Herbicide Residue Research in India

Environmental Chemistry for a Sustainable World

Shobha Sondhia · Partha P. Choudhury  A.R. Sharma Editors

Herbicide Residue Research in India

Environmental Chemistry for a Sustainable World Volume 12

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Shobha Sondhia  •  Partha P. Choudhury A. R. Sharma Editors

Herbicide Residue Research in India

Editors Shobha Sondhia ICAR-Directorate of Weed Research Jabalpur, Madhya Pradesh, India

Partha P. Choudhury ICAR-Directorate of Weed Research Jabalpur, Madhya Pradesh, India

A. R. Sharma ICAR-Directorate of Weed Research Jabalpur, Madhya Pradesh, India

ISSN 2213-7114     ISSN 2213-7122 (electronic) Environmental Chemistry for a Sustainable World ISBN 978-981-13-1037-9    ISBN 978-981-13-1038-6 (eBook) https://doi.org/10.1007/978-981-13-1038-6 Library of Congress Control Number: 2018954480 © Springer Nature Singapore Pte Ltd. 2019 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, express or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Singapore Pte Ltd. The registered company address is: 152 Beach Road, #21-01/04 Gateway East, Singapore 189721, Singapore

Preface

Herbicides are chemicals used for killing plants which are known as weeds. These are basically organic compounds synthesized after intensive research to block a physiological process by deactivating the enzyme system, leading to complete death or considerable suppression of growth of the plants. A major discovery in the synthesis of such chemicals was achieved in the 1940s when 2,4-­dichlorophenoxyacetic acid was found to control broadleaved weeds in certain cereal grain crops. This led to a sort of revolution in chemical weed management as several chemicals were invented during the 1950s and thereafter for killing weed flora in cropped as well as non-cropped situations. Presently, there are about 500 chemicals used as herbicides globally, which have become an important input in the modern agriculture systems. Herbicides constitute about 60% of the total pesticides consumed globally. In India, the use of herbicides started initially in tea gardens and picked up in the 1970s when the dwarf high-yielding varieties of crops like rice and wheat were introduced. Presently, 60 herbicides are registered in the country for controlling a broad-­ spectrum of weeds in all the major crops including cereals, pulses, oilseeds, fibre and tuber crops, and also in the non-crop situations. These chemicals are becoming increasingly popular because of efficient weed killing effects and relatively lower cost compared with manual or mechanical weeding operations. Development of low-cost high-potency post-emergence herbicides during the past decade has provided several alternatives to the growers. The contribution of herbicide to total pesticide use, which was only 10–15% during the first decade of twenty-first century, has now increased to about 25%. In fact the annual growth rate of herbicides is 15–20%, which is much higher than insecticides and fungicides. The herbicide consumption is expected to increase further due to labour scarcity in most regions and higher cost of crop production. Herbicides are chemically designed to kill a specific group of plants. But being biochemically active molecules, herbicides have the potential to also damage beneficial flora and fauna. Harmful effects of these chemicals on non-target organisms and in the foodchain are an issue of serious concern, particularly when these are used indiscriminately and without following required protocols. Toxic ­concentrations v

vi

Preface

of such chemicals and their metabolites have been recorded in the soil, water, crop produce, and also in the body parts of humans and animals. These issues are likely to become more important in future with the growing use of herbicides in modern agricultural production systems. This is despite the fact the herbicides are considered relatively safe and less hazardous compared with other pesticides due to high lethal dose (LD50) values, application during the early stages of the crop growth and degradation due to various biotic and abiotic factors. Research on pesticide residues in India was started during 1970s when such chemicals were introduced on a greater scale along with high-yielding variety seeds, irrigation and fertilizers for increasing crop production. However, the herbicide residue research was not given much emphasis until 1990s because their use was almost negligible (5000

IV IV

Clodinafop-propargyl Chlormequatchloride Cinmethylene Chlorpropham

III III III III

50–500 700– 1350 >5000 >5000 >5000 >2000

IV IV IV III

III

Paraquat dichloride

40–150

I–II

Copper sulphate Cyhalofop-butyl Diclofop-methyl Diclosulam Dazomet Diuron Ethoxysulfuron Fenoxaprop-P-ethyl Fluchloralin

2276 522 4553 1200– 3800 1369– 2077 30 >5000 563–593 5000 >2000 3400 3270 3110 1550

Methabenzthiazuron Metolachlor Metribuzin Metsulfuron-methyl Mesosulfuron-methyl + iodosulfuron-methyl sodium Methyl bromide Methyl chlorophenoxy acetic acid (MCPA) Orthosulfamuron Oxadiargyl Oxadiazon Oxyfluorfen

>2000 1254 500– 2000 1000 2877 1090 >5000 >5000

I IV III IV III III IV III III

Pyrithiobac-sodium Pendimethalin Penoxsulam Pinoxaden Pretilachlor Propanil Propaquizafop Pyrazosulfuron-ethyl Quizalofop-ethyl

Fluazifop-P-butyl Forchlorfenuron Fomesafen Fluchloralin

3030 4917 >5000 5580

III III IV IV

Ametryn Anilofos Atrazine

Oral LD50 (rat) (mg/kg) 375– 1200 930– 1350 508 >2000 3090

Azimsulfuron Bensulfuron-methyl Bentazone Bispyribac–Na Butachlor

Herbicide 2,4-dichlorophenoxy acetic acid Alachlor

Clomazone

3300 4050 >5000 >5000 6099 3269 >5000 5000 1210– 1670 Quizalofop-P-tefuryl 1012 Sodium paranitrophinolate 345 Sulfosulfuron >5000 Thiobencarb (benthiocarb) 1033

III III III IV IV

II III

III IV IV IV IV III IV III III III II IV III (continued)

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S. Sondhia

Table 1 (continued)

Herbicide Flufenacet Glufosinateammonium Glyphosate Hexazinone Halosulfuron-methyl

Oral LD50 (rat) (mg/kg) 371– 1365 2170

Toxicity rating* II–III

Herbicide Topramezone

Oral LD50 (rat) (mg/ Toxicity kg) rating >2000 III

III

Tembotrione

>2000

III

>2000 1690 7758

III III IV

Triallate Triasulfuron Trifluralin

1200 >5000 >5000

III IV IV

Source: Central Insecticides Board and Registration Committee (2017); http://cibrc.nic.in/ Table 1* is showing toxicity rating of herbicides, extremely hazardous (category I), highly hazardous (category II), moderately hazardous (category III), and unlikely to pose any hazards (category IV)

Others 11% Plantation crops 10%

Wheat 44%

Soybean 4%

Rice 31%

Fig. 1  Relative use of herbicides in various crops in India, showing its maximum use in wheat, rice and plantation crops. A view of lysimeter (a) used for leaching of herbicides; (b) pond-plot research facilities for conducting herbicide runoff studies

Environmental Fate of Herbicide Use in Central India

33

2  Herbicide Persistence and Accumulation After the application of a herbicide, a number of processes begin to dissipate the compound from the original site of application. Eventual fate of herbicide in the soil mainly depends on leaching, volatilization, runoff and bio and photochemical processes (Fig. 2). Persistence of herbicides in the soil is expressed as half-life, and this mainly depends on soil properties, chemical nature of herbicide, and climatic conditions. In general, applied herbicide should persist long enough to control weeds until the end of critical period of crop-weed competition but it should not persist beyond the crop harvest, because this would be harmful to the susceptible crops grown in rotation (Cornish 1992; Brandenberger 2007; Sondhia 2009a, b, c, d, e, f, 2013a, b, c). However, soil conditions prevailing during and after the application of a herbicide, herbicides chemical structure as well as application method also influence ultimate fate of herbicides in the soil (Elefttherohorinos 1987; Latchanna 1987; Webster and Shaw 1976, 1996; Sondhia 2005; Sondhia and Singhai 2008a). Heavy rains cause greater runoff and leaching. In general, sandy soils have a higher leaching potential than clay soil due to bigger pore spaces and less cation exchange capacity (CEC) (Sondhia and Yaduraju 2005; Sondhia 2007a; Sondhia 2008a, b, c, d, e, f, g, h, 2009a, b, c, d, e, f). Chemical reactions also govern chemical degradation of herbicide in soil. Anilines, phenols and dinitroanilines are chemically degraded by redox reactions; however fluchloralin, bentazon, and olefins  are chemically degraded by hydrolysis, ester formation, oligomerization/

Herbicide application in/on soil/plants

Volatilization

Absorption by plants

Photodecomposition Runoff Chemical and microbial degradation

Herbicide in soil

Absorption/Uptake by roots

Above ground level Below ground level

Dissolution and Adsorption

Capillary flow and leaching

Fig. 2  Fate of herbicide after its application. Figure  showing various routes of degradation  of herbicides in the soil and environment; main route of degradation are adsorption by plants, volatilization, runoff above the ground and absorption by roots, leaching, biochemical degradation, dissolution and adsorption below the ground

34

S. Sondhia

polymerization reactions which are catalyzed by clay surface and photolysis. Biotic oxidative transformations such as β-oxidation, C-hydroxylation, C-cleavage, N-oxidation, ether cleavage, N-demethylation, C-reduction, N-reduction, hydrolysis and mineralization are common with phenoxy alkanoic acids, anilines, aromatic compounds and phenylureas group of herbicides (Sondhia 2014a, b, c, d, e, f, g, 2016a, b, c, d, 2017). However, the  herbicides belonging to alkenes, alkines and nitro-compounds degrade by reductive transformation. Hydrolytic processes of transformation are common with sulphates, carboxylic esters and 2, 6 dichlorobenzonitriles. In a 3 year study, residues of fentazamide at 240 g/ha application rate were found to be 0.03–0.04 mg/kg in the soil of rice crop with a half-life of 20 days; however, residues were below the detection limit in rice straw and husk (Tandon et al. 2012). In a monitoring study, butachlor residues were 61% in the soil  followed by pendimethalin (36%), and fluchloralin (3%) and alachlor was not detected in all the locations. These herbicides were found in the range of