Behaviour and persistence of trifluralin in soil

The growth response of sorghum to trifluralin, on various soils and soil mixtures, was significantly correlated with organic matter (ranging from <0–1% to 20–4%) but not with clay content (ranging from 3% to 63%). However, in soils with a similar, low organic matter content, the activity of trifluralin increased with increasing clay content. No correlation was found between phytotoxicity of trifluralin and lime content of soils. The persistence of trifluralin incorporated in soil was examined by repeated reseedings of sorghum. Phytotoxicity lasted longer in soil dried and mixed at each interval between seedings than in soil left undisturbed; after 2 months about 50% of the original 4 ppm trifluralin remained in undisturbed soil vs 60 % in repeatedly mixed soil. The rate of degradation, after 2 months of incubation at 50% field capacity, increased with temperatures from 10°to40° the concentration of trifluralin required for a given growth reduction was approximately eight times greater after incubation at 40° than at 10°C. Comportement et persistattce de la trifluraline dans le sol Les effets de Ia trifluraline sur la croissance du sorgho cultivé dans divers sols ou mélanges de sol se sont révlés être en corrélation significative avec la matiere organique (entre < 0,1 % et 20,4 %) mais pas avec la teneur en argile (de 3 % A 63 %). Toutefois dans les sols contenant un taux analogue et faible de matiére organique, l'activité de la trifluraline s'est accrue en même temps que Ia leneur en argile. Aucune corrélation n'a été constatée entre la phytotoxicité de la trifluraline et la teneur en calcaire des sols. La persistance de la trifluraline incorporée dans le sol a été examinée au moyen de ressemis répétés de sorgho. La phytotoxicité dura plus longtemps dans le sol séché et remuéà chaque intervalle entre les semis que dans le sol non travaillé; au bout de 2 mois, 50% environ des 4 ppm de trifluraline apportés à. I'origine restaient dans le sol non remué contre 60% dans le sol plusieurs fois remué. Le taux de degradation, aprés deux mois d'inciibation à 50% de la capacityé au champ, augmenta avec la température de 10°à 40°C; la concentration de trifturaline nécessaire pour obtenir une réduction de croissance donnée fut approximativement huit fois plus grande aprés incubation. à 40° qu'aprés incubation à 10°C. Verhalten und Perststenz von Trifluralin im Boden Die Wachstumsreaktion von Hirse gegenubcr Trifluralin in verschiedenen Böden und Bodenmischungen war signifikant mit dem Gehalt an organischer Substanz (<0–1 %–20–4%) korreliert, nicht aber mit dem Tongehalt (von 3%-63%). Jedoch nahm in Böden mit annähernd gleich niedrigen Gehalten an organischer Substanz die Wirksamkeit von Trifluralin mit steigendeni Tongehalt zu. Zwischen der Phytotoxizität von Trifluralin und dem Kalkgehalt der Böden wurde keine Korrelation gefunden. Die Persistenz von in den Boden eingearbeitetem Trifluralin wurde durch wiederholte Einsaat von Hirse untersucht. Die Phytotoxizität dauerte im Boden, der jeweils zwischen den Einsaaten getrocknet und gemischt worden war, langer an als im nicht derartig behandelten Boden. Nach 2 Monaten waren im letzteren Boden ungefähr 50% der ursprüinglichen 4 ppm Trifluralin verblicben gegenüber 60% im wiederholt durchmischten Boden. Nach 2 Monatlen Inkubation bei 50% Feldkapazität stieg die Abbaurate, wenn die Temperatur von 10° auf 40°C stieg; die für eine gegebene Wachstumsreduktion benötigte Trifluralinkonzentration war bei 40° annShernd achtfach grösser als bei 10°C.     

Metribuzin mobility in soil columns as affected by urea fertiliser

Application of urea fertilisers to soils influences the soil solution characteristics and thus may affect the sorption of soil-applied herbicides. The present investigation reports the influence of urea co-application on sorption and leaching of metribuzin, a triazine herbicide. Urea application at 60 and 120 kg N ha(-1) increased metribuzin sorption in soils over that in untreated natural soil. The Kf (Freundlich adsorption coefficient) values of metribuzin for natural, 60 and 120 kg N ha(-1) treatments were 0.43, 0.46 and 0.84 microg(1 - 1/n) g(-1) ml1/n respectively. Downward mobility of metribuzin was studied in packed soil columns (300 mm length x 59 mm i.d.) at two irrigation intensities, 720 m3 ha(-1) (72 mm) and 3600 m3 ha(-1) (360 mm). After 720 m3 ha(-1) irrigation, metribuzin did not leach out of any column and was not detected in the leachate. Urea amendment slowed the leaching of metribuzin by 20 and 40% in 60 and 120 kg N ha(-1) urea-treated columns respectively. Also, following urea application, greater amounts of metribuzin were retained in the application zone. Upon increasing the irrigation intensity fivefold, urea application did not have any effect on metribuzin mobility, and its breakthrough from both natural and urea-amended columns occurred after 126 mm irrigation. However, there was a marked difference in the maximum concentration of metribuzin in the breakthrough curves obtained from natural and urea-amended columns. The study indicated that co-application of metribuzin and urea fertiliser is a safe practice as far as leaching of herbicide is concerned.     

Persistence of terbacil and trifluralin under different soil and climatic conditions

Soil samples were collected from forty-three field trials conducted on ten soil types to investigate the residual activity of terbacil and trifluralin at the end of the cropping season, approximately 6 months after application. The soil was bioassayed in a glasshouse using soya beans and German millet for terbacil and trifluralin respectively. At 1 kg/ha terbacil phytotoxic residues occurred in a majority of the trials, while at 2 kg/ha such a carry-over could be found in every case. Trifluralin doses of up to 1 kg/ha did not persist in toxic amounts in most soils, while application of 2 kg/ha showed residual activity in 74% of the trials and application of 4 kg/ha killed German millet in all instances. Results are also presented from the time-rate dissipation studies conducted on both herbicides by assaying soil samples collected at monthly intervals. Both organic matter and clay content of the trial sites affected the persistence of terbacil, while trifluralin residues were influenced only by the soil organic matter content. Trial sites receiving high rainfall showed considerably less residues of terbacil, but the persistence of trifluralin was not affected by rainfall to any appreciable extent.     

氟乐灵的微生物生态效应

研究了3种浓度氟乐灵对南疆棉田2种土壤(沙土、黏土)4种土壤酶(过氧化氢酶、转化酶、脲酶和磷酸酶)活性的影响。结果表明,同一时间同一浓度氟乐灵处理土壤除过氧化氢酶外,其余3种酶均表现为沙土高于黏土;过氧化氢酶酶活性变化趋势为“下降—升高—趋于平缓”。转化酶和脲酶的变化趋势类似,为“下降—升高—下降—趋于平缓”。磷酸酶变化趋势为“上升—剧烈下降—逐渐升高并趋于平缓”。即不同酶对氟乐灵的反应不同。3种浓度的氟乐灵处理两种土壤,其酶活性经过显著性分析无明显差异,即棉田用氟乐灵作土壤封闭处理对酶活性无影响。     

Availability and biodegradation of metribuzin in alluvial soils as affected by temperature and soil properties

Herbicide degradation in soils is highly temperature‐dependent. Laboratory incubations and field experiments are usually conducted with soils from the temperate climatic zone. Few data are available for cold conditions and the validation of approaches to correct the degradation rate at low temperatures representative of Nordic environments is scarce. Laboratory incubation studies were conducted at 5, 15 and 28°C to compare the influence of temperature on the dissipation of metribuzin in silt/sandy loam soils in southern and northern Norway and in a sandy loam soil under temperate climate in France. Using ¹⁴C‐labelled metribuzin, sorption and biodegradation were studied over an incubation period of 49 days. Metribuzin mineralisation and total soil organic carbon mineralisation rates showed a positive temperature response in all soils. Metribuzin mineralisation was low, but metabolites were formed and their abundance depended on temperature conditions. The rate of dissipation of ¹⁴C‐metribuzin from soil pore water was strongly dependent on temperature. In Nordic soils with low organic content, metribuzin sorption is rather weak and biodegradation is the most important process controlling its mobility and persistence.     

Growth and leaf chemistry of Atriplex species from Northern Mexico as affected by salt stress

Atriplex species are tolerant to salinity and water stress and thus they are suitable for restoration of many degraded ecosystems. In addition, many Atriplex species offer good value as forages. We compared growth and leaf chemistry of Atriplex canescens, a well-known halophyte, and A. acanthocarpa, a poorly-studied species, as affected by salinity in a greenhouse study. Seeds and soil were collected in northern Mexico, the native range of these species. Plants were grown in pots containing native soil and irrigated with NaCl solutions of 0, 50, and 100 mM. Shoot growth of A. canescens declined 37% as NaCl treatments increased from 0 to 100 mM while shoot growth of A acanthocarpa was not significantly affected by salinity. The high salt tolerance of A. acanthocarpa was linked to a high accumulation of leaf sodium (Na) (7- to 13-fold higher than A. canescens). A. acanthocarpa had also higher growth rate than A. canescenes, making the former species a good candidate for cultivation, especially under saline conditions. Tissue concentration of potassium (K) in both species was minimally affected by the salinity treatments. Leaf nitrogen (N) concentration increased as plants faced higher salinity treatments, especially in A. canescens. The high salt tolerance and higher Na accumulation of A. acanthocarpa make this species an attractive choice for reclamation of saline areas. We suggest A. acanthocarpa should be explored as viable forage for cultivation and for reclamation of degraded areas just as A. canescens has been throughout the world.     

新疆阿其克苏河沿岸土壤盐分与离子含量关系研究

通过选取新疆艾比湖湿地国家级自然保护区阿其克苏河东大桥管护站至塌桥子管护站15km为研究区域,在研究区内中德合作项目胡杨样地及垂直河道胡杨、柽柳混交林处采挖地下水测点,分层采集土样,实验室实测土壤含盐量及主要离子(K+、Na+、ca2+、Mg2+、Cl-、CO23-、HCO3-、SO24-)含量,研究结果表明:研究区土...     

Quantitative aspects of Orobanche crenata infestation in faba beans as affected by abiotic factors and parasite soil seedbank

The interactions between the root parasitic weed Orobanche crenata Forsk. and its host plant faba bean ( Vicia faba L.) were quantified under controlled and field conditions at ICARDA's Tel Hadya research station. In the field experiments conducted in 1993–94 and 1994–95 faba beans were sown on two dates, in plots with 0, 50, 200 and 600 O. crenata seeds kg^–1 soil, under both limited and sufficient moisture supply. The effects of temperature on the duration of the early developmental stages of O. crenata were investigated in a growth chamber. The extent of O. crenata infestation was closely related to the number of parasite seeds in the soil. The seed-density treatment with 600 seeds kg^–1 soil resulted in complete crop failure. Furthermore, O. crenata infestation was higher under sufficient than under limiting water supply conditions, irrespective of sowing date. Only in the moderately infested plots, did shifting of the planting time of faba bean result in a significant decrease in parasite dry weight and an increase in crop seed yield. The timing of germination, attachment and further developmental stages of O. crenata was not related to faba bean growth stage and was affected primarily by soil temperature. The duration of O. crenata developmental stages was estimated using the thermal time concept. The relationship between total number of parasite attachments at the harvest of the faba bean crop and O. crenata seed density was dependent on maximum faba bean root-length density measured by the start of pod-filling in each treatment combination of sowing date and moisture supply. The results are discussed with reference to implications for the development of a dynamic simulation model for the prediction of faba bean yield losses caused by O. crenata .     

Characterization of residues in soybeans grown in soil treated with 1,3-dichloropropene soil fumigant

The metabolism of cis- and trans-1,3-dichloropropene (1,3-D) was studied in soybean plants grown in soil treated 24 days prior to planting with [U-¹⁴C]E- and Z-1,3-dichloropropene at 380 liters ha^?1. Isolation and identification of the ¹⁴C residue from soybean plants at 84 days (forage) and 176 days (mature) after application showed that no 1,3-dichloropropene or its putative metabolites, 3-chloroallyl alcohol and 3-chloroacrylic acid, could be detected in any of the tissues. The components of the ¹⁴C residue included major plant constituents (i.e. fatty acids, protein, pigments, organic acids, sucrose and other carbohydrates, and lignin).     

Sorption/desorption behaviour of sulfonylurea herbicides as affected by the addition of fresh and composted olive cake to soil

The olive industry generates residues which can be applied as amendments to soils in their original form (olive cake) or after composting or vermicomposting processes. The addition, fresh or incubated, of these amendments to soil and of their different organic fractions was studied in relation to the sorption/desorption of three sulfonylurea herbicides, bensulfuron‐methyl, chlorsulfuron and prosulfuron. Herbicide sorption was low or very low, slightly promoted by the addition of the agricultural by‐products, especially olive cake, and mainly affected by pH of the soil solution, with the organic carbon content having no significant effect on herbicide retention. Desorption was only reduced when fresh olive cake was added. The incubation of soil and amendments for 3 months did not modify herbicide sorption, but made desorption reversible except for olive cake. The transformation of the organic matter of the amendments due to humification and maturity processes are likely to be responsible for this behaviour. Different organic fractions were removed to assess the influence of each fraction on sulfonylurea sorption. Only the removal of all studied organic fractions increased herbicide sorption, revealing the role of humin and mineral fractions in this process. Therefore, the use of organic amendments is not useful for reducing the risk of movement of ionisable molecules in soil.     

Phytotoxicity and persistence of chlorsulfuron as affected by activated charcoal

Two bioassay procedures, using petri-dishes and pots, based on the root growth of pregerminated maize were used to study the residual phytotoxicity of chlorsulfuron under field conditions. Both bioassay procedures appeared to be equally reproducible and sensitive with residues of chlorsulfuron being detectable from 0·25 to 10·0 ng g^-1. The results indicated that persistence, movement and phytotoxicity increased with increasing rate of chlorsulfuron, but persistence of the herbicide was shorter in wet compared to dry field conditions. As little as 1 g a.i. ha^-1 of incorporated chlorsulfuron under warm and dry field conditions caused a stunting effect on maize plants (Hybrid F₁, Damon) and reduced yield by 53% compared to untreated control plants; while 5·0 and 10·0 g a.i. ha^-1 of incorporated chlorsulfuron killed all maize plants. However, under wetter field conditions, incorporated chlorsulfuron at 1·25, 2·5 and 5·0 g a.i. ha^-1 caused a stunting effect on maize plants (Hybrid F₁, ARIS) and decreased yield by 16, 57 and 92%, respectively, compared to untreated control. Incorporation of 50 kg ha^-1 of activated charcoal inactivated completely chlorsulfuron incorporated at 1·25 and 2·5 g a.i. ha^-1 and did not affect yield of maize compared to untreated control. Higher rates of activated charcoal such as 100 and 200 kg ha^-1 also inactivated chlorsulfuron applied at 1·25–5·0 g a.i. ha^-1 and did not affect grain yield of maize. Phytotoxicité et persistance du chlorsulfuron Deux méthodes d'essais biologiques, à savoir en boîte de Petri ou en pot, Basées sur la croissance des racines de maïs prégermé ont été utilisées pour étudier la phytotoxicité résiduelle du chlorsulfuron en conditions de plein champ. Les deux méthodes sont également reproductibles et sensibles à des niveaux de détection pour les résidus de chlorsulfuron de 0,25 à 10 ng g^-1. Les résultats montrent que la persistance et la phytotoxicité augmentent avec des doses croissantes de chlorsulfuron, mais la persistance est plus courte dans des conditions de plein champ humides que séches. Une dose aussi faible que 1 g de matiére active ha^-1 de chtorsulfuron incorporé en conditions chaudes et séches a causé un effet retard sur les plants de maïs (hybride F₁, Damon) et a réduit de 53% le rendement par rapport au témoin non traité; des doses de 5 à 10 g de matiére active ha^-1 de chlorsulfuron incorporé ont tué tous les pieds de maïs. Cependant, en conditions plus humides, le chlorsulfuron incorporéà 1,25, 2,5 et 5 g de matiére active ha^-1 a causé un effet retard sur le maïs (hybride F₁ ARIS) et a réduit le rendement par rapport au témoin non traité respectivement de 16, 57 et 92%. L'incorporation de 50 kg ha^-1 de charbon actif a complément inactive le chlorsulfuron incorporéà 1,25 et 2,5 g de matiére active ha^-1 et n'a pas eu de répercussion sur le rendement par rapport au témoin non traité. Des doses plus élevées de charbon actif comme 100 et 200 kg ha^-1 ont inactivé le chlorsulfuron appliquéà 1,25–5 g matiére active ha^-1et n'ont pas affecté le poids en grain du maïs. Ueber die Beeinflussung von Phytotoxizität und Wirkungsdauer von Chlorsulfuron durch Aklivkohle Zum Studium der Residualwirkung von Chlorsulfuron unter Feldbedingungen wurden zwei Bioassaymethoden, eine in Petrischalen, die andere in Töpfen, eingesetzt. Beide Methoden basierten auf dem Wurzelwachstum von vorgekeimtem Mais. Es zeigte sich, dass beide Versuchsverfahren in gleichem Masse reproduzierbar und empfindlich und in der Lage sind Rückstände von 0,25–10,0 ng g^-1 nachzuweisen. Mit steigender Chlorsulfurondosis wurde eine zunehmende Phytotoxizität, Persistenz und Mobilität des Herbizids festgestellt. Die Persistenz war unter feuchten Feldbedingungen kürzer als bei Trockenheit. Bis zu einer unteren Grenze von 1,0 g a.i. ha^-1 verursachte inkorporiertes Chlorsulfuron, unter trockenen und warmen Feldbedingungen an Mais (Hybride F₁, Damon) Wachstumshemmungen und Erntereduktionen von 53%, verglichen mit unbehandelten Kontrollpflanzen. Unter feuchteren Bedingungen, jedoch, hatten 1,25, 2,5 and 5,0 g a.i. ha^-1 eingearbeitetes Chlorsulfuron an Mais (Hybride F₁ ARIS) Wachstumshemmungen und Ernteverluste von 16, 57 und 92% zur Folge. Die Einarbeitung von 50 kg ha^-1 Aktivkohle inaktivierte 1,25 g und 2,5 g ha^-1 inkorporierles Chlorsulfuron vollständig und hatte keinerlei negative Auswirkungen auf die Maisernte, im Vergleich zu unbehandelten Kontrollen. Höhere Mengen von Aktivkohle, wie 100 und 200 kg ha^-1, inaktivierten auch Chlorsulfuronmengen von 1,25–5 g ha^-1 und hatten keinen Einfluss auf den Kömerertrag.     

Potassium forms in calcareous soils as affected by clay minerals and soil development in Kohgiluyeh and Boyer-Ahmad Province,Southwest Iran

Potassium(K) is known as one of the essential nutrients for the growth of plant species. The relationship between K and clay minerals can be used to understand the K cycling, and assess the plant uptake and potential of soil K fertility. This study was conducted to analyze the K forms(soluble, exchangeable, non-exchangeable and structural) and the relationship of K forms with clay minerals of calcareous soils in Kohgiluyeh and Boyer-Ahmad Province, Southwest Iran. The climate is hotter and drier in the west and south of the province than in the east and north of the province. A total of 54 pedons were dug in the study area and 32 representative pedons were selected. The studied pedons were mostly located on calcareous deposits. The soils in the study area can be classified into 5 orders including Entisols, Inceptisols, Mollisols, Alfisols and Vertisols. The main soil clay minerals in the west and south of the study area were illite, chlorite and palygorskite, whereas they were smectite, vermiculite and illite in the north and east of the province. Due to large amount of smectite and high content of organic carbon in soil surface, the exchangeable K in surface soils was higher than that in subsurface soils. It seems that organic matter plays a more important role than smectite mineral in retaining exchangeable K in the studied soils. Non-exchangeable K exhibited close relationships with clay content, illite, vermiculite and smectite. Although the amount of illite was the same in almost all pedons, amounts of structural and non-exchangeable K were higher in humid regions than in arid and semi-arid regions. This difference may be related to the poor reservoir of K~+ minerals like palygorskite and chlorite together with illite in arid and semi-arid regions. In humid areas, illite was accompanied by vermiculite and smectite as the K~+ reservoir. Moreover, the mean cumulative non-exchangeable K released by CaCl_2 was higher than that released by oxalic acid, which may be due to the high buffering capacity resulting from high carbonates in soils.     

Metabolism of trifluralin,profluralin, and fluchloralin by rat liver microsomes

Three structurally related [¹⁴C]dinitroaniline herbicides, trifluralin, profluralin, and fluchloralin, were extensively metabolized in vitro by both normal and phenobarbital-induced rat liver microsomes. Identification of the metabolites in the ethyl acetate extracts indicated that aliphatic hydroxylation, N-dealkylation, reduction of a nitro group, and cyclization were the predominant metabolic routes for these herbicides in vitro. Of particular interest was the formation of a benzimidazole metabolite.     

Response of plant physiological parameters to soil water availability during prolonged drought is affected by soil texture

Soil water deficit is increasingly threatening the sustainable vegetation restoration and ecological construction on the Loess Plateau of China due to the climate warming and human activities. To determine the response thresholds of Amygdalus pedunculata (AP) and Salix psammophila (SP) to soil water availability under different textural soils, we measured the changes in net photosynthetic rate (P_n), stomatal conductance (G_s), intercellular CO₂ concentration (C_i), leaf water potential (ψ_w), water use efficiency (WUE) and daily transpiration rate (T_d) of the two plant species during soil water content (SWC) decreased from 100% field capacity (FC) to 20% FC in the sandy and loamy soils on the Loess Plateau in the growing season from June to August in 2018. Results showed that P_n, G_s, WUE and T_d of AP and SP remained relatively constant at the beginning of soil water deficit but decreased rapidly as plant available soil water content (PASWC) fell below the threshold values in both the sandy and loamy soils. The PASWC thresholds corresponding to P_n, G_s and C_i of AP in the loamy soil (0.61, 0.62 and 0.70, respectively) were lower than those in the sandy soil (0.70, 0.63 and 0.75, respectively), whereas the PASWC thresholds corresponding to P_n, G_s and C_i of SP in the loamy soil (0.63, 0.68 and 0.78, respectively) were higher than those in the sandy soil (0.58, 0.62 and 0.66, respectively). In addition, the PASWC thresholds in relation to T_d and WUE of AP (0.60 and 0.58, respectively) and SP (0.62 and 0.60, respectively) in the loamy soil were higher than the corresponding PASWC thresholds of AP (0.58 and 0.52, respectively) and SP (0.55 and 0.56, respectively) in the sandy soil. Furthermore, the PASWC thresholds for the instantaneous gas exchange parameters (e.g., P_n and G_s) at the transient scale were higher than the thresholds for the parameters (e.g., T_d) at the daily scale. Our study demonstrates that different plant species and/or different physiological parameters exhibit different thresholds of PASWC and that the thresholds are affected by soil texture. The result can provide guidance for the rational allocation and sustainable management of reforestation species under different soil conditions in the loess regions.     

冻融对北疆盐碱地长期滴灌棉田土壤盐分的影响

为了解北疆积雪覆盖条件下,冻融作用对盐碱地膜下滴灌棉田土壤盐分分布及变化的影响。采用时空变异法,以连续应用膜下滴灌0、4、6、8、10、15 a 6块棉田初春土壤盐分的变化为例进行分析。结果表明,"冻层滞水"及积雪消融入渗对80~100cm深度土体中盐分具有天然淋洗作用,冻融前后土壤盐分分布呈"广口杯"状。4月5日至14日在水分(直接驱动力)运动影响下,60~80 cm土层含盐量降低,其中一部分随毛管水向上蒸发,滞留于0~40 cm土壤;另一部分受重力水作用向下淋洗,80 cm以下土层含盐量升高。滴灌0 a地块0~140 cm土体内储盐量为29 063.00 g,滴灌15 a后,降至5 778.86 g。冻融对盐分的淋洗作用在应用滴灌年限较短地块表现得相对明显,即土壤中含盐量越高,淋洗作用越显著;冻融后滴灌0 a棉田0~140 cm土体储盐量降低8 941.33 g,滴灌15 a棉田降低614.62 g。提出冻融循环对土壤中盐分的天然淋洗作用是北疆盐碱地长期膜下滴灌棉田土壤盐分降低的重要因素之一。