Effects of several kinds of organic fertilizer on Yantakao soil series improvement and super sweet corn yield   Siangjeaw Piriyaprin Chaveevan Leaungvutivirog Pitayakon Limitong Vanlada Sunanthapongsak and Pracha Nakapraves   ABSTRACT         Study on the effect of organic fertilizers on some properties of Yantakao soil series and super sweet corn yield was conducted at Land Development Station, Songkhla Province during 1994 - 1997. The experimental plan was completely randomized block design. There were 6 treatmentes 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 in seed rate 5 kgs per rai and added sole chemical fertilizer (15-15-15) 50 kgs per rai: The results indicated after harvesting corn yield, application of animal manure had effect increasing cellnlohytic bacteria and fungi from 6.19 and 4.53 to 7.38 and 5.68 log no. per gm of soil. Soil plant nutrients such as phosphorus calcium mangnesium and sulphur were increased from 6.5, 89, 21 and 9 to 13.3, 131, 32 and 14 ppm respectively. Which had shown significantly statistic when compared with non-organic fertilizer application. Furthermore, the level of soil pH raised form 3.7 to 4.7 For the consideration of corn yield, compast addition gave the highest yield to 340.4 kgs. per rai. Compost application had gotten net income 1,388 bath per rai where as applied chemical fertilizer had no getting net income which had unprofit 740.50 bath per rai.         Keyword : organic fertilizers, super sweet corn, Yantakao soil series