Study of degradation trend of phosalone and diazinon residues in fresh, ensiled alfalfa and baled alfalfa hay

An experiment was conducted to compare the degradation rate of phosalone and diazinon residues in fresh, ensiled alfalfa and baled alfalfa hay under farm conditions. Part of an alfalfa field selected, divided into equal plots and then was sprayed with diazinon and phosalone. The samples of fresh or ensiled alfalfa and baled alfalfa were taken at specified intervals (up to15 days, 14 and 24 weeks after spraying, respectively). Pesticides residues were measured by gas chromatography-Mass spectrometry (GC-MASS). In the 15th day after spraying, the phosalone and diazinon residues were 57.33±2.13 and 24.75±1.51 mg/kg DM of fresh alfalfa respectively. The half-life of diazinon and phosalone in fresh alfalfa were 4.34 and 3.62 days, respectively. No diazinon residues were observed at 14 weeks after baling; however, phosalone residue was 3.32 mg during 24 weeks after baling. No residues of diazinon and phosalone were observed in alfalfa at weeks 12 and 14 after ensiling, respectively. Phosalone compared to diazinon, had a less degradation rate in fresh, ensiled alfalfa and baled alfalfa hay, and both pesticides can remain relatively stable in alfalfa for a long term. Ensiling compared to baling was also more effective in degradation of pesticides residues with passage of time.