Effect of organic amendments (biochar and manure) on Metribuzin adsorbtion and leaching in sandy loam soil

Presence of pesticides in ground water resources has grown in the past few years and has become an intensive and burning issue of discussion. Groundwater contamination not only affects the health of human beings as it is being directly used for drinking purpose, but also can act as source of contamination for food chain, when used for irrigation. Awareness of the fate of the use of soil pesticides is necessary to reduce the mobility of these compounds in the soil and protect the environment. present study reports the effect of organic manure and biochars amendments on adsorption and metribuzin downward mobility in soil columns.

organic amendments (manure and biochr) was added to soil at a level of 1% and the effect of soil (T), soil + manure (TM), soil + biochar (TB) treatments on adsorption and leaching of metribuzin pesticide was studied under saturated and unsaturated moisture conditions. Adsorption experiment with Batch method and soil leaching experiment with Soil column method were conducted in Laboratory of Gorgan Agricultural Sciences and Natural Resources university with two replications.

The results showed that adsorption’s experiment data was matched to the Freundlich model. The adsorption of metribuzin herbicide increased both in TM and TB organic amendment and the Freundlich constant (Kf) for T, TM and TB treatments was 1.2, 2 .3 and 2.6, respectively which were 70% higher in organic amendment treatments than control treatments. Application of manure and biochar at 1% level in soil reduced the downward movement of the pesticide, and maximum concentration of pesticide in the lechate. The total amount of pesticide recovered in TB, TM, T treatments was 77%, 50% and 47%, respectively. Also, the maximum amount of pesticides recovered in unsaturated conditions in treatment T ,TM, TB respectivly were 27%, 10% and 13% less than in compared to saturated conditions.

the application of manure (TM) and biochar (TB) in soil at 1 % level increased the metribuzin retention in the soil and reduced the downward movement of pesticides and affected breakthrough time and maximum concentration of metribuzin in the leachate. Application of biochar in soils is effective in agricultural sustainability and environmental conservation. A better understanding of the benefits of using biochar requires long-term and continuous studies on agro-environmental issues. Also, according to the data of this study, in all treatments. pesticide leaching was higher in saturated conditions than in unsaturated conditions.