Cover Crop Straw Interferes in the Retention and Availability of Diclosulam and Diuron in the Environment

Abstract

Pre-emergent herbicides are applied directly in the soil or over the straw in no-till systems and can be retained, reducing the product’s availability. The current study characterizes the retention of diclosulam and diuron in forage turnip (FT), buckwheat (BW), and black oat (BO) straws. Radiometric techniques evaluated the sorption–desorption and leaching processes. Spectroscopic and microscopic methods characterized chemical and morphological alterations in the straw. Sorption rates (Kf) of diclosulam and diuron followed the order BO > BW > FT. Irreversible sorption (hysteresis < 0.7) occurs to diclosulam applied to BO straw. The BO straw showed porous structures, indicating physical entrapment of the herbicides. Straw fragments (<1 mm) increased the sorption of herbicides. The increase in straw amount (2.5 to 5 t ha−1) reduced herbicide leaching to 18.8%. Interactions between chemical groups (C-Cl, C-F, and C-N) from herbicides with straw characterize a chemical barrier. The present research suggests that entrapment and chemical interaction are involved in the sorption–desorption process of herbicides, such as diclosulam and diuron, in the straw matrix, directly interfering with their availability in the environment. This process can reduce the herbicide environmental risk but can decrease weed control efficiency.

A decade of advances in the study of buckwheat for organic farming and agroecology (2013-2023)

“…Finally, buckwheat mulching not only can be useful for weed control. In conventional cropping systems, buckwheat mulching successfully prevented leaching of herbicides (such as diclosulam and diuron) to the soil by creating a chemical barrier which involves the prevention of soil contamination ( Munhoz-García et al., 2023 ). Moreover, it was observed that after covering the field with buckwheat residues, the daily temperature fluctuations were reduced, and the moisture increased at depths between 0 - 40 cm, improving soil broccoli production compared to a field without mulching ( Kosterna, 2014b ).…”

Evaluation of a System to Assess Herbicide Movement in Straw under Dry and Wet Conditions

“…This is due to the herbicides adhering to the surface of the straw, which compromises the management of difficult-to-control weeds and significantly influences the final fate of herbicides in the environment [19,20]. This influence arises from the increase in the soil organic matter content, leading to a strong sorption of herbicides [21][22][23][24][25]. The retention of herbicides in the straw impedes the movement of these products through water, preventing them from reaching the soil; in addition to reducing their effectiveness, this can also prolong their persistence in the environment [26,27].…”