Review of some of Coating Seed Factors in Rotary Pan Coater

Introduction Today, hybrid seeds are expensive because the company that produces them spends a lot of money on research and development that often takes years to accomplish. So precise planting of seeds in order to create the best growing condition for all seeds is important. Modified size and shape of seeds for precision planting, providing macro and micro nutrients since the start of seed germination and control pests and diseases are goals that are possible by coating seeds. The overall process of seed coating or seed pelleting comprises a number of important stages: 1- Droplet formation 2- Droplet travel 3- Impingement 4- Wetting 5- Spreading 6- Coalescence. Seed coating was largely borrowed from the confectionery industry which had developed this technique over the ages and is still widely used today. The seed industry concentrated on using the rotary drum or pan. This type of pan or drum was used for batches of up to 150–200 kg. Some rotary drum coater were developed subsequently which improved handling, particularly in the way the drying air was introduced and extracted. The pan of drum rotary coater is placed at the end of a tilted rotating shaft that is turned at a constant speed about 15- 20 rpm. Then a nozzle is spraying proper amount of coating solution on the seeds. The aim of this study was to evaluate technology and determine the factors affecting its quality coverage. Materials and Methods This experiment lay out in factorial experiment based on random complete block design with three replications. The first factor was vertically distance nozzle from seed bed in two levels 150 and 300 mm, second factor was the nozzle installed location in two levels installed in 1/4 diameter upper center and in center of cylinder, and third factor was concentration of binder polyvinylpyrrolidone (PVP) in three levels 50, 75 and 100 g kg-1 kaolin. In order to measure the pellet error percent, first 100 pellets were selected and broken. No seed or multi-seed pellets were counted. For measuring physical strength of pellets, instron machine were implemented in physical properties laboratory in Aborihan department of Tehran University. Its load cell capacity was 490 N. Forward speed of the instron was 5 mm per minute. Germination test were performed in the laboratory in dryland agricultural substitute Sararood, Kermanshah. Results and Discussion The results showed that the nozzle distance from the seed bed had a significant effect on all measured traits (1% level). With increasing distance from the seed bed, the physical strength of pellet and the percentage of pellet error decreased but germination increased. In fact, with increasing nozzle distance from 150 mm to 300 mm, the physical strength of pellet decreased from 22.8 N to 21.4 N, the pellet error decreased from 4.1% to 2.1% but germination increased from 71.3 to 73.4 percent. The used binder quantity had a significant effect on all measured traits (1% level). By increasing of using binder, the physical strength of pellet and the percentage of pellet error increased but germination strongly decreased. In the other word, with increasing used binder from 50g to 100g per one kilogram kaolin, the physical strength of pellet increased from 13.9N to 29.1N, the pellet error increased from.2.01 to 4.18 percent but germination decreased from 90.42 to 53.17 percent. The nozzle installed location had a significant effect only on the pellet error (1% level). In the other word, the nozzle installed on the cylindrical center is better than nozzle installed in 1/4 diameter upper center. There was negative significant correlation (r=-0.96) between physical strength shell characteristics and germination. So increasing the physical strength of the shell is reduced germination. There was a significant correlation (r= 0.621) between physical strength and pellet error percentage. So with increasing physical shell strength, pellet error was increased