Effect of exogenous organic carbon on sorption of atrazine herbicide in two contrasting soils of Rawalakot and Attock

Abstract

Pesticides are chemical substances employed in agriculture to manage crop-damaging pests like insects, weeds, and diseases. The global use of pesticides has risen in response to the growing human population. Farmers aim to maximize their agricultural output by using significant quantities of pesticides. Nonetheless, this practice raises environmental concerns due to the persistent nature of pesticides and their interactions with diverse soil conditions. The presence of pesticides in soils is influenced by factors such as soil organic matter (SOM), clay content types, their quantity, and soil pH. The objective is to analyze how atrazine herbicide interacts with agricultural soils in Azad Jammu & Kashmir and Attock, which exhibit significant differences. Additionally, the study aims to explore the impact of added organic carbon on the sorption characteristics of atrazine herbicide in two contrasting soils selected from Azad Jammu & Kashmir (Rawalakot) and Attock (Punjab). These soils were amended with different types of organic sources such as biochar, compost, poultry manure, and FYM and sewage sludge. The sorption coefficient, K_d, values were found to be affected by soil organic carbon and the accumulation of different sources to soil also influenced the sorption. AJK soil has organic carbon 7.6 g kg-¹ whereas Attock soil has 1.7 g kg-¹ and k_d value for these soil has 11.69 Lkg^-1 and 4.67 Lkg^-1, respectively. Higher value of AJK un-amended was due to the presence of high organic carbon 7.6 g kg-¹ and low soil pH as compared to Attock un-amended 1.7 g kg-^1, respectively. Overall positive relation was observed in all treatments with the addition of organic sources. Maximum value of K_d observed were 16.11 LKg^-1 in AJK soil and it was 8.49 LKg^-1 in Attock soils.  The sorption normalized on the basis of per unit organic carbon (K_oc) was 2120 LKg^-1 in AJK soil and in Attock soil 4999 LKg^-1, respectively. The current study showed that soils of AJK had more sorption capacity of atrazine as compared to Attock soil. The difference in their sorption capacity of atrazine in the soils (AJK & Attock) was due to differences in their mineralogy and soil chemicals properties including soil pH, SOM which are considered the key factors for the atrazine sorption. Therefore, it was concluded from these findings that rate and amount of pesticides applied to soils must be regarded soil chemicals and physicals properties which effect its movement into soils. The study also suggests that in order to reduce the soil amendments with the organic sources play as key role