B. Collection of Vegetable and Soil Samples
At each sampling sites, 20g each of the five vegetables namely, spinach, lettuce, cabbage, tomato and onion were collected from three different locations in each area to provide replicate samples of each crop. The Vegetables samples were collected in clean polyethylene bag; labeled and transported to the laboratory and preserved in a refrigerator at 4 OC, pending extraction.
Soil samples were collected from ten plots, from Alau Dam and Gongulong Agricultural areas. In each plot, three soil samples were collected at three depths (0-10cm, 10-20cm and 20-30cm), using spiral auger of 2.5cm diameter. The Soil samples were then randomly selected and bulked together to form a composite sample before being placed in clean plastic bags and transported to Chemistry Laboratory University of Maiduguri.