The present research work was carried out in tropical crops Institute experimental plot (ICT) sector 'Laguna Venice' of the province and Department of San Martin in order to determine the effect of dosage of NPK fertilization and amendments of Ca + Mg (magnecal) most appropriate to get the highest yield in the culture of marigold (tagetes erecta l.) under conditions of very acidic soil. PH of 4.3 to 5.0, low, sandy loam texture soil: organic matter, nitrogen and phosphorus, with a high content of potassium and zero of limestone. The experimental design used was the "Complete blocks at random" with seven treatments and four replications. Nitrogen levels were 0.89, 178 and 336 kg of N/ha, using as source nitrogen Urea (46%); phosphorus levels were used 0,49,98, and 196 Kg/ha using as a source triple superphosphate (46%); potassium levels were 0.1 00,200 and 400 Kg/ha using as a source I ch...