Survey of soil fertility and nutritional status of alfalfa of Uruguay

White clover (Trifolium repens) is a forage legume widely used in eastern Uruguay for forage and/or seed production. This survey evaluated the soil fertility and its nutritional status at 40 farms of eastern Uruguay. Soil analysis showed moderate acidity (average pH 5.6), absence of exchangeable aluminum (Al), organic matter contents of 2.5 to 6.3 percent, low P availability (average of 6.9 ppm Bray P), low to medium exchangeable K (average of 0.28 cmol_c/kg or 109 ppm), and adequate micronutrient availability except for Zn, which showed medium availability levels. Plant analysis showed important N deficiencies that could be associated with low plant P and S contents. Plant P contents were lower than the critical level in almost 80 percent of the farms, indicating that P fertilization rates have been low. Plant K contents were below the critical level for 44 percent of the sites and were related to soil exchangeable K and the K saturation percentage of the cation exchange capacity (CEC). Boron (B) was the only micronutrient that showed plant contents below the critical level (15 percent of the sites). URUGUAY-01