Plant Nutrition of Greenhouse Crops
(book excerpts)Maintaining adequate nutrition is among the most critical aspects of producing greenhouse crops. There are two aspects of crop nutrition that the grower must consider. One aspect of nutrition involves the overall level of nutrients available to the plant. The absolute quantity of nutrients a plant needs will increase as plant size and fruit load increase. An important concept to understand regarding fertilization is that plant growth is controlled by the mineral nutrient in shortest supply, even when sufficient quantities of other nutrients exist. Thus, a single nutrient element may be the only factor limiting to plant growth even if all other elements are supplied in sufficient quantities. The second aspect of nutrition involves the optimal ratio or balance of nutrients available to the plant. Nutrient balance controls the tendency for the plant to produce either vegetative or reproductive growth (i.e., leaves and stems vs. flowers and fruits). Maintaining the proper balance between vegetative growth and fruit load is the key to the long-term productivity of the crop. In some cases, when nutrients are out of balance, severe deficiencies or toxicities may occur. The proper balance of nutrients to one another seems to be relatively consistent among plant species. In order to control nutrition, growers need to have a rapid and reliable method of monitoring the nutrient status of the growing medium using electrical conductivity analysis. The pH affects individual nutrient availability. Therefore, as pH varies, the nutrient balance available to the crop will change. Knowing the nutrients required to grow plants is only one aspect of successful crop production. Optimum yield also requires knowing the rate to apply, the method and time of application, the source of nutrients to use, and how the elements are influenced by substrate and greenhouse environmental conditions.
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Topics Within This Chapter:
- Essential Plant Nutrients
- Nitrogen
- Forms of Nitrogen Taken up by Plants
- Physiological Functions
- Nitrogen Deficiency in Plants
- Nitrogen Sources
- Phosphorus
- Forms of Phosphrous Taken up by Plants
- Physiological Functions
- Phosphorus Deficiency in Plants
- Phosphorus Sources
- Potassium
- Forms of Potassium Taken up by Plants
- Physiological Functions
- Potassium Deficiency in Plants
- Potassium Sources
- Calcium
- Forms of Calcium Taken up by Plants
- Physiological Functions
- Calcium Deficiency in Plants
- Calcium Sources
- Magnesium
- Forms of Magnesium Taken up by Plants
- Physiological Functions
- Magnesium Deficiency in Plants
- Magnesium Sources
- Sulfur
- Forms of Sulfur Taken up by Plants
- Physiological Functions
- Sulfur Deficiency in Plants
- Sulfur Sources
- Boron
- Copper
- Molybdeum
- Iron
- Manganese
- Zinc
- The Concept of the Limiting Factor
- Nutrient Mobility within the Plant
- Antagonistic and Synergistic Effects of Soil Nutrients
- Diagnosing Plant Nutrient Deficiencies
- Common Defciency Symptoms
- Monitoring Nutrient Status
- Visual Symptoms
- Plant Tissue Analysis
- Media Testing
- Electrical Conductivity of Growing Medium
- Why Is EC Useful?
- Measuring Electrical Conductivity
- Substrate Extraction Methods
- Electrical Conductivity Meters
- Limitations of EC Measurement
- Closed Irrigation Systems
- Managing Substrate EC
- pH Management of Greenhouse Crops
- Measuring pH
- Substrate Extraction Methods
- pH Meters
- Managing Substrate pH
- Lowering Growing Media pH
- Raising Growing Media pH
- Greenhouse Fertilization Programs
- Pre- Versus Post-Plant Fertilization Programs
- Pre-Plant Fertilization
- Post-Plant Fertilization
- Fertilization Frequency
- Fertilization Rates
- Substrate Influence
- Application of Biostimulants in Greenhouse Production
- Benefits of Biostimulants
- Biostimulant Categories
- Time of Application
