ChileanJAR

Twenty eight superficial and subsuperficial soil samples were sown with ryegrass (LoIium perenne x L. multiflorum), in a pot trial. Al) soils proceeded from the Caütín province and were low in available P. The interpretation of the dry matter yields, harvested four times, was made with the fertility diagram, and two equivalent NPKCaS fertilizations were compared: a. chemical substances of analytical quality (pa.), and b. commercial fertilizers, potassium sulphate and superphosphate (conc.). Ryegrass responded to the micronutrient impurities of the fertilizers, correcting soil deficiency in many soils. In sorne samples, the addition of the micronutrients in the fertilizers to those in the soil, produced an excessive accumulation, and yields were lower when commercial fertilizers substituted analytical chernicals. For other few samples, the responses to both NPKCaS treatments were low, be- cause a rnicronutrients deficiency subsisted. A general interpretation of results is discussed. It this differential behavior to both NPKCaS fertilizations occurs also in the field with difterent crops, it would signify that the number of soils poor in micronutrients has been underestimated. To evaluate the extension of the areas affected and o identify the rnicronutrients involved, it is mandatory to use chemical substances free of the searched micronutrients.