Experimental test are carried out on a semi-heavy duty Motorsazan MT4.244 agricultural engine at various loads in order to evaluate performance and emissions of DI diesel engine using the blends of diesel fuel with 5%, 10%,15%,20%, 30%(by volume) Castor oil and pure diesel fuel separately. The result show that maximum decreasing of PM emission is 73.2% and is observed in B15 at 50%load and the maximum increasing of BSFC and NO are 10.7% and 15.6% than that of the diesel fuel and are observed in B30 at 50% load and B20 at 50% load respectively. The results show that in B15 at 25% load, NO and PM emissions decreases 6% and 64% respectively and BSFC increases 1.5%.