提高旱地麦田土壤的蓄水保墒能力,达到“伏雨春用”的目的,本研究在山西闻喜县旱地麦田将休闲期耕作与覆盖相结合,采用大田试验方法研究了前茬小麦收获后15d或45d进行深翻,而后立即采取渗水地膜或液态地膜覆盖对旱地小麦土壤水分、产量及其构成、品质形成的影响效果,试图探索旱地小麦蓄水保墒技术新途径。结果表明,前茬小麦收获后45 d深翻较15 d可显著提高麦收后65 d至孕穗期100～300 cm土壤蓄水量,可显著提高播前至孕穗期0～300 cm总土壤蓄水量,且覆盖的蓄水效果可延续至开花期,以渗水地膜覆盖效果较好。前茬小麦收获后45 d深翻覆盖较15 d可显著提高穗数、产量、籽粒蛋白质及其组分含量、籽粒蛋白质产量,且以渗水地膜覆盖效果较好。此外,播前80～200 cm土壤蓄水量与穗数、产量显著相关;播前和开花期120～300 cm土壤蓄水量与籽粒蛋白质及其组分含量、籽粒蛋白质产量显著相关,播前80～280 cm、开花期40～60 cm、100 cm、240～300 cm土壤蓄水量与谷醇比显著相关。总之,休闲期等雨后深翻并采用渗水地膜覆盖有利于提高旱地小麦土壤蓄水量,达到伏雨春用的目的;有利于优化产量结构,提高产量;有利于提高籽粒蛋白质品质,实现优质。     

大垄沟及其改良栽培措施对玉米生长及产量的影响

为了改良黄土丘陵半干旱地区大垄沟种植技术，在延安选用沈单10号玉米品种采用大垄沟配合地膜、液态地膜、保水剂、土壤改良剂(PAM)等4种化学材料覆盖，及大垄沟玉米间作大豆共5个处理，以平作和大垄沟不覆盖处理为对照，对大垄沟种植技术进行改良研究。结果表明，5种改良措施均能明显促进玉米的生长势，增加玉米的光合面积，提高株高、干物质积累量和籽粒产量；其中，大垄沟与地膜或液态地膜配合使用的增产效果最佳，是适合延安半干旱地区玉米种植的栽培措施。     

不同耕作覆盖措施下延收对春玉米产量及籽粒品质的影响

选用5种耕作覆盖方式和7个采收时期研究延收对籽粒产量、千粒重、籽粒蛋白质、脂肪、淀粉含量及其对应的产出量的影响,为玉米获得高产优质提供依据。结果表明：适时延收可使玉米产量及主要营养成分产出量明显增加,延收15 d ,产量增幅为10．19％～15．62％,千粒重增幅为14．70％～20．39％;籽粒蛋白质含量增加0．26％～1．29％,产出量增加117～230 kg·hm－2;脂肪含量增加0．05％～0．40％,产出量增加54～78 kg·hm－2;淀粉含量虽然降低0．5％～4．9％,但产出量仍然增加340～773 kg·hm－2。黄土高原地区春玉米延收15 d具有明显的增产和提高籽粒品质产量的效果,但增幅因耕作和覆盖方式不同而存在差异。     

种植模式对旱地玉米光合特性和产量的影响

为进一步优化陇中半干旱区玉米高产栽培技术,提高有限水土资源利用效率,2014—2015年采用田间试验,研究了玉米马铃薯间作和单作下全膜沟垄作、全膜平作和露地平作对玉米抽雄期光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)、胞间CO_2浓度(Ci)及子粒产量的影响。结果表明:(1)不同种植模式下玉米抽雄期叶片Pn和Tr的日变化均呈先升后降的单峰曲线,峰值出现在中午12∶00左右,全膜沟垄作高于平作和露地,间作高于单作;全膜沟垄作玉米间作马铃薯下的玉米Pn、Tr和Gs均最高。(2)全膜沟垄作、全膜平作和露地平作的玉米间作马铃薯,土地当量比(LER)均大于1,以全膜沟垄作玉米间作马铃薯优势最为突出,其间作下玉米子粒产量为5 451.35kg·hm~(-2),较露地间作提高了66.00%,特别是在降水量偏少的年份,增产效果更明显。因此,在陇中雨养农业区进一步提高玉米产量和水土资源利用效率,引入间作是可行的,全膜沟垄作玉米间作马铃薯是较佳的种植模式。     

调亏灌溉对夏玉米根冠生长关系的调控效应

以夏玉米(zea may L. cv.)为试验材料,采用防雨棚下桶栽土培方法,进行调亏灌溉(Regulated deficit irrigation,RDI)对根、冠生长的影响研究,旨在寻求适宜的水分调亏阶段和调节亏水度,为建立节水高产、优质高效作物RDI模式提供技术参数。试验采用二因素随机区组设计,设置4个水分调亏阶段:三叶～拔节(Ⅰ),拔节～抽穗(Ⅱ),抽穗～灌浆(Ⅲ),灌浆～成熟(Ⅳ);每个调亏阶段设置3个水分调亏度:轻度调亏(L)、中度调亏(M)和重度调亏(S),土壤相对含水率分别为60%～65%FC(Field capacity)、50%～55%FC和40%～45%FC;设全生育期保持适宜土壤水分(75%～80%FC)作为对照(CK)。分别在水分调亏期间和复水后测定各处理根系参数和地上干物质质量。结果表明,玉米生长中、后期水分调亏具有促进根系发育和减缓根系衰亡的"双重效应",反映出玉米根系在生育后期比生育前期对水分适应能力强的特性。玉米根冠比(R/S)受水分影响最大的阶段是三叶-拔节期,受水分影响最小的阶段是灌浆期;拔节-抽穗期水分调亏期间能显著增大R/S,复水后分配到冠层与根系的物质比较平衡,维持较为适宜的R/S,表明此阶段为通过RDI调控玉米R/S的适宜阶段。玉米三叶-拔节期水分调亏改善了穗部性状,表明在作物营养生长阶段的适度水分调亏有利于作物生殖生长。RDI可以有效调控根/冠生长关系,提高经济产量。     

堆肥替代化肥对玉米产量和水分利用效率的影响

本试验研究了河西绿洲灌区在堆肥施用量为30 000 kg·hm~(-2)和60 000 kg·hm~(-2),替代化肥用量10%、20%和30%时对玉米产量和水分利用效率的影响。结果表明,在不同堆肥用量条件下,替代化肥处理均较对照提高了玉米产量和水分利用效率;其中,堆肥用量60 000 kg·hm~(-2),替代化肥用量30%的平均3年玉米经济产量和水分利用效率均最高,分别为16 609.02 kg·hm~(-2)和25.08 kg·mm~(-1)·hm~(-2),较对照分别提高29%和23.73%。因此,在堆肥施用量为60 000 kg·hm~(-2),传统化肥减量30%时,玉米的增产和节水效果最佳,为河西绿洲灌区堆肥替代化肥的最佳施用量。     

Weed flora and soil seedbanks in fields dominated by Imperata cylindrica in the moist savannah of West Africa

Imperata cylindrica (L.) Raeuschel is a dominant and infamous grass weed in the savannah of West Africa. Research to reduce the weed to non-damaging levels is a priority activity at many agricultural institutions. The successful development and implementation of long-term I. cylindrica management strategies depend on the ability to predict changes in weed composition after I. cylindrica has been controlled effectively. The weed flora and soil seedbank were assessed from 329 fields dominated by this species in the fringes of the humid forest (HFF), coastal/derived savannah (CDS) and in the southern Guinea savannah (SGS) in 1996 and 1997. The objectives of the study were to correlate species composition of the weed flora with that of the soil seedbank and to determine the effect of management factors and soil properties on the composition of the weed flora. Species richness in the weed flora and in the weed seedbank was higher in the SGS than in the CDS and HFF. Mean weed density per field was generally higher in the HFF (156 ± 25.0 weeds m^–2) than in the CDS (108 ± 8.1 weeds m^–2) and in the SGS (92 ± 6.3 weeds m^–2). Weed composition varied with agroecological zone as well as with management factors and soil properties. Sørenson's index of similarity was low (mean=0.20) in all zones, indicating poor similarity between the weed flora above-ground and the soil seedbank.     

不同种植方式对旱地玉米产量的影响

在甘肃庆阳市开展了不同种植方式对旱地玉米产量及产量相关因子的影响试验,以探讨旱地玉米的高产栽培模式。试验以5个优良品种:郑单958(C1)、东单13号(C2)、登海1号(C3)、登海3521(C4)、先玉335(C5)为材料,采用裂-裂区设计,在膜侧种植(A1),膜上种植(A2),露地种植(A3)3种不同种植方式和35 cm(B1),20 cm和50 cm交替使用(B2)2种株距条件下,对种植方式、株距、品种及三者之间互作效应与玉米产量的关系进行研究,分析其对玉米生育期、产量及产量性状的影响。结果表明:膜侧种植(A1)、膜上种植(A2)与露地种植(A3)比玉米各生育期显著提前,出苗期分别提前2.0 d和1.2 d,成熟期则分别提前7.4 d和11.4 d。两种株距对生育期影响不大。膜侧种植(A1)、膜上种植(A2)玉米产量及百粒重显著高于露地种植(A3),分别增产543.0 kg·hm~(-2)和432.6 kg·hm~(-2),百粒重分别提高了2.36 g和1.82 g。5个品种中登海3521在两年试验中产量显著高于其它品种,平均产量达到11 051.15 kg·hm~(-2)。总种植密度不变情况下,株距与品种之间表现出交互作用,B1×C4连续两年获得高产,平均产量达到11 039.7 kg·hm~(-2),不等距种植可以使玉米增产,但不是适用于所有品种,大穗稀植型品种登海3521(C4)在等距种植条件下才能获得高产。     

播期对玉米生长发育和产量的影响

基于2012—2014年在辽宁省庄河市和锦州市进行的玉米分期播种试验资料,对辽宁地区玉米生长及产能受温度影响情况进行分析。试验分为5个播期,播期间隔10~15 d不等,种植密度约为4.2株·m~(-2),每个播期分为4个重复小区,分别观测玉米生长指标。结果表明:在日照和水分条件适宜的情况下,玉米在各生长发育期所持续的时间与相应期间的温度存在着负相关关系。播种~出苗阶段持续时间在日最低气温15℃以下随着温度升高而逐渐缩短,15℃以上则逐渐增加。吐丝~成熟阶段持续时间则随着播期的延后而延长。玉米在出苗~吐丝阶段,各播期温度条件相当,差别并不显著。吐丝~成熟期≥10℃的活动积温和气温日较差分别在1 500℃·d左右和8℃~8.5℃的范围内对产量的形成更加有利。     

施用硫肥对关中地区夏玉米硫素吸收及产量的影响

为了解关中地区小麦-玉米轮作条件下玉米硫素吸收及籽粒产量对不同施硫量的响应,于2011年6月-2011年10月进行单因素硫肥大田试验,设置0、37．5、75、112．5 kg S·hm-2和150 kg S·hm-25个施硫水平,研究夏玉米硫素吸收利用效率及干物质积累特征。结果表明：大喇叭口期玉米硫吸收强度最高,达到288．4～378．6 g·hm-2·d-1,施硫可提高玉米硫吸收强度。112．5～150 kg S·hm-2处理显著提高玉米群体干物质积累量;75～112．5 kg S·hm-2处理显著提高玉米籽粒产量,施硫水平达到150 kg S·hm-2时籽粒产量有下降趋势。玉米硫肥偏生产力和农学利用率随施硫量的增加而下降;玉米硫肥吸收利用率均在5％以下。结论：夏玉米对硫肥的响应明显,112．5 kg S·hm-2施硫量是当地夏玉米的适宜施硫量。     

Effect of epoxiconazole on rice blast and rice grain yield in China

Sensitivity to epoxiconazole of 90 single-spore isolates of Magnaporthe oryzae was determined. The EC₅₀ values for epoxiconazole in inhibiting mycelial growth of the 90 M. oryzae isolates were 0.11–0.86 μg/ml, with an average EC₅₀ value of 0.260?±?0.082 μg/ml. There was no correlation between sensitivity to epoxiconazole and sensitivity to carbendazim or iprobenfos. In protective and curative tests, epoxiconazole applied at 200 μg/ml provided over 70 % control efficacy, while tricyclazole exhibited better protective than curative activity. The results of four field trials performed in 2010 and 2011 at two sites showed that epoxiconazole at 112.5 g a.i/ha provided over 75 % control efficacy, which was similar to tricyclazole with 300 g a.i./ha and better than carbendazim with 562.5 g a.i./ha.     

有限灌溉对沙地春玉米底墒利用及籽粒产量影响的研究

在干旱环境下耕作层保水能力较差的新垦沙地进行了春玉米有限灌溉试验研究,结果表明:有限灌溉可以促使春玉米更多地利用土壤底墒,灌水最少的处理MI1底墒利用率最高,分别比MI2、MI3、对照CK高8.0％、10.4％、14.3％.4种灌水处理以灌水最多的对照CK玉米籽粒产量最高,但水分利用效率最低;灌水相对较少的处理MI2水...     

Assessment of loss in yield due to sorghum downy mildew (Peronosclerospora sorghi) of maize in Nigerian guinea savanna

Abstract

The losses in yield due to sorghum downy mildew of maize induced by Peronoscleospora sorghi were assessed from 1982 to 1984 in the epidemic‐prone area of Nigeria. Plots of maize with different downy mildew incidences were obtained by planting seedlots containing different percentages of metalaxyl‐treated seeds. The losses in yield were directly proportional to the incidence of the disease. There was highly significant negative correlation between the incidence of downy mildew and grain yield.     

秸秆和紫云英覆盖还田对玉米光合生理特性的影响

为探究秸秆和紫云英覆盖还田对玉米光合生理特性的影响,设置半量秸秆覆盖(HS)、全量秸秆覆盖(WS)、紫云英覆盖(M)、半量秸秆加紫云英覆盖(HS+M)、全量秸秆加紫云英覆盖(WS+M)、无覆盖(CK)6个处理,于玉米乳熟期测定光合气体交换参数的日变化、光响应曲线以及叶片生理指标和干物质量等。结果表明,净光合速率和气孔导度都呈“双峰”曲线变化,胞间二氧化碳浓度（C_i）和蒸腾速率(T_r)整体呈“单峰”曲线变化;HS+M处理的日平均净光合速率(P_n)、气孔导度(G_s)、蒸腾速率(T_r)最高且较CK处理分别显著增加了33.44%、60.81%、33.36%,而各处理间的日平均胞间C_i差异不大;光响应曲线中,WS+M处理的P_nmax和LSP的实测值在各处理中最高,分别为23.46、1 900 mol·m^-2·s^-1,且各处理的光响应曲线拟合决定系数均高于0.99;Rubisco和PEPC的活性在各处理间均表现为：WS+M>HS+M>M>WS>HS>CK,各处理中,以WS+M处理的Rubisco和PEPC活性最高分别为12.92 U·L^-1、6.59 U·L^-1,且较CK处理高出1.12和1.59倍;玉米穗位叶叶面积和地上部分单株干物质量都以WS+M处理最高,分别较CK处理显著增加了16.40%、46.32%;气体交换参数与玉米叶片生理指标间均呈正相关关系。本研究结果表明,将秸秆、绿肥覆盖还田可提高玉米的光合作用能力,促进玉米地上部分干物质积累,为玉米最终增产提供物质基础。