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P. JANAKI Herbicide Residue Chemist DWSR Centre, Department of Agronomy, Tamil Nadu Agricultural University, Coimbatore-641 003, Tamil Nadu, India e-mail:

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Presentation on theme: "P. JANAKI Herbicide Residue Chemist DWSR Centre, Department of Agronomy, Tamil Nadu Agricultural University, Coimbatore-641 003, Tamil Nadu, India e-mail:"— Presentation transcript:

1 P. JANAKI Herbicide Residue Chemist DWSR Centre, Department of Agronomy, Tamil Nadu Agricultural University, Coimbatore , Tamil Nadu, India

2 Introduction

3 Production Scenario in India CropProductivity (kg ha -1 ) Rice 2203 Maize 1912 Soybean 1063

4 Herbicides Use in India

5 Herbicide - Indian market

6 Purpose Controlling weeds Increasing the yield crops

7 Herbicide residues concern Prone to leaching and contaminate soil and water Bioaccumulation in crop produce and food chain Health hazard to non target organisms Environmental safety

8 Residues status in major crops CropNo of locations MRLBDL Rice16556 Soybean6114 Maize5113

9 Objectives Study the persistence and degradation behavior of commonly used herbicides in vertisols applied to rice, maize and soybean crops.

10 Methodology

11 Experimental Details Soil PropertiesRice soilMaize soilSoybean soil Soil type Clay loamSandy Clay loam Organic Carbon (g kg -1 ) Available N (kg ha -1 ) Available P (kg ha -1 ) Available K (kg ha -1 ) Infiltration rate (cm hr -1 ) Bulk Density (g cm -3 ) Porosity (%)

12 CropsHerbicidesDosesDeterminationRecovery (%) RiceButachlorX (1 kg ha -1 ) 2X (2 kg ha -1 ) GC-ECD86-88 PretilachlorX (1 kg ha -1 ) 2X (2 kg ha -1 ) GC-ECD82-84 MaizeAtrazineX (1 kg ha -1 ) 2X (2 kg ha -1 ) GC-FID78-83 AlachlorX (0.75 kg ha -1 ) 2X (1.50 kg ha -1 ) GC-ECD> 80 SoybeanPendimethalinX (1 kg ha -1 ) 2X (2 kg ha -1 ) GC-ECD81-82 MetolachlorX (0.75 kg ha -1 ) 2X (1.50 kg ha -1 ) GC-ECD> 80 Treatments and methodology

13 Results and Discussion

14 Initial deposition of applied herbicides

15 Field dissipation of applied herbicides in vertisols

16 Half-life Herbicides persistence in the soil is expressed as half life or time required for degradation of fifty percent of the original molecule. The persistence varies with the nature of a chemical, soil and climatic conditions.

17 Sampling intervals after herbicide application (Days) Butachlor Residue (mg kg -1 ) x (1 kg/ha)2 x (2 kg/ha) BDL BDL 90BDL HarvestBDL Sampling intervals after herbicide application (Days) Pretilachlor Residue (mg kg -1 ) x (1 kg/ha)2 x (2 kg/ha) BDL BDL HarvestBDL Persistence in Rice grown soil

18 Persistence in Soybean grown soil

19 Sampling intervals after herbicide application (days) Atrazine residue (ppm) 1.0 kg/ha2.0 kg/ha BDL0.052 HarvestBDL Sampling intervals after herbicide application Alachlor Residue (ppm) X (0.75 kg/ha) 2X (1.50 kg/ha) BDL BDL 60 BDL HarvestBDL Persistence in Maize grown soil

20 Degradation rate in rice soil

21 Half Life days for Atrazine Degradation rate in maize soil

22 Half Life days for metolachlor Degradation rate in soybean soil

23 Optimized first order field dissipation curves HerbicidesDT 50 Goodness of fit Rice Butachlor – x Butachlor – 2x R² = R² = Pretilachlor – X Pretilachlor – 2 x R² = R² = Soybean Pendimethalin - x Pendimethalin – 2x R² = R² = Metolachlor – x Metolachlor - 2x R² = R² = Maize Atrazine - x Atrazine – 2 x R² = R² = Alachlor – x Alachlor – 2x R² = R² = 0.797

24 Summary Initial deposits vary with the concentration applied Gradual and continuous dissipation was observed as a function of time Dissipation followed the first order kinetics Half life increased with increase in concentration Mean half life of herbicides : 5.88, 12.44, 31.45, 4.78, and days for butachlor, pretilachlor, atrazine, alachlor, pendimethalin and metolachlor

25


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