This lesson is part of the series called, Fertilizers, Chemistry, and the Environment.  These lessons introduce students to chemistry and environmental science concepts. Activities are modeled after real-life challenges that modern farmers face while producing our food, fiber, and fuel. Labs are inquiry based and promote critical thinking skills. Other related lessons include:

• One in a Million
• Concentrate on the Solution
• Matter of Fact
• What's Your pH?
• Know Your Nitrogen

Whether we are talking about your lawn, flower garden, or the wheat in your pasta dinner, plants need nutrients to grow. When crops are harvested the nutrients they utilized from the soil are removed with them. These nutrients must be replaced back into the soil so it remains fertile and can continue to grow crops in future years. Farmers and home gardeners use a variety of fertilizers to provide plants with essential nutrients. There are many different types of fertilizers that fit the needs of different crops and growing conditions. You may be familiar with fertilizers if you have applied compost, fish emulsion, animal manure, or other pre-packaged fertilizer to your lawn or garden. These fertilizers play an important role in growing beautiful flower gardens, green lawns, and providing affordable and nutritious food.

The use of any type of fertilizer comes with the responsibility to precisely follow instructions for storage, preparation, and application. From farms to home gardens and golf courses, we all must ensure that fertilizers are used correctly. Strict regulations, scientific research, and developments in new technology ensure that modern farming methods involve the selection of the appropriate fertilizer, application method, application timing, and monitoring of nutrients to provide crops with enough nutrients for optimum yield, while also protecting the environment. Applying too much fertilizer to crops can have adverse effects on the environment as well as the crop, and is an unnecessary expense. Replacing nutrients with fertilizer at the right time and in the right amount helps farmers grow enough food for an increasing world population as the amount of available farmland decreases. Achieving optimum yields without applying excessive nutrients is a goal of all farmers.

This lesson provides students with insight into one method farmers use to determine the amount of nitrogen fertilizer their crop may need. Of the primary nutrients, farmers are especially interested in nitrogen for several reasons. Nitrogen is required for plants to form proteins which make up much of their tissues, and nitrogen availability is often limited in the soil. While 78% of our atmosphere is nitrogen gas, most plants cannot use this form of nitrogen. Nitrogen is most available to plants when it is in the nitrate (NO3-) form or when it is in the ammonium (NH4+) form. Nitrogen can be made available in plant-usable forms of nitrogen through the action of nitrogen-fixing microbes found in the soil and the root nodules of some types of plants, such as legumes. These forms of nitrogen can also be supplied to plants through the use of various types of fertilizers.

Before applying fertilizers, farmers test their soil to determine factors such as texture, pH, porosity, organic matter, nutrient content, and more. Farmers also test the tissues of the crops they are growing to compare with the nutrient components from the soil analysis. These factors are important in determining which nutrients to use, how much and when to apply, and how to irrigate. These considerations ensure the best utilization by plants for healthy and efficient crop production.

Throughout the nation, many organizations fund research on new techniques for managing agricultural nitrogen and develops workshops and training programs for farmers and ranchers. State and regional water boards regulate, monitor, and provide financial assistance to protect water resources and achieve water quality objectives. For more information see Answers to Commonly Asked Questions.