Malting Sludges as Soil Amendment

Nutrient depletion is a major form of soil degradation. The sludge from effluent treatment plants in agro-industrial processes is a potential source of organic fertilisers (Roy et al., 2003) that can be used to restore the fertility of agricultural soils with better prospects than even inorganic or conventional fertilisation. When biosolids are incorporated as an amendment, many micronutrients that are not incorporated with conventional (synthetic) fertilisation are provided. This incorporation is an advantage, given that the design of fertiliser dosages at the micro-level would be notably costly. The bioavailability of trace elements, such as micronutrients or toxic elements, is not determined by the total concentrations of the elements in question; rather, it depends directly on the chemical properties of the soil, particularly the pH and cation exchange capacity. The application of biosolids, organic (plant/animal) waste to the soil should be reconsidered as an economic practice, both from the standpoint of operating costs and from the standpoint of the environment, given the facts that matter is recycled and it can effectively compete with chemical fertilisers at lower environmental costs. All of these factors support the pursuit of an effectively sustainable agricultural-livestock production method. The use of organic waste would also be an advantage for countries with relatively low industrialisation that could more easily "close" the cycle of nutrient recycling in contrast to highly industrialised countries. Ideally, sustainable agricultural-livestock production would be stable when organic waste arising from the study area is reused within the same area (Schulz et al., 1997). This stability is possible when the surface areas of agricultural land are large, and the generation of agribusiness and domestic waste is not excessive, as is the Argentina situation. One way to improve or restore long-term soil quality is to intervene in the complex processes of agro-ecosystem biocycles.

Taking into account the limiting soil factors for growing crops in marginal zones of the Argentine Pampas, such as the southwestern regions of the province of Buenos Aires (sub-humid – semi-arid zones), atypical Mollysol soil (Argiudol suborder) was tested with the objective to propose practices, such as amendment with biosolids (organic waste), like malting sludges that would improve the soil quality and increase the sustainable productivity of cereals and fodder to prevent deterioration of the ecosystem. Sludge from waste biomass (activated sludge treatment of malting effluents), mainly organic matter had a chemical composition about 50% cellulose, hemicellulose 20%, 18% of lignin, 6% protein, 5% amino acids and sugars and other pectin, waxes, pigments, etc.