Salt, Soil and Seeds      To compare the growth of seeds planted in 'soil' with different salinity (or saltiness).      2 plastic or paper cups Cotton wool (cotton balls) 10 wheat seeds (or bean seeds) Salt Clear plastic wrap (optional)      1. Cover the bottom of two cups with cotton wool. 2. Sprinkle some salt over the bottom of one cup. Label this cup 'salt added'. 3. Place five seeds in each cup. It helps if you place the seeds with their grooved side upwards. 4. Wet the cotton wool in both cups and put in a light place. 5. Keep the seeds moist - you can cover the cups with clear plastic wrap to prevent the seeds from drying out. 6. Within four or five days, the seeds should begin to grow. Which seeds begin to grow first - the seeds with or without salt? Observe the seeds growing for a few more days. What difference do you see?      The increasing amount of salt in the soil (salination) is one of Australia's biggest environmental problems. In 1990, 50 000 square kilometres of land were affected by salinity. This area is almost the same as the whole state of Tasmania! Salts occur naturally in the soil and are carried by water. If the underground water level is close to the surface, the soil becomes too salty for many plants to grow. Tree planting programs can help reduce this problem. So too can the planting of crops which grow well in salty soils (salt tolerant).      Experiment with different amounts of salt to find out how much will stop wheat from growing. Try putting salt on the wheat seeds after they have sprouted. Try growing different types of seeds. Which plants will grow in salty soil?