Degradation Characteristics of Nicosulfuron and Its Damage Threshold of Tobacco in Different Texture Soils

To clarify the damage threshold of tobacco and safety interval of nicosulfuron in different texture soils, and to provide a theoretical basis for the reasonable and safe use of herbicides in the previous crop of tobacco, field experiments were conducted on typical sandy loam soil and clay loam soil to study the degradation characteristics of nicosulfuron, pesticide damage threshold of tobacco, safety interval and the effects on soil properties in Bijie tobacco-planting areas.The results showed that the half-life of nicosulfuron degradation in sandy loam was 9.5-14.7 d, and in clay loam was 9.0-17.3 d.In this study, the damage threshold of nicosulfuron and the safe isolation period were determined to be 1.50 μg/kg and 70.6 d in sandy loam, 2.47 μg/kg and 52.4 d in clay loam, respectively.After 80 days of application, with the increase of the application dose of nicosulfuron(0 to 1-fold), the soil organic matter content did not change much.The alkaline nitrogen content showed a trend of first increasing and then decreasing, while the soil available phosphorus and available potassium content showed a trend of decreasing.The change trend of the physic-chemical properties in sandy loam and clay loam after application was consistent, but the change magnitude was different, which might be related to the interactions between the degradation of nicosulfuron and tobacco in two texture soils.So, the results of this study can provide important guidance for the rational and safe use of nicosulfuron herbicides and the degradation and control of residual in different texture soils of tobacco-planting areas.