The objective of this study was to evaluate the effect of various organic amendment on weed suppression, soil content and yield components of sweet com (Zea mays L.) grown under organic or sustainable agriculture regimes. Field experiments were conducted during 2004, 2005 and 2006 to study the effect poultry manure, cow manure and barley mulch, used at three rates (half, recommended. double). Sweet com ({Zea mays L.) was planted. Two experiments were conducted each year. Experiment I was in combination with nitrogen fertilization (nitrogen was added in each treatment according to the nitrogen content of each amendment; the amount added was equal to that needed to bring all treatments to the rate of 240 kg N/ha). Experiment II was purely organic.