نوع مقاله : مقالات پژوهشی
1 مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی فارس، سازمان تحقیقات، آموزش و ترویج کشاورزی، داراب، ایران
2 گروه اگروتکنولوژی، دانشکده کشاورزی، دانشگاه فردوسی مشهد
3 موسسه تحقیقات گیاهپزشکی کشور
4 دانشکده داروسازی، دانشگاه علوم پزشکی مشهد
عنوان مقاله [English]
Widespread application of herbicides to control weeds during the past few decades has resulted in serious ecological and environmental problems, such as resistance and shifts in weed populations. Sulfonylurea herbicides are acetoacetate synthase inhibitors. These herbicides will be used effectively to control a wide range of grassy and broad leaf weeds. Nicosulfuron is one of the main ALS inhibitors that was registered for corn in Iran. Under certain conditions some sulfonylurea herbicides can persist at phytotoxic concentrations in soils long enough to affect sensitive crops in the following season. There are many factors affecting persistence of herbicides, included soil type, soil organic matter, soil pH, soil temperature and moisture. Bioassay and HPLC methods are the most common methods for determining herbicide residues in soil. HPLC methods is a time-consuming, costly, and expensive. But bioassay method is a simple, fast, and inexpensive that uses sensitive plants to detect low concentrations of residual in the soil. Several bioassay methods for sulfonylurea herbicides have been reported using lentil (Lens culinaris L.), lettuce (Lactuca sativa L.), sunflower (Helianthus annuus L.), corn (Zea mays L.) pea (pisum sativum L.), and lupin (Lupinus angustifolius L.). This study was aimed to understanding the nicosulfuron persistence in soil using HPLC and bioassay methods.
Materials and Methods
In order to study the soil persistence of nicosulfuron using bioassay and HPLC, an experiment was carried out as a factorial arrangement based on completely randomized block design with three replications in Research Field of Ferdowsi University of Mashhad during 2014-2015. Treatments included of the application of organic and bio-fertilizers in four different levels of cow manure (40 t ha-1), vermicompost (10 t ha-1), mycorrhiza (2.5 t ha-1) fertilizers and control as first factor. The second factor was nicosulfuron doses (40 and 80 g a.i ha-1), and the third factor was the application of nicosulfuron with and without of Hydromax adjuvant. The herbicide was applied at four leaf stages using an overhead trolley sprayer equipped with an 8002 flat fan nozzle tip delivering 200 L ha-1 at 2 bar spray pressure. To determine nicosulfuron residue in soil sampling was performed at different periods of 0, 2, 5, 8, 16, 30, 60, 90 days after spraying from 0-15 cm depth of soil. The herbicide residue was determined using HPLC and bioassay methods. Garden cress (Lepidium sativum L.) was the bio-indicator in bioassay method.
Results and Discussion
Results showed by increasing of nicosulfuron dose, it’s soil residue increased, however; nicosulfuron half time (DT50) was not affected. Application of Hydromax decreased nicosulfuron degradation rate (K) and increased its half-life of nicosulfuron. However, the application of organic and biological fertilizers increased degradation rate and decreased its half-life of nicosulfuron. So that the highest nicosulfuron degradation rate was indicated (0.066 and 0.073 μg kg-1 soil) and the lowest DT50 (10.5 and 9.50 days) were indicated in HPLC and bioassay methods respectively, when nicosulfuron applied in the dose of 40 g a.i ha- + cow manure mixed in soil. Based on the results, significant positive correlation (r2 = 0.97) was observed between HPLC and bioassay methods in degradation rates and half-life of nicosulfuron herbicide. According to bioassay method, garden cress is high sensitive to nicosulfuron residue in soil. Therefore, garden cress especially it’s root bioassay is recommended as an acceptable method for nicosulfuron soil residue detection and can be used as desirable bio-indicator for tracing of nicosulfuron persistence and soil residue.
The application Hydromax decreased nicosulfuron degradation rate and increased DT50 of nicosulfuron. But organic fertilizers increased nicosulfuron degradation rate and decreased DT50. Based on this sudy results garden cress is desirable bio-indicator for tracing of nicosulfuron persistence in soil.
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