Nutrient Needs of Common Crops
The nutrient needs of hydroponic and aquaponic crops are crucial for achieving healthy growth, high yields, and optimal flavour and nutritional content. Common hydroponic and aquaponic crops have varying nutrient requirements, but they generally need a balance of essential macro and micronutrients.
An example of commercial hydroponic nutrients.
Leafy greens (lettuce, spinach, kale):
Leafy greens have relatively low nutrient demands and are often grown using a “lettuce formula” nutrient solution. They require higher nitrogen (N) levels for leaf development and adequate potassium (K) for overall growth. The nutrient solution should also contain sufficient calcium (Ca) and magnesium (Mg) to prevent deficiencies.
Tomatoes, cucumbers, peppers, and eggplants:
These fruiting vegetables have higher nutrient requirements than leafy greens. They need balanced levels of nitrogen (N), phosphorus (P), and potassium (K) to support both vegetative growth and fruit development. Calcium (Ca) and magnesium (Mg) are essential to prevent blossom end rot and promote overall plant health.
Herbs (basil, mint, cilantro):
Herbs generally have moderate nutrient needs. They require balanced levels of nitrogen (N), phosphorus (P), and potassium (K) to support vigorous growth and flavour development. Adequate levels of secondary nutrients like calcium (Ca) and magnesium (Mg) are important for herb production.
Flowers (lavender, marigolds, petunias):
Flowering plants require a well-rounded nutrient profile to support both vegetative growth and flower formation. Nitrogen (N), phosphorus (P), and potassium (K) are crucial for overall plant development. Calcium (Ca) and magnesium (Mg) are important to prevent nutrient imbalances and deficiencies.
Strawberries:
Strawberries have specific nutrient requirements for fruit production. They need higher potassium (K) levels to promote flower and fruit development. Adequate levels of calcium (Ca) are essential to prevent fruit disorders.
Fruiting vines (melons, squash, cucumbers):
These crops have similar nutrient needs to other fruiting vegetables, requiring a balanced nutrient solution with a focus on nitrogen (N), phosphorus (P), and potassium (K) for both vine and fruit growth.
It’s important to regularly monitor and adjust nutrient levels in the nutrient solution to prevent deficiencies or excesses that could harm plant growth. Nutrient solutions are typically prepared using commercial hydroponic nutrient mixes, which can be adjusted based on the specific requirements of the crops being grown. Keep in mind that factors such as growth stage, water quality, and environmental conditions also play a role in determining nutrient needs.
pH and EC Range for Common Crops
The pH and EC (Electrical Conductivity) of the nutrient solution are critical factors in hydroponic and aquaponic cultivation, as they affect nutrient availability and plant health. Different crops have varying pH and EC preferences.
pH and EC values for common crops.
|
Crop |
pH Range |
EC Range |
|
Leafy greens (lettuce, spinach, kale): |
5.5 – 6.5 |
1.0 – 2.0 mS/cm |
|
Tomatoes, cucumbers, peppers, and eggplants: |
5.8 – 6.8 |
2.0 – 3.0 mS/cm |
|
Herbs (basil, mint, cilantro): |
5.5 – 6.5 |
1.5 – 2.5 mS/cm |
|
Flowers (lavender, marigolds, petunias): |
5.8 – 6.8 |
1.5 – 2.5 mS/cm |
|
Strawberries: |
5.5 – 6.5 |
1.8 – 2.8 mS/cm |
|
Fruiting vines (melons, squash, cucumbers): |
5.8 – 6.8 |
2.0 – 3.0 mS/cm |
A. Fish
The pH range in an aquaponic system is influenced by both the nutrient needs of the plants and the preferred pH range of the fish species. In general, a pH range of 6.8 – 7.2 is considered suitable for most aquaponic setups.
B. Important Considerations
pH: pH levels impact nutrient availability. If the pH is too high or too low, certain nutrients may become less accessible to plants. Regular pH monitoring and adjustments are crucial to prevent nutrient deficiencies or toxicities.
EC: EC is a measure of the nutrient concentration in the water. It reflects the total dissolved salts, including essential nutrients. Adjusting EC helps maintain a balanced nutrient solution and prevent over- or under-fertilisation.
Crop stage: Keep in mind that the pH and EC requirements may vary depending on the growth stage of the plant. Seedlings and mature plants may have different preferences.
Water source: The pH and EC of the water source used to prepare the nutrient solution can influence the final solution’s values. It’s important to test the source water and adjust accordingly.
Regular monitoring of pH and EC and making appropriate adjustments ensures that crops receive the necessary nutrients in optimal proportions. Testing kits or meters are commonly used to measure pH and EC levels in hydroponic and aquaponic systems. Always refer to specific crop guidelines and adjust nutrient solutions accordingly to achieve the best results.
Leaf and Water Analysis
Leaf and water analysis results are valuable tools for fine-tuning nutrient solutions in hydroponic and aquaponic systems. These analyses provide insights into the nutrient status of plants and the composition of the growing environment. By interpreting these results, growers can make informed decisions to adjust nutrient solutions for optimal plant health and growth.
A. Leaf Analysis
Leaf analysis involves collecting and analysing plant tissue samples to determine the nutrient levels within the plants themselves. This analysis provides an accurate snapshot of the nutrients being taken up by the plants and identifies any deficiencies or excesses. Here’s how leaf analysis results are used:
Identifying nutrient imbalances: The analysis reveals whether certain nutrients are deficient, adequate, or in excess within the plant tissue.
Adjusting nutrient solutions: If specific nutrient deficiencies are identified, growers can adjust the nutrient solution’s composition to supply the lacking elements. For example, if a leaf analysis indicates low nitrogen levels, the grower can increase the nitrogen concentration in the nutrient solution.
Preventing nutrient toxicities: Leaf analysis also helps prevent nutrient toxicities. If certain nutrients are excessively present, adjustments can be made to avoid over-fertilisation and potential harm to the plants.
Fine-tuning ratios: By knowing the nutrient ratios within the plants, growers can achieve balanced nutrient solutions that match the plants’ needs at different growth stages.
Nutrient deficiency symptoms on tomato leaves.
B. Water Analysis
Water analysis involves testing the nutrient content of the water used to prepare nutrient solutions. This analysis helps determine the baseline nutrient composition of the solution and its potential impact on plant growth. Here’s how water analysis results are used:
Understanding water quality: Water analysis provides insights into the water’s natural nutrient content, pH, and mineral composition.
Adjusting nutrient solutions: If the source water contains significant levels of certain nutrients, growers can account for these nutrients when formulating nutrient solutions. For example, if the water source is high in calcium, adjustments can be made to the calcium content in the nutrient solution.
pH adjustment: Water analysis also helps anticipate pH-related challenges. If the source water has a high pH, growers can take steps to adjust the pH of the nutrient solution as needed.
C. Important Considerations
Sampling method: Proper sampling techniques are essential to obtain accurate analysis results. Follow the recommended guidelines for collecting representative samples of both plant tissue and water.
Sampling frequency: Regular sampling and analysis throughout the growing season provide a more comprehensive understanding of nutrient dynamics and changes over time.
Crop-specific guidelines: Different crops have varying nutrient requirements and preferences. Refer to specific guidelines for the crops being grown to interpret analysis results effectively.
Leaf and water analysis results are not standalone solutions but tools to guide adjustments in nutrient solutions. They provide data-driven insights that help growers optimise nutrient delivery, prevent imbalances, and ultimately promote healthier and more productive plants. Collaborating with agricultural extension services or experts can also enhance the interpretation and application of analysis results.