| Compared with common pesticide formulations , microcapsules have many advantages such as prolong controlling effect, improve using efficiency, avoid decomposition and invalidation, abate toxicity and harmfulness, reduce environment pollution, and so on. The pendimethalin which is a kind of dinitroaniline-type herbicide applied pre-emergence or early post-emergence to control mainly annual grasses and some annual broad-leaved weeds. Most of pendimethalin formulations used are emulsifiable concentrates. However, concern for the impact of contamination by it in waterways and groundwater has led to its use restricted , but pendimethalin microcapsules can avoid forenamed problems. So we have studied pendimethalin microcapsules with UF-resin via in-situ polymerization, obtained the optimal conditions of preparation system, and main contents is as the following aspects:1. For the screening the formaldehyde/ urea (F/U) mole ratio, the optimal F/U mole ratios were 1.75. with reaction temperature was 70℃and time was 1h,pH was 8.0. The UF-resin which prepared with these pre-polymer had good toughness, the UF-resin particles were very minuteness and arranged compactly. Under these F/U mole ratio microcapsules showed excellent surface morphology and the product displayed high encapsulation efficiencies. Identified pendimethalin CS particle size distribution, the release of the performance of hot and cold storage stability, control release and so on.2. Several encapsulating parameters including acidification time and curing temperature on microcapsule appearance quality such as encapsulation rate,particle size,and size distribution were investigated again. The results suggest that the forming of UF-resin microcapsules should be processed under the fundamental conditions of: (1) the concentration of formaldehyde/ urea (F/U) resin is at least 3.25 wt%. (2) NaOH is greater than 0.5 wt%, so that we could obtain final product of microcapsules with better formation and dispersion. As experimental results, the particle size of microcapsules was decreased with increasing stirring rate. When the stirring rate was over 1500 rpm and at least 30min, acidifying for 90min,and the curing temperature under 65℃for 60 min.the mean diameter of microcapsules could be decreased under 5～10μm. The product displayed good stability and its encapsulation efficiencies were higher than 95%. 3. The preparation of microcapsules of pendimethalin by means of in-situ polymerization, with 9 different sodium lignosulphonate as dispersant. The factors affecting the morphology and the encapsulation efficiency and the particle-size were investigated, and the stability was also determined. The results showed that the viscosity of microcapsules suspension were higher than 12 mPa.s prepared with the four sodium lignosulphonate of which degree of sulfonation were about 0.8, while the viscosity of microcapsules were lower than 10 mPa.s with other five dispersant of which degree of sulfonation were about 3.0 and 3.5. The particle-size of the microcapsule prepared with the same degree of sulfonation ligninsulfonate was decreased with the molecular weight increasing. The microcapsules prepared with sodium lignosulphonate of high molecular weight and high degree of sulfonation had higher stability and suited to the requirements of microcapsules. When the molecular weight sodium lignosulphonate was under 5000,the microcapsules were ease to be cracked. The molecular weight and degree of sulfonation had little effect on the encapsulation ratio. All the encapsulation ratios prepared with different sodium lignosulphonate were above 95%.4. Emulsifiable concentrate (EC) of pendimethalin was compared with capsule-suspension (CS) of the herbicide for activity and bioefficacy in laboratory experiments. Petri-dish bioassay, based on bud response of broomcorn was used for their activity in sand and soil, and for determination of pendimethalin concentrations in soil solution (not absorbed) and mobility studies respectively. EC- pendimethalin showed higher activity in sand and in soil. Activity of both formulations of pendimethalin decreased with increasing organic matter content, but CS- pendimethalin less inhibitory in the sand-organic matter mixtures. Both formulations of pendimethalin were tested further in laboratory tests, based on bud length of Echinochloa crusgalli, it indicated that, while CS- pendimethalin had a longer persistence than EC- pendimethalin, it also did not hider the level of potency necessary for early weed control.5. The results of field trial indicted Pendimethalin 30% CS had good control effect to the weeds in garlic field. The suitable dosage was 750-1000g/hm2(a.i.),The control effect was over 80% after 140 days. It was safe and effective for the weeds control in garlic fields. The experiment proved that effective duration of pendimethalin 30% CS was evidence longer than pendimethalin 20% EC.6. The rapidly toxicity of CS- pendimethalin to Brachydanio rerio and Coturnix coturnix had been determined. The result showed that compared with EC- pendimethalin, the security of EC- pendimethalin to Brachydanio rerio and Coturnix coturnix was higher. Microcapsules could reduce the effect of pesticide to environment.
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