A field scale experiment comprising three continuous crop (CC) rotations and four crop-pasture rotations (CPR) was established at INIA La Estanzuela Experimental Station located in Uruguay (34oS, 57oW) in 1963 on an Argiudoll soil. Conventional tillage was used throughout the experiment. Rotation systems have different soil use intensities for crops and cattle production ranging from continuous cropping systems with or without fertilizer to pluriannual legumes and/or grass mixtures. After a period of 40 years, crop rotations including pastures showed the highest total organic carbon (TOC) levels due to a higher residue return in crops and pastures and a reduction in soil erosion. Thus, this treatment maintained the TOC levels of 1963 (2.18 %). Meanwhile, CC with fertilizer showed declines in TOC levels (1.53 %) due to a lower residue return and an increase in soil erosion. Crop-pasture rotations had the greatest grain and forage yields which also determined a higher gross margin and a higher stability in periods of agricultural commodities prices depression. The inclusion of legumes in the rotation reduced the use of nitrogen fertilizer by up to 50 %. Other inputs such as pesticide and herbicide use were also reduced significantly by the inclusion of pastures when compared to continuous cropping. Crop pasture rotations have been widely adopted by farmers in SW Uruguay. Farmers plan their crop rotation based on soil type, crop and pasture species, prevalent weeds and plant diseases, production objective (agriculture, beef, dairy), machinery availability, expected dry matter yields (amount and distribution), profit and farmers background. In the last decade other experiments have shown that the inclusion of no tillage on CPR have proved to be an efficient way to decrease soil erosion and to maintain or even increase TOC.