The Study On The Efficacy Of Two Hydrogel Encapsulated Herbicides And Their Behavior In The Maize-Soil System

Chemical pesticides are essential agricultural materials,which can increase crop yields,and also arouse the concerns of ecological environmental security,quality safety of agricultural products and human health.Based on this phenomenon,"quantity reduction and efficiency reinforcement for pesticides" has become one of the most crucial strategic needs for guaranteeing quality safety of agricultural products and ecological environment security.Development of new pesticide application process and improvement of its formulation have become one of the main research directions of "quantity reduction and efficiency reinforcement for pesticides",which can contribute to ensuring pesticide efficacy and reducing pollution and its detriment to human health.Acetochlor and atrazine are the effective herbicides that widely used in maize field.The lab prepared HGE-acetochlor and HGE-atrazine initially by hydrogel encapsulated techniques.In order to explore the efficacy and the behavior of the HGE-acetochlor and HGE-atrazine in the maize-soil system,we spread HGE-acetochlor and HGE-atrazine to the soil that has been cultivated with target weeds to detect their weed control efficacy under current laboratory condition.And the comparison of the absorption,residue distribution and bioconcentration of HGE-14C-acetochlor and 14C-acetochlor in maize(Zea mays L.)seedlings and the comparison of extractable residue and bound residue in soil were observed through 14C-isotope tracing method.The main results were as follows:(1)The EC90 of HGE-acetochlor to Poaannua L.was 0.293μg ai·g-1,which was lower than the minimum of the recommended concentration of acetochlor in the field,indicating the high herbicidal activity of HGE-acetochlor.However,compared with 14C-acetochlor treatment,the hydrogel encapsulated formulations still keep high the herbicidal activity at acertain extent.The absorption of both HGE-14C-acetochlor and 14C-acetochlor by maize seedlings was limited.After 15 days treatment,the absorption of HGE-14C-acetochlor and 14C-acetochlor by maize seedlings repectively were 3.60%and 4.04%of the applied amount.The absorption of active compound derived from HGE-acetochlor was significantly lower than acetochlor in maize seedlings(p<0.05),which showed that hydrogel encapsulated formulations hindered the absorption of acetochlor.The bioconcentration factor of HGE-14C-acetochlor was 9.98 in the shoot of maize seedlings,less than the 14C-acetochlor(12.35)treatment,which indicated that HGE-acetochlor may be safer for the growth of maize in the field compared with spread acetochlor treatmnet.The extractable residue of HGE-acetochlor and acetochlor in soil decreased as time increased.The extractable residue of HGE-acetochlor in soil was 71.16～57.19%and acetochlor was 74.25～53.79%.At the early stage of the treatment(DAT≤13 d),the extractable residue of HGE-acetochlor was significantly lower than that of acetochlor.After 13 days,it showed the opposite result,and there was a significant difference between HGE-acetochlor and acetochlor treatments(p<0.05).The bound residue of HGE-acetochlor and acetochlor in soil increased as time increased.At the early stage of the treatment(DAT≤13 d),soil-bound residue of HGE-acetochlor was higher than that of acetochlor significantly(p<0.05).After 13 d,the soil-bound residue of HGE-acetochlor and acetochlor was 34.07%and 36.08%,and the difference between HGE-acetochlor and acetochlor treatments was significate(p<0.05).(2)The EC90 of HGE-atrazine to Trifoliumrepens L.was 0.275 μg·ai g-1,which was notably lower than the minimum of the recommended concentration of atrazine in the field(0.522 μg ai·g-1),indicating the high herbicidal activity of HGE-atrazine.However,compared with the atrazine treatment,the hydrogel encapsulated formulations still keep high herbicidal activity at a certain extent.The absorption of HGE-atrazine in maize seedlings was significantly lower than that of atrazine(p<0.05).After 15 days treatment,the absorption of HGE-atrazine and atrazine was respectively 4.75%and 5.12%of the applied amount.Hydrogel encapsulating reduced the residue of atrazine in the maize seedlings.The bioconcentration factors of HGE-14C-atrazine in the root and shoot of maize seedlings was significantly less than those of 14C-atrazine,which indicated that HGE-atrazine can be safer for the growth of maize in the field.The extractable residue of HGE-atrazine and atrazine in soil decreased as time increased.The extractable residue of HGE-atrazine and atrazine in soil was 88.96～75.66%and 91.06～73.17%respectively.At the early stage of the treatment(DAT≤13d),the extractable residue of HGE-atrazine in soil was significantly lower than that of atrazine(p<0.05),the opposite results with the significant difference were also found after 13 d.The bound residue of HGE-atrazine and atrazine in the soil increased as time increased.At the early stage of the training(DAT≤13d),soil-bound residue of HGE-atrazine was higher than that of atrazine significantly.After 13 d,the soil-bound residue of HGE-atrazine was 15.01%,and the soil-bound residue of acetochlor was 16.76%with the significant difference between the hydrogel encapsulated formulations and control treatment(p<0.05)presented.Our research reveals that both HGE-acetochlor and HGE-atrazine remained the high herbicidal activity.In maize-soil system,hydrogel encapsulated formulations can reduce the residue in the corn,and can influence the extractable residue and bound residue in soil.This study provides basic data for the proper application of HGE-acetochlor and HGE-atrazine,and provides scientific basis for deep understanding of the safety of HGE-pesticides.