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?: 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.

A fertilizer is any natural or manufactured material added to the soil or water to increase or replace one or more nutrients needed for plant growth. In California, all commercial fertilizers are monitored by the California Department of Food and Agriculture (CDFA) and are required to follow specific label guidelines. The three numbers on the fertilizer package are standardized and represent the percentages of nitrogen (N), phosphorus (P), and potassium (K) in that order.

Manures and commercial fertilizers are illustrated in this lesson so that students can compare and contrast two basic types of fertilizers. The issues revolving around plant nutrients are complex. Plant nutrient requirements are not a “one size fits all” situation.

Different amounts of nutrients are required for different crops, and nutrients may be taken up at different rates during various growth stages of the plant. The percentages of N, P, and K are lower in manure than in commercial inorganic fertilizers. Commercial inorganic fertilizers require mining and the use of fossil fuels for manufacturing. Commercial inorganic fertilizers are generally easier to apply than manure and composts.

Manures provide the organic matter needed to increase the water absorption and aeration of soils. Discuss with your students the importance of continuing research in the area of nutrient requirements of plants and sustainable practices that will conserve resources and produce enough food for the growing population.

Farmers and home gardeners may find that their soil is lacking in important plant nutrients. Soils can be improved in a variety of ways. A visit to your local garden center will give you an idea of just how many choices are available for improving your soil with nutrients. You might find yourself asking how to choose the best fertilizer for your garden, and may want to ask one of the garden center experts to help compare different products. In this lesson, students will research a specific soil supplement that they have been assigned. The research will provide background information for an advertisement students will design to entice consumers to purchase their product.

Advertising plays a major role in marketing new and existing products to consumers. Your students will practice what it takes to persuade someone to purchase and use a product. This lesson provides a perfect opportunity for you to lead a class discussion on supply and demand, the cost of items, and how advertising affects what people purchase. At the same time, the students will learn about the different soil supplements that can be used to grow healthy plants.