Soil microbial community response to surfactants and herbicides in two soils

The environmental impacts of herbicides on desirable plants and the soil biota are of public concern. The surfactants that are often used with herbicides are also under scrutiny as potentially harmful to soil biological systems. To address these concerns, we used two soils, a silt loam and a silty, clay loam from south central Missouri, to investigate the impacts of herbicides and surfactants on soil microbial communities using phospholipid fatty acid (PLFA) analysis. The surfactants used in this study were alkylphenol ethoxylate plus alcohol ethoxylate (Activator 90), polyethoxylate (Agri-Dex), and a blend of ammonium sulfate, drift reduction/deposition polymers and anti-foam agent (Thrust). The herbicides were glyphosate, atrazine and bentazon. Surfactants and herbicides were applied to soils at label rate, either alone or combined, to 4000 g soil per pot. The two soils differed in history, texture, some chemical characteristics and several microbial community characteristics. A few of the chemicals altered some of the components of the microbial community after only one application of the chemical at field-rate. The Cole County, MO silt loam showed larger changes in the microbial community with application of treatments. For the Boone County, MO silty clay loam, Activator 90, Agri-Dex and bentazon treatments increased microbial biomass determined by PLFA; Thrust decreased PLFA markers, bacteria to fungi ratio; and Agri-Dex at both rates decreased monounsaturated fatty acids. Changes in the microbial community due to herbicides or surfactants were minimal in this study of a single application of these chemicals, but could be indicators of potential long-term effects. Long-term studies are needed to determine the changes in the microbial community after several years of annual applications of herbicides and surfactants on a wide array of soil types and management practices.     

几种除草剂对绿豆田杂草的防治效果及绿豆病害影响的研究

绿豆(Vigna radiata)是重要的粮食、蔬菜和药用作物,营养价值和药用价值均很高,在农业种植结构调整和种植模式的优化中具有重要的作用。研究通过10种除草剂组合防除绿豆田杂草,比较不同组合间杂草防除效果的差异,筛选出适用于辽宁地区的杂草防除方法。结果表明,除草效果最好的是4号组合(氟磺胺草醚高效氟吡甲禾草灵苗后喷雾),5号组合(拿捕净氟磺胺草醚苗后喷雾)和10号组合(精喹禾灵、氟磺胺草醚苗后喷雾),防治效果分别为92.3%、95.5%和93.5%,其中产量最高的是10号组合,产量为1 326.9 kg/hm2。此外,1号组合(异丙甲草胺氟磺胺草醚播后苗前喷雾)、5号组合(拿捕净氟磺胺草醚苗后喷雾)和11号组合(精喹禾灵、乙羧氟草醚苗后喷雾)还能有效对绿豆田间病害起到一定的防治作用,其中11号组合的防治效果最好,绿豆尾孢菌叶斑病和细菌性疫病的发病级别分别仅为3.2和4.2。研究通过分析10种不同除草剂组合对绿豆田间杂草的防治效果,对绿豆产量的影响以及田间常见病害的发病情况的影响,为辽宁地区绿豆田间草害的综合防治提供技术指导。     

球形微电解填料预处理除草剂生产废水的研究

[目的]探究采用球形微电解填料预处理除草剂生产废水的效果。[方法]采用球形微电解填料预处理除草剂生产废水,研究了pH、填料投加量和反应时间对处理效果的影响,测定了最佳条件下预处理前后水质变化,并对该技术的运行成本进行了分析。[结果]在pH为3、填料投加量为1.0 kg/L废水、反应时间为3.0 h的最佳反应条件下,COD去除率为26.3%;色度去除率为86.4%;TP去除率为95.6%;BOD5/COD比值由0.10升高到0.35,废水的可生化性得到明显提高;水处理成本为1.0元/t,与取得同等COD去除率的电解法相比成本较低。[结论]球形微电解填料预处理除草剂生产废水效果较好、成本较低、不板结,为后续生化处理奠定了基础。     

2种除草剂对黑麦早期幼苗生长的影响

[目的]了解除草剂对黑麦幼苗早期生长的影响。[方法]从生理生化和细胞水平分析了2种除草剂[阿特拉津（Atrazine）和甲酰胺草磷（Amiprophos methyl,APM）]对黑麦早期幼苗生长的影响。[结果]Atrazine可明显降低黑麦幼苗叶绿素a、b和可溶性蛋白质的含量。当用0.100和1.000 mg/LAtrazine处理黑麦幼苗16h时,叶绿素a、b含量分别从对照的1.26（a）、0.49（b） mg/g（FW）下降至1.15（a）、0.46（b） mg/g（FW）和0.81（a）、0.33（b） mg/g（FW）。可溶性蛋白质含量则随着Atrazine处理浓度的增加而减少。Atrazine对黑麦分生组织细胞有丝分裂和染色体结构无显著影响。APM处理后,黑麦幼苗叶绿素a、b和可溶性蛋白质含量无显著变化,但分生组织细胞有丝分裂和染色体结构变异如桥、多极分裂、滞后染色体和不均等分裂中期细胞数量显著增加。[结论]黑麦中Atrazine使用的临界剂量为0.100～1.000 mg/L,而APM为4.000mg/L。     

除草剂混用和剂量对谷子k864-3农艺性状及产量的影响

为筛选出能应用于谷子生产使用的除草剂,我们分别对四种除草剂混合后各按照1倍,1.5倍和2倍浓度进行喷施。试验结果表明谷草青和拿捕净混合处理的药害最高,二甲四氯钠拿捕净处理和2-4D拿捕净药害最低,且药害随浓度提升而明显提高。综合各项数据,可以得出施用1倍剂量2-4D拿捕净处理、1.5倍剂量2-4D拿捕净处理和1倍、1.5倍二甲四氯钠拿捕净处理对作物的各项影响最小,对田间杂草也可以进行有效控制。     

中国除草剂产业现状、面临的问题及发展趋势

从中国除草剂发展的现状出发，进行除草剂市场的分析和预测，在综合分析除草剂产业存在问题基础上，研究了除草剂发展的趋势和相应的对策。中国除草剂产业未来发展趋势：以非专利品种为主导，以“灭生性除草剂＋抗除草剂转基因作物”为主要模式，适当引进国外先进的除草剂，除草剂品种开发以粮食作物为主，以经济作物为辅，兼顾发展除草剂混剂和增效剂，杂草治理向综合防治方向发展。     

Effects of different pesticides on microbial populations,nitrogen mineralisation,and thiosulphate oxidation in the rhizosphere of jute (Corchorus capsularis L. cv.)

Summary A field experiment was carried out to investigate the effects of three pesticides (a herbicide, Basalin, and two fungicides, Dithane M-45 and Bengard), separately or in combination, on jute rhizosphere microflora (total bacteria, ammonifying bacteria, aerobic non-symbiotic N₂-fixing bacteria, thiosulphate-oxidising bacteria, actinomycetes, and fungi), N mineralisation, and thiosulphate oxidation in soil. The pesticide treatments had significantly different effects on the rhizosphere microflora and their activities, depending on the kind of pesticide, the mode of application (individually or in combination), and the stage of growth of the jute plants. Although the pesticides hindered growth in the early stages, later stages were not affected because the effects on the rhizosphere microflora subsided. In addition, the combination of the herbicide Basalin (a dinitroaniline compound) and the fungicide Bengard (a benzimidazole derivative) virtually cancelled out each other's effects.     

Tillage and application effects on herbicide leaching and runoff

Herbicides are key products in sustaining agricultural production and, to minimize agro-environmental concerns regarding their use, continued assessment of their behavior under different management practices is required. Leaching and runoff losses of four herbicides applied preplant-incorporated (PPI) were evaluated in two tillage systems over a 3-year period (1989–1991). Scant leaching during the droughty 1991 growing season limited treatment evaluations to 2 years. Herbicides were applied at recommended rates (1.7 and 2.2 kg active ingredient (a.i.) ha⁻¹) to conventional tillage (CT) and mulch tillage (MT) corn (Zea mays L.) fields on Hagerstown silty clay loam (fine, mixed, mesic Typic Hapludalf). Tillage treatments were defined as moldboard plow-disk-harrow (CT) and single-disking (MT). During this study, CT followed 5 years of corn production in a comparable CT system on this site and, similarly, MT followed a 5-year no-tillage (NT) system. Herbicides were applied preemergence (PRE) to CT and NT in the 5-year study and preplant-incorporated (PPI) in this study. Herbicide mobility in subsurface drainage was evaluated from herbicide mass transported to pan lysimeters installed 1.2 m deep. Surface drainage losses of these chemicals were determined from residues in runoff collected with automated sampling and recording equipment.

Leachate volumes were greater from MT than CT in 1989 and 1990 and exceeded all seasonal losses during the previous 5 years under NT management. Comparisons of total seasonal leachate discharged to pan lysimeters within and among studies and herbicide mass leached showed that timing of leachate-inducing precipitation relative to herbicide application was the key factor in regulating herbicide translocation. Herbicide mass transported through the root zone averaged from less than 0.1% to 0.9% of applied rates in CT and from 1.4% to 5.1% in MT.

Leachate-availability of herbicide residues and extent of herbicide longevity in this soil under MT conditions were similar to previous findings under NT management. Despite these behavioral similarities for herbicides among tillages, herbicide mass discharged per unit of percolate was most often lower for MT compared with NT, particularly in early growing seasons of comparable precipitation. Thus, the PPI treatment in MT appeared to reduce leaching of these chemicals compared with PRE application in NT.

Runoff losses of PPI herbicides ranged from 0.35% to 0.77% of applied rates in CT and from 0.13% to 0.28% in MT. Losses of PRE-applied herbicides from NT averaged less than 0.1% of applied rates; maximum yearly losses ranged from 0.06% to 0.18%. Thus, the character of the disked, minimally tilled surface provided a level of impedance to runoff that was greater than achieved with the tilled surface on this 3 to 5% slope, but less than previously obtained with an untilled, mulch-covered surface.     

Changes in the atrazine extractable residues in no-tilled Mollisols

The effect of application dose and soil organic matter (SOM) stratification on changes in atrazine (6-chloro-N²-ethyl-N⁴-isopropyl-1,3,5-triazine-2,4-diamine) extractable residues (ER) were investigated. Two soils [Entic Haplustoll (EH) and Typic Hapludoll (TH)] with contrasting SOM content and form and without previous atrazine exposure were selected. Sampling was carried out at two depths: 0–2 and 2–5 cm. Atrazine ER were measured at 0, 3, 7, 14, 28, and 56 days in laboratory incubation. Atrazine concentration recovered 1 h after of its application (C_t0) was used as an index of the soil capacity to reduce the atrazine extractable fraction. SOM stratification was studied by means of physical fractionation. In both soils, the higher OC concentration was found in the 200–2000 μm fraction (OC_{f 200–2000}). Soils differed in terms of the OC_f 50–200/OC_{f 200–2000} ratio. This ratio increased with depth in EH soil: 0.23 (0–2 cm) and 2.00 (2–5 cm). In TH soil, the ratio was 0.80 (0–2 cm) and 0.50 (2–5 cm). The t_1/2 values ranged from 9 to 19 days, depending on soil type and atrazine application dose. The upper layer C_t0 and k were higher for higher atrazine doses. Implementation of a split application dose of atrazine may be an effective alternative to extend its half-life in soil solution, as well as involving a lower potential risk of soil accumulation or vertical movement in the soil profile towards deep soil layers and groundwater.     

几种玉米大田除草剂对AM真菌侵染及其酶活性的影响

在接种G intraradices和G etunicatum的玉米植株盆栽钵中 ,按大田常规用量 ,施用乙草胺、丁草胺、灵达、骠马、百草敌和使它隆 6种除草剂 ,对玉米植株的生物量、AM真菌菌丝根段侵染率、菌丝碱性磷酸酶 (ALP)和琥珀酸脱氢酶 (SDH)活性及土壤中AM真菌菌丝的总量均有显著影响。第 1 0周取样 ,对玉米植株生物量影响较大的除草剂为骠马 (植株生物量为 2 1 1～ 31 3g) ,影响较小的为灵达 (植株生物量为 5 9 7～ 6 5 5g) ,而对照的生物量为 84 4～ 95 7g ;对AM真菌侵染率影响较大的为丁草胺 (AM真菌侵染率为 1 3 7%～1 8 1 %) ,影响较少的为使它隆 (AM真菌侵染率为 30 4 %～ 36 6 %) ,而对照侵染率为 6 3 0 %～ 88 2 %;对AM真菌菌丝ALP和SDH酶活性影响较大的为丁草胺 (ALP为 8 1 %～ 1 0 4 %,SDH为 1 0 6 %～ 1 4 6 %) ,影响较小的为使它隆 (ALP为 1 7 0 %～ 2 0 6 %,SDH为 2 3 1 %～ 2 8 2 %) ,而对照的ALP为 38 0 %～ 5 0 3%,SDH为4 9 7%～ 72 4 %;此外 ,除草剂对土壤中AM真菌菌丝的总量也有显著影响。