广灭灵生理机制与安全性评价

简介了除草剂广灭灵基本特点和应用现状及其除草活性的相关作用机理 (主要包括选择性机理、除草机制、代谢降解机理 ) ,并对施用广灭灵所产生的生态环境安全性进行评价 ,展望其研究及应用前景     

水稻土中广灭灵残留动态及降解影响因子的研究

对水稻土中广灭灵残留消解动态及降解影响因子研究结果表明 ,广灭灵在 4种水稻土中降解符合 1级动力学方程C =C0 e-kt,其降解半衰期为 5 7～ 2 2 0d。广灭灵降解以微生物降解为主 ,土壤灭菌处理大大降低广灭灵降解速率 ,土壤理化性质、温度、湿度、pH值是影响广灭灵降解的重要因素。广灭灵降解速率与不同类型水稻土有机质含量呈显著负相关关系 ,相关系数为 - 0 8336。随温度上升而广灭灵降解有加速趋势 ,但常温 2 5℃时广灭灵降解速率高于 35℃处理 ,增加土壤湿度及施用石灰增加土壤 pH值均加快广灭灵降解速率     

胡麻田施用噻吩磺隆对后茬作物的安全性研究

为了探明胡麻田施用除草剂噻吩磺隆对后茬作物的安全性,以期为施用噻吩磺隆胡麻田后茬作物的合理布局提供依据。采用大区对比试验设计,设15%噻吩磺隆低剂量和高剂量两个施药处理和清水对照,研究对后茬作物玉米、春油菜、荞麦、大豆、向日葵、马铃薯出苗生长和产量的影响,结果表明,胡麻田喷施15%噻吩磺隆345 g/hm2(低剂量),对玉米、大豆、向日葵、荞麦和马铃薯等5种后茬作物的出苗、株高、产量均无明显影响,相对出苗率均超过98.4%,株高抑制率为0.14%~1.41%,减产幅度在1.00%左右。喷施15%噻吩磺隆525 g/hm2(高剂量),对上述5种后茬作物株高和产量的负面影响均有所增强,对玉米、大豆、向日葵和马铃薯出苗率无明显影响,相对出苗率均达96.6%以上;对荞麦出苗影响显著,相对出苗率为95.93%,株高抑制率为0.42%~6.74%。胡麻田喷施低剂量、高剂量噻吩磺隆对后茬玉米、大豆、向日葵、荞麦和马铃薯均安全,对春油菜具药害。结合作物的抗药性及对环境的适应性综合评判,在甘肃省陇东地区,施用噻吩磺隆的胡麻田后茬可安排种植玉米、大豆、向日葵和马铃薯,不宜种植荞麦和春油菜。     

两种除草剂对紫茎泽兰光合特性的影响

紫茎泽兰是一种重要的外来入侵生物,已在我国西南地区泛滥成灾。为了探明甲嘧磺隆和氨氯吡啶酸对紫茎泽兰光合特性的影响,为紫茎泽兰高效化学防除提供参考依据,采用单因素随机区组设计,对盆栽紫茎泽兰喷施不同浓度的甲嘧磺隆可溶性粉剂和氨氯吡啶酸水剂,测定施药后1～7 d紫茎泽兰几个光合特性参数。结果表明,随浓度和时间的增加,紫茎泽兰的光合速率（Pn）、气孔导度（Gs）、蒸腾速率（Tr）、胞间CO2浓度（Ci）及叶绿素含量呈下降趋势。0.12 g.L-1甲嘧磺隆和1.75 g.L-1氨氯吡啶酸能有效地抑制紫茎泽兰的光合作用,这两种药剂用量几乎减少一半。     

氯嘧磺隆对土壤微生物类群及土壤呼吸强度的影响

通过实验室培养试验研究了氯嘧磺隆对土壤微生物种群动态变化和土壤呼吸强度的影响。测定了0、5、10、20、100μg kg-1的氯嘧磺隆对土壤中三大类微生物种群动态变化的影响,结果表明,氯嘧磺隆促进土壤细菌和真菌的生长,抑制放线菌的生长,真菌是氯嘧磺隆胁迫下的优势菌群。密闭法测定了0.01、0.1、1、10、100μg g-1的氯嘧磺隆对土壤呼吸的影响,结果表明,0.01、0.1、1、10μg g-1的氯嘧磺隆轻微抑制土壤呼吸,但受抑制的土壤逐渐恢复,除10μg g-1外,其它处理可恢复到对照水平,高浓度100μg g-1的氯嘧磺隆促进土壤呼吸,不能恢复到对照水平,但根据危害系数法的分级方法计算,氯嘧磺隆属于无实际毒害的农药。     

氯嘧磺隆对土壤微生物数量,酶活性及呼吸强度的影响

氯嘧磺隆是一类高效广谱除草剂,研究其对土壤微生物的影响对其合理使用具有重要意义。通过室内瓶培养实验研究了不同浓度氯嘧磺隆对土壤呼吸强度、土壤微生物数量和土壤酶活性的影响。结果表明:氯嘧磺隆施入土壤2周后,可明显提高土壤呼吸强度,且浓度越大,提高效果越明显;氯嘧磺隆施入土壤1周后,不同浓度氯嘧磺隆处理均可提高土壤细菌和放线菌数量,45 d时表现出抑制作用,60 d可恢复到对照水平;氯嘧磺隆对土壤真菌数量表现为抑制作用,而后恢复到对照水平,45 d时田间施用量可抑制土壤真菌的增殖,但60 d可恢复到对照水平。土壤培养前1周,氯嘧磺对土壤过氧化氢酶、土壤转化酶、土壤脲酶活性均表现出不同程度的抑制作用,且浓度越大抑制作用越明显。之后三种酶表现出一定的激活作用,培养60 d可恢复到对照水平。以上试验结果可为合理施用氯嘧磺隆提供理论依据。     

几种典型除草剂对冬麦田N20排放及其相关土壤生化因子的影响

通过田间原位观测试验,研究了几种典型除草剂单,混施对冬麦田N2O排放及其土壤生化因子的影响。结果表明：在除草剂施用后的10d内,乙草胺和混剂苯磺隆＋精嗯唑禾草灵都显著抑制了N2O的排放（P〈0．05）,其N：O排放通量均值较对照降低了50％左右,精嗯唑禾草灵和苯磺隆处理N2O排放通量均值分别比对照减少28．6％和26．0％,但未达到显著水平（P〉0．05）;在余下的测定期内,乙草胺、苯磺隆、精嗯唑禾草灵和混剂苯磺隆＋精嗯唑禾草灵对麦田N2O排放都无显著影响,其NzO排放通量均值分别为对照的95.3％、101．8％、92．5％和88．7％。乙草胺对土壤脲酶活性一直有激活作用（P〈0．05）,精嗯唑禾草灵和混剂苯磺隆＋精嗯唑禾草灵表现为抑制激活交替作用,而苯磺隆对土壤脲酶活性基本无影响。在除草剂施用后的10d内,N：O排放通量与土壤水分WFPS（P〈0．01）、土壤反硝化细菌数量（P〈0．01）以及土壤氨氧化细菌数量（氏0．05）呈显著正相关关系,与可溶性有机碳含量呈显著负相关关系（P（0．05）,与土壤硝化细菌、土壤硝态氮和铵态氮含量以及脲酶活性无显著相关关系（P〉0．05）。乙草胺和混剂苯磺隆＋精嗯唑禾草灵能显著降低麦田N20的排放,主要源于明显降低了土壤中反硝化细菌数量,混剂苯磺隆＋精噫唑禾草灵还明显降低了氨氧化细菌数量。苯磺隆和精嗯唑禾草灵对麦田N20排放无显著影响,主要是对氨氧化细菌和反硝化细菌表现为促进抑制的交替作用。     

吡嘧磺隆对稻田土壤真菌群落结构及土壤酶活性的影响

采用PCR-DGGE和比色法,在室内培养条件下研究施用不同浓度吡嘧磺隆(0.4,4,40mg/kg)对土壤真菌群落结构及土壤酶活性的影响。结果表明:施用吡嘧磺隆7d时提高了土壤脱氢酶及多酚氧化酶活性,抑制葡聚糖酶活性,真菌多样性指数无明显变化;14d时,随着施药浓度的增大,脱氢酶活性减弱,多酚氧化酶活性增强,真菌多样性指数逐渐增大。21d时,随施用吡嘧磺隆浓度增大,土壤脱氢酶和多酚氧化酶活性会降低,而土壤葡聚糖酶恢复至对照水平,真菌多样性指数增大。试验结果为全面了解吡嘧磺隆对土壤微生态环境的影响提供数据依据。     

玉米与赤霉素对向日葵列当种子萌发、防除以及对后茬作物向日葵生长的影响

向日葵列当(Orobanche cumana Wallr.)是一种根寄生草本植物,对向日葵等经济作物造成严重危害。为了减少向日葵列当对向日葵的寄生,降低土壤中向日葵列当种子库,本试验以新疆地区广泛种植的玉米品种‘京糯一号’和‘新玉57号’为研究材料,通过穴盘试验研究在不同时期(出苗后10 d和15 d)施加两种不同浓度赤霉素(10~(-4 )mol·L~(-1)和10~(-5 )mol·L~(-1))对上述两个品种玉米生长发育和分泌列当萌发刺激物质的影响;24 d后收集并提取玉米根系分泌物,用其进行刺激向日葵列当种子的萌发试验,从而筛选出刺激向日葵列当种子萌发能力较强的玉米品种进行盆栽试验。通过盆栽试验,在玉米种植后的不同时期(20 d和40 d)喷施10~(-4 )mol·L~(-1)赤霉素以探究玉米与赤霉素共同防除向日葵列当种子的效果,收获时(105 d后)采集玉米地上部、根和根际土样品,用其甲醇浸提液刺激向日葵列当种子萌发;次年在种植过玉米的盆中种植后茬作物向日葵,收获时测定向日葵的农艺指标并统计向日葵列当的出土数。结果表明:穴盘试验中施加赤霉素对玉米的株高有显著增高作用,对玉米根系分泌萌发刺激物质没有抑制作用,即在玉米生长时期可以施加10~(-4 )mol·L~(-1)和10~(-5 )mol·L~(-1)赤霉素。此外,‘新玉57号’根系分泌物的100倍稀释液刺激向日葵列当种子的萌发率显著高于‘京糯一号’,因此选取‘新玉57号’作为盆栽试验的玉米品种。盆栽试验中不同时期施加10~(-4 )mol·L~(-1)赤霉素,玉米株高同样显著高于对照,增长率分别为22.5%、19.1%。次年种植后茬作物向日葵,在第20 d向玉米施加赤霉素处理的盆中种植的向日葵的花盘直径比对照(种植玉米时不施加赤霉素)显著增加57.1%。与对照相比,在种植玉米后的20 d和40 d施加赤霉素的处理种植向日葵,向日葵列当的出土数分别是1.3个·盆~(-1)、1.8个·盆~(-1),分别降低76.4%和67.3%。因此,可以在玉米种植的后20 d和40 d施加10~(-4 )mol·L~(-1)赤霉素,与玉米共同诱导向日葵列当种子"自杀发芽",以减少向日葵列当对向日葵植株的危害。     

Modelling production of field crops and its requirements

Simulation models are being developed that enable quantitative estimates of the growth and production of the main agricultural crops under a wide range of weather and soil conditions. For this purpose, several hierarchically ordered production situations are distinguished in such a way that the results of simulations on one hierarchical situation are used as input for the calculations of another. For the highest hierarchical production situation, water and plant nutrients are optimally available; in the next situation water may be limiting at times, whereas in further situations limited supplies of the main plant nutrients are also taken into account. The reclamation activities and the yield-increasing inputs that are needed to achieve the simulated yield levels for the various situations are estimated.

The weather data and the physical soil data that are needed for the calculations in the first two hierarchical production situations are specified. It is shown that environmental heterogeneity contributes considerably to the complexity of the problem and that especially the averaging of weather data over time and soil data over space leads to distortion or even destruction of data. To avoid this, the data from the original observation sites should remain accessible at all times. The easy accessibility of computers and data base management systems implies that there is no excuse anymore to average first and then calculate, instead of the other way round.     

Patch spraying of weeds in spring cereals: Simulated influences of threshold level and spraying resolution on spraying errors and potential herbicide reduction

Abstract

A major obstacle to patch spraying of broad-leaved weeds in cereals is a cost-effective method to assess within-field heterogeneity of the weed population. One method could be a camera mounted in front of the spraying vehicle, online image analysis, and field sprayer shifting between ‘on’ and ‘off’ as the predefined weed damage threshold level is reached. Because such a camera will capture a very limited area (<1 m²) compared to the sprayer width (several m), success of this method requires that spraying decisions vary little within boom width, thereby causing few spraying errors. This approach was evaluated by simulations for varying boom widths and three levels of a weed damage threshold model. Potential herbicide reductions compared to blanket application were also simulated. The average potential herbicide reductions estimated as proportions of fields below the threshold, were 60%, 64% and 53% for the original, 25% increased and 25% reduced threshold levels, respectively. The simulated herbicide reductions were not influenced by boom width, but varied significantly between fields, and between threshold levels. As evaluated by spraying errors, the suitability of the suggested approach will increase by decreasing boom width, vary between fields, and in some fields vary between the threshold levels. For boom widths of 15 m and 24 m, the spraying errors were about 10% and 15%, respectively, where omission of spraying areas above the threshold constituted 5% and 8%, respectively.     

Effects of tillage and fertilizer on nematode communities in a Japanese soybean field

No-tillage (NT) cropping systems develop distinct soil ecosystems characterized by a diverse soil fauna and slow fungal decomposition. However, nematode community analyses sometimes fail to detect these characteristics because the treatment before study or the sampling period is too short or the studies are not comprehensive. Different nematode taxa may occur depending on the geographic region and soil type, thereby affecting the usefulness of nematode analyses for soil biological assessment. However, studies in Asia are scarce. Thus, in this 2-year study, we compared nematode populations, community structures, and soil physicochemical properties between long-term NT and conventional tillage (CT) treatments combined with chemical (CF), organic (OF), or no (NF) fertilizer treatments in a Japanese soybean field. We then examined whether nematode diversity and community indices could detect differences among the treatments in the Japanese andosols. Although the effects of tillage on nematode densities were significant, the overall trend in NT–CT differences was not clear, except for omnivores and Meloidogyne. The effects of tillage on nematode diversity and community indices were apparent: diversity indices, maturity index (MI) and related indices, structure index, and channel index were higher, whereas enrichment index (EI) was lower in NT because of higher densities of K-strategy taxa, fungal and facultative root feeders, and lower densities of r-strategy bacterial feeders. Fertilizer treatments also affected nematode densities: most feeding groups were less abundant in NF and predatory nematodes were more abundant in OF than in other treatments. OF increased nematode diversity via an increase in microbivorous and predaceous nematodes. However, the effects of fertilizer on most community indices were not apparent. Interactions between tillage and fertilizer effects were significant for Pratylenchus and total nematode densities, MI, and EI. Among the soil properties differing among treatments, Ca and Mg content, cation exchange capacity, and percent total nitrogen affected nematode community structure. In conclusion, nematode community analyses using index calculations are useful for assessing soil biological properties under different tillage treatments in Japanese andosols, as well as in soil types in other countries. However, index calculations were less sensitive at detecting fertilizer treatment effects, probably because of simultaneous increases in r- and K-strategy nematodes and OF compost that was too decomposed. Other community analyses such as indicator species analysis or diversity evaluations should be used to detect fertilizer effects.     

不同形态氮素对种植大豆土壤中微生物数量及酶活性的影响

采用框栽试验方法,研究6种不同形态氮素[生物固氮(N0)、硝态氮(N1)、铵态氮(N2)、氨基酸态氮(N3)、蛋白态氮(N4)和酰胺态氮(N5)]对种植大豆土壤中微生物数量及土壤酶活性动态变化的影响。结果表明:各大豆生育期内真菌、细菌、放线菌数量和土壤脲酶、蔗糖酶活性对不同形态氮素的反应不同;三大菌群在组成上以细菌数量占绝对优势,数量上均在花期时达到峰值,即均随着大豆生育期的推进呈单峰曲线变化;花期不同形态氮处理下的土壤微生物总数量有差异,具体表现为N5N3N2N1N4N0。土壤多样性指数的变化趋势随着生育期的推进呈缓慢下降趋势,与土壤微生物数量的变化趋势不一致,因此,评价土壤生物多样性指数应将两者结合起来。土壤脲酶和蔗糖酶活性随着生育期的推进亦为单峰曲线变化趋势,但脲酶与蔗糖酶活性的变化趋势不同,其高峰期出现在鼓粒期。     

Effects of dolomite and gypsum on weeds

Abstract

Liming is recognized by most growers in the United States as an essential part of crop production on acid soils. Greenhouse and field studies were conducted on a sandy, siliceous, hyperthermic Ultic Hapliquod (Pomona fine sand) soil to determine the effects of dolomitic limestone and gypsum on weed populations. Under greenhouse conditions, addition of dolomite increased weed populations in pots of soil. Optimum conditions for weed growth occurred at pH 5.3 to 5.5. At pH levels greater than 5.5, weed populations were stable or showed a general decrease in number. Under field conditions, dolomite and gypsum were applied prior to plantings of three different grass species (stargrass, bahiagrass, and annual ryegrass). Addition of dolomite reduced weed populations because of a more favorable soil pH for rapid grass growth. Competition from the grasses was greater at a pH level near 5.8 to 6.0, whereas greatest weed numbers occurred at a pH of 4.8 to 4.9. Results of these studies indicate that liming is needed on acid soils for optimum crop growth, and that crops need to be established quickly as weeds are encouraged at a higher pH (5.3–5.5). Nomenclature: Stargrass, Cynodon nlemfuensis Vandersyst. var. nlemfuensis ‘Florona'; bahiagrass, Paspalum notatum Flugge ‘Pensacola'; annual ryegrass, Lolium multiflorum Lam. ‘Gulf.     

大豆和玉米影响后茬作物氮素供应的研究进展

  【目的】  为提高轮作系统的生产力和土壤肥力的可持续性,我们从作物根系形态、残留养分有效性和土壤结构等方面,综述了大豆和玉米生产对土壤物理特性和后茬作物氮素供应能力的影响机理及原因。  主要进展  大豆根系呈网状分布,分枝侧根多,生长过程中新老根频繁更替,收获后土壤团聚体由原来的简单形态变为多级复合形态,团聚体内部孔隙增多,利于后茬作物的根系发育。大豆形成的稳定土壤团聚结构也是土壤氮素循环的良好基础,可有效提升土壤有机氮的总矿化和转化量,增强土壤对后茬作物的供氮潜力。玉米生产一般氮肥施用量较高,故收获后残留在土壤中的肥料氮相对较多。残留氮以NO₃–-N和微生物氮形态存在的比例高,由于NO₃–-N在土壤中不稳定、易损失,因此,不易于为后茬利用。大豆秸秆C/N低,翻压还田后易于被土壤微生物利用,加速土壤氮循环,易于后茬作物的吸收利用。加之豆科作物生长过程中死亡的根瘤和根形成的沉积物数量大,根系分泌物含有较高的甘氨酸和丝氨酸,且根际沉积物C/N较低,更易矿化转化为后季作物的重要氮源。因此,大豆较玉米更有利于后茬作物的生长和氮素营养。  展望  为更好地利用轮作优势,需要在以下几方面加强研究:提高大豆残留氮素高效利用的关键驱动因素比例;减少玉米收获后土壤残留氮素损失的氮素管理方法;残留氮素转移转化过程中的根–土–微生物互作机制。由于秸秆腐解会加快土壤有机碳的释放,因此减少大豆秸秆还田带来的轮作周年CO₂等温室气体的排放,提高土壤的碳汇功能也将成为今后研究重点。     

玉米/大豆、玉米/花生间作对作物氮素吸收及结瘤固氮的影响

禾本科与豆科作物间作具有显著的增氮作用。为探明玉米/大豆、玉米/花生间作模式的氮素吸收、氮营养竞争能力及豆科结瘤特性的变化,解释玉米与豆科间作体系的增氮效应,通过田间试验,设置玉米单作（MM）、大豆单作（SS）、玉米/大豆间作（MS）、花生单作（PP）、玉米/花生间作（MP）等5种种植模式,研究不同种植模式对作物氮素积累、氮营养竞争强弱及豆科结瘤固氮特性的调控作用。结果表明,与单作相比,间作显著降低玉米和大豆的氮素积累量,对花生的氮素积累量影响不显著。5种模式系统氮素积累总量表现为MS > SS > MP,PP和MM处理最低且差异不显著,MS处理比MP处理显著高21.8%。与MM处理相比,MS和MP处理的玉米氮素积累量分别降低20.5%和11.7%,其中MP处理籽粒、叶片和茎秆氮素积累量比MS处理高8.9%、21.2%和14.3%。与SS处理相比,MS处理的大豆氮素积累量降低28.5%,其中,中行、边行分别降低10.1%、15.4%。玉米相对大豆氮营养竞争比率表现为强（CR_ms>1）,相对花生则表现为弱（CR_mp<1）。与SS处理相比,五叶期MS处理的大豆根瘤数量显著增加,根瘤鲜重无显著差异,盛花期后根瘤数量和鲜重均显著降低;MS处理的大豆根瘤固氮酶活性均降低,且中行降低幅度更大。与PP处理相比,开花期MP处理的花生根瘤数量和鲜重均显著增加,下针期后均显著降低;MP处理的花生根瘤固氮酶活性均降低,且边行降低幅度更大。各间作模式作物的氮素积累量虽然降低,但间作模式的系统氮素积累量却显著高于各单作模式,两种间作模式中MS处理的氮素积累总量最高。     

改进MobileViT网络识别轻量化田间杂草

为解决现有的田间杂草识别方法无法兼顾高准确率与实时性的问题,该研究提出了一种基于改进MobileViT网络的轻量化杂草识别方法。首先,该方法使用高效的MobileViT网络构建杂草特征提取网络,在保证特征提取能力的同时实现更少的模型参数量与计算量;其次,通过高效通道注意力机制加强下采样后特征图中的重要特征,进一步提升模型的特征提取能力;最后,特征提取网络中的MobileViT模块被用于同时学习局部语义信息和全局语义信息,仅通过少量模块的组合便能够准确地捕捉到不同类别杂草与作物间细微差异。为验证该方法的有效性,该研究以农田环境下采集的玉米幼苗及其4类伴生杂草图像为数据进行了模型训练,试验结果表明,该方法的识别准确率、精准度、召回率和F1分数分别为99.61%、99.60%、99.58%和99.59%,优于VGG-16、ResNet-50、DenseNet-161、MobileNetv2等常用卷积神经网络;同时,可视化结果表明该方法能够有效提取杂草图像中的关键特征,并抑制背景区域对识别结果的影响。该研究提出的方法能够精准、快速地区分出农田环境下形态相似的多种杂草与作物,可为智能除草设备中的杂草识别系统设计提供参考。     

华北地区夏玉米-田杂草防治的生态观点

在北京、烟台地区大田条件下研究了夏玉米田杂草治理的生态经济阈值,建立了夏玉米产量损失 率与杂草密度的关系。结果表明,杂草与夏玉米的竞争随其密度增加而加剧,夏玉米产量逐渐下降,当杂草密度达到200株/m²时,夏玉米产量损失率达53.07%。华北地区夏玉米田杂草治理的生态经济阈值为4.21～6.91株/m²,即当杂草密度低于生态经济阈值时,对玉米产量的影响很小,可任其生长;高于生态经济阈值时则应及时有效地防治。