Effects of Types and Duration of Weeds on Yield Parameters of Cocoyam (Xanthosoma saghtifolium)

Weeds reduce yields of all tropical crops significantly, and these effects vary with different species. Thus, the influence of time of weed control and types of weeds on yield parameters of cocoyams ( Xanthosoma sagittifolium ), a tropical tuber crop, was determined by two experiments conducted simultaneously. In one experiment, weeds were removed at different times during crop growth. In the other, different weed types were removed selectively to leave either one or two of the identified categories, namely grasses, broadleaves and sedges. The presence of weeds throughout the growth cycle of the crop reduced yields of cocoyams by 60 %. Removal of weeds at early growth stages produced greater yields than weeds were present beyond 18–22 weeks after planting. The presence of weeds at the time of tuber initiation had the greatest adverse effect on yield parameters. Weeds had a delaying but not an inhibitory effect on cormel initiation. However, all other yield parameters were reduced by weeds. Broadleaved weeds, which have similar growth patterns as cocoyams reduced yields to a greater extent than grasses. Sedges had no significant impact on cocoyams. The presence of grasses and broadleaves together reduced growth and yields of this crop to a greater extent than any other combination.     

Predicting spring barley yield from variety-specific yield potential, disease resistance and straw length, and from environment-specific disease loads and weed pressure

For low-input crop production, well-characterised varieties increase the possibilities of managing diseases and weeds. This analysis aims at developing a framework for analyzing grain yield using external varietal information about disease resistance, weed competitiveness and yield potential and quantifying the impact of susceptibility grouping and straw length scores (as a measure for weed competitiveness) for predicting spring barley grain yield under variable biotic stress levels. The study comprised 52 spring barley varieties and 17 environments, i.e., combinations of location, growing system and year. Individual varieties and their interactions with environments were analysed by factorial regression of grain yield on external variety information combined with observed environmental disease loads and weed pressure. The external information was based on the official Danish VCU testing. The most parsimonious models explained about 50% of the yield variation among varieties including genotype-environment interactions. Disease resistance characteristics of varieties, weighted with disease loads of powdery mildew, leaf rust and net blotch, respectively, had a highly significant influence on grain yield. The extend to which increased susceptibility resulted in increased yield losses in environments with high disease loads of the respective diseases was predicted. The effect of externally determined straw length scores, weighted with weed pressure, was weaker although significant for weeds with creeping growth habit. Higher grain yield was thus predicted for taller plants under weed pressure. The results are discussed in relation to the model framework, impact of the considered traits and use of information from conventional variety testing in organic cropping systems.     

Effect of Weed Removal on Productivity of Chickpea (Cicer arietinum L.) and Lentil (Lens culinaris Med.) in a Mediterranean Environment

Three field experiments were conducted on chickpea ( Cicer arietinum L.) and four on lentil ( Lens culinaris Med.) at different winter-sown rainfed locations in Jordan from 1988/89 to 1990/91 to study the effect of the duration of weed-free and weed-infested conditions on yields and yield components of the crops. Chickpea seed yields were reduced on average by 81 % and straw yields by 63 % when fields remained weed infested until harvest compared with weed-free conditions throughout the growing season. The corresponding lentil seed and straw yield decreases were 63 % and 55 %. As the duration of weed-free period increased and the duration of weed-infested period decreased, yields increased. However, the critical period of weed interference was between 35 and 49 days after emergence in chickpea and between 49 and 56 days after emergence in lentil, when these crops were at an advanced stage of vegetative growth. There were significant negative correlations between the weed dry weight and the seed or straw yields. The reduction in seed yields in both crops because of weed interference occurred mainly through the reduced number of pods /plant, which in turn was partly the result of reduced number of secondary branches. In chickpea, some reduction also occurred through reduced 100-seed weight.     

河套黄灌区麦田杂草绿色防控措施

为解决河套黄灌区麦田杂草绿色防控问题,在河套黄灌区小麦田杂草严重发生的区域,对小麦与杂草竞争关系观测的基础上,试验测定了采用不同小麦品种、种植密度、有机肥、耕翻次数、地膜覆盖方式等绿色控草措施的效果和小麦产量。结果表明,以藜科杂草、籽粒苋和稗草危害为主的麦田,杂草出土滞后于小麦10天以上。杂草主要分布于行（穴）间,株数分别占66.6%（条播）、97.6%（穴播）,且行（穴）中杂草长势较弱,单株鲜重较行（穴）间降低39.3%~41.9%,小麦生长前期生态抑草作用明显;绿色控草措施中除品种和种植密度对控草效果差异不显著外,其余措施控草效果明显。综合比较得知,黑色地膜全覆膜穴播、常规覆膜穴播、增加耕翻次数、无杂草草籽污染有机肥的株数防效分别为82.3%、71.7%、22.0%、8.6%;黑色地膜全覆膜穴播、常规覆膜穴播、增加耕翻次数、无杂草草籽污染有机肥的鲜重防效分别为98.0%、97.1%、23.9%、9.6%;黑色地膜全覆膜穴播、常规覆膜穴播、增加耕翻次数分别增产69.4%、56.4%、21.1%,可实现有机小麦生产机械化绿色控草以及低成本、高产量、规模化生产的目的。     

不同类型地膜覆盖的抑草与水热效应及其对马铃薯产量和品质的影响

地膜覆盖被广泛应用于马铃薯栽培中,随之而来的白色污染以及杂草问题十分严重。为筛选适宜黄淮海地区的马铃薯专用地膜,以马铃薯品种荷兰15为供试材料,在2013—2015年进行大田定位试验,设置黑白配色地膜(BW)、透明生物降解地膜(BI)和普通聚乙烯地膜(CK)覆盖3个处理,研究其抑草与水热效应及其对马铃薯产量和品质的影响。结果表明,与CK相比,BW和BI分别减少杂草密度44.1%~58.5%和26.7%~38.3%。马铃薯生育前期,CK增温效果明显;在淀粉积累期,BW的温度日变化幅度较小,控温效果显著。干旱年份(2014)BW保墒效果显著优于BI和CK。与CK相比,降水正常(2013)和干旱年份BW分别增产6.2%和8.2%;干旱年份BI增产7.1%;而湿润年份(2015),不同地膜处理间马铃薯产量无显著差异。与CK相比,BW处理淀粉含量提高18.3%~37.6%,BI提高7.0%~28.9%;BW维生素C含量提高1.0%~4.3%;BW与BI均显著降低了马铃薯块茎中蛋白质含量。因此,用黑白配色地膜和生物降解地膜替代普通地膜,可降低膜下杂草密度,创造更适宜的土壤温度和水分条件,有利于马铃薯增产和改善品质。     

Allelopathic Effect of Eucalyptus globulus Labill. on Cyperus rotundus L. and Cynodon dactylon L. Pers.

The allelopathic potential of Eucalyptus globulus Labill. (gum tree) fresh and dried leaf leachates was studied using two perennial weeds, viz. purple nutsedge (Cyperus rotundus L.) and bermuda grass (Cynodon dactylon L. Pers) as test weeds. Aqueous leachate of fresh leaves of eucalyptus significantly suppressed the establishment of vegetative propagules and early seedling growth of the weeds. Leachate of fresh leaf cuttings had growth inhibitory effect on bermuda grass but showed growth promotion effect on purple nutsedge. Similarly the leachate of dried leaves of eucalyptus had differential influence on the growth of the two weeds. There is a possibility to harness the allelochemicals of eucalyptus leaves as herbicides for the management of these perennial weeds.     

Photocontrol of Weeds

The reduction of weed emergence resulting from night‐time tillage in worldwide conducted field trials was very variable. The efficacy of night‐time tillage ranged from a reduction of weed ground cover of 97.5 % to an increase in weed seedling emergence of 80 % compared with daytime tillage. In most of the field trials, the reduction in the weed density as a result of night‐time tillage was <30 %. Important factors affecting this variation were: (1) the different light sensitivity of weed species, (2) the different light sensitivity of populations within the same species, (3) the dormancy status of the seeds, (4) the seasonal and short‐term variation of light sensitivity of seeds, (5) the variation of soil water content and (6) the type of soil tillage implement used. Less important were the small light intensity during night‐time tillage which cannot be excluded, and the penetration of light into the soil the days following night‐time tillage. The influence of different environmental factors on the effect of photocontrol of weeds is rather unclear because there are presumably complex interactions between environmental factors and the light‐dependent germination of weed seeds under field conditions. However, some field trials indicate that dry soil conditions reduce the efficacy of photocontrol of weeds. Several trials in the literature suggest that photocontrol of weeds during daytime using implements with a light‐proof cover was as effective as night‐time tillage. This review summarizes the results in research of photocontrol of weeds (soil cultivation in darkness), particularly those derived from field trials. Moreover, important factors are discussed, which might influence the effect of photocontrol of weeds.     

冬油菜苗期化学除草效果和经济效益研究

为筛选出经济、高效、安全的化学除草方法,有效控制油菜田间杂草危害,提高油菜产量和种植效益,通过试验,研究了2种化学除草剂不同使用浓度的安全性和苗期化学除草效果,并以人工除草和不除草方法为对照,对比分析不同除草方法的投入和产出情况。结果表明：不同除草方法间油菜产量差异显著;化学除草方法对油菜田间杂草有较好的防除效果,并可显著降低油菜生产的劳动力和生产成本投入,进而提高经济效益;不同化学除草方法均于施药35天后表现出较好的除草效果;每公顷用21.2%喹·胺·草除灵悬浮剂900 mL于油菜4—5叶期、杂草3—4叶期兑水900 kg及时喷施的方法除草效果好,对油菜生长安全,可以作为冬油菜田的苗期化学除草方法在生产上应用。     

Reduced inter-row distance improves yield and competition against weeds in a semi-dwarf durum wheat variety

Weed and nutrient management in cropping systems of semi-arid areas is a major constraint to cereal yield. Where the use of herbicides is banned or discouraged, the competitive ability of a crop is crucial to reduce weed growth and diffusion. Genotypic differences in the competitive abilities of crops are an important trait to reduce weeds, especially for plant height. However, there is contrasting information about the interactions of other management practices and genotypic traits on wheat yield and competitive ability against weeds and weed growth. The present study investigated yield and quality of durum wheat (Triticum durum Desf.) and weed growth and composition for two wheat cultivars with contrasting competitive abilities against weeds. Wheat was grown under three spatial arrangements (5-cm, 15-cm, 25-cm inter-row distance) and three sowing densities, and broadleaf weeds were either removed or not. The sowing rate did not affect the yield of these wheat cultivars or the weed growth. Reduced inter-row distance dramatically reduced weed biomass for both wheat cultivars, and increased wheat yield and nitrogen uptake in the low-competitive, high-yielding, semi-dwarf cv. ‘PR22D89’, when both weed free and with weeds. These results have direct implications for weed and nutrient management in low-input and organic cropping systems.     

Growth and Development of Six Barley (Hordeum vulgare ssp. vulgare L.) Cultivars in Response to a Model Weed (Sinapis alba L.)

The aim was to study the growth and development of six spring barley (Hordeum vulgare ssp. vulgare L.) cultivars as a response to a model weed population of Sinapis alba L. The development of light interception profiles over time was characterized for each cultivar in weed‐free stands. The cultivars were chosen such that they represent a range of weed‐suppressive abilities based on previously performed trials. One field experiment each was conducted in 1996 and 1997 at a site SE of Uppsala, Sweden. The two cultivars with low competitive ability against weeds, Etna and Blenheim, allowed the highest weed biomass and the lowest crop biomass in competition with the weeds. These two cultivars transmitted more photosynthetic active radiation through the canopy down to 20 and 40 cm height than did the other cultivars. Although the biomass of cv. Etna was low, the grain yield was higher than that of the other cultivars when grown in competition with weeds. In 1997, cv. Svani with good competitive ability against weeds transmitted least light and had greater grain yield than most other cultivars. The absence of a relationship between high grain yield and low weed suppressive ability in the present study indicates that it should be possible for plant breeders to combine high grain yielding capacity with approved weed‐competitive ability.     

几种除草剂对当茬玉米生长发育的影响

除草剂为作物产量提供保障的同时,对作物造成的药害也频繁发生。为此,本文以目前陇东旱塬区主栽玉米品种为试验材料,选用对恶性杂草具有良好防除效果的除草剂,明确了75%二氯吡啶酸SG、90%莠去津WG和56% 2甲4氯钠盐SP 3个单剂及其2个混配配方对玉米主要农艺性状及产量的影响,以期为玉米的安全生产提供依据。结果表明：参试除草剂在药后0~7天及不同生育期对玉米生长均无直观影响。75%二氯吡啶酸SG、90%莠去津WG、75%二氯吡啶酸SG+90%莠去津WG对苗期玉米株高稍有影响,但随着玉米自身防御能力的增强,除草剂对之后各生育期的玉米株高无显著抑制作用。不同除草剂对各生育期玉米茎粗无抑制作用,玉米果穗粗、果穗有效长、穗粒数和百粒重无显著差异。各除草剂处理后玉米产量较空白对照增加21.93%~30.22%,较人工除草对照增加-2.91%~3.69%。可见,供试除草剂对玉米安全性高,可应用于玉米田的杂草防除。     

Influence of Soil Moisture and Fertilizer Potassium on the Vegetative Growth of Mungbean (Vigna radiata L. Wilczek) and Cowpea (Vigna unguiculata L. Walp)

Tropical food legumes are grown in a wide range of environments, and water stress is considered the principal environmental factor limiting growth and yield. Potassium fertilizer mitigates the impact of water stress in plants. However, the benefits of potassium in overcoming stress in tropical food legumes have not been investigated in comparative studies. The purpose of this study was to determine the benefits of potassium in overcoming water stress in mungbean and cowpea, two important tropical food legumes with different adaptabilities to soil moisture regimes. The experiment carried out under controlled conditions placed emphasis on vegetative growth and selected physiological parameters. The impact of potassium was different in the two legumes grown at optimal and suboptimal soil moisture. Potassium increased shoot growth of mungbean to a greater extent than in cowpea under suboptimal moisture conditions. The roots of cowpea showed a greater response to potassium fertilizer than in mungbean under suboptimal soil moisture. The plant water relations and photosynthetic rates of mungbean were improved to a greater extent by potassium under suboptimal soil moisture than those of cowpea. Although differences were observed in the responses of the vegetative growth of these species to moisture and potassium, in overall terms potassium promoted growth of both species when subject to suboptimal soil moisture. While field studies are required to validate the results, the application of potassium fertilizer can be considered a significant factor in overcoming soil moisture stress in these legumes commonly grown in tropical cropping systems.     

施肥与光照强度对冬小麦田杂草野老鹳草和大巢菜生长及竞争的影响

为了研究施肥及光照强度对冬小麦田杂草的影响,以有效利用施肥模式综合治理冬小麦田间优势杂草。通过盆栽试验,研究了施肥对2种冬小麦田主要杂草野老鹳草(Geranium carolinianum)和大巢菜(Vicia sativa)种子萌发的影响,以及不同光照强度下施肥对2种杂草生长及竞争的影响。结果表明,野老鹳草种子与大巢菜种子相比,萌发起始较早,萌发较快,萌发率也较高。在萌发的过程中不同营养元素对2种杂草种子萌发的作用不同,并且混合播种时大巢菜种子比野老鹳草种子表现出了更强的竞争力。不同光照条件影响施肥对2种杂草生长的作用,在2种杂草竞争的情况下,随着光照强度的降低野老鹳草对各营养元素的竞争力逐渐增强,表现出了更强的适应性。由以上结果可知,2种杂草在不同生长发育阶段对养分元素的竞争能力差异较大,并且不同光照条件可以改变2种杂草对养分元素的竞争,这就为农业生产中合理施肥进行田间杂草综合防治提供了可能。     

Modellversuch zur Beschreibung von Konkurrenzvorgängen zwischen Sommerweizen und einer aus Capsella bursa-pastoris L., Stellaria media L. und Alopecurus myosuroides Huds. bestehenden Mischverunkrautung

Investigation to Describe the Competition between Spring Wheat and a Weed Population Consisting of Capsella bursa-pastoris L., Stellaria media L. and Alopecurus myosuroides Huds.
When controlling weeds in cereals using economic threshold as criteria, weed populations must be evaluated for their potential to cause damage at a very early stage. As well as information of actual weed density or weed ground cover, further knowledge about the species specific growth and competition between weed populations is important.
For this purpose the growth and competition between the weeds Capsella bursa-pastoris L., Stellaria media L., Alopecurus myosuroides Huds. and spring wheat ( Triticum aestivum L.) as a model of a typical weed mixture in cereals were studied in a container experiment. The growth with time of individual species was documented using true colour image processing. In that these measurements are non-invasive, the system lends itself specially to time-dependent analyses. The increasing amount of ground covered by leaves between two observation times served as a parameter to evaluate the increase in biomass over this time period and could be used as a evaluation of the competitiveness of the weed species studied.
The results can be summarized as follows: 1) Stellaria media L. proved to be the most competitive of the studied species. 2) The competition to spring wheat from each weed species was similar. 3) A multi species weed population had a tendenci to a lower competitiveness to spring wheat, than a weed population of only-one species.
The importance of this and other similar studies for the improvement for the prediction of economic weed thresholds to estimate weed populations in early stages will be indicated.     

杂草与棉花的竞争作用

概述了国内外杂草与棉花竞争作用的研究进展和现状,归纳总结了杂草种类、杂草密度及杂草与作物的不同共生期对棉花产量、生长发育、品质、农事操作等影响。但现有研究主要集中在棉花最终产量和最终生长指标的分析上,而对棉花生长发育动态影响,尤其是内在机制的研究还比较少。因此,进一步细化研究棉花生长发育动态的形态指标和生理生化指标及与环境之间的关系,才能全面分析杂草与棉花的竞争作用,探明棉花响应杂草竞争胁迫的内在机制。     

The effects of simulated weed pressure on early maturity soybeans

Breeding for increased weed suppression would be a sustainable contribution to improved soybean weed management, because weed infestation is a major constraint to soybean production world-wide and in organic farming in particular. However, genetic variation in the soybean–weed interaction would be necessary to enable plant breeders to select soybean genotypes based on a superior weed suppression behavior. As there is a lack of information on variation between soybean cultivars in their competitive ability against weeds, the effects of weed pressure on ten early maturity soybean genotypes were studied in a controlled field experiment over three years in Austria. Winter oilseed rape was sown into the soybean stand to simulate pressure from a seed-propagated type of weed. Weed pressure significantly affected soybean yield as well as other agronomic, phenologic and seed quality characters. In two seasons, strong competition from weeds caused a soybean yield reduction of 370 and 560 kg/ha, respectively. In a third season a significant yield increase over weed-free controls was observed at relatively low levels of weed pressure which is explained by non-competition effects of a weak weed ground cover on soybean growth. Yield loss due to weed pressure was lower in early than in late maturity genotypes which appears to be the effect of a better weed tolerance rather than weed suppression. Genotype by weed treatment interaction was not significant, and genetic variation in ground cover development or leaf area was low or not significant in the early maturity soybean cultivars investigated. As such characters are considered important for weed suppression, their variation needs to be increased to enable selection for improved weed suppressive ability.     

两种除草剂对云南秋播苦荞田除草效应及其产量的影响

为了探讨除草剂对云南秋播苦荞田的防除效果、苦荞的安全性和产量的影响,以‘云荞1号’为材料,对云南秋播苦荞田进行不除草、人工除草、化学除草(金都尔、乙草胺)苗前土壤喷雾4个处理。试验结果表明,金都尔和乙草胺除草剂对秋播荞麦田的杂草有较好的防除效果,并且金都尔除草剂对阔叶杂草的防除效果大于禾本科杂草的防除效果,而乙草胺除草剂对禾本科杂草的防除效果大于阔叶杂草的防除效果;但两种除草剂对苦荞的出苗和幼苗生长都有一定的抑制作用,并且严重影响苦荞产量。因此在生产中,以阔叶杂草为主的苦荞田建议使用金都尔除草剂、以禾本科杂草为主的苦荞田建议使用乙草胺除草剂,但尚需进一步研究防除效果好又不影响产量的适合苦荞田除草剂浓度的筛选。     

Legume Production and Irrigation Strategies in the Aral Sea Basin: Yield,Yield Components,Water Relations and Crop Development of Common Bean (Phaseolus vulgaris L.) and Mungbean (Vigna radiata (L.) Wilczek)

With world population expected to reach 9.2 billion people by 2050, improved irrigation methods will be needed to increase the productivity of agricultural land and improve food supply worldwide. The objective of this work was to examine the effect of regulated deficit irrigation (RDI) and alternate furrow irrigation (AFI) on the yield and yield components of two legume species (common bean and mungbean) produced as a second crop following winter wheat in Uzbekistan, Central Asia. Water relations and crop development were also examined. The research was conducted during two successive growing seasons in the Fergana valley. Production of mungbean using the severe stress RDI treatment in combination with AFI resulted in the highest yields with the lowest quantity of applied water in 2004. In addition, yields of common bean in the moderate stress treatment were not different from the recommended schedule, although irrigation events were decreased from 4 to 2. AFI did not reduce yields, and it did not interact with RDI to reduce yields further. In general, mungbean yields were higher than those of common bean. The combination of AFI and RDI can allow legume production with reduced water inputs.     

Effect of Two Row Spacings and Hemp Sesbania Competition on Sunflower

The competitiveness of hemp sesbania ( Sesbania exaltata [Raf.] RYBD. EX A. W. Hill) with sunflower ( Helianthus annuus L.) grown in two row spacings was evaluated at the University of Arkansas at Pine Bluff Agricultural Experiment Station in 1982 and 1983. Sunflower and hemp sesbania at densities of 3 to 5 and 13 to 16 plants per meter row, respectively, were interseeded in 61 and 91 cm row spacings in field test plots. Hemp sesbania plants were removed at different sunflower growth stages. In 1982, weed removal treatments were: (1) weedy check, (2) weed-free check, (3) weed removal at 15-leaf stage, (4) removal at 20%, (5) 50% and (6) 100% sunflower anthesis. Treatments in 1983 consisted of: (1) weedy check, (2) weed-free check, (3) weed removal at 10-leaf stage, (4) bud stage, (5) pre-anthesis, (6) 10% anthesis, and (7) 100% anthesis. Sunflower yields were significantly decreased by hemp sesbania competition each year, except for the weed competition treatments in 91 cm row spacing in 1982. Generally, the longer the weeds were allowed to compete with sunflower, the greater the sunflower yield reduction. Yield reductions of 5% to 6% and 25% or more were observed when hemp sesbania was allowed to compete with sunflower until the 10-leaf and anthesis stages of sunflower growth, respectively. When hemp sesbania was allowed to compete with sunflower for the entire growing season, yield was reduced by as much as 35%. Reducing row width from 91 cm to 61 cm did not improve sunflower's ability to compete with hemp sesbania. Thus, hemp sesbania is quite competitive with sunflower and should be controlled during early vegetative growth in order to minimize yield loss.     

氮肥减量条件下间作绿豆压青对甘蔗生长及氮代谢的影响

以甘蔗单作常规施氮量为对照（CK）,设氮化肥减量20%+间作绿豆压青（A）、氮化肥减量40%+间作绿豆压青（B）和氮化肥减量60%+间作绿豆压青（C）3个处理,通过测定甘蔗农艺性状、蔗茎产量和甘蔗叶片氮代谢相关生理生化指标,研究氮肥减量条件下间作绿豆压青对甘蔗生长及氮代谢的影响。结果表明,间作绿豆影响新植蔗分蘖,分蘖率显著低于CK,但对甘蔗有效茎数影响不显著。新植蔗产量表现为A>B>CK>C。氮化肥减量条件下间作绿豆压青对宿根蔗发株率、株高、有效茎数、甘蔗茎径有促进作用。宿根蔗蔗茎产量表现为A>B>C>CK。2年的甘蔗蔗糖分含量表现为C>B>A>CK。氮化肥减少20%条件下间作绿豆压青对提高甘蔗叶片谷氨酰胺合成酶、硝酸还原酶活性和游离氨基酸、可溶性糖含量有促进作用。综合甘蔗农艺性状、蔗茎产量、氮代谢相关指标测定结果和经济效益的表现,试验以氮化肥减量20%+间作绿豆压青的A处理最优。