Mineralization and Nutrient Release of an Organic Fertilizer Made by Flour, Meat, and Crop Residues in Two Vineyard Soils with Different pH Levels

The mineralization and nutrient evolution of an organic fertilizer compost of flour, meat, and crop residues was evaluated in two vineyard soils. A lysimetric testing, using 2.2-L Buchner funnels, was carried out to study the evolution of pH, electrical conductivity, and nutrients during the 400-day experiment. The net mineralization for two different doses of the fertilizer mixed with the soils was compared with an unfertilized control. The pH value of the acidic soil decreased to values less than 4.5 because of the yield of hydrogen (H+) in the organic fertilizer mineralization, whereas the soluble aluminium (Al3+) increased quickly in the leachates. The mineralization process was quicker in the alkaline soil (with a maximum mineralization rate of 0.83 mg nitrogen (N) kg(-1) day(-1) for the 8 Mg ha(-1) dose and 0.43 mg N kg(-1) day(-1) for the 4 Mg ha(-1) dose) in comparison with the acidic soil, which reduced these rates up to 50%. The N-nitrate (NO3) amounts yielded in a year were 150 and 79 kg N ha(-1) for the 8 and 4 Mg ha(-1) doses respectively in the alkaline soil, enough to cover the vineyard N demand. These values were reduced to 50% and 60% of N-NO3 for the acidic soil, indicating the important effect of pH in the mineralization.