Use of industrial diatomite wastes from beer production to improve soil fertility and cereal yields

One promising way to reuse and recycle brewery spent diatomite sludge (BSDS) is by direct application to croplands as a soil amendment. This paper assesses the value of BSDS as a soil amendment and organic fertilizer. BSDS samples of different ages were analyzed to determine physicochemical properties and trace metal concentrations. All BSDS samples were alkaline (pH 8.3-8.7) with high concentrations of available phosphorus (373-416 mg kg−1) and potassium (883-3297 mg kg−1). Organic carbon and total nitrogen content were also found to be relatively high (3.1% and 0.22%, respectively) in the freshly dumped BSDS. The total porosity and available water holding capacity of BSDS were found in the range of 71-73% and 145-176 mm m−1, respectively, which indicate favorable conditions for plant growth. Concentrations of potentially toxic trace metals in BSDS were much lower than the standards set for land application, implying that BSDS is safe for use as organic fertilizer. In addition, field trials with teff (Eragrostis abyssinica Zucc.) and wheat (Triticum aestivum L.) were conducted to measure the effects of BSDS amendments on grain yield as compared to recommended inorganic fertilizers and farmyard manure. For both cereals, application of BSDS resulted in two-fold higher grain yields than the control and 50% increases over farm yard manure. Post-harvest analysis also revealed an improvement in physicochemical properties of soil. Wheat and teff grown in fields treated with BSDS showed higher grain protein content than controls, and nearly as high as those treated with recommended inorganic fertilizers. In conclusion, BSDS has great potential to be used as a soil amendment to increase crop productivity and nutritional quality.