Utilization of grain milling waste for plant growth and nutrient availability in soil

Abstract

This study optimized fermentation process of grain milling waste (wheat bran, wheat flour and mill dust) using Lactiplantibacillus plantarum (LP) or Bacillus subtilis (BS). The experiment included two parts: (I) in vitro optimization and evaluation of the fermentation of mill waste in two inoculum levels and three mill waste ratios; (II) fermented mill waste (FMW) was tested in a pot experiment. Three different application routes were tested: soil incorporation, foliar and soil drenching. FMW was compared with NPK fertilization, compost and vermicompost. Growth parameters of the Zea Mays and soil quality of were evaluated. Results in vitro showed a two-fold increase in total protein concentration, a 6.5-fold increase in lactic acid concentration, and a two-fold increase in free phosphorus availability in FMW compared to control. Soluble mineral ions were significantly ( p  < 0.05) increased Ca (3–9 mg/L), Fe (4.5–9.9 mg/L), Mg (7.5–13 mg/L), Mn (13–15 mg/L) and Zn (8.5–9.3 mg/L) compared to control in dependence of microorganism dosing and mill waste composition. FMW soil fertilization increased soil N min (22.2 mg/kg) compared to control (12.95 mg/kg). FMW applied directly into the soil or via soil drenching resulted in increased content of P (23%), K (50%), Ca (31%), S (36%) Fe (40%), and Mn (86%) compared to control. In contrast with control (9.02 mg/kg), compost (13.37 mg/kg) and vermicompost (13.23 mg/kg), FMW generally provided higher soil mineral nitrogen availability (23.8 mg/kg) and enhanced accumulation of several nutrients in plant tissues demonstrating potential as a complementary organic amendment with possible biostimulant effect depending on application method.