The Potential of Human Urine and Biochar Integration for Soil Health and Maize Productivity: A Review

The decline in soil fertility and the excessive increase in the cost of in-organic inputs in sub-Saharan Africa, including Malawi, necessitate the need for integrated soil fertility management that includes organic inputs. Human urine and biochar have recently been promoted as sustainable sources of essential nutrients for maize production, especially for the resource-constrained smallholder farmers. Studies conducted have reported that human urine contains essential nutrients such as nitrogen (N), ranging from 3 to 12 g/l, available phosphorus (P), ranging from 1.25 to 2.8 g/l, and potassium (K), ranging from 0.65 to 3g/l. Urine has also been reported to increase maize grain yield, biomass, grain weight, and plant growth parameters. Urine can increase maize grain yield up to 6.82 t/ha which is above average maize grain yield (2000 kg/ha) produced by small holder farmers in Malawi. Human urine may contain traces of pharmaceuticals such as ampicillin, ciprofloxacin, ibuprofen, and trimethoprim sulfamethoxazole, especially if the individual is on medication, which can be harmful to soil microbes, plants and humans if urine is used untreated or in excessive amounts. However, fresh urine from healthy individuals is generally sterile, it should be properly treated and diluted before agricultural use to minimize health and environmental risks. Similarly, biochar has also been reported with large surface areas, high porosity, high carbon content, high conductivity. Additionally, biochar contains essential plant nutrients such as phosphorus, potassium, magnesium and calcium but in low concentrations which can be available for crop growth and development when it is applied in higher rates or when integrated with other sources of soil nutrient amendments. Furthermore, there is a lot of variations in the effects of both urine and biochar as influenced by inherent soil properties and materials they are integrated with during application. This review focuses on synthesis of information to provide clearly messages on the potential of urine, biochar and their combined effects on maize productivity and soil health. Key words: biochar, maize productivity, urine, soil health, elements, phytochemical, rate, nutrients