HIGHLIGHTS:
Waste from vermiculite extraction improves soil chemical and biological attributes.
Cattle manure and beneficial microorganisms increase nutrient release rate from vermiculite waste.
Vermiculite residue can be a complementary source of nutrients for maize crop.
ABSTRACT
Vermiculite mining residues, although of low solubility, contain nutrients such as calcium, magnesium, and potassium at concentrations that allow their agricultural use. Beneficial bacteria can increase the solubility of this waste and its efficiency. The objective of the present study was to evaluate the influence of bio-inoculation of vermiculite residue, associated with cattle manure, on the release of nutrients and initial growth of maize. A completely randomized design was performed in a greenhouse with seven treatments and four replications. The treatments were: T1 - soil without fertilization; T2 - soil fertilized with soluble sources of nutrients (conventional fertilization); T3 - application of vermiculite residue (VR); T4 - VR enriched with cattle manure (CM); T5 - VR + CM with Bacillus subtilis; T6 - VR + CM + B. amyloliquefaciens, and T7 - VR + CM +B. subtilis + B. amyloliquefaciens). Regardless of the use of cattle manure or beneficial microorganisms, vermiculite mining waste increased the availability of Ca and K in the soil, but was not able to match the soluble sources of nutrients. Mining waste associated with cattle manure and beneficial microorganisms (B. subtilis and B. amyloliquefaciens) increased microbial activity and enhanced the release of available calcium for maize. VR increased the growth and the dry mass production of maize compared to the non-fertilized soil, but was consistently inferior to conventional fertilizer.
Key words:
beneficial bacteria; vermiculite residue; remineralizers; solubilizers
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T1- Soil without fertilization; T2 - Soil fertilized with soluble sources; T3 - Application of vermiculite residue (VR); T4 - VR enriched with cattle manure (CM); T5 - VR+CM with Bacillus subtilis; T6 - VR+CM+ B. amyloliquefaciens and T7 - VR+CM+ B. subtilis + B. amyloliquefaciens). Data are means ± S.E. Lowercase letters compare the treatments by the Scott-Knott test at 0.05 significance level
T1- Soil without fertilization; T2 - Soil fertilized with soluble sources; T3 - Application of vermiculite residue (VR); T4 - VR enriched with cattle manure (CM); T5 - VR+CM with Bacillus subtilis; T6 - VR+CM+ B. amyloliquefaciens, and T7 - VR+CM+ B. subtilis + B. amyloliquefaciens). Data are means ± S.E. Lowercase letters compare the treatments by the Scott-Knott test at 5% significance level
T1- Soil without fertilization; T2 - Soil fertilized with soluble sources; T3 - Application of vermiculite residue (VR); T4 - VR enriched with cattle manure (CM); T5 - VR+CM with Bacillus subtilis; T6 - VR+CM+ B. amyloliquefaciens, and T7 - VR+CM+ B. subtilis + B. amyloliquefaciens). Data are means ± S.E. Lowercase letters compare the treatments by the Scott-Knott test at 5% significance level
T1- soil without fertilization; T2 - soil fertilized with soluble sources; T3 - application of vermiculite residue (VR); T4 - VR enriched with cattle manure (CM); T5 - VR+CM with Bacillus subtilis; T6 - VR+CM+ B. amyloliquefaciens, and T7 - VR+CM+ B. subtilis + B. amyloliquefaciens). EC - Electrical conductivity; SDM - culm dry mass; TDM - Total dry mass; NUE - Nitrogen use efficiency; PUE - Phosphorus use efficiency; KUE - Potassium use efficiency; C-mic - Microbial biomass carbon, and qCO2 - Metabolic quotient