Effects of Several Kinds of Organic Fertilizer on Tha-Yang Soil Series Improvement and Super Sweet Corn Yield   Pitayakon Limitong Chaveevan Leungvutivirog Siangjeaw Piriyaprin Vanlada Sunanthapongsak and Pracha Nakapraves   ABSTRACT         Study on the effect of organic fertilizer on some properties of Tha-Yang soil series and super sweet corn yield was conducted at Land Development Station, Ratchaburi Province during 1994-1997. The experimental plan was completely randomized block design. There were 6 treatments in 3 replications which consisted of organic fertilizers as compost, animal manure and cooparated rice straw in 3 ton per rai, cooparated Sesbania green manure as see rate 5 kgs per rai and added sole chemical fertilizer (15-15-15) 50 kgs per rai: The results indicated after harvesting corn yield, cooperated rice straw had effect increasing cellnlohytic bacteria, actinomyces and fungi from 8.31, 7.53 and 5.47 to 9.16, 8.45 and 6.34 log no. per gm of soil. Soil plant nutrients such as phosphorus potassium calsium mangnesium and sulphur were increase form 13.3, 155, 867, 186 and 11 to 29.6, 403, 1951, 223 and 40 ppm respectively. Which had shown significatly statistic when compared with non-organic fertilizer. Furthemore, the level of soil pH raised form 5.9 to 6.4. For the consideration of corn yield, cooperated rice straw additon gave the highest yield form 314.0 to 574.8 kgs. per rai and had gotten net income 6,467 bath per rai where as applied sole enemical fertilizer had on getting net income which 2,319.50 bath per rai.         Keywords: organic fertilizer, super sweet corn, Tha-Yang soil series