Effects of formulation,spray parameters and sampling methods on initial residue of mancozeb in cole

Effects of formulation,spray parameters and sampling methods on initial residue in cole(Brassica ampestris L.) was studied using mancozeb.The results showed that the initial residues in cole of different formulations of mancozeb with same application rate were different.The initial residues in cole by spraying of mancozeb 300 suspension concentrate(94.4 －115.8 mg/kg)was significantly higher than mancozeb 700 wettable powder(34.3 －86.1 mg/kg) and mancozeb 750 water dispersible granule(61.1 －82.4 mg/kg).Under condition of same formulation and same application rate,the applied spray volume was decisive.The initial residues of mancozeb tended decreasing with increase of spray volume.When the nozzle diameter changed from 0.7 to 1.6 mm,the initial residues of mancozeb in cole decreased from 86.3 to 65.1 mg/kg,while spraying pressure had no significant effects on initial residues.In case of diagonal sampling,there was significant difference between the sampled plants of 5,15,and 25,while in the case of random sampling,there was no significant difference between sampled plants of 25,50 and 100.It indicated that formulations,spray parameters and sampling methods are the main factors that led to changing of initial residues.