The hypothesis is that the loam soil with fertilizer added will have the highest level of electrical conductivity.

You will measure the electrical conductivity of different types of soil, including sand, clay, loam, and loam mixed with fertilizer.

You will need 200g of sand, 200g of clay, 400g of loam, 50ml of liquid fertilizer, 800ml of water, 4 beakers, 1 DC12V battery, 3 jumper wires with crocodile clips at both ends, 2 copper electrodes, 1 miliammeter, 1 digital weighing scale, 1 measuring cylinder, 1 ruler, and 1 clock.

The results showed that loam mixed with fertilizer had the highest electrical conductivity, while sand had the lowest. This proves that the hypothesis was correct.

This science project is interesting because it shows how soil fertility affects electrical conductivity. It also demonstrates how different types of minerals can affect the conductivity of the soil.

To vary the experiment, you could add different types of minerals to the soil samples and compare their electrical conductivity. You could also measure the effects of other factors on electrical conductivity, such as the amount of water added, the temperature of the environment, or the pH of the soil.