Cyperus rotundus control using a mechanical digger and solar radiation

Cyperus rotundus (purple nutsedge) is considered one of the most noxious weeds affecting agricultural areas worldwide. With its fast growth rate, it competes with annual crops for water, minerals, light and space. It excretes allelopathic materials that impede crop development. Controlling this weed is difficult and is done mostly by manual weeding, cultivation and herbicides, with limited effectiveness. A method was developed for the control of C. rotundus. A machine penetrates the soil and rearranges it, so that the tubers are lifted to the upper soil layer, where they are left exposed to the hot summer climate, dehydrate and die. The method was tested in seven field experiments on various soil types. Two months after the experimental plots were irrigated, 70–100% weed control was observed. The machine's speed (at 1.2 or 1.8 km h^?1) and the number of treatments (one, or two treatments a month apart) did not influence the level of weed control. The method has a very high potential to replace manual weeding and application of herbicides. Further work will test whether the treatment has a long‐term effect or should be repeated every season.     

Rhamphicarpa fistulosa,a widespread facultative hemi‐parasitic weed,threatening rice production in Africa

Rhamphicarpa fistulosa is a facultative hemi‐parasitic plant of the Orobanchaceae family, adapted to wet soils. Apart from tropical Australia, it is only found in sub‐Saharan Africa, where it is considered a minor weed in cereal crops such as rice. Due to this status, the species has received only sporadic attention. Recent field observations and encounters with rice farmers in several African countries showed that R. fistulosa is, however, a more serious and increasing production constraint than previously thought. Results from a systematic literature review and a global herbarium study support this. The species has a broad distribution over Africa (at least 35 countries from Madagascar to Senegal and from Sudan to South Africa) and a wide range in altitude (0–2150 m a.s.l.) and environment (waterlogged swamps to moist free‐draining uplands). Rhamphicarpa fistulosa is relatively independent and persistent because of the presumably wide host range, the facultative nature of its parasitism and its prolific seed (estimated 100 000 seeds m^?2 under moderate infestation levels). Finally, R. fistulosa causes severe yield losses (average 60%) and high regional annual economic losses (estimated US $175 million), while effective control options are scant and awareness of the species among important R&D stakeholders is almost absent. An integrated approach is advocated to assist the rice sector to reduce current R. fistulosa‐inflicted losses and to prevent further spread of the species into new areas.     

Comparison of management strategies for controlling Nassella trichotoma in modified tussock grasslands in New Zealand: a spatial and economic analysis

The weedy grass Nassella trichotoma (nassella tussock), historically an economically damaging invader of modified tussock grasslands in New Zealand, currently causes little if any reduction in farm production. This is a result of successful historical regional management programmes in which plants have been removed manually (by grubbing) each year before they seed. To inform a debate about the need for ongoing regional management, we developed a stage‐structured spatially explicit integrodifference equation population model and linked this to a cost analysis. We used the model to compare the weed's future population trajectories and related regional control costs over 50 years under three alternative management scenarios. The total discounted (3% p.a.) costs of no management, three‐yearly grubbing and continued annual grubbing were NZ $417 million, $736 million and $131 million respectively. These analyses indicate that annual grubbing of N. trichotoma returns a net benefit of $286 million ($417 – $131 million) compared with doing nothing and a net benefit of $605 million ($736 – $131 million) compared with a 3‐yearly grubbing programme. These results support the continuation of annual grubbing as the long‐term economically optimal management strategy for N. trichotoma on pastoral farms infested by the weed in New Zealand.     

Using the age shift method to determine gains from weed management for Pinus radiata in New Zealand

Understanding the effects of interspecific competition on long‐term growth of plantation forestry crops is critical to forest management decisions around methods used for weed control. A series of permanent sample plots (31) incorporating trees maintained either weedy or weed‐free until canopy closure were established across New Zealand between 2000 and 2002. We used the age shift method to characterise growth responses of Pinus radiata, in New Zealand, to interspecific competition over the first third of a typical rotation. Eight years after planting, age shifts between treatments ranged between ?0.60 years and +3.07 years. On average, the age shift due to weed control increased from 0.62 to 0.96 years between 4 and 8 years of age. This was due to divergent tree growth between weedy and weed‐free plots at 55% of the sites, while at 32% and 13% of sites, respectively, differences between treatments remained constant or decreased beyond age 4 years. The magnitude of the age shift was found to be related to the type of weed dominating early interspecific competition, with woody weeds associated with significantly greater age shifts. Continued divergence in tree growth between weedy and weed‐free treatments up to 8 years after planting at the majority of sites was an unexpected result and contrasts with previous literature. In situations where growth divergence continues beyond 2 years, managers should consider continued treatment of weeds to mitigate the detrimental impacts of on‐going competition.     

Effects of weed harrowing and undersown clover on weed growth and spring cereal yield

Weed competition and nutrient scarcity often restrict organic cereal production, especially where the availability of livestock manure is limited. While harrowing of annual weeds and legume cover crops can be used, these methods are both executed in early spring and may hinder each other. Two cycles of a 2‐year crop rotation were carried out in south‐east Norway (60°42′N, 10°51′E, altitude 250 m) with weed harrowing and undersown cover crops (WHCC) at two fertiliser rates (40 and 100 kg nitrogen ha^?1). The effect of the WHCC treatments was measured by weed density and species, weed biomass, changes in weed seedbank and grain yield. The weed density depended on the interaction between WHCC, fertiliser and year. On average, pre‐emergence weed harrowing reduced weed density by 32% and weed biomass by 49%, while pre‐ and post‐emergence weed harrowing reduced weed density by 59% and weed biomass by 67% compared with the untreated control. Spergula arvensis became more abundant at low rather than at high fertiliser rates. On average, white clover cover crop sown after pre‐emergence weed harrowing resulted in the highest yields for both oat (+12.1%) and wheat (+16.4%) compared with the untreated control. Despite differences in weed population density and biomass among WHCC treatments within years, the weed biomass, weed density and seedbank increased for all WHCC treatments over the 4‐year period. More research is required into improving the efficacy of mechanical and cultural weed suppression methods that organic systems rely on.     

除杂灌和松土抚育措施对柚木及其林下植被的影响

为了解除杂灌、松土抚育措施对柚木、林下植被的影响及柚木与林下植被的相互作用,笔者于造林后第2年在柚木幼林中布设了除杂灌（全砍与全铲）和松土（松土与不松土）抚育试验。结果表明：不同除杂灌、松土处理措施对柚木生长和林下植被生长影响显著：（1）全砍与全铲除杂灌处理相比,柚木树高、胸径分别减少39.2%和39.5%;林下灌木高度、盖度和干重分别增加32.6%、76.2%和184.0%,草本则分别增加36.8%、5.8%和39.3%;灌木和草本种类分别减少16.7%和50.0%。（2）松土与不松土措施相比,柚木树高、胸径分别提高13.5%和11.0%;对林下灌木及草本的生长也有显著影响,但较除杂灌措施程度小。（3）柚木树高和胸径生长与林下草本盖度存在显著负相关关系。     

甘蔗除草地膜全膜覆盖栽培技术应用效果研究

介绍了甘蔗除草地膜全膜覆盖栽培技术应用效果,认为甘蔗全膜覆盖栽培技术配合甘蔗除草地膜技术对甘蔗栽培节本增效显著;同时,阐述了该栽培技术推广过程中存在问题,如除草、残留地膜污染、整地质量等问题,并提出了解决措施,建议使用甘蔗除草光降解地膜替代不可降解的除草地膜。     

Weed suppression by cover crops: comparative on‐farm experiments under integrated and organic conservation tillage

Cover crops are increasingly being used for weed suppression and to enhance the sustainability of agro‐ecosystems. However, the suitability of cover crops for weed suppression in integrated and organic conservation tillage systems is still poorly investigated. Therefore, a 2‐year field study at eight sites was conducted to test the weed suppressive potential of six legume‐based cover crops, with the aim to reduce herbicide input or mechanical weed management interventions. In all experiments, cover crops were directly sown after cereals before next year's main crop (grain maize or sunflower). The presence of cover crops caused a 96% to 100% reduction of weed dry matter at the four sites managed under integrated production, while effects were lower at the four sited managed under organic production, ranging from 19% to 87%. Cover crops that covered soil quickly and which produced much dry matter had the best weed suppressive potential. However, their weed suppressing effect was difficult to predict, as it depended on the year of the investigation, experimental site, cover crop species, the speed of soil cover in autumn and the density of the resulting mulch layer in spring. The study demonstrated that cover crops are a useful tool to suppress weeds under integrated and organic conservation tillage practices. Our recommendation for supporting weed management in conservation tillage systems is to use locally adapted cover crops that have rapid establishment, good soil coverage and high dry matter production. However, additional weed management measures are required for reliable weed control under on‐farm conditions.     

辽宁盘锦稻区杂草地与稻田中蜘蛛动态

采用吸虫器法,系统调查了辽宁盘锦稻区杂草地与稻田中蜘蛛种类及优势度情况,以及蜘蛛优势种、种类数和个体数的年度变化趋势。结果表明,杂草地全年共有4个优势种,为草间钻头蛛、横纹金蛛、三突花蛛和黄褐新圆蛛。水稻生长期内稻田共有3个优势种,为草间钻头蛛、横纹金蛛、粽管巢蛛。杂草地与稻田中优势蜘蛛数量与蜘蛛个体数量变化趋势大体一致,均为缓慢上升趋势,最高峰均在8月中下旬,分别达到139头/m2和155头/m2,至水稻成熟期迅速减少。水稻插秧前与收割后,杂草地蜘蛛种类数最高值分别为23种/10m2和34种/10m2,均高于稻田;稻田中蜘蛛种类为缓慢增加,至收割前达到峰值23种/10m2。两个生境蜘蛛种群的相似性系数为0.666 7。     

皖西南直播棉田杂草群落出苗模式

为明确皖西南直播棉田杂草群落出苗模式及其与气象因子的相关性,采用定点定时调查法,于2010—2012年对棉田杂草种类、数量及群落结构进行调查,分析物种多样性,并以灰色关联度法分析直播棉田杂草群落出苗数量与气象因子的相关性。结果表明,皖西南棉区直播棉田杂草种类有13科24种。棉田杂草出苗有2次高峰,分别在5—6月和8—9月。棉田杂草群落多样性指数年度间变化较一致,但物种丰富度变化较大。周积温、周最高积温和周最低积温是影响皖西南直播棉田杂草群落出苗数量季节变化的主要因素,另外还受降水量影响。5—6月的杂草出苗高峰期是棉田杂草重点防治时期;相对占优势的杂草有牛筋草、千金子、旱稗、通泉草和马齿苋,是棉田杂草重点防治对象。