This lesson is part of a series called, Too Much? Too Little? created to introduce middle school students to the connection between soil nutrients and the food they eat. The lessons consist of a series of demonstrations and hands-on experiments that show that plants require nutrients in certain quantities. The lesson series allows students to investigate soil properties, learn how to properly prepare fertilizer nutrient solutions, identify deficiencies in plant nutrients using a key, and much more. Other related lessons include:

• Plant Parts and Functions:Anatomy and physiology of a plant.
• Digging Into Nutrients: How plants obtain nutrients from the soil.
• The Right Solution: How fertilizer solution is properly calculated and applied.
• Can We Have Too Much of a Good Thing?: The effects of applying too much or too little fertilizer.
• The Right Diet for Your Plants: Read fertilizer labels and choose the best fertilizer.
• Let's Vote On It: How soil nutrients effect local communities and economies.
• It's a Dirty Job: How earthworms benefit soil.

Plants require 17 different essential elements for successful growth and reproduction. Carbon, oxygen, hydrogen, nitrogen, phosphorus, and potassium are required in relatively large quantities and are classified as macronutrients. These elemental nutrients are obtained from the air and from water in the soil. Macronutrients are needed in relatively large quantities for healthy plant growth. Nitrogen (N) is known as the builder. Nitrogen is needed to make proteins and to carry out photosynthesis. Phosphorus (P) is known as the energy supplier and is needed for energy transfer in photosynthesis and is important for seed germination and efficient water use. Potassium (K) is known as the regulator because it plays an important role in catalyzing chemical reactions involved in plant growth and protection from stress. 

Eleven other elements are also important to plants but are classified as micronutrients because they are needed in smaller quantities than macronutrients. It is important that plants receive the correct amount of nutrients for proper growth and reproduction. There are many different types of fertilizers that can provide needed nutrients to plants. Farmers have been fertilizing their crops for thousands of years. As the human population continues to grow, farmers must produce more, from the same amount of land. In order to sustain soil health, nutrients must be replaced after they are removed from the soil with harvested crops. A variety of different fertilizers are available for farmers and home gardeners. Organic fertilizers, such as manures, undergo very little processing before being applied to a crop. Commercial fertilizers are made from natural ingredients that undergo chemical processing in order to increase their nutrient content and ensure that they deliver a guaranteed amount of nutrients. Many farmers use both types and make their selections based upon the needs of their crop, the characteristics of their soil, climate, topography, and many other factors. 

Many liquid plant “foods” are purchased in concentrated forms. Before they are used they must be diluted with the proper amount of water. Fertilizers in solid form also have a specific amount that should be applied in order to provide only what will be taken up by the crop. Just as a person can become sick after taking more vitamins than the recommended dosage, plants can be harmed if a gardener or farmer applies more fertilizer nutrients than recommended. In addition, farmers and home gardeners must follow fertilizer application instructions to protect the environment by making sure that the nutrients applied are the amount that will be taken up by plants and will not run off into waterways and other fields. The fertilizer manufacturer, through extensive research and testing, provides instructions on the proper application of the fertilizer, including concentrations, proper dilution, frequency of application, and storage. This research guides farmers and gardeners to use the 4-Rs when managing fertilizer application: Right Rate, Right Time, Right Place, Right Product.