A Step-by-Step Fertigation Guide for Blackberry Growers in Florida

Introduction

Blackberry cultivation offers significant opportunities for fruit producers in subtropical regions. Effective fertilizer management is essential for maximizing production. However, determining the optimal fertilizer application can be challenging as a result of variations in soil types and climate. To achieve the best results, it is important to follow the 5 Rs of nutrient stewardship. (There are usually only 4 Rs outside the unique environmental conditions of Florida.) These principles focus on applying the right fertilizer source at the right rate, at the right time, in the right place, and with the right irrigation (Dixon and Liu 2020; Sriti et al. 2024). This guide provides Florida blackberry growers with practical recommendations for efficient fertigation practices to boost blackberry yields and improve nutrient use efficiency. It is intended for commercial growers, agricultural consultants, farm managers, Extension agents, Extension specialists, and others interested in blackberry production and sustainable farming.

Fertigation, the process of applying fertilizers through irrigation systems, is gaining popularity worldwide for its ability to enhance both water use and nutrient use efficiencies, ultimately increasing crop yields (Thompson et al. 2018). This method improves nutrient efficiency by facilitating frequent split applications directly to the root zone (Bryla 2011). Small, repeated applications reduce nutrient losses such as ammonia volatilization and nitrogen denitrification, while also minimizing nutrient leaching and fixation, particularly for phosphorus. Fertigation ensures precise timing and even distribution of both water and nutrients, helping crops meet their specific needs at the right time (Narda and Chawla 2002; Patel and Rajput 2000). Additionally, fertigation offers better control over nutrient concentrations in the soil solution and improves the cost-effectiveness of fertilizer use (Solaimalai et al. 2005).

In blackberry cultivation, fertigation plays a crucial role by delivering nutrients directly to the plant roots through the irrigation system. This method enhances nutrient uptake, reduces waste, and ensures that plants receive the optimal nutrients at the right time, supporting healthy growth and fruit production.

Step-by-Step Guide

If a drip irrigation system is already installed, simply connect the fertilizer injector to the system and begin fertigating. If no drip irrigation system is in place, you will need to set one up first.

1. Prepare the irrigation system.

Key components for the irrigation system include:

• Connectors and fittings (elbows, tees, end caps)
• Pressure regulator to maintain consistent water pressure
• Filter to prevent debris from clogging the system
• Hole punch tool to install emitters securely
• Timer to automate the irrigation process for consistent watering schedules (Figure 1)

To set up an effective drip irrigation system for blackberry production, follow these steps:

1. Install the main supply line: Begin by laying down ½-inch or ¾-inch polyethylene tubing as the primary water supply line. This tubing will deliver water to all the plants, whether they are in pots or planted in the field.
   1. For field production, you can use ½-inch or ¾-inch polyethylene tubing with built-in emitters and anti-clogging features. This option simplifies the system and ensures consistent water distribution throughout the field.
   2. In potted blackberry production systems, connect ¼-inch drip tubing to the main supply line. This smaller tubing allows for accurate and efficient water delivery directly to each plant.
2. Properly place emitters: Install emitters along the ¼-inch tubing, ensuring they are spaced appropriately to provide each pot with the right amount of water. The emitters regulate the flow of water to the plants, preventing overwatering or underwatering. Adjust the flow rate to suit the needs of the blackberry plants.

For detailed guidance on designing and installing a drip irrigation system, refer to the comprehensive instructions in Ask IFAS publication HS1144, “Drip-Irrigation Systems for Small Conventional Vegetable Farms and Organic Vegetable Farms.” This resource will help you optimize your irrigation system to maximize water efficiency and promote healthy blackberry growth.

2. Set up the fertigation system.

Once the drip irrigation system is installed, set up the fertigation system to efficiently deliver liquid or water-soluble fertilizers directly to the plant root zones. The key component of the fertigation system is the fertilizer injector, which can be powered either by water (e.g., Venturi or Dosatron [NEWTRY, Clearwater, Florida] injectors) or by electricity or fuel (e.g., peristaltic or centrifugal pumps).

Fertilizer Injector

The selection of the right fertilizer injector for a particular fertigation system often depends on specific needs, farm size, and preferences. For small-scale fertigation, injectors like the Venturi injector, Dosatron injector, or peristaltic pump are often ideal due to their efficiency and simplicity. However, for large-scale fertigation systems, a centrifugal pump may be required to handle the higher volumes and pressures needed for effective nutrient delivery. These details further describe the different injector types:

• Venturi Injector: This injector uses a pressure differential to create a vacuum, drawing fertilizer from a tank into the irrigation system (Figure 2). It is commonly employed in drip irrigation systems where uniform nutrient delivery is required. Venturi injectors are cost-effective and require neither electricity nor fuel, making them ideal for remote areas. They are best suited for small and medium-sized farms where high flow rates or advanced automation are not critical.
• Dosatron Injector: The Dosatron is a water-powered fertilizer injector that automatically mixes liquid fertilizers or nutrient solutions with water (Figure 3). It operates using the flow of water through the system, powering an internal piston or motor, thus eliminating the need for electricity or fuel. The system draws fertilizer from a tank via a suction tube and proportionally mixes it at a pre-set, adjustable ratio. This ensures efficient and consistent nutrient delivery to plants, making it suitable for small-to-medium-scale operations.
• Peristaltic Pump: This type of positive displacement pump moves liquids through a flexible tube by compressing and releasing sections of the tube (Figure 4). Peristaltic pumps are widely used in fertigation systems for their precise and controlled delivery of fertilizers and nutrients. They are ideal for small-to-medium-scale fertigation, such as in greenhouses or hydroponic systems, where accurate dosing is crucial. While they can be used for larger-scale systems, centrifugal pumps are often more efficient for handling higher volumes of fluid.
• Centrifugal Pump: A centrifugal pump injects a precise amount of fertilizer solution into the irrigation line (Figure 5). It is typically powered by a gas-fueled engine or electricity. These pumps are essential for ensuring accurate and consistent fertilizer delivery, which is crucial for optimizing plant growth, especially in large-scale systems where high flow rates and pressures are necessary.

Fertilizer Injection Technologies: By integrating a fertilizer injection pump into irrigation systems, growers can have better control over plant nutrition, ensuring plants receive the right nutrients at the right time, maximizing yield, and minimizing environmental impact.

Table 1. Overview of fertilizer injector technologies for drip irrigation systems.

Injector type	Power source	Farm size suitability	Pros	Cons
Venturi injector (Figure 2)	Water-powered (relies on pressure differential)	Small to medium	Cost-effective. No electricity/fuel needed. Effective in low-pressure systems. Ideal for remote areas.	Requires a pressure differential (can reduce main line pressure). Flow rate can be less precise if pressure fluctuates. Not suitable for high flow rates.
Dosatron injector (Figure 3)	Water-powered (internal piston/motor)	Small to medium	Automatically mixes at pre-set, adjustable ratios. No electricity/fuel needed. Consistent nutrient delivery regardless of water flow/pressure variations.	Higher initial cost than Venturi. Maintenance can be more complex. Some models may have flow rate limitations for very large systems.
Peristaltic pump (Figure 4)	Electricity or fuel	Small to medium	Highly precise and controlled delivery. Ideal for accurate dosing of concentrated solutions. Can handle viscous fluids. Low maintenance (tubing replacement).	Flow rate limitations for very large volumes. Tubing wears down over time and needs replacement. Pulsed flow at low speeds (can be mitigated with dampeners).
Centrifugal pump (Figure 5)	Electricity or fuel (e.g., gas engine)	Large	Delivers larger volumes and higher pressures quickly. Suitable for extensive systems. Robust for continuous operation.	Requires external power. Can be less precise for small dose adjustments. Not self-priming (often requires manual priming or being placed below fluid level). Can be damaged if it runs dry.

View Table

Fertilizer Tank

A fertilizer tank (Figure 6) is a key component in systems designed to deliver nutrients to crops via fertigation, often in conjunction with irrigation systems such as drip or sprinkler irrigation. The primary function of a fertilizer tank is to store liquid fertilizers or dissolved nutrient solutions that will be injected into the irrigation water and delivered directly to plants. This helps ensure plants receive consistent and accurate doses of nutrients, optimizing growth and yield.

An Example of Fertigating Blackberry Bushes

This example shares details from a blackberry trial at the UF/IFAS Plant Science Research and Education Unit in Citra, Florida, focusing on fertigation.

4. Fertigating Blackberry Bushes

To prepare the fertilizer solution for fertigation, follow these steps:

1. Add 25 gallons of water directly into the fertigation tank.
2. Measure 4.4 gallons of Dyno Flo 5-2-8 YZ fertilizer and gradually add it to the tank. Since this liquid fertilizer contains only NPK, additional micronutrients will need to be incorporated.
3. Next, measure 0.25 ounces of Microplex (a brand/product name for a fertilizer micronutrient mix, often from Miller Chemical) and add it to the tank for each fertigation event. Mix the solution thoroughly to ensure complete dissolution and uniform distribution of both Dyno Flo 5-2-8 YZ and Microplex.
4. After dissolution, check to ensure that no undissolved particles remain, that the solution is homogeneous and well-mixed.
5. Initiate fertigation:
   • Start by applying irrigation to pressurize the system before introducing the fertilizer. This step is crucial for enhancing nutrient absorption and ensuring even distribution. Water the soil enough to reach the root zones without over-saturating it, aiming for a moist, not waterlogged, condition. Ensure the water is evenly distributed to support uniform fertilizer application.
   • Activate the fertigation system: After irrigating for 10 minutes to pressurize the system, run the fertigation system to begin delivering the fertilizer solution.
   • Monitor the application: Continuously monitor the system during the application to ensure even distribution and to check for any issues such as clogs or uneven flow.
6. Perform post-fertigation practices:
   • Flush the system: After applying the fertilizer solution, flush the fertigation system with irrigation water to remove any remaining fertilizer and prevent buildup that could cause clogging issues.
   • Inspect the plants: Monitor the plants for signs of nutrient uptake and ensure they are responding positively to the fertigation.
7. Record and evaluate:
   • Document the application: Record key details of the fertigation event, including the volume of solution applied and any observations made during the process.
   • Evaluate for effectiveness: Assess the impact of the fertigation on plant growth and health. Use these observations to adjust future applications based on the plants' evolving needs.

By following these steps, you can ensure efficient fertilizer application through irrigation, optimize nutrient uptake, and promote healthy plant growth.

References

Bryla, D. R. 2011. “Application of the ‘4R’ nutrient stewardship concept to horticultural crops: Getting nutrients in the ‘right’ place.” HortTechnology 21 (6): 674–682. https://doi.org/10.21273/HORTTECH.21.6.674

Dixon, M. M., and G. D. Liu. 2020. “Tomato Production in Florida Using Fertigation Technology: HS1392, 10/2020.” EDIS 2020 (5). https://doi.org/10.32473/edis-hs1392-2020

Hakkim, A., J. E. Abhilash, G. Ajay, and K. Mufeedha. 2016. “Fertigation: A Novel and Efficient Means for Fertilizer Application.” International Journal of Current Research 8 (8): 35757–35759.

Liu, G., and G. McAvoy. 2012. “How to Reduce Clogging Problems in Fertigation: HS1202, 6/2012.” EDIS 2012 (7). https://doi.org/10.32473/edis-hs1202-2012

Liu, G., J. Williamson, G. England, and A. Whidden. 2012. “How to Calculate Fertigation Injection Rates for Commercial Blueberry Production: HS1197, rev. 3/2012.” EDIS 2012 (3). https://doi.org/10.32473/edis-hs1197-2012

Narda, N. K., and J. K. Chawla. 2002. “A Simple Nitrate Submodel for Trickle Fertigated Potatoes.” Irrigation and Drainage 51 (4): 361–371. https://doi.org/10.1002/ird.65

Patel, N., and T. B. S. Rajput. 2000. “Effect of Fertigation on Growth and Yield of Onion.” Micro Irrigation, CBIP Publication 282: 451–454.

Solaimalai, A., B. Mani, A. Sadasakthi, and K. Subburamu. 2005. “Fertigation in High Value Crops—A Review.” Agricultural Reviews 26 (1): 1–13.

Sriti, N., J. Williamson, S. Sargent, Z. Deng, and G. Liu. 2024. “Principles and Significance of Nitrogen Management for Blackberry Production.” Agriculture 14 (9): 1444. https://doi.org/10.3390/agriculture14091444

Strik, B.C., and A. J. Vance. 2016. “Leaf Nutrient Concentration in Blackberry—Recommended standards and sampling time should differ among blackberry types.” Acta Horticulturae 1133: 311–318. https://doi.org/10.17660/ActaHortic.2016.1133.48

Thompson, R., I. Delcour, E. Berckmoes, and E. Stavridou, eds. 2018. The Fertigation Bible. FERTINNOWA.