Soil and irrigation water quality assessment for maize production in Buhle farm in Howick, Kwazulu-Natal province, South Africa

Abstract

The continuous monitoring of soil health and irrigation water quality influences the crop yield and the quality of agricultural produce. In this study, various physicochemical parameters were measured to monitor the soil profile, irrigation water and maize quality harvested from the Buhle farm located in Howick in the KwaZulu-Natal Province of South Africa to ensure steady high quality food supply for the consumer. The maize crop was sampled from the maize stalk, the corresponding soil samples were collected from the upper surface of the soil (0-15 cm surface layer) using the soil auger and the irrigation water sample was taken from the irrigation tanks using polyethylene sample bottles. The physicochemical parameters considered for irrigation water were pH, electrical conductivity, alkalinity and chloride due to their ability to affect water quality which consequently affect crop growth and quality. The soil physicochemical parameters considered were moisture content, pH, electrical conductivity, texture, total nitrogen and nutrients (protein, fat, fibre, starch, total mineral matter and elements). These parameters determine the soil quality, water content, the ratio of absorbed and lost energy, concentration of ions and elements present which in turn affect or promote the yield and quality of crops. Maize was analysed for nutritional content and medicinal health-promoting compounds to assess the influence of soil and irrigation water on the maize quality and consequently the health of the consumers. The concentrations of total nitrogen (N), phosphorus (P) and potassium (K) in soil, which were translated into high soil fertility were 2700, 19 and 222 mg kg-1, respectively. The results obtained were within the required specification for high quality maize production. The levels of sodium, sodium adsorption ratio and electrical conductivity in the irrigation water were 0.05 mg L-1, 2 and 1.81 µS m-1, respectively, indicating safe water of low salinity. Maize was high in starch (58.6%) while fibre, protein and fat contents in the maize were 23.4, 9.01 and 4.55%, respectively, indicating suitability for consumption. Furthermore, the total anthocyanin, total flavonoids and total phenolic acid content of the maize were 8.5, 49.5 and 100 mg L-1, respectively. Overall, this study showed the presence of health-promoting compounds in the maize crop which is associated with its high quality for consumption. The validity of the analysis methods was tested using certified reference materials. The concentrations of the reference materials were not statistically different from the certified values, attesting to the validity of the analysis methods. Key words: Soil profile, water quality, soil fertility, nutrition, antioxidants