Study on certain planting time for Crotalaria seed production   Pracha Nakapraves and Preede Deerugsa   ABSTRACT         The study on certain planting time for Crotalaria seed production was conducted at the area of Land Development Regional Office 5, Khon Kaen province during 1991 - 1994. The research was done on Warin series which was recognized in low fertility soil composing of pH 5.77, OM 0.66%, N 0.035%, P2o5 2.73 ppm and K2O 15.78 ppm and its structure is sandy soil with poor in physical property. The randomized complete block design (RCBD) was used in this trial comprising of 12 treatments of planting time interval and 3 replications. The 20 kgs/rai of chemical fertilizer (15-15-15) were added after 1 mouth of Crotalaria growing. The results showed that the suitable planting time interval started from July to August because there was adequate amount of rainfall to make highly of Crotalaria seed yield which was 77.05-79.30 kgs/rai and crop residue was about 1,289.33-1,330.30 kgs/rai which could be sold to pulp factory to make pulp or could be made compost for soil improvement.         Keywords : crop residue, pulp