Reutilization of granite powder as an amendment and fertilizer for acid soils.
The properties of granite powders--a granite manufacturing waste product-were analyzed to assess their potential use as amendments and fertilizers on acid soils. Two types of powders were characterized: one produced during cutting of granite with a diamond-edged disc saw, comprising only rock powder, the other produced during cutting with a multi-blade bandsaw, containing calcium hydroxide and metal filings added during the cutting procedure. The acid neutralizing capacity of the granite powders was assessed in short- (2-3 h) and medium-term (1-30 d) experiments. The powders showed a buffering capacity at around pH 8, which corresponded to the rapid dissolution of basic cations, and another buffering effect at pH<4.5, attributable to the dissolution of Fe and Al. The acid neutralizing capacity (ANC) determined in the short-term experiments, to a final pH of 4.5, varied between 5 and 61 cmol H+kg(-1) powder. The ANC to pH 4.5 obtained in the medium-term experiments was much higher than that obtained in the short-term experiments, reaching a maximum ANC value of 200 cmol H+kg(-1) powder. There was no great difference in the neutralizing capacity determined at between 1 and 30 d. The most abundant elements in acid solutions obtained at the end of medium-term experiments were Mg and Ca for disc saw powders, whereas Ca and Fe (at pH<5) were the most soluble elements in the bandsaw powders. The rapid release of these cations suggests the possible effective use of the granite powders as a source of nutrients on being added to acid soils.
Barral Silva
M T
MT
Departamento de Edafología y Química Agrícola, Facultad de Farmacia, Universidad de Santiago, Santiago de Compostela 15782, Spain. edbarral@usc.es
Silva Hermo
B
B
García-Rodeja
E
E
Vázquez Freire
N
N
D002021:Buffers; D002118:Calcium / Q000032:analysis; D002412:Cations; D005308:Fertilizers; D006863:Hydrogen-Ion Concentration; D007220:Industrial Waste; D008274:Magnesium / Q000032:analysis; D019216:Metals, Heavy / Q000032:analysis; D010316:Particle Size; D011188:Potassium / Q000032:analysis; D012822:Silicon Dioxide; D012987:Soil; D012995:Solubility
D002021:Buffers; D002412:Cations; D005308:Fertilizers; D007220:Industrial Waste; D019216:Metals, Heavy; D012987:Soil; C007886:granite; D012822:Silicon Dioxide; D008274:Magnesium; D011188:Potassium; D002118:Calcium