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.

Fertilizers are used to provide nutrients that are not present in soil in amounts necessary to meet the needs of the growing crop. Plants can tolerate a wide range of watering and nutritional conditions, but for a commercial farming operation it is important to maximize production while minimizing environmental impact. Optimum watering and nutritional conditions vary depending on a variety of factors, including plant species, stage of life cycle, climate, and environmental conditions. Many growers purchase fertilizer in a concentrated solid or liquid form. The fertilizer is then mixed with water to create a fertilizer solution that can be applied to plants.

When fertilizer is applied in the field, farmers will calculate nutrient requirements in pounds per acre. However, in greenhouse production, the industry standard is parts per million. Greenhouses are often used for growing flowers, vegetables, fruits, and transplants. Greenhouses allow for greater control over the growing environment of plants. Depending upon the type of greenhouse, key factors that may be controlled include temperature, light, water, fertilizer, and atmosphere.

Proper fertilization of greenhouse plants is essential for producing a high-quality crop. Some nutrients (such as calcium and magnesium) may be mixed into the growing medium, or soil, prior to planting, but most of the nutrients are applied after planting using water-soluble fertilizers. Fertilizer injectors are used by most growers to deliver fertilizer to plants. These devices inject a small quantity of concentrated fertilizer into the irrigation line so that the solution leaving the hose is diluted to the proper concentration. Fertilizer injectors can be set at different ratios depending upon the needs of the plants. If the injector ratio in a greenhouse operation is 1:100, the injector delivers one gallon of fertilizer concentrate with every 99 gallons of water (one part out of 100 parts is concentrated fertilizer).