1. When a farmer has grown corn in the same field for several years, the nitrogen content of the soil can become severely depleted. Nitrogen is necessary for healthy plant growth, so in order to combat this problem, a farmer who grows organic produce may also grow legumes such as soybeans in the same field, next to the corn. How does the use of legumes help the farmer solve the problem?

2. Nitrogen accounts for approximately what percent of the air in the atmosphere?

3. Many farmers who grow organic produce are against the use of artificial fertilizers that contain synthetic nitrogen-containing compounds. Which of the following is an alternative method that an organic farmer might use to increase the nitrogen content of the soil?