Perfecting PourThru: Nutrient monitoring strategies for fall greenhouse crop success

As the summer season winds down and fall production ramps up, greenhouse growers turn their attention to a range of crops spanning from aster to viola. Each of these crops brings unique nutritional needs and challenges, making regular nutrient monitoring a foundation of successful fall floriculture crop production.

Implementing routine nutritional monitoring helps growers detect and address nutritional imbalances early, preventing the onset of nutritional disorders before they impact plant quality and marketability. This article provides practical guidance on using the PourThru method and actionable strategies for correcting substrate pH and EC, both of which are essential tools for maintaining plant health and quality throughout the fall production season.

The importance of routine nutrient monitoring

Nutrient monitoring is a proactive approach that goes beyond simply reacting to problems as they arise. By regularly checking substrate pH and electrical conductivity (EC, also referred to as soluble salts), growers canmaintain optimal root zone conditions throughout the crop cycle.

This practice is especially important for fall crops, many of which are grown outdoors, where excessive rainfall may lead to nutrient leaching or where fluctuating temperatures require frequent irrigations. If substrate pH drifts outside crop-specific optimal ranges (Figure 1), or if nutrient levels in the root zone become insufficient or excessive, nutritional deficiencies or toxicities can develop, ultimately affecting plant health and marketability.

Recognizing symptoms of low or high substrate pH and EC disorders is essential for timely intervention. Low substrate pH may cause lower leaf black spotting, bronzing and stunted growth, while high substrate pH commonly results in interveinal chlorosis (yellowing) and stunted growth — with severe cases showing whitening and necrosis (death).

Low EC levels often lead to stunted growth and reddening or yellowing of leaves, whereas high EC can cause stunted growth, marginal leaf necrosis and root necrosis. By understanding these symptoms, growers can better correlate visual signs with monitoring data to make informed management decisions.

One of the most effective tools for routine nutrient monitoring in container-grown crops is the PourThru method. This technique provides a reliable snapshot of the root zone environment, allowing growers to make data-driven decisions about fertilization and pH management before visible symptoms appear. With a clear understanding of the importance of nutrient monitoring and the value of the PourThru method, let’s explore how to conduct the PourThru test and interpret the results for your fall crops.

How to conduct a Pour Thru test, step-by-step

The PourThru method is widely recognized for its simplicity and reliability. Here’s how to perform it correctly:

Select representative plants: Choose three to five plants per crop to ensure your results reflect overall crop status.

Irrigate to container capacity: Thoroughly water the selected plants until water drains from the bottom of the containers, using clear or fertilized water as you normally would.

Wait for equilibration: Allow the containers to sit for 30 to 60 minutes so that the nutrient solution in the substrate can equilibrate.

Prepare for sample collection: Place saucers under each container to collect leachate once the containers have stopped dripping.

Apply distilled water: Evenly pour distilled water onto the substrate surface, circling the plant. The volume of distilled water depends on container size:

4-inch (10-cm) container: 1.7 fl. oz (50 mL)
5-inch (12-cm) container: 2 fl. oz (60 mL)
6.5-inch (16-cm) container: 3.3 fl. oz (100 mL)
8-inch (20-cm) container: 4 fl. oz (120 mL)
12-inch (30-cm) container: 5 fl. oz (150 mL)14-inch (35-cm) container: 8.5 fl. oz (250 mL)

Table 2. Key steps for correcting high and low substrate pH and EC.

Collect leachate: The distilled water will displace solution held in the substrate, which will leach out of the bottom of the container into the saucer.

Calibrate pH and electrical conductivity (EC) meter(s): Calibrate your meter(s) using fresh standard solutions before each use, following the manufacturer’s instructions to ensure accurate readings.

Test and record results: Immediately test leachate samples for pH and EC (often referred to as soluble salts), recording values for each plant. Test samples promptly, as pH can change within two hours, while EC remains more stable if evaporation is minimized.

Interpret results: Compare your results to the optimal ranges for your specific crops using e-GRO’s Nutritional Monitoring pH and EC library, available at numonitoring.egromobi.com.

To effectively interpret your results, compare collected pH and EC values to the crop-specific optimal ranges listed in Table 1. This comparison allows you to quickly identify imbalances and make data-driven adjustments before symptoms appear.

Corrective procedures

When PourThru testing indicates that substrate pH or EC values are below or above the optimal range for your crop, respond quickly with appropriate corrective actions. Prompt intervention helps restore substrate pH or EC, prevents potential crop stress and supports healthy plant development.

Addressing these issues ensures nutrients remain available to your plants, minimizing production risks and promoting consistent quality throughout the production season. Table 2 summarizes the key steps for correcting low and high substrate pH and EC.

Overall, successful production of fall floriculture crops relies on a proactive approach to nutrient management. By integrating PourThru testing into your routine and responding promptly when substrate pH or EC values drift from the optimal range, you can optimize plant health, reduce waste and consistently deliver high-quality crops to market.

Remember, catching potential issues early through regular monitoring is the best way to prevent nutrient-related setbacks. Make nutrient monitoring a regular part of your greenhouse management strategy this fall production season.