草甘膦对土壤微生物的影响

以东北地区黑土为材料,探讨草甘膦对土壤呼吸、土壤可培养菌种群数量、大豆固氮根瘤菌和大豆根腐镰刀菌数量的影响。研究结果表明,随着草甘膦浓度的加大,土壤呼吸的抑制作用增强,土壤中草甘膦含量为1 mg&;#8226;kg-1、10 mg&;#8226;kg-1、100 mg&;#8226;kg-1时,危害系数分别为1.20、0.322、0.0760,远小于无危害标准系数20,确定草甘膦对土壤微生物低毒或无实际危害。不同浓度的草甘膦对土壤真菌、放线菌种群数量具有一定影响。土壤可培养菌种群数量随草甘膦浓度的升高抑制作用逐渐增强,随着草甘膦加入时间的延长,真菌、细菌、放线菌的种群数量有所恢复,其中放线菌与真菌同细菌相比对草甘膦敏感,土壤细菌对草甘膦具有较强的耐受或降解能力。草甘膦对大豆根瘤菌和大豆根腐镰刀菌有一定影响,对大豆根瘤菌的抑制作用与草甘膦浓度呈正比;低浓度草甘膦对镰刀菌产生激活作用,高浓度草甘膦对镰刀菌具有抑制作用;伴随草甘膦加入时间的延长,其对大豆根瘤菌和大豆根腐镰刀菌的抑制作用逐渐减弱。     

Responses of wheat and barley to liming on a sandy soil with subsoil acidity

A 3 years field trial examined the effect of newly and previously applied lime on the growth and yield of two near-isogenic wheat genotypes differing only in aluminium (Al) tolerance (Triticum aestivum L. Al-sensitive line ES8 and Al-tolerant line ET8), and barley (Hordeum vulgare cv. Mundak) on an acid soil (pH_CaCl2 4.6 in 0–10 cm and pH 4.1–4.3 in 10–40 cm) in the medium rainfall region of Western Australia. The trial consisted of four lime treatments: (i) no lime control; (ii) surface liming at 1.5 t ha⁻¹ in 1999; (iii) surface liming at 2.5 t ha⁻¹ in 1984; (iv) liming in 1984 and re-liming in 1999. Wheat crops were grown in 1999 and 2001, and barley was grown in 2000.

Liming in 1984 increased the pH in both topsoil and subsoil and decreased toxic Al in the subsoil. Liming in 1999 largely increased soil pH in the 0–10 cm in previously unlimed and limed plots, but only slightly increased the pH in 10–20 cm 2 years after application. In 1999, there was an overall 14% grain yield increase by growing ET8, mostly due to much better performance (41%) of ET8 over ES8 in the treatment with surface liming in 1999. In 2001, ET8 had yield 24% higher in the no lime control and 14% higher in the treatment with liming in 1999 compared with ES8. While both genotypes had similar root length density in the topsoil, root length density in acid subsoil was 22–160% higher for ET8 than for ES8. Wheat genotypes produced 23–24% higher yield due to the liming in 1984 compared to the no lime control. In 2000 season, shoot biomass of barley increased by 45–70% in the limed treatments compared with the no lime control. Liming at 2.5 t ha⁻¹ in 1984 or liming at 1.5 t ha⁻¹ in 1999 increased yield by 25%. Liming in 1984 and re-liming in 1999 increased the yield by over 50%. The results suggest that surface liming can ameliorate subsoil acidity as measured 15–17 years after application, and that growing an Al-tolerant crop in combination with surface liming provides a good strategy to combat subsoil acidity. The genotypic variation in response to liming appears to result from the difference in the sensitivity of root proliferation to low pH and high Al.     

Responses of three early potato cultivars to subsoiling and irrigation regime on a sandy soil

A compact subsoil restricts rooting and reduces the volume of soil from which plant roots can obtain water and nutrients. A reduced water supply may result in severe plant water stress between irrigations. A study was conducted on a sandy soil to evaluate the responses of three early potato cultivars (Norgold Russet, HiLite Russet, and Russet Norkotah) to subsoiling to loosen a compact subsoil and to four irrigation regimes. Differences among cultivar responses to irrigation and subsoiling treatments were minor. All performed best with daily irrigation to replace évapotranspiration (ET) and poorest when irrigation was interrupted during tuber bulking. With daily irrigation to replace ET, subsoiling had little benefit, but with inadequate irrigation, subsoiling improved yield and quality of tubers compared to not subsoiling. Averaged over all treatments, HiLite was the lowest yielding cultivar and had the least U.S. No. 1 and the most undersize tubers. Norkotah had the most U.S. No. 1 and the fewest undersize tubers.     

Concentrations in soil and efficacy of drip-applied 1,3-D+chloropicrin and metam sodium in plastic-mulched sandy soil beds

Concentrations in soil and efficacy of 1,3-dichloropropene (1,3-D)+chloropicrin and methyl isothiocyanate (MITC) against the survival of Phytophthora capcisi, Rhizoctonia solani and yellow nutsedge (Cyperus esculentus L.) were studied in plastic-mulched Southern Georgia sandy soil beds. Beds were treated with InLine (60.8% 1,3-D+33.3% chloropicrin) at 93.5, 187, and 280.5 l ha⁻¹ and Vapam (42% metam sodium) 233.8, 467.5 and 701.3 l ha⁻¹. 1,3-D+chloropicrin and MITC concentrations in soil were monitored after drip application for 7 d and 240 h, respectively, from pre-selected sites in beds. 1,3-D+chloropicrin and MITC concentrations decreased with time and distance from the emitter. Survival of P. capsici, R. solani and yellow nutsedge in treated beds was higher with distance from the emitter. These methyl bromide alternatives did not diffuse laterally at effective concentrations beyond the point of application. Improved application techniques are required to improve the lateral distribution of these alternatives.     

Effect of K fertilization on yield and leaf nutrient concentrations of potatoes grown on a sandy soil

A large percentage of winter and spring potatoes (Solanum tuberosum, L.) grown in the USA is produced in northeast Florida (NEF) on sandy soils with low cation exchange capacity. Maintaining adequate K nutrition is a major concern. A study was conducted on an Elzey fine sand (sandy, siliceous, hyperthermic Typic Humaquept) in NEF to relate yield and leaf K to soil and fertilizer K levels. In 1981, Mehlich-I soil K in the 0–15 cm depth averaged 73 mg/kg. Yields of 35 t/ha were obtained without any K fertilization and no response to K sidedressed at rates up to 70 kg/ha was obtained. In the following three years, soil K prior to fertilization was < 40 mg/kg. In 1982 and 1983, significant differences in yield were obtained as a result of K fertilization at planting at rates up to 186 kg/ha. In 1984, no yield differences were obtained with K fertilizer rates ranging from 94 to 280 kg/ha. Differences in maximum tuber yields from year to year were related to the number of growing-degree days accumulated between planting and harvest. Yield-leaf K relationships for leaf samples taken late in the season showed that the critical leaf K concentration for 35 t/ha yields was no more than about 20 g/kg; that for yields approaching 40 t/ha was no more than about 45 g/kg. The results of this study indicated that current K fertilizer recommendations are higher than necessary for the yields being obtained by most NEF potato growers.     

Rice plant growth and nutrient leaching under different patterns of split chemical fertilization on sandy soil using a pot

Paddy and Water Environment - Savannakhet Province has 25% of the total lowland rice cultivation area of Lao People’s Democratic Republic (Laos). However, most of the fields are rainfed, with...     

Effect of time of spraying of glyphosate on the vegetation of an upland deep peat soil

The vegetation of an upland deep peat soil consisting mainly of Festuca rubra, Holcus mollis, Molinia caerulea, Juncus acutiflorus and Potentilla erecta was sprayed with 1·5 kg a.i. per ha glyphosate applied to separate plots at monthly intervals from April to August. In July of the following year, April and May applications showed no effect on sward composition while June, July and August treatments resulted in increasing proportions of mosses and bare ground. August spraying gave almost complete control of the indigenous species with the exception of F. rubra and mosses. The results are discussed in relation to the establishment of improved pastures in upland areas by surface seeding.     

酸性土壤中大豆根际微生物群体感应的初步研究

采用盆栽及室内模拟实验对铝胁迫下大豆根际微生物的群体感应进行了初步探索。利用高效检测菌株根癌农杆菌Agrobaoterium tumefaciens KYC55(pJZ372;pJZ384;pJZ410)对在酸性土壤中种植了耐铝大豆BX10和铝敏感大豆BD2的根际土、非根际土中群体感应信号分子高丝氨酸酰基内酯(AHL)进行检测。结果表明,在大豆根际土中AHL活性显著高于非根际土,且BX10根际土中AHL含量显著高于BD2(P<0.01);随大豆生长时期的推移,BX10和BD2根际土及非根际土中AHL均逐渐升高。模拟酸铝环境的室内实验表明,不同浓度的铝胁迫对中华根瘤菌Sinorhizobium sp.1128的生长、AHL产生水平、胞外多糖的产生以及根毛吸附作用均产生显著影响,从而进一步验证了铝胁迫对群体感应的影响。     

Uses and benefits of glyphosate in German arable farming

Glyphosate is world-wide seen as the most widely used herbicide ingredient. In Germany, from 1999 to 2010, the use of glyphosate based herbicides (GBH) increased by 100%. Many agronomical benefits are attributed to glyphosate, but there is also public criticism. To analyse current application patterns and to assess the agronomical importance of GBH in Germany, a survey was carried out among 896 arable farmers. The survey took place in early 2011, taking 2009 as a reference year. In Germany, cultivation of transgenic crops is generally not permitted and, therefore, herbicide resistance trait does not play any role in application patterns.Based on farmer's statements, a calculated application area of 4.3 million hectare arable land was estimated, representing 39% of total arable area. Three application modes receive major proportions of glyphosate use, these are: pre-sowing (20.7% of application area), pre-harvest (11.2%) and stubble application (68.1%). Among the field crops, oilseed rape (including oilseed rape stubbles) is treated with 27.5% of the nation-wide glyphosate amount followed by winter barley (20.1%) and winter wheat (15.8%). Without using glyphosate, farmers expect an increase in the share of ploughed arable land from 38.1% to 71.4%. Also, without glyphosate the use of cultivator on stubble land is expected to increase about 1.6 passes on average. If applied pre-sowing, glyphosate could save herbicide applications in the following crop. Saving one application of a post-emergence herbicide was estimated by farmers for corn and sugar beet (46% of pre-sowing applications), silage maize (40%), oilseed rape (27%), and winter wheat (22%). Most applications are applied on off-crop fields, so farmers did not quote any observation of yield savings due to glyphosate. The nation-wide economic benefit of glyphosate due to savings of other agricultural measures such as soil cultivation and post emergence herbicides is calculated between 79 and 202 million Euro per year, depending on glyphosate price.We conclude, that glyphosate offers large benefits to farmers, though some routine applications results in only moderate economic benefit compared to the non chemical practices being replaced. Developing decision rules for farmers might allow for an optimum allocation of glyphosate use.     

气相色谱法检测茶园土壤中有机氯农药残留量

采用气相色谱法检测茶园土壤中8种有机氯农药组分的残留量,方法的平均回收率在76．5%～105．4%之间,相对标准偏差在3．82%～10．97%之间,检出限为0．0001～0．001mg/kg。结果表明:本方法方便、快速、准确性高,适用于土壤样品的农残检测。     

Effect of declining or interrupted irrigation on yield and quality of three potato cultivars grown on sandy soil

Many potatoes in the Northwest are grown on sandy soils with sprinkler irrigation. The low water holding capacity and restricted rooting often associated with coarse-textured soils create conditions where water stress injury is likely. Temporary water shortage due to irrigation system failure is a hazard on these soils. The Russet Burbank cultivar is often severely injured by such water stress. It is not known how the cultivars Nooksack and Lemhi respond to these conditions. A study was conducted to compare the responses of Russet Burbank, Nooksack, and Lemhi cultivars to interruptions in irrigation during tuber initiation or during bulking, and to gradually increasing water stress from declining water application rates during the last 8 to 10 weeks of the growing season. In most categories evaluated, Russet Burbank was most injured by water stress, especially in percent U.S. No. 1 tubers. Much of the decrease in U.S. No. 1 tubers was due to small size. Nooksack generally was the least affected by water stress while Lemhi was affected slightly more than Nooksack. Both Nooksack and Lemhi withstood periods of water stress and produced satisfactory yields and grades of tubers while Russet Burbank did not produce profitable levels of marketable tubers.     

黄棕壤和酸紫砂土施用不同磷肥对油菜产量的影响

为实现油菜磷肥减施增效和保障生态环境,利用土壤有效磷含量较低的黄棕壤和酸紫砂土开展试验,建立土壤-磷肥-作物体系相匹配的磷肥施肥方案.以甘蓝型油菜中双11号和圣光168为材料,采用盆栽试验研究黄棕壤和酸紫砂土上施用过磷酸钙(SSP)、磷酸二铵(DAP)、聚磷酸铵(APP)和钙镁磷肥(CMP)对油菜苗期生长及成熟期产量、...     

Efficacy of a new glyphosate formulation for weed control in maize in southwest Nigeria

A field trial in 2003 and 2004 assessed the efficacy of a new formulation of glyphosate, Touchdown Forte HiTech (glyphosate-TF) and two older versions, Roundup (glyphosate-RP) and Touchdown (glyphosate-TD) for weed control in Nigeria. Treatments were glyphosate-TF at 0.25–1.25 kg a.i./ha, glyphosate-RP at 1.8 kg a.i./ha, and glyphosate-TD at 1.0 kg a.i./ha. Weeded and unweeded treatments were controls. Visual evaluations of weed control at 4 and 8 weeks after treatment (WAT) in both years indicated that glyphosate-TF at all doses gave moderate to complete control of all major weeds (50–100%). At 4 WAT, control of Ageratum conyzoides L., Commelina benghalensis L., Ipomoea involucrata P. Beauv., Brachiaria comota [Hochst ex A. Rich] stapf, and Acalypha ciliata Forssk was at a level similar to that in the weeded control. In 2003, all herbicide formulations and the weeded control reduced Imperata cylindrica (L.) Beauv. shoot dry biomass to the same level at 8 WAT (91–100%) and at maize harvest (83–88%). In 2004, 0.50–1.25 kg a.i./ha of glyphosate-TF and 1.8 kg a.i./ha of glyphosate-RP gave 95% reduction at 8 WAT and 97% at harvest, similar to the weeded control. Maize grain yield in the weeded control and herbicide treatments was 2.8 times higher than that in the unweeded control in both years. These results indicate that glyphosate-TF is effective for weed control in maize at herbicide doses lower than the older formulations.     

Natural silicates mixed with organic fertilizers enhance corn adaptation to salt stress and improve physical characteristics of sandy soil

Soil salinity is one of the major environmental constraints to crop productivity worldwide. Therefore, the development of cost-effective and environment-friendly techniques allowing increased crop productivity and soil fertility under saline conditions is rather urgent today. The objective of this investigation was to study the effects of mixtures containing natural silicates (analcite, bergmeal, and potassium silicate) and organic fertilizers (sapropel, peat) in corn (Zea mays L.). We specifically evaluated tolerance of corn to salinity stress and certain characteristics of saline soil (viz., redox potential, conductivity, and phytotoxicity) using a factorial pot experiment, modeling NaCl salinity levels of 0, 50, 100, 150, and 200 mM under greenhouse conditions. Growth, water balance, photosynthesis, catalase activity, and accumulation of nonenzymatic antioxidants (flavonoids and anthocyanins) were measured and evaluated. Salinity stress reduced shoot and root biomass by 8–49%, photosynthetic pigment content in leaves by 15–30%, deteriorated water balance, and activated nonspecific adaptive reactions (i.e., accumulation of enzymatic and nonenzymatic antioxidants) in the corn seedlings. All the tested silicon-containing mixtures stimulated corn seedling resistance to salt stress and reduced soil phytotoxicity. This was reflected in the stimulation of growth of the corn seedlings (accumulation of shoot biomass, and formation and growth of lateral roots). The content of photosynthetic pigments, flavonoids, anthocyanins, catalase activity increased 1.3–2 times compared with plants that received NaCl only. The difference between treatments and control was most pronounced at moderate levels of salinity (100–150 mM). The mixture containing silicon minerals and sapropel (9:1 proportion) showed the highest protective effect against salinity stress.     

Control of winter cereals in the spring with glyphosate

Poor survival of winter cereals due to winter conditions in Ontario can necessitate destruction of the stand in the spring to allow the subsequent seeding of an alternative crop. Winter cereals were seeded in the autumn of 2004 and 2005 at the Huron Research Station and at the University of Guelph Ridgetown Campus in Ontario to evaluate two formulations of glyphosate [potassium (K) vs diammonium (DA) salt] at different doses (225, 450, 675, 900, or 1350 g a.e. ha⁻¹) for the burn-off of soft white winter wheat (SWW), soft red winter wheat (SRW), hard red winter wheat (HRW) and autumn rye (AR) in either late April or early May. There was no difference between the glyphosate formulations for the control of winter cereals at 1, 2, 3, and 4 weeks after treatment (WAT). There was generally improved control with glyphosate applications made in early May compared to late April however results were not always statistically significant. Generally, control of winter cereals increased as the glyphosate dose was increased from 225 to 1350 g a.e. ha⁻¹. The minimum dose of glyphosate required for providing 90% or greater control of SWW, SRW, HRW, and AR was 675 g a.e. ha⁻¹ at 4 WAT. Glyphosate applied at 675 g a.e. ha⁻¹ caused a 98, 97, 98, and 99% reduction in shoot dry weight of SWW, SRW, HRW, and AR, respectively. Based on this study glyphosate (K or DA) applied in late April or early May can be used at doses as low as 675 g a.e. ha⁻¹ to adequately control SWW, SRW, HRW, and AR in the spring.     

Effect of tillage systems and herbicide treatments on weed abundance and diversity in a glyphosate resistant crop rotation

The effect of exclusive application of glyphosate and glyphosate in combination with residual herbicides on weed species density and composition in summer crops was studied over 2 years. Field experiments consisted of three rotations including soybean and maize glyphosate-resistant cultivars in two tillage systems. Regardless of the tillage system, both glyphosate application alone and in combination with residual herbicides had a pronounced impact on the reduction in density and richness of summer herbaceous annual weeds, but the effect was greater with glyphosate in combination with residual herbicides.     

大豆对大豆花叶病毒SC-11株系抗性的遗传及基因定位

大豆花叶病毒病(soybean mosaic virus,SMV)是世界性大豆病害,严重危害大豆的产量和质量.SC-11为我国黄淮夏大豆区以及北方春大豆区SMV主要流行株系.研究大豆品种对SC-11的抗性遗传方式,不同大豆材料对SC-11抗性位点的等位性关系,并对抗性基因进行了SSR标记定位.结果表明:齐黄1号对SC-11的抗性由一对显性基因(RSC-11)控制;齐黄1号、齐黄22,广吉和早熟18对SC-11的抗病基因是等位的或紧密连锁的;经分离群体组群分析法研究发现,齐黄1号抗SC-11的位点RSC-11位于F连锁群,与SSR标记Saull4、Satt334、Sat_234和Sct_033紧密连锁,距离分别为11.1 cM、8.9 cM、4.6 cM和4.7 cM;选取F连锁群上亲本间有多态的18对引物构建了F连锁群的遗传图谱,全长254.8cM,标记间平均距离为13.41cM.研究结果为大豆抗病育种以及抗性基因的精细定位和图位克隆奠定了基础.     

甘蓝型油菜抗草甘膦基因遗传转化及抗性鉴定

为自主研发抗除草剂的甘蓝型油菜,从细菌（Isotericola variabilis）中克隆I.variabilis-EPSPS*基因,使油菜产生草甘膦抗性。通过农杆菌介导法将I.variabilis-EPSPS*转入甘蓝型油菜自交系育127,获得转I.variabilis-EPSPS*基因单株E₁。草甘膦耐受性结果表明,转I.variabilis-EPSPS*基因T₁代在不同浓度草甘膦的培养基中能够正常生长,而非转基因对照生长严重受阻。I.variabilis-EPSPS*成功整合于油菜基因组并可稳定遗传,草甘膦处理后表达量增加,而且在草甘膦浓度改变时仍保持稳定表达。在温室用41%草甘膦异丙胺盐商品制剂（农达）600倍稀释液（1/3田间生产推荐中剂量）处理转I.variabilis-EPSPS*基因E₁的T₁植株,体内莽草酸累计量远低于非转基因对照。通过对角果长、每角果粒数和千粒重等农艺性状考察发现,转基因植株和对照相比无显著性差异。田间喷施农达400倍液（1/2田间生产推荐中剂量）,发现转基因E₁T₁植株正常生长而对照全部死亡。鉴于I.variabilis-EPSPS*基因在转基因油菜中能够稳定遗传并赋予了油菜草甘膦除草剂抗性,认为该抗草甘膦转基因油菜是一份新种质。     

Effects of simulated grazing on growth and persistence of Artemisia frigida in a semiarid sandy rangeland

Abstract To assess the tolerance of fringed sagewort (Artemisia frigida Willd.) to grazing in semiarid sandy rangeland, forty‐five fringed sagewort plants of similar size were chosen randomly from sandy rangeland and divided into three cohorts (fifteen plants per cohort) that were subjected to simulated grazing management in 1998. Plants were cut in spring on 24 April and again in summer on 26 July at either 2–3 cm (severe), or at5–6 cm (moderate), or uncut to serve as the control. Plant responses to intensity of cutting were monitored over two consecutive years differing substantially in the amount and seasonal distribution of rainfall. Cutting in spring (moderate or severe) did not influence plant height, average canopy diameter, the number of branches, and specific branching density measured in July 1998. Moderate cutting in summer reduced plant height compared with the uncut treatment but did not influence other plant growth variables in September 1998. However, severe cutting in summer during the reproductive stage strongly reduced plant height, canopy size, the number of branches, individual shoot weight and specific branching density in September 1998 compared with moderate and no cutting and its negative impacts on the growth of this species were evident in the following year. Severe cutting in spring significantly increased the number of flowering shoots, whereas cutting in summer (at either level) reduced the capacity of fringed sagewort to produce flowering shoots. Also, the negative impact of summer cutting on seed production continued in the following year. The production of plant biomass was similar in the three treatments in 1998, but it was significantly lower in cut than uncut plants in 1999. The reduced biomass was due to a decline in plant height, canopy size, number of branches and specific branching density. Compared with the uncut plants, the cut plants tended to allocate a greater proportion of their biomass to vegetative shoots and leaves than to flowering shoots in 1998; in 1999, although cutting treatments had ceased, the cut plants still allocated a greater proportion of new biomass to vegetative shoots and less to flowering shoots, but a similar proportion to leaves.