| A series of experiments were carried out in the laboratory and greenhouse to determine the result of new seed coating agent. The seeds used in the experiments were alfalfa (Medicago sativa) with 7 seed lots harvested from 1999-2005 at tongwei county, Gansu province, China. The seed coating agents in the experiment included two commercial seed coating formulations and a new seed coating formulation developed in the laboratory. The measurement of coated seeds included seed laboratory germination, seedling emergence rate, seedling death rate, plant height, aboveground biomass and underground biomass. The effects of the seed film coating on seedling emergence and establishment, plant development, biomass were also studied in field experiment. Main results obtained showed that:The new seed coating agent was superior to other seed coating agents tested. Comparing with no coated seed, it increased obviously seed laboratory germination, seedling emergence rate, plant height, aboveground biomass and underground biomass; decreased seedling death rate. All three seed coating agents showed that compared with those of non-coated the seed germination percentage increased by 3.8 %-8.7%,1.1%-4.8% and 2.0%-8.6%, the plant height increased by 5.8%-38.1%,7.3%-37.7% and 6.9%-40.3%, the root height increased by 6.1%-34.1 %,1.5%-34.1% and 1.5%-17.6%, whereas the herbage dry matter yield increased by 33.9%-105.9%,9.1%-78.5% and 33.9%-105.9%, and the root biomass increased by 27.7%-122.3%,12.8%-86.4% and 21.3%-90.9%.And the other two seed coating agents had the same results with the new seed coating agent, but reached no results significantly. The results from laboratory and green house experiment showed 15% Thiram·Thiophanate suspending seed coating agent has a better effect than other two commercial seed coating formulation, so it was used in the later field experiment.Field experiments were conducted in two district, which has different precipitation, including Yuzhong(300mm) and Qingyang(500mm), from August to October. Main result obtained from field experiment are as follows:15% Thiram-Thiophanate suspending seed coating formulation has an effect on seedling emergence and growth, plant height, root height, number of leaf and hair root, biomass significantly. The result showed that compared with those of non-coated the seed emergence percentage increased by 16.4%-28.4% with the average of 19.1% in Yuzhong,19.1%-25.9% with the average of 28.6%, the plant height increased by 2.2%-18.4%, the root height increased by 11.7%-20.6%, and the number of leaves increased by 6.6%-17.1%, whereas the herbage dry matter yield increased by 3.7%-22.5%, and the root biomass increased by 13.5%-52.4%.The field control effect experiment in Yuzhong and Qingyang indicated that the controlling efficacy of the seed coating formulation against leaf spot disease was 64.8 %-79.8% and 65.6%-77.8% at the rate of fungicide and seed 1:20,1:40,1:60, separately.By contrast in different ecology condition, considering ecology suitability and use effect, using seed film coating with 1:40 to 1:60 in Yuzhong and 1:20 to 1:40 in Qingyang, have better field use value.Researches indicated that 15% Thiram·Thiophanate suspending seed coating agent is a new type alfalfa seed coating formulation with better effect and few toxin, which has enriched forage seed coating agent variety in China.
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