Physicochemical Assessment of Soil, Water and Nutritional Composition of Spinach andLettuce from Selected Farms in Kano

Abstract

Lettuce (Lactuca sativa) and spinach (Spinacia oleracea) are widely consumed leafy vegetables in Nigeria, valued for their nutritional and health benefits. However, their quality and safety depend on the soil and water used during cultivation. The study aim evaluated the physicochemical properties of soil and irrigation water, alongside the proximate composition of lettuce and spinach cultivated in Chalawa, Fagge, and Sharada farms of Kano State, Nigeria. Soil and water samples were analysed using standard methods for pH, electrical conductivity (EC), organic carbon (OC), organic matter (OM), macronutrients, and trace elements. Proximate parameters of vegetable samples included moisture content (MC), ash, crude protein (CP), fats, crude fibre (CF), and carbohydrate (CHO). The study showed that pH ranged from 5.90 ± 0.36 in the control to 7.87 ± 0.38 in Chalawa, with EC peaking at 1895.33 ± 906.12 µS/cm in Fagge. Organic matter was highest in Fagge at 2.05 ± 0.39%, indicating higher fertility. Water EC was highest in Sharada (5580 ± 3145.67 µS/cm), suggesting possible saline intrusion. Lettuce and spinach from Sharada had the highest CP content of  20.13 ± 0.35% and 18.56 ± 1.12%, respectively, whereas moisture content was generally low (3.77–5.77%), promoting better storage. Carbohydrate content was highest in spinach from Chalawa (56.25 ± 2.78%) and lowest in lettuce from Sharada (52.51 ± 2.22%). These differences reflect both soil and water quality influences. All farms produced nutritionally adequate vegetables, with Sharada farm showing the highest protein and carbohydrate profiles, suggesting its potential for high-nutrient yield. However, elevated EC and COD in irrigation water at some sites may pose long-term soil degradation or salinity risks. Therefore, regular monitoring of irrigation water quality be enforced, and sustainable soil management practices adopted to preserve nutritional quality and environmental health.

Keywords: Lettuce, Spinach, Proximate composition, Soil quality, Irrigation water, Electrical conductivity