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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-641 003, Tamil Nadu, India e-mail: janakibalamurugan@rediffmail.com

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 ) 3.9 2.30 3.00 Available N (kg ha -1 ) 314 137 190 Available P (kg ha -1 ) 15.24 9.0 11.20 Available K (kg ha -1 ) 796 904 642 Infiltration rate (cm hr -1 ) 1.68 1.59 1.52 Bulk Density (g cm -3 ) 1.23 1.32 1.33 Porosity (%) 42 46 48

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) 0 0.3280.658 10 0.1940.300 20 0.0070.020 30BDL 0.005 45BDL 90BDL HarvestBDL Sampling intervals after herbicide application (Days) Pretilachlor Residue (mg kg -1 ) x (1 kg/ha)2 x (2 kg/ha) 00.2140.486 150.0960.246 300.0580.189 450.0200.058 60BDL0.014 90BDL 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 00.2120.426 50.1560.314 100.0820.218 200.0680.152 300.0500.121 450.0420.094 60BDL0.052 HarvestBDL Sampling intervals after herbicide application Alachlor Residue (ppm) X (0.75 kg/ha) 2X (1.50 kg/ha) 00.5301.003 50.3160.586 100.1120.249 200.0360.102 30 BDL 0.018 45 BDL 60 BDL HarvestBDL Persistence in Maize grown soil

20 Degradation rate in rice soil

21 Half Life - 31.45 days for Atrazine Degradation rate in maize soil

22 Half Life - 22.42 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 5.44 6.28 R² = 0.869 R² = 0.790 Pretilachlor – X Pretilachlor – 2 x 13.16 11.72 R² = 0.886 R² = 0.923 Soybean Pendimethalin - x Pendimethalin – 2x 13.24 16.02 R² = 0.828 R² = 0.837 Metolachlor – x Metolachlor - 2x 21.13 24.71 R² = 0.944 R² = 0.957 Maize Atrazine - x Atrazine – 2 x 30.81 32.09 R² = 0.714 R² = 0.784 Alachlor – x Alachlor – 2x 5.15 4.41 R² = 0.771 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, 14.63 and 22.42 days for butachlor, pretilachlor, atrazine, alachlor, pendimethalin and metolachlor

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