Micronutrients in selected food crops in Muguga, Kenya

Micronutrients are essential for growth of plants and although they are required in small quantities, inadequate supply of one or more of these results in reduced yields and quality of crop products. Micronutrients are transferred through the food chain to human beings and are important for health, growth and development. Deficiency of these poses a threat to the social-economic development of a nation due to the associated effects which include increased mortality rate, impaired physical and cognitive development and reduced labor productivity. In the 2011 national food and nutrition security policy, it was reported that due to inadequacy of food quality and diversity in the regular diet among Kenyans, over 10 million people suffer from chronic food insecurity and poor nutrition. There is therefore need to carry out research on the levels of micronutrients in food crops and this would be helpful in the establishment of plant quality monitoring systems as well as micronutrient bank and management systems in Kenya so as to monitor plant health and thus come up with possible interventions. The study was aimed at finding out crop response to micronutrients available in the soils on which they were grown and comparing the micronutrient levels among different food crop species. Leaves/whole plant of beans (Phaseolus vulgaris), potatoes (Solanum tuberosum) and maize (Zea mays) were sampled from Muguga, Kenya, following an offset grid sampling pattern in which plots of 100*100 m were marked out and samples randomly collected within a radius of 3 meters from the grid intersection and composited. All the samples were analyzed for micronutrients (Mn, Fe, Ni, Cu and Zn) by Total reflection X-ray Fluorescence (TXRF). The mean concentration for Mn in beans, potatoes and maize were 215.594, 168.876 and 177.756 respectively. For Fe, the means were 750.262, 553.318 and 917.031 respectively. The means for Ni were 2.354, 1.342 and 0.788 respectively while Cu had means of 9.374, 11.914 and 10.082 respectively. Zn showed means of 65.852, 40.045 and 67.393 respectively (all concentration levels are in units of mg/kg). The results did not show deficiency among the micronutrients in all the food crops analyzed. However, following the coefficients of variation (CVs) the concentrations of Mn and Fe varied significantly between the crops while Ni, Cu and Zn showed no significant variation. Each plant takes up the available nutrients differently and this research showed that beans had the best response to available nutrients with a correlation of 0.9424. More research is to be conducted in other parts of the country for sufficient and conclusive micronutrient mapping.