An experiment was conducted in Alstroemeria (Alstroemeria aurantiaca D. Don, cultivar ‘Napoli’) cultured in pots under greenhouse conditions. Two different types of pig slurry, pig slurry and thermal dried pig slurry, were applied as fertilizer. The aim was to evaluate the possible effect on pollution of leaching nutrients of the two pig slurries. Rates studied were 0 (without fertilization), 1 (the rate 1 that covered the nitrogen culture requirement) and 2 (the double of rate 1). The nutrients concentration of the leaching depended of the volume of leached water. Four leachings by pot were made at spring, summer, autumn and winter. The NH4 +-N, NO3-N, phosphorus and potassium, variables were studied. The methodology to adjust estimation and to compare the models was the nonlinear mixed model. Treatments (pig slurry and thermal dried pig slurry, and the two rates, 1 and 2) were significantly different. The thermal dried pig slurry treatment and the rate 2 treatment were the most polluting in the four studied variables.