From October 1994 to February 1995 a field trial was conducted at the Fabio Baudrit Agricultural Experimental Station, University of Costa Rica, to evaluate the effects of different periods (weeks) of solarization, namely: 0, 2 (103), 4 (188) and 7 (288) - figures in parenthesis are cumulative hours of sunshine - in combination with chicken manure additions (4,1 t/ha) on propagule survival of the weeds Rottboellia cochinchinensis, Bidens pilosa and Cyperus Rotundus. The propagules were placed at the following depths (cm): 0-5; 5,1-10; 10,1-15; 15,1-20 and 20,1-25. In additional an inventory of the native weed seed bank was conducted as well as the growth and yield of cilantro Coriandrum sativum as an indicator crop. The greatest propagule death occurred after 7 weeks of solarization, the addition of chicken manure further decreased the propagules of C. rotundus and B. pilosa. This treatment also sharply decreased the soil weed seed bank, shorter periods not were as effective. Growth and yield of the indicator plants increased in the seven week treatment by 320 %. In addition the roots looked better developed and lacked the root-nodule nematode galls caused by Meloidogyne arenaria that were observed in the control treatment. The economic benefits of solarization in the context of the indicator plant is discussed.